Эмблема МГУ
Московский государственный университет имени М.В.Ломоносова
Л.Н.Шевырдяева
NATURALLY SPEAKING
Учебное пособие
по развитию навыков чтения
и устной речи
2010
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Данное учебное пособие предназначено для студентов 2-3 курсов и аспирантов
биохимических специальностей биологических факультетов университетов и имеет своей целью
дальнейшее совершенствование уже полученных навыков чтения и устной речи. Пособие
содержит оригинальные тексты на английском языке, взятые из научных журналов (Science,
Scientific American, New Scientist). Тексты и задания, представленные в пособии, рассчитаны на
обучающихся продвинутого уровня и содержат задания для обсуждения и вопросы,
предполагающие значительный уровень как лингвистической подготовки, так и знаний в сфере
биологии.
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Введение
Данное учебное пособие предназначено для студентов биологического факультета 2-3
курсов и аспирантов биохимического отделения и имеет своей целью совершенствование уже
полученных навыков чтения и устной речи. Тексты и задания, представленные в пособии,
рассчитаны на обучающихся продвинутого уровня и содержат задания для обсуждения и
вопросы, предполагающие значительный уровень как лингвистической подготовки, так и знаний в
сфере биологии.
Учебное пособие состоит из 3 разделов (section) по 5 уроков (unit) в каждом в соответствии с
возрастанием объема и сложности текстов и заданий. Каждый раздел рассчитан на один семестр,
а каждый урок – на 3-4 занятия. Тематическая подборка текстов и их расположение определяются
помимо прочего и информированностью студентов: некоторые темы в полном объеме и с
достаточным знанием фактического материала они могут обсуждать только к 3 курсу.
Чтение в данном учебном пособии представлено не только как цель, но и как средство
обучения, выступая в качестве содержательной базы при совершенствовании навыков говорения.
В каждом уроке представлены тексты, направленные на развитие трех основных видов чтения –
просмотрового чтения (reading for general information), чтения с выборочным извлечением нужной
информации (reading for specific information) и чтения с полным пониманием (reading for detail).
После текстов даются задания, развивающие навыки монологического и диалогического
высказывания, ведения беседы и аргументации, для совершенствования которых и
предназначено учебное пособие. По этой же причине в него не включены упражнения по
грамматике. В плане формирования грамматических навыков чтения задачи данного учебного
пособия ограничиваются лишь увеличением количества легко распознаваемых грамматических
явлений и развитием на этой базе механизма структурной антиципации.
В ходе обучения осуществляется совершенствование умения говорить как в диалогической,
так и в монологической форме. При развитии диалогической формы речи акцент сделан на
диалоге-обмене мнениями и информацией. При обучении монологической форме речи большое
внимание уделяется работе над рассуждением, выражением своего отношения, сравнительной
оценкой мнений и позиций, интерпретацией и выражением причинно-следственных связей.
В пособии представлены оригинальные неадаптированные тексты (в некоторых случаях –
фрагменты текстов или их сокращенный вариант), взятые из авторитетных научных изданий и их
интернет-версий – Nature, Scientific American, New Scientist, а также научной колонки The New York
Times. Необходимо отметить, что приведенные в текстах точки зрения зачастую имеют
провокационный характер и могут вызвать сильную реакцию учащихся – несогласие, неодобрение
и даже полное отрицание заявленных фактов. Некоторые тексты прямо противоречат друг другу.
Такая стратегия выбрана автором вполне сознательно и представляется оправданной, поскольку
напрямую отвечает целям пособия – на основе прочитанного совершенствовать навыки устной
речи, ведения научной дискуссии и аргументации. В задачи автора входило сделать каждый урок
учебного пособия познавательным и интересным для студентов всех специальностей, сталкивая
альтернативные мнения, и создавая тем самым условия для взаимообогащающего общения.
При отборе текстов пристальное внимание уделялось и их терминологической
насыщенности; освоение лексики подчинено методическому принципу «снежного кома», когда
лексика предыдущих уроков и текстов снова встречается и отрабатывается в последующих.
Некоторые темы также перекликаются друг с другом, и уже проработанные ранее вопросы
расширяются в следующих уроках. Так, например, нарушения сна и их причины (урок Sleep)
позднее рассматриваются при обсуждении воздействия алкоголя на организм человека (урок
Alcohol). Основные термины урока Human Genetics пересекаются с терминами урока Human
Evolution.
Каждый урок (unit) открывается эпиграфом, отражающим его основную мысль. В первом
упражнении предлагаются вопросы для обсуждения по теме урока (What do you know about…), а
также в некоторых уроках даны основные термины, которые студенты должны объяснить.
Разделы различаются не только по объему и степени сложности текстов, но и по их
количеству и предлагаемым упражнениям. В первом разделе даются самые простые небольшие
тексты, а также упражнения на отработку лексики, которые далее уже не встречаются. Во втором
и третьем разделах тексты становятся сложнее и длиннее с нарастающей степенью
терминологической насыщенности. Предлагаемые к текстам задания в форме вопросов
множественного выбора (multiple choice), вопросов «верно-неверно» (true/false), задания на
заполнение пропусков (blank filling) и соотнесение информации (matching information) проверяют
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умение студентов извлекать информацию из текстов, выявлять причинно-следственные связи,
интерпретировать отношение говорящего.
В связи с тем, что учебное пособие полностью построено на аутентичных текстах разного
характера, большое значение придается самостоятельному обращению учащихся к словарям и
справочным изданиям, тем самым у студентов и аспирантов формируется потребность и
развивается умение использования одно- и двуязычной справочной литературы и источников.
Последним заданием каждого урока является составление краткого обзора всех
рассмотренных в его рамках вопросов. Данное задание направлено на развитие навыков анализа,
реферирования и устных презентаций.
В конце каждого из трех разделов учебного пособия (section) приводится список
рекомендуемых тем для устных докладов и презентаций студентов.
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Contents
Section 1
Unit 1. Human body ……………………………………………………………………..…..3
Unit 2. Water ………………………………………………………………………………….6
Unit 3. Fungi …………………………………………………………………………………..9
Unit 4. Bacteria ……………………………………………………………………………….12
Unit 5. Domesticated animals …………………………………………………………..…15
Recommended Report and Presentation Topics ………………………………………18
Section 2
Unit 6. Brain ………………………………………………………………………….…………19
Unit 7. Sleep …………………………………………………………………………………….22
Unit 8. Coffee …………………………………………………………………………………...25
Unit 9. Human Genetics and Diversity …………………………………………….……….28
Unit 10. Animal adaptations ………………………………………………………….………31
Recommended Report and Presentation Topics …………………………………………34
Section 3
Unit 11. Human Evolution ………………………………………………….……………….35
Unit 12. Alcohol ……………………………………………………………………………….39
Unit 13. Sex and Gender …………………………………………………………………….43
Unit 14. Aging ………………………………………………………………………...……….47
Unit 15. Food ……………………………………………………………………….………….51
Recommended Report and Presentation Topics ………………………………………..57
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Section 1.
Unit 1. Human Body
Any lover of humanity who looks back on the
achievements of medical science must feel his heart glow
and his right ventricle expand with the percardiac
stimulus of a permissible pride.
Stephen B. Leacock, Canadian economist and humorist
Exercise 1. What do you know about the human body?
1. How is our body prepared for the physical stresses and wear of human life? Speak about each system of
organs.
2. What are the most surprising abilities of the human body?
3. What is the adaptive significance of four-chambered heart and greater and lesser circulation?
4. How does the human body adapt to changes?
5. What medical achievements have most significantly changed human life and health care?
Exercise 2. Match the terms which will be used in the text (1-6) with their definitions (A-F).
1. corpus callosum
2. cerebral hemispheres
3. stroke
4. cerebrospinal fluid
5. seizure1
6. congenital
A. A pair of structures, originating from the forebrain, that contain the
centers concerned with the major senses, voluntary muscle activities,
and higher brain functions, such as language and memory.
B. Describes phenotypic character or condition recognizable at, and usually
before, birth. The term usually refers to hereditary or inborn conditions
that are most often harmful.
C. A clear watery fluid containing glucose, salts, and a few white blood
cells, that is found in the internal cavities and between the surrounding
membranes of the central nervous system. It cushions and protects
nerve tissues.
D. A paroxysmal event due to abnormal, excessive, hypersynchronous
discharges from an aggregate of CNS neurons. Epilepsy is diagnosed
when there are recurrent numerous events due to a chronic, underlying
process.
E. A thick band of nerve fibers that connects the two cerebral hemispheres
in the brain of placental mammals. It enables coordination of the
functions of the two hemispheres.
F. A rapidly developing loss of brain function(s) due to disturbance in the
blood supply to the brain, caused by a blocked or burst blood vessel.
Exercise 3. Now read the text about a unique brain operation.
Strange but True: When Half a Brain Is Better than a Whole One
You might not want to do it, but removing half of your brain will not significantly impact who you are
By Charles Choi
The operation known as hemispherectomy—where half the brain is removed—sounds too radical to ever
consider, much less perform. In the last century, however, surgeons have performed it hundreds of times for
disorders uncontrollable in any other way. Unbelievably, the surgery has no apparent effect on personality or
memory.
The first known hemispherectomy was performed on a dog in 1888 by German physiologist Friedrich Goltz.
In humans, neurosurgeon Walter Dandy pioneered the operation at Johns Hopkins University in 1923 on a brain
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Note. Causes of seizures:
a. for neonates (less than 1 month old) include perinatal hypoxia and ischemia, intracranial hemorrhage and trauma,
acute CNS infection, metabolic disturbances (hypoglycemia, hypocalcemia, hypomagnesemia, pyridoxine deficiency),
drug withdrawal, developmental disorders, genetic disorders;
b. for infants and children (up to 12 years of age) the causes are febrile seizures, genetic disorders (metabolic,
degenerative, primary epilepsy syndromes), CNS infection, developmental disorders, trauma, idiopathic;
c. for adolescents (12–18 years) – trauma, genetic disorders, infection, brain tumor, illicit drug use, idiopathic;
d. for young adults (18–35 years) – trauma, alcohol withdrawal, illicit drug use, brain tumor, idiopathic.
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tumor patient. (That man lived for more than three years before ultimately succumbing to cancer.) The procedure is
among the most drastic kinds of brain surgery—"You can't take more than half. If you take the whole thing, you've
got a problem," Johns Hopkins neurologist John Freeman quips.
One side effect Canadian neurosurgeon Kenneth McKenzie reported in 1938 after a hemispherectomy on a
16-year-old girl who suffered a stroke was that her seizures stopped. Nowadays, the surgery is performed on
patients who suffer dozens of seizures every day that resist all medication, and which are due to conditions that
mostly affect one hemisphere. "These disorders are often progressive and damage the rest of the brain if not
treated," University of California, Los Angeles, neurosurgeon Gary Mathern says. Freeman concurs:
"Hemispherectomy is something that one only does when the alternatives are worse."
Anatomical hemispherectomies involve the removal of the entire hemisphere, whereas functional
hemispherectomies only take out parts of a hemisphere, as well as severing the corpus callosum, the fiber bundle
that connects the two halves of the brain. The evacuated cavity is left empty, filling with cerebrospinal fluid in a day
or so. The strength of anatomical hemispherectomies, a specialty of Hopkins, lies in the fact that "leaving even a
little bit of brain behind can lead seizures to return," Freeman says. On the other hand, functional
hemispherectomies, which U.C.L.A. surgeons usually perform, lead to less blood loss. "Our patients are usually
under two years of age, so they have less blood to lose," Mathern says. Most Hopkins hemispherectomy patients
are five to 10 years old.
Neurosurgeons have performed the operation on children as young as three months old. Astonishingly,
memory and personality develop normally. A recent study found that 86 percent of the 111 children who underwent
hemispherectomy at Hopkins between 1975 and 2001 are either seizure-free or have nondisabling seizures that do
not require medication. The patients who still suffer seizures usually have congenital defects or developmental
abnormalities, where brain damage is often not confined to just one hemisphere, Freeman explains. Another study
found that children that underwent hemispherectomies often improved academically once their seizures stopped.
"One was champion bowler of her class, one was chess champion of his state, and others are in college doing very
nicely," Freeman says.
Of course, the operation has its downside: "You can walk, run—some dance or skip—but you lose use of the
hand opposite of the hemisphere that was removed. You have little function in that arm and vision on that side is
lost," Freeman says. Remarkably, few other impacts are seen. If the left side of the brain is taken out, "most people
have problems with their speech, but it used to be thought that if you took that side out after age two, you'd never
talk again, and we've proven that untrue," Freeman says. "The younger a person is when they undergo
hemispherectomy, the less disability you have in talking. Where on the right side of the brain speech is transferred
to and what it replaces is something nobody has really worked out."
Mathern and his colleagues have recently conducted the first functional magnetic resonance imaging study
into hemispherectomy patients, investigating how their brain changes with physical rehabilitation. Probing how the
remaining cerebral hemispheres of these patients acquire language, sensory, motor and other functions "could
shed a great deal of light on the brain's plasticity, or ability to change," Freeman notes. Still, having half a brain—
and therefore only the use of one hand and half a field of vision in each eye—is a condition most would prefer to
avoid. (From Scientific American Online, May 24, 2007)
Exercise 4. The words on this list are all verbs (some of them were used in the text). What are the
corresponding noun forms? Write them in the second column. The first one has been done for you as an
example.
1. to diagnose - diagnosis
2. to examine - _______________
3. to prescribe - ______________
4. to suffer - _________________
5. to operate - _______________
6. to cure - __________________
7. to recover - _______________
8. to analyse - _______________
9. to infect - _________________
10. to carry - ________________
11. to replace - ______________
12. to degenerate - ___________
13. to paralyse - ______________
14. to treat – _________________
15. to affect – ________________
16. to damage - _______________
Exercise 5. Rewrite the sentences below, changing the verbs (which are in bold) to nouns. Do not change
the meaning of the sentences, but be prepared to make grammatical changes if necessary. The first one
has been done for you as an example.
1. I diagnosed that the patient had a heart condition.
1. My diagnosis was that the patient had a heart
condition.
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2. I examined the patient fully.
3. I prescribed a course of antibiotics.
4. He suffered very little.
5. Ten per cent of the population are thought to carry the
bacteria.
6. This disease cannot be cured.
7. He has recovered fully.
8. The lab analysed the blood sample.
9. We found that the tissue was infected.
10. We operated immediately.
11. We replaced the patient's hip.
12. His condition has degenerated.
13. His arm was paralysed after the stroke
2. I made a full
3. I wrote a
4. He experienced very little
5. Ten per cent of the population are thought to be
6. There is no
7. He has made a full
8. The lab made an
9. We found an
10. The
11. The patient was given a hip
12. There has been a
13. He suffered
Exercise 6. Now make up your own sentences with the following verbs and corresponding nouns: to treat,
to affect, to damage.
Exercise 7. Using the information from the text in Exercise 3 speak on the following:
1. History of hemispherectomy.
2. Surgical indication.
3. Difference between functional and anatomical hemispherectomy.
4. Positive and negative consequences of hemispherectomy.
5. Implications of the operation for fundamental science.
Exercise 8. Prove that the human body has unique adaptive abilities. Use the information from the text in
Exercise 3 and additional facts, if necessary. Combine all the information into one report.
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Unit 2. Water
Water, thou hast no taste, no color, no odor; canst not
be defined, art relished while ever mysterious. Not
necessary to life, but rather life itself, thou fillest us with
a gratification that exceeds the delight of the senses.
Antoine de Saint-Exupery, The Wisdom of the Sands
Exercise 1. What do you know about water?
1. What are the functions of water in human organism? What processes is water involved in?
2. What is the function of water in photosynthesis?
3. Can water produce negative effect on the human body?
4. What is dehydration? What negative consequences can it cause?
5. Why does daily water consumption of different classes of animals – amphibians, reptiles, birds, mammals –
differ?
6. Do freshwater and saltwater kinds of fish have any difference in metabolism?
7. Why can’t we use distilled water for drinking?
Exercise 2. How long can the average person survive without water?
Now read the explanation given by Randall K. Packer, a professor of biology at George Washington
University, and check if your answer was correct.
It is impossible to give an answer to this seemingly simple question because many variable factors determine
a person's survival time. Under the most extreme conditions, death can come rather quickly. For example, a child
left in a hot car or an athlete exercising hard in hot weather can dehydrate, overheat and die in a period of a few
hours. An adult in comfortable surroundings, in contrast, can survive for a week or more with no, or very limited,
water intake.
To stay healthy, humans must maintain water balance, which means that water losses must be made up for
by water intake. We get water from food and drink and lose it as sweat and urine. Another major route of water loss
usually goes unnoticed: because we exhale air that is water saturated, we lose water each time we exhale. On a
cold day we see this water in the air as it condenses.
Exposure to a hot environment and vigorous exercise both increase body temperature. The only
physiological mechanism humans have to keep from overheating is sweating. Evaporation of sweat cools blood in
vessels in the skin, which helps to cool the entire body. Under extreme conditions an adult can lose between one
and 1.5 liters of sweat an hour. If that lost water is not replaced, the total volume of body fluid can fall quickly and,
most dangerously, blood volume may drop. If this happens, two potentially life-threatening problems arise: sweating
stops and body temperature can soar even higher, while blood pressure decreases because of the low blood
volume. Under such conditions, death occurs quickly. Because of their relatively larger skin surface-to-volume ratio,
children are especially susceptible to rapid overheating and dehydration.
The combination of dehydration and overheating sends thousands of people to hospital emergency rooms
each year, but diarrhea, excessive vomiting, and kidney failures of various sorts can also cause dehydration. A
person can stay hydrated by drinking many different kinds of fluids in addition to water, with one exception. Drinking
alcoholic beverages actually causes dehydration because ethanol depresses the level of the anti-diuretic hormone
arginine vasopressin (AVP). As a result, urine volume increases such that more fluid is lost in urine than is gained
by consuming the beverage.
Exercise 3. Give definitions to the following terms connected with water:
To dehydrate / to rehydrate, to condense, fluid, water balance, hormone, kidney, sweating, evaporation.
Exercise 4. According to the text in Exercise 2, what is more damaging for one’s health? Why?
a. hot weather
b. high blood pressure
c. sweating
d. drinking alcoholic beverages
e. low blood pressure
f. physical exercise
g. vomiting
Exercise 5. Now read the article about water overdose.
Strange but True: Drinking Too Much Water Can Kill
In a hydration-obsessed culture, people can and do drink themselves to death.
By Coco Ballantyne
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Liquid H2O is the sine qua non of life. Making up about 66 percent of the human body, water runs through
the blood, inhabits the cells, and lurks in the spaces between. At every moment water escapes the body through
sweat, urination, or exhaled breath, among other routes. Replacing these lost stores is essential but rehydration
can be overdone. There is such a thing as a fatal water overdose.
Earlier this year, a 28-year-old California woman died after competing in a radio station's on-air waterdrinking contest. After downing some six liters of water in three hours in the contest, Jennifer Strange vomited,
went home with a splitting headache, and died from so-called water intoxication. There are many other tragic
examples of death by water. In 2005 a fraternity hazing at California State University, Chico, left a 21-year-old man
dead after he was forced to drink excessive amounts of water between rounds of push-ups in a cold basement.
Club-goers taking MDMA ("ecstasy") have died after consuming copious amounts of water trying to rehydrate
following long nights of dancing and sweating. Going overboard in attempts to rehydrate is also common among
endurance athletes. A 2005 study in the New England Journal of Medicine found that close to one sixth of
marathon runners develop some degree of hyponatremia, or dilution of the blood caused by drinking too much
water.
Hyponatremia, a word cobbled together from Latin and Greek roots, translates as "insufficient salt in the
blood." Quantitatively speaking, it means having a blood sodium concentration below 135 millimoles per liter, or
approximately 0.4 ounces per gallon, the normal concentration lying somewhere between 135 and 145 millimoles
per liter. Severe cases of hyponatremia can lead to water intoxication, an illness whose symptoms include
headache, fatigue, nausea, vomiting, frequent urination and mental disorientation.
In humans the kidneys control the amount of water, salts and other solutes leaving the body by sieving blood
through their millions of twisted tubules. When a person drinks too much water in a short period of time, the kidneys
cannot flush it out fast enough and the blood becomes waterlogged. Drawn to regions where the concentration of
salt and other dissolved substances is higher, excess water leaves the blood and ultimately enters the cells, which
swell like balloons to accommodate it.
Most cells have room to stretch because they are embedded in flexible tissues such as fat and muscle, but
this is not the case for neurons. Brain cells are tightly packaged inside a rigid boney cage, the skull, and they have
to share this space with blood and cerebrospinal fluid, explains Wolfgang Liedtke, a clinical neuroscientist at Duke
University Medical Center. "Inside the skull there is almost zero room to expand and swell," he says. Thus, brain
edema, or swelling, can be disastrous. "Rapid and severe hyponatremia causes entry of water into brain cells
leading to brain swelling, which manifests as seizures, coma, respiratory arrest, brain stem herniation and death,"
explains M. Amin Arnaout, chief of nephrology at Massachusetts General Hospital and Harvard Medical School.
Where did people get the idea that guzzling enormous quantities of water is healthful? A few years ago
Heinz Valtin, a kidney specialist from Dartmouth Medical School, decided to determine if the common advice to
drink eight, eight-ounce glasses of water per day could hold up to scientific scrutiny. After scouring the peerreviewed literature, Valtin concluded that no scientific studies support the "eight x eight" dictum (for healthy adults
living in temperate climates and doing mild exercise). In fact, drinking this much or more "could be harmful, both in
precipitating potentially dangerous hyponatremia and exposure to pollutants, and also in making many people feel
guilty for not drinking enough," he wrote in his 2002 review for the American Journal of Physiology—Regulatory,
Integrative and Comparative Physiology. And since he published his findings, Valtin says, "not a single scientific
report published in a peer-reviewed publication has proven the contrary."
Most cases of water poisoning do not result from simply drinking too much water, says Joseph Verbalis,
chairman of medicine at Georgetown University Medical Center. It is usually a combination of excessive fluid intake
and increased secretion of vasopressin (also called antidiuretic hormone), he explains. Produced by the
hypothalamus and secreted into the bloodstream by the posterior pituitary gland, vasopressin instructs the kidneys
to conserve water. Its secretion increases in periods of physical stress—during a marathon, for example—and may
cause the body to conserve water even if a person is drinking excessive quantities.
Every hour, a healthy kidney at rest can excrete 800 to 1,000 milliliters, or 0.21 to 0.26 gallon, of water and
therefore a person can drink water at a rate of 800 to 1,000 milliliters per hour without experiencing a net gain in
water, Verbalis explains. If that same person is running a marathon, however, the stress of the situation will
increase vasopressin levels, reducing the kidney's excretion capacity to as low as 100 milliliters per hour. Drinking
800 to 1,000 milliliters of water per hour under these conditions can potentially lead to a net gain in water, even
with considerable sweating, he says.
While exercising, "you should balance what you're drinking with what you're sweating," and that includes
sports drinks, which can also cause hyponatremia when consumed in excess, Verbalis advises. "If you're sweating
500 milliliters per hour, that is what you should be drinking." But measuring sweat output is not easy. How can a
marathon runner, or any person, determine how much water to consume? As long as you are healthy and
equipped with a thirst barometer unimpaired by old age or mind-altering drugs, follow Verbalis's advice, "drink to
your thirst. It's the best indicator." (From Scientific American Online, June 21, 2007)
Exercise 6. Are the following statements true or false, according to the text? Why? Explain your choice.
1. Water is the basic substance in the human organism.
2. Drinking excessive amounts of water can lead to death.
3. Hyponatremia is a Latin word which means “water overdose”.
4. Hyponatremia is a serious disorder characteristic for sportsmen.
10
5.
6.
7.
8.
9.
Liver filters water and plays the key role in excreting wastes.
Excessive amounts of water are particularly damaging for the brain.
A considerable body of evidence confirms the advice to drink much.
Excessive water intake combined with physical exercise may result in serious health problems.
It’s not recommended to drink while exercising.
Exercise 7. These sentences all give very good advice, but they have been divided into separate halves.
Match the half-sentences in Column A with the half-sentences in Column B to make 14 sentences which
are correct, complete and true.
Write five other pieces of advice for healthy life.
A
1. Regular exercise is ...
2. A balanced diet should ...
3. Medicines should ...
4. A patient in shock should ...
5. Not taking any exercise is ...
6. Reading in bad light can ...
7. You should do ...
8. A normal adult should drink ...
9. HIV can be transmitted ...
10. Bad posture can ...
11. People with fair complexions ...
12. Surgical instruments must ...
13. Babies should ...
14. Hemorrhage control routinely should ...
В
a) ... burn easily in the sun.
b) ... cause back pain.
c) ... be inoculated against diphtheria.
d) ... be kept out of the reach of children.
e) ... be kept warm and lying down.
f) ... about 2.5 litres of fluid each day.
g) ... good for the heart.
h) ... five minutes' exercise every morning.
i) ... be sterilised before use.
j) ... make the eyes ache.
k) ... provide all the nutrients needed, in the correct proportions.
l) ... an unhealthy way of living.
m) ... be by pressure and elevation.
n) ... by using non-sterile needles
Exercise 8. Summarize everything you now know about significance and effects of water into one report.
11
Unit 3. Fungi
Every man carries a parasite somewhere.
Japanese proverb
Exercise 1. What do you know about fungi?
1. What is a fungus? Why are fungi classified into a separate Kingdom?
2. Are fungi unicellular or multicellular organisms?
3. Are fungi stationary or moving organisms?
4. What is the difference between a fungus and a mushroom? Do all fungi have a fruiting body?
5. Are fungi hetero- or autotrophs?
6. What ecological functions are performed by fungi?
7. What cases of symbiotic relationship between fungi and other organisms do you know? Give examples of
mutualism and parasitism.
8. What is the significance of fungi for humans?
Exercise 2. Explain the following terms in English:
chitin
extracellular digestion
yeast
saprophyte
mold
mutualist
hypha (hyphae)
parasite
mycelium
haustoria
asexual reproduction
sexual reproduction
spore
fragmentation
budding
Exercise 3. Can you believe that fungi are the largest and fastest organisms on Earth? Why? Why not?
Read the following two texts (Text A and Text B) to find out.
Text A. The Largest Organism on Earth Is a Fungus
The blue whale is big, but nowhere near as huge as a sprawling fungus in eastern Oregon
By Anne Casselman
Next time you purchase white button mushrooms at the grocery store, just remember, they may be cute and
bite-size but they have a relative out west that occupies some 2,384 acres (965 hectares) of soil in Oregon's Blue
Mountains. Put another way, this humongous fungus would cover 1,665 football fields, or nearly four square miles
(10 square kilometers) of turf. The discovery of this giant Armillaria ostoyae in 1998 heralded a new record holder
for the title of the world's largest known organism, believed by most to be the 110-foot- (33.5-meter-) long, 200-ton
blue whale. Based on its current growth rate, the fungus is estimated to be 2,400 years old but could be as ancient
as 8,650 years, which would earn it a place among the oldest living organisms as well.
A team of forestry scientists discovered the giant after setting out to map the population of this pathogenic
fungus in eastern Oregon. The team paired fungal samples in petri dishes to see if they fused, a sign that they were
from the same genetic individual, and used DNA fingerprinting to determine where one individual fungus ended.
This one, A. ostoyae, causes Armillaria root disease, which kills swaths of conifers in many parts of the U.S.
and Canada. The fungus primarily grows along tree roots via hyphae, fine filaments that mat together and excrete
digestive enzymes. But Armillaria has the unique ability to extend rhizomorphs, flat shoestringlike structures, that
bridge gaps between food sources and expand the fungus's sweeping perimeter ever more. A combination of good
genes and a stable environment has allowed this particularly ginormous fungus to continue its creeping existence
over the past millennia. "These are very strange organisms to our anthropocentric way of thinking," says biochemist
Myron Smith of Carleton University in Ottawa, Ontario.
All fungi in the Armillaria genus are known as honey mushrooms, for the yellow-capped and sweet fruiting
bodies they produce. Some varieties share this tendency for monstrosity but are more benign in nature. In fact the
very first massive fungus discovered in 1992—a 37-acre (15-hectare) Armillaria bulbosa, which was later renamed
Armillaria gallica—is annually celebrated at a "fungus fest" in the nearby town of Crystal Falls, Mich. Myron Smith
was a PhD candidate in botany at the University of Toronto when he and colleagues discovered this exclusive
fungus in the hardwood forests near Crystal Falls. "This was kind of a side project," Smith recalls. "We were looking
at the boundaries of [fungal] individuals using genetic tests and the first year we didn't find the edge."
Next, the microbiologists developed a new way to tell an individual apart from a group of closely related
siblings using a battery of molecular genetic techniques. The major test compared fungal genes for signs of
inbreeding, where heterozygous strips of DNA become homozygous. That's when they realized they had struck it
big. The individual Armillaria bulbosa they found weighed over 100 tons (90.7 metric tons) and was roughly 1,500
years old.
Ironically, the discovery of such huge fungi specimens rekindled the debate of what constitutes an individual
organism. "It's one set of genetically identical cells that are in communication with one another that have a sort of
common purpose or at least can coordinate themselves to do something," explains Tom Volk, a biology professor
at the University of Wisconsin–La Crosse. Both the giant blue whale and the humongous fungus fit comfortably
within this definition. So does the 6,615-ton (six-million-kilogram) colony of a male quaking aspen tree and his
clones that covers 107 acres (43 hectares) of a Utah mountainside.
12
And, at second glance, even those button mushrooms aren't so tiny. A large mushroom farm can produce as
much as one million pounds (454 metric tons) of them in a year. "The mushrooms that people grow in the
mushroom houses - they're nearly genetically identical from one grower to another," Smith says. "So in a large
mushroom-growing facility that would be a genetic individual—and it's massive!" In fact, humongous may be in the
nature of things for a fungus. "We think that these things are not very rare," Volk says. "We think that they're in fact
normal." (From Scientific American Online, October 4, 2007)
Text B. Seedy but Speedy: Fungus Spews Spores at 55 Mph
By Susannah F. Locke
In a finding that could help control harmful fungus, researchers have discovered a high-speed mechanism
the germs use to project their spores into the air. Scientists from Miami University (M.U.) in Oxford, Ohio, and the
College of Mount St. Joseph in Cincinnati report in the journal PLoS ONE that fungi may be one of the fastest land
species, clocking speeds of up to 55 miles (88 kilometers) per hour and producing accelerations 180,000 times
greater than gravity.
Fungi are the most common crop pathogens in the world. Most are fairly harmless to people, although like
other allergens they sometimes exacerbate allergies and asthma. But certain varieties such as Stachybotrys
chartarum, commonly referred to as black mold, that thrive in damp places like basements may also infect the
lungs of people who have compromised immune systems or chronic bronchitis. Biologists once believed that mild
air currents were enough to release fungi's spores, but are increasingly finding that molds employ elaborate
methods to spew their seeds away from the nest. Using ultrahigh-speed video, the researchers calculated that
some fungi use their own natural water pressure like squirt guns to eject their spores.
Lead study author Nicholas Money, a fungus biologist at M.U., studied fungi that grow on cow patties and
other herbivore dung. These species play a critical role in the ecosystem by breaking down waste to recycle its
nutrients into the soil. The fungi project their spores away from the resident dung because cows will not eat near
feces. By shooting them up to eight feet (2.5 meters) away, a grazing animal will be more inclined to eat them,
thereby spreading the fungal spawn via its own manure.
The research video camera shot 250,000 frames per second to capture fungi spurting their spores into the
air, trailing glistening liquid behind them. The researchers used the video to clock the spores speeding along at 55
mph. The team also identified how several fungi build up water pressure to power a spore launch. First, the fungi
accumulate sugars and other small molecules in their cells, which, in turn, brings in more water. Targeting the first
step of this process could be a key to developing new fungicides. "By understanding the basic mechanism," he
says, "you might find ways to remediate a mold-damaged home." (From Scientific American Online, September 17,
2008)
Exercise 4. Answer the following questions using the information from the texts:
1. What animal is generally considered the biggest organism on earth?
2. What extraordinary characteristics does the discovered Armillaria ostoyae fungus possess?
3. Why is Armillaria ostoyae characterized as a pathogenic fungus?
4. What conditions allowed the fungus to grow to such enormous size?
5. How can scientists distinguish an individual from a group of closely related siblings?
6. What effect do fungi produce on people and the environment?
7. What mechanisms does Stachybotrys chartarum black mold use to spurt its spores into the air?
8. Why do fungi have to employ such complicated techniques?
Exercise 5. Earlier you discussed parasitic fungi. Now read the article which describes one example
of multi-species relationship in detail.
Fungus genome boosts fight to save North American forests
DNA sequence could advance efforts to control pine beetle infestations.
By Elie Dolgin
Canadian researchers have decoded the DNA of the tree-killing fungus found in the mouths of mountain pine
beetles, the destructive bugs that wipe out entire North American forests. Further genome sequencing of the beetle
and pine tree species should help forest managers design better pest-control tactics, the authors say. "It's really
getting to a systems-level understanding of the mountain pine beetle epidemic," says study co-author Jörg
Bohlmann, a chemical ecologist at the University of British Columbia in Vancouver, Canada, who is leading the
multi-species genome initiative. "What really happens in nature is not confined to one species, but is happening at
the intersection when one species interacts with another."
Mountain pine beetles (Dendroctonus ponderosae) have eaten their way through vast swathes of western
North American pine forests, including around 15 million hectares in British Columbia alone. As the burrowing
beetles tunnel under the bark to feed and lay eggs, they release spores of the blue-stain fungus (Grosmannia
clavigera), which stops the production of a protective toxic resin released by the tree and allows the beetles to
continue to infest.
Bohlmann and his colleagues assembled the fungus's 32.5-million-base-pair genome, which is around a
hundredth the size of the human genome, using a combination of next-generation and traditional sequencing
13
technologies — the first time that a complex eukaryotic organism has been sequenced from scratch using such a
hybrid approach. The genome was reported online this month in the journal Genome Biology.
For the other two species — the beetle and the tree — the researchers are concentrating mainly on
expressed gene sequences, fragments of the complete DNA sequence, rather than the genomes in their entirety.
They've already amassed one of the largest insect libraries of gene transcripts for the bark beetle from more than a
dozen beetle life stages and body parts. The lodgepole pine (Pinus contorta) and jack pine (Pinus banksiana) are
still at a much earlier stage of sequencing.
The goal, says Dezene Huber, a chemical ecologist at the University of Northern British Columbia in Prince
George, Canada, is to predict the dynamics between the organisms under various climatic conditions. "We should
be able to look at particular genes and say which population of trees is interacting with which population of fungus
and which population of beetles," he says. "It's really going to push science in a big way," says Brian Aukema of the
Canadian Forestry Service in Prince George, who plans to incorporate the genomic data into landscape ecological
models. "Once you have that information, you can hopefully feed that into models and understand where these
beetle populations might be the most susceptible to treatments, intervention strategies and mitigation."
Multi-species genomic interactions have been studied for some human diseases, including malaria, and a
few symbiotic ecological relationships such as leaf-cutter ants and their microbial partners, but the approach has
never before been applied on this scale for an outbreaking forest nuisance.
Already, the University of British Columbia researchers, led by mycologist Colette Breuil, have taken the
fungus genome, pinpointed the gene responsible for staining the pine wood blue and created a knockout strain that
does not produce any pigment. The blue staining reduces the commercial value of affected timber, but it is not clear
what role the colouring plays in driving infestation. The researchers are now testing this strain to tease that apart.
But the full utility of the fungus genome might only be realized after other related species are also
sequenced, says Diana Six, who studies the interaction between bark beetles and fungi at the University of
Montana in Missoula. Comparing the blue-stain fungus with free-living or pathogenic fungi will shed light on how the
beneficial fungus helps the beetles thrive, she says.
Using genomics to stop the bark beetles is a "bit of a long shot, for sure", admits Chris Keeling, a research
associate in Bohlmann's lab. But it might offer the best strategy for containing the forest pests, which have already
started to jump host species from lodgepole pine, which is found only west of the Rockies, to jack pine, which
stretches east across the entire continent. "We might be able to tweak the system to reduce the beetle populations
or prevent them from spreading further east," Keeling says. (From Nature online, 18 Sept. 2009)
Exercise 6. Speak in detail on the multi-species interaction described in this article according to the
following plan:
1. What species are involved in the relationship? What is the role of each?
2. Why do scientists study this phenomenon on the genetic level?
3. What main steps have researchers taken so far? What results have they obtained?
4. What are the perspectives of such genomic investigations?
Exercise 7. Put the words given in the brackets in the correct word-form.
Gene Study Suggests Early Evolution of Land Plants and Fungi Changed Earth's Climate
By Harald Franzen
Land plants and fungi may have arisen far earlier than previously thought, according to a study published
today in the journal Science. The gene-based research suggests that the (1)_________ (to emerge) of these
organisms may have led to major climate and animal (2)_________ (to evolve) events.
The Pennsylvania State University research team, led by (3)__________ (to evolve) biologist Blair Hedges,
based their (4)___________ (to find) on the so-called molecular clock. Genes (5)___________ (to know) to
accumulate (6)____________ (to mutate) at a constant rate, much like a ticking clock, can be used to determine
when a species originated. To figure out when land plants and fungi originated, the team analyzed 119 such
molecular clock genes common to (7)___________ (to live) species of animals, plants and fungi. Their
(8)_________ (to result) proved startling. In contrast to fossil-based studies that place the (9)__________ (to
appear) of land plants and fungi at around 480 million years ago, the genetic findings indicate that land plants and
fungi evolved approximately 700 million and 1,300 million years ago, respectively.
The early (10)______________ (to present) of plants and fungi on land would have reduced the amount of
carbon dioxide in the atmosphere, producing a (11)____________ (to cool) effect, the authors note. At the same
time, the plants boosted atmospheric oxygen levels, thus paving the way for the (12)__________ (to evolve) of
complex animals. (From Scientific American Online, August 10, 2001)
Exercise 8. Speak about fungi and their role on our planet. Summarize all the facts which have been
discussed in this unit.
14
Unit 4. Bacteria
Soap and water and common sense are the
best disinfectants.
Sir William Osler, Canadian physician and
Oxford professor of medicine
Exercise 1. What do you know about bacteria?
1. What is a bacterium? Why are bacteria classified into a separate Kingdom?
2. What is the difference between eubacteria and archaebacteria?
3. How are archaebacteria adapted to survive in the extreme conditions of their habitat?
4. What processes and mechanisms do bacteria use to obtain energy and nutrients?
5. What is the purpose of Gram staining?
6. How do bacteria reproduce? What is the difference between binary fission and conjugation?
7. What are the functions of bacteria in the environment?
8. What is their significance for humans?
9. In what ways do disease-causing bacteria damage human organism?
Exercise 2. Explain the following terms in English:
prokaryote
antibiotics
strain
resistance (to antibiotics)
colony
nitrogen fixation
pathogen
obligate aerobes
endospore
obligate anaerobes
coccus
bacillus
spirillum
Staphylococcus bacteria
Streptococcus bacteria
Exercise 3. Read and translate the following text.
Antibacterial Products May Do More Harm Than Good
Antibacterial soaps and other cleaners may actually be aiding in the development of superbacteria.
By Coco Ballantyne
Tuberculosis, food poisoning, cholera, pneumonia, strep throat and meningitis: these are just a few of the
unsavory diseases caused by bacteria. Hygiene—keeping both home and body clean—is one of the best ways to
curb the spread of bacterial infections, but lately consumers are getting the message that washing with regular
soap is insufficient. Antibacterial products have never been so popular. Body soaps, household cleaners, sponges,
even mattresses and lip glosses are now packing bacteria-killing ingredients, and scientists question what place, if
any, these chemicals have in the daily routines of healthy people.
Traditionally, people washed bacteria from their bodies and homes using soap and hot water, alcohol,
chlorine bleach or hydrogen peroxide. These substances act nonspecifically, meaning they wipe out almost every
type of microbe in sight—fungi, bacteria and some viruses—rather than singling out a particular variety. Soap
works by loosening and lifting dirt, oil and microbes from surfaces so they can be easily rinsed away with water,
whereas general cleaners such as alcohol inflict sweeping damage to cells by demolishing key structures, then
evaporate. "They do their job and are quickly dissipated into the environment," explains microbiologist Stuart Levy
of Tufts University School of Medicine.
Unlike these traditional cleaners, antibacterial products leave surface residues, creating conditions that may
foster the development of resistant bacteria, Levy notes. For example, after spraying and wiping an antibacterial
cleaner over a kitchen counter, active chemicals linger behind and continue to kill bacteria, but not necessarily all of
them. When a bacterial population is placed under a stressor—such as an antibacterial chemical—a small
subpopulation armed with special defense mechanisms can develop. These lineages survive and reproduce as
their weaker relatives perish. "What doesn't kill you makes you stronger" is the governing maxim here, as
antibacterial chemicals select for bacteria that endure their presence.
As bacteria develop a tolerance for these compounds there is potential for also developing a tolerance for
certain antibiotics. This phenomenon, called cross-resistance, has already been demonstrated in several laboratory
studies using triclosan, one of the most common chemicals found in antibacterial hand cleaners, dishwashing
liquids and other wash products. "Triclosan has a specific inhibitory target in bacteria similar to some antibiotics,"
says epidemiologist Allison Aiello at the University of Michigan School of Public Health.
When bacteria are exposed to triclosan for long periods of time, genetic mutations can arise. Some of these
mutations endow the bacteria with resistance to isoniazid, an antibiotic used for treating tuberculosis, whereas
other microbes can supercharge their efflux pumps—protein machines in the cell membrane that can spit out
several types of antibiotics, Aiello explains. These effects have been demonstrated only in the laboratory, not in
households and other real world environments, but Aiello believes that the few household studies may not have
been long enough. "It's very possible that the emergence of resistant species takes quite some time to occur…; the
potential is there," she says.
15
Apart from the potential emergence of drug-resistant bacteria in communities, scientists have other concerns
about antibacterial compounds. Both triclosan and its close chemical relative triclocarban (also widely used as an
antibacterial), are present in 60 percent of America's streams and rivers, says environmental scientist Rolf Halden,
co-founder of the Center for Water and Health at Johns Hopkins Bloomberg School of Public Health. Both
chemicals are efficiently removed from wastewater in treatment plants but end up getting sequestered in the
municipal sludge, which is used as fertilizer for crops, thereby opening a potential pathway for contamination of the
food we eat, Halden explains. "We have to realize that the concentrations in agricultural soil are very high," and
this, "along with the presence of pathogens from sewage, could be a recipe for breeding antimicrobial resistance" in
the environment, he says.
Triclosan has also been found in human breast milk, although not in concentrations considered dangerous to
babies, as well as in human blood plasma. There is no evidence showing that current concentrations of triclosan in
the human body are harmful, but recent studies suggest that it acts as an endocrine disrupter in bullfrogs and rats.
Further, an expert panel convened by the Food and Drug Administration determined that there is insufficient
evidence for a benefit from consumer products containing antibacterial additives over similar ones not containing
them. "What is this stuff doing in households when we have soaps?" asks molecular biologist John Gustafson of
New Mexico State University in Las Cruces. These substances really belong in hospitals and clinics, not in the
homes of healthy people, Gustafson says.
Of course, antibacterial products do have their place. Millions of Americans suffer from weakened immune
systems, including pregnant women and people with immunodeficiency diseases, points out Eugene Cole, an
infectious disease specialist at Brigham Young University. For these people, targeted use of antibacterial products,
such as triclosan, may be appropriate in the home, he says. In general, however, good, long-term hygiene means
using regular soaps rather than new, antibacterial ones, experts say. "The main way to keep from getting sick,"
Gustafson says, "is to wash your hands three times a day and don't touch mucous membranes." (From Scientific
American Online, June 07, 2007)
Exercise 4. Using the information from the text and other facts you know prove that:
1. Hygiene is one of the most important medical achievements of human civilization.
2. Pharmaceutical companies and the media are heavily promoting antibacterial products.
3. There are a lot of traditional substances effective to maintain hygiene.
4. Antibacterial components of modern cleaners stimulate the development of resistant bacteria.
5. Bacteria can develop resistance even to those antibiotics they have never come in contact with.
6. More research is needed to demonstrate the negative effects of antibacterial products in the household.
7. Antibacterial products can contaminate both households and the environment.
8. They can also present potential danger for human health.
9. There are some categories of people who really require additional antibacterial protection.
Exercise 5. Make 15 two-word expressions connected with medical treatment by combining words from the
two lists: A and B. Then match each expression with the appropriate phrase below. The first one has been
done for you as an example.
A
allergic
balanced
bedside
biological
bone
brain
clinical
digestive
general
general
heart
malignant
plastic
primary
surgical
B
anaesthetic
attack
clock
death
diet
intervention
manner
marrow
practitioner
reaction
surgery
system
tooth
trial
tumour
1. A condition in which the heart has a reduced blood supply because one of the arteries becomes blocked by a
blood clot, causing myocardial ischaemia and myocardial infarction (heart attack)
2. A substance given to make someone lose consciousness so that a major surgical operation can be carried out
3. Soft tissue in cancellous bone.
4. The treatment of disease or other condition by surgery.
5. Any one of the first twenty teeth which develop in children between about six months and two-and-a-half years of
age, and are replaced by the permanent teeth at around the age of six.
16
6. Surgery to repair damaged or malformed parts of the body.
7. A condition in which the nerves in the brain stem have died, and the person can be certified as dead, although
the heart may not have stopped beating.
8. The way in which a doctor behaves towards a patient, especially a patient who is in bed.
9. An effect produced by a substance to which a person has an allergy, such as sneezing or a skin rash.
10. A trial carried out in a medical laboratory on a person or on tissue from a person.
11. A tumour which is cancerous and can grow again or spread into other parts of the body, even if removed
surgically.
12. A doctor who provides first-line medical care for all types of illness to people who live locally, refers them to
hospital if necessary and encourages health promotion.
13. The rhythm of daily activities and bodily processes such as eating, defecating or sleeping, frequently controlled
by hormones, which repeats every twenty-four hours.
14. The set of organs such as the stomach, liver and pancreas which are associated with the digestion of food.
15. A diet that provides all the nutrients needed in the correct proportions.
Exercise 6. Fighting Bacteria.
Divide into two groups. Each group should read either Text A or Text B about two unusual methods of
fighting bacteria. Then in pairs discuss your text with the partner. Try not to miss any details.
Text A. Tea Aids Oral Health
By Sarah Graham
A spot of tea may offer more than just a pleasant way to pass the afternoon. Research findings presented
this week at the 103rd General Meeting of the American Society for Microbiology in Washington, D.C. suggests that
it can help fight bad breath and may boost the powers of toothpaste.
Christine Wu and Min Zhu of the University of Illinois at Chicago College of Dentistry isolated chemical
components of tea leaves known as polyphenols and tested them against three species of bacteria known to cause
bad breath. The researchers found that the compounds, specifically catechins and theaflavins, inhibited growth of
the oral bacteria over a 48-hour incubation period. What is more, lower concentrations of the chemicals interfered
with the enzyme that catalyzes the production of hydrogen sulfide, which has the notorious smell of rotten eggs,
and reduced its production by 30 percent. The compounds studied by the scientists are present in both green tea
and black tea, although they are more abundant in the latter.
In a second study, researchers reported that green tea may provide additional benefits. Milton Schiffenbauer
of Pace University and his colleagues tested tea's ability to fight bacteria that cause infections such as strep throat
and dental caries. They found that green tea extracts and polyphenols--particularly those from caffeinated
beverages--inhibited bacterial growth. Adding these agents to toothpaste and mouthwash, he notes, may make
them more effective at combating microbial agents. (From Scientific American Online, May 21, 2003)
Text B. Scientists Explain Why Vegetable Recipes Skimp on Spices
By Kate Wong
Several years ago, a team of researchers from Cornell University proposed that the spices used in traditional
meat-based cuisines originally served not as flavor, but to stave off bacteria and fungi. Now new research is
providing further food for thought: findings reported in the June issue of Evolution and Human Behavior explain why
vegetable-based dishes tend to lack such spiciness.
Plants, it turns out, don't require so much protection against microorganisms as meats because they have
their own natural chemical and physical defenses, which continue to function after cooking. Cornell neurobiologist
Paul W. Sherman and undergraduate Geoffrey Hash thus predicted that if spices first served as antimicrobials,
especially in warmer climates, vegetable recipes in the same countries surveyed for the meat research should
feature fewer spices. Subsequent investigation bore this out. Analyzing 2,129 traditional vegetable recipes from 36
different countries, the team found that spice usage was far lower than that found in meat-based dishes from the
same cultures. Indeed, of the 41 spices considered, 38 appear more frequently in meat recipes; the three that don't
fit this pattern - sesame, caraway and sweet pepper - offer little protection anyway.
"Humans have always been in a co-evolutionary race with parasites and pathogens in foods, and our
cookbooks are the written record of that race," Sherman asserts. "We haven't had to 'run' as hard when we ate
vegetables. We haven't had to use extra pharmaceuticals to make vegetables safe for consumption." (From
Scientific American Online, July 11, 2001)
Exercise 7. Speak about bacteria and their role on our planet. Summarize all facts which have been
discussed in this unit.
17
Unit 5. Domestic and Domesticated Animals
A horse! A horse! My kingdom for a horse!
William Shakespeare
The Tragedy of King Richard the Third
I have known the horse in war and in peace, and there
is no place where a horse is comfortable. The horse
has too many caprices, and he is too much given to
initiative. He invents too many ideas. No, I don’t want
anything to do with a horse.
Mark Twain
Exercise 1. What do you know about domestication of animals?
1. What domestic animals do you know? What wild animals do they come from?
2. What was the first domesticated animal? Why?
3. What purposes were domesticated animals used for?
4. How does the process of domestication take place?
Exercise 2. Read the following two texts (Text A and Text B) about domestication of dogs and goats to
check your answers in Exercise 1.
Text A. The Origin of Dogs
Where did our best friend originate? Researchers are looking to DNA to dig up answers about where, when and
why pooches became popular
By Katherine Harmon
From Chihuahua to Great Danes, all domestic dogs (Canis familiaris) seem to be descended from the
Eurasian gray wolf (Canis lupis). But what we still don't know is exactly when and where our best friends
transformed from predators into partners. And such knowledge might help solve the long-disputed question of
exactly why dogs were the first animal to be domesticated.
The dog genome was first decoded in 2005—and even before that researchers had been using genetic tools
to track Fido's first home. Early research pointed toward east Asia as the locus of first taming after the discovery of
high genetic diversity and other key markers in dog populations from various villages there. Some investigators,
however, have since pointed out that the genetic search sampled more east Asian village dogs, neglecting similar
pups roaming other villages around the globe. That's where the Village Dog Genetic Diversity Project at Cornell
University comes in. Starting with a recent genetic analysis of dogs in African villages, the Cornell group hopes
ultimately to create a detailed DNA-based map of canine ancestry worldwide, which in turn should provide a new
understanding of the ancient humans who took them in.
One part of that new insight appeared earlier this month in the Proceedings of the National Academy of
Sciences (PNAS), in a study that calls into question the assumption of dogs' east Asian origin. A team led by Adam
Boyko, a researcher at Cornell's Carlos D. Bustamante Lab, sampled 318 village dogs in Africa (as well as
hundreds of dogs from North America and Europe for comparison) and discovered that the high genetic diversity of
canines there resembles that found in east Asia. "We found almost without exception they're descended from
different ancestral populations," Boyko says of the village dogs sampled in Africa. That means they may have been
there just as long as others had been in east Asia.
Researchers have also yet to figure out when people first began raising dogs. The going theory is that dogs
were domesticated somewhere between 15,000 and 40,000 years ago. But, Boyko explains, genetic testing has
not gone deep enough to come up with a more refined date. To try to track down some more clues, field crews
have fanned out around the globe this summer to test village dogs in Vietnam, New Guinea, Malaysia and other
locations in Eurasia in order to get more data.
Of course, scrappy village dogs aren't often the focus of heartfelt conservation efforts, and some even face
active elimination programs. But these pups also have challenges from newly arrived European-descent dogs,
which threaten to make a splash in the regional gene pool. "It is unclear the degree to which older populations will
be able to maintain their genetic identity and persist in the face of modernity," Boyko and his co-authors wrote in
the PNAS paper. So time is of the essence in digging up a solid answer about doggie descent.
Looking back into the pooch family tree will help researchers learn more not only about dogs, but about
ancient people, as well. A genetic map of dog domestication could reveal important information about human
migration and trade routes. "We may be able to turn dogs into a genetic marker for what human populations were
doing," Boyko says. He adds that he and his colleagues also plan to "look for which regions of the genome went
under selection earliest," and from that "we'll also learn what traits were selected for at that time." That knowledge,
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along with a little help from archaeologists, may be able to uncover sniff out just why the dog was so special and
became most likely the first domesticated species. (From Scientific American Online, August 20, 2009)
Text B. Gene Study Suggests Goats Got Around Through Early Human Commerce
At the dawn of human history, long migrations were not for weaklings. Early travelers, however, could count
on a sturdy, reliable and self-propelling source of food during their trips, a French study has just revealed.
Researchers from Joseph Fourier University in Grenoble and the Muse National d’Histoire Naturelle in Paris, in
collaboration with scientists from the University of Geneva in Switzerland, discovered that our ancestors likely used
goats as "walking larders" some 10,000 years ago. Their findings, which are published on today's issue of the
Proceedings of the National Academy of Sciences (PNAS), come from an analysis of DNA extracted from goat
mitochondria -small organelles that work as cellular power plants.
The short string of DNA contained in the mitochondria (mDNA) - which accounts for only a small fraction of
the total cellular DNA - accumulates mutations at a relatively regular rate and so researchers can use variations in
its genes to measure evolutionary changes. The more differences two individuals or species show in the nucleotide
composition of their mDNA, the more distantly related they are. Moreover, because mitochondria are only inherited
from mothers, the DNA is not subject to the gene shuffling that affects the rest of the genome after fertilization.
Therefore mDNA points researchers to only one or a few common female ancestors from which different
populations originated.
For their studies, Gordon Luikart from Grenoble University and his colleagues collected mDNA from more
than 400 wild and domesticated goats in Europe, Asia, Africa and the Middle East, representing 88 breeds
distributed across the Old World. Their results suggest that all of the world's 700 million domestic goats originated
from only three ancestors, which were domesticated at different times in different places during prehistory. The first
goats were probably domesticated about 10,000 year ago at the dawn of the Neolithic in a region of the Middle
East known as the Fertile Crescent.
Intriguingly, the genetic analysis showed that, unlike other domestic animals such as cattle, sheep and pigs,
today's descendants of the first domesticated goats are rather evenly distributed in all continents of the Old World.
This pattern suggests that goats followed humans in their early migrations. "Goats have been a highly mobile
species, probably as small and portable units of human trade throughout history," researchers David MacHugh and
Daniel G. Bradley note in a commentary to the PNAS paper.
Goats can live on little food in harsh climates and still provide a major source of meat, skin and fibers for
millions of people in the developing world. Strange as it might seem, we should rightfully include those skinny
animals in the short list of man's best friends. (From Scientific American Online, May 8, 2001)
Exercise 3. Do you agree with the following statements? Why? Why not? Explain your answer.
1. Studies of animal domestication may shed light on human origin, development and migrations.
2. Scientists know exactly when and where different wild animals were domesticated.
3. Dogs were first domesticated in Africa.
4. Genetic material from numerous breeds and populations of animals is used for investigation.
5. Mitochondrial DNA is used to determine the origin of species.
6. Goats were extremely useful for ancient people.
7. Dogs and goats were domesticated in the same region.
8. All modern goats originate from the same common ancestor.
Exercise 4. Divide into two groups. Each group should read either Text A or Text B on domestication of
wild horses. In pairs, share your information with your partner and discuss both texts to combine all the
details, so you could answer the questions in Exercise 5.
Text A. DNA Hints at Origins of Domestic Horses
By Sarah Graham
The last sighting of a wild horse population occurred in 1969 in Mongolia. A far more common sight is a
domestic horse, whether on a farm or a racetrack. Now scientists have shed new light on how these magnificent
beasts came to be controlled by humans. According to a report published online this week by the Proceedings of
the National Academy of Sciences, modern horses were domesticated from several distinct ancestral populations.
And because horse domestication may have played a key role in the spread of some European languages, the
findings could further the study of language evolution.
To track the trail of domestic horses, Thomas Jansen of Biopsytec Analytik in Rheinbach, Germany, and his
colleagues sequenced DNA from 318 horses representing 25 different breeds. Specifically, the team analyzed
mitochondrial DNA (mtDNA), which is inherited from the mother, and compared the recent samples to previously
published DNA data from 334 other animals. The researchers identified 17 distinct types of mtDNA and calculated
that at least 77 different wild mares must have been domesticated in order to account for today's domestic horses.
Just how these animals were domesticated remains unclear, however. Because of the necessary diversity of the
mares, the team posits that several separate and geographically diverse populations participated in the process.
One theory holds that domestication occurred independently at a number of locales. Alternatively, the procedure
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may have slowly spread from a single starting point. In that case, the authors write, "the knowledge and the initially
domesticated horses themselves would have spread, with local mares incorporated en route, forming our regional
mtDNA clusters." (From Scientific American Online, July 16, 2002)
Text B. Modern Horses Have Many Origins
By Julia Karow
About 6000 years ago, somewhere in the Eurasian grassland steppe, man started to capture and tame wild
horses--at least that's what remains from archaeological sites in Ukraine and Kazakhstan, tell scientists. Initially,
people did not only use horses for transport, but also for food; at the time, dogs, cows, sheep and goats had
already lived with humans for several thousand years. Now genetic evidence from modern and ancient horses,
published in today's Science, completes the picture: the taming of horses did not occur in only one place, but in
several, geographically distant locations.
Researchers from Sweden and the U.S. analyzed parts of the mitochondrial DNA of 191 domestic horses
from ten different breeds, including the Icelandic Pony, the Arabian horse and the (American) Standardbred. They
also included DNA sequences from 12,000 to 28,000-year-old horse bones found in Alaska and from 1,000 to
2,000-year-old horse remains from Northern Europe in the comparison. Mothers alone pass on mitochondria to
their offspring, which is why the data represents only the maternal line. But the DNA samples from the modern
horses differed so much from each other that they probably originated from several different groups of
domesticated horses. And the genetic variation within each breed indicates that probably more female horses and
only a few studs were used for breeding--a practice that continues today.
Rather than giving away domesticated horses, people in Eurasia probably taught each other techniques for
capturing and keeping wild horses from their own area. That's why today's breeds still carry the genetic hallmarks
of many different wild populations. (From Scientific American Online, January 19, 2001)
Exercise 5. Answer the following questions:
1. When was a wild horse population seen for the last time?
2. What methods were used to determine the time of horse domestication?
3. What genetic material was used in each study described in the texts?
4. When and where did domestication of horses start?
5. How was domestication of horses performed?
Exercise 6. Make up a list of the 10 key facts about studies of domestication. Agree on the final list of facts
with the whole group.
Then summarize everything you now know about domestication of wild animals into one report.
20
Section 1. Recommended Report and Presentation Topics
1. Seizures: classifications, etiology, treatment.
2. Epilepsy.
3. Malignant tumours.
4. Unique abilities of the human body.
5. Unique abilities of the human brain.
6. Do fresh water and sea water animals drink?
7. What do marine organisms drink?
8. Why is water considered the most valuable resource of the future?
9. Water conservation.
10. Poisonous mushrooms.
11. Symbiotic partnerships inside the human body.
12. Do bacteria packed yoghurts really benefit our health?
13. Extreme bacterial habitats.
14. How did different breeds of domestic dogs originate?
15. Why were cats domesticated?
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Section 2.
Unit 6. Brain
I’ll give you my opinion of the human race . . .
Their heart’s in the right place, but their head is
a thoroughly inefficient organ.
W. Somerset Maugham
It is good to rub and polish our brains against
that of others.
Michel de Montaigne
Exercise 1. What do you know about the human brain?
1. What is the structure of the nervous system?
2. What are the functions of the brain?
3. What is each region of the brain responsible for? Speak about forebrain, midbrain, hindbrain, cerebellum,
medulla oblongata, cerebral cortex, etc.
4. What is a neuron?
5. What are the functions of neurotransmitters?
6. What do you know about nerve cell growth (neurogenesis) and neuroplasticity?
7. What is intelligence?
8. What is memory?
Exercise 2. Read introduction to the text. What do you think the possible methods to improve brainpower
are?
Six Ways to Boost Brainpower
The adult human brain is surprisingly malleable: it can rewire itself and even grow new cells. Here are some habits
that can fine-tune your mind
By Emily Anthes
Amputees sometimes experience phantom limb sensations, feeling pain, itching or other impulses coming
from limbs that no longer exist. Neuroscientist Vilayanur S. Ramachandran worked with patients who had so-called
phantom limbs, including Tom, a man who had lost one of his arms. Ramachandran discovered that if he stroked
Tom’s face, Tom felt like his missing fingers were also being touched. Each part of the body is represented by a
different region of the somatosensory cortex, and, as it happens, the region for the hand is adjacent to the region
for the face. The neuroscientist deduced that a remarkable change had taken place in Tom’s somatosensory
cortex: because Tom’s cortex was no longer getting input from his missing hand, the region processing sensation
from his face had slowly taken over the hand’s territory. So touching Tom’s face produced sensation in his
nonexistent fingers.
This kind of rewiring is an example of neuroplasticity, the adult brain’s ability to change and remold itself.
Scientists are finding that the adult brain is far more malleable than they once thought. Our behavior and
environment can cause substantial rewiring of the brain or a reorganization of its functions and where they are
located. Some believe that even our patterns of thinking alone are enough to reshape the brain. Researchers now
know that neurogenesis (the birth of new neurons) is a normal feature of the adult brain. Studies have shown that
one of the most active regions for neurogenesis is the hippocampus, a structure that is vitally important for learning
and long-term memory. Neurogenesis also takes place in the olfactory bulb, which is involved in processing smells.
But not all the neurons that are born survive; in fact, most of them die. To survive, the new cells need nutrients and
connections with other neurons that are already thriving. Scientists are currently identifying the factors that affect
the rate of neurogenesis and the survival of new cells. Mental and physical exercise, for instance, both boost
neuron survival.
Exercise 3. Now divide into pairs or small groups and read about each method. Then tell other students
what you have read about. Try not to miss any detail.
METHOD 1: EXERCISE
Mice that run on wheels increase the number of neurons in their hippocampus and perform better on tests of
learning and memory. Studies of humans have revealed that exercise can improve the brain’s executive functions
(planning, organizing, multitasking, and more). Exercise is also well known for its mood-boosting effects, and
people who exercise are less likely to get dementia as they age. Among those who are already aged, athletic
22
senior citizens have better executive function than do those who are sedentary; even seniors who have spent their
entire lives on the couch can improve these abilities just by starting to move more in their golden years. You don’t
need to be Chuck Norris (thankfully) to get the brain benefits of exercise. Studies of senior citizens have shown that
as little as 20 minutes of walking a day can do the trick.
A variety of mechanisms might be responsible for this brain boost. Exercise increases blood flow to the brain,
which also increases the delivery of oxygen, fuel and nutrients to those hard-working neurons. Research has
shown that exercise can increase levels of a substance called brain-derived neurotrophic factor (BDNF), which
encourages growth, communication and survival of neurons. Exercise also improves sleep quality, a pile of studies
suggests. And immune function. Is there anything it can’t do?
METHOD 2: DIET
The brain needs fuel just as the body does. So what will really boost your brainpower, and what will make
you lose your mind? Saturated fat, that familiar culprit, is no better for the brain than it is for the body. Rats fed diets
high in saturated fat underperformed on tests of learning and memory, and humans who live on such diets seem to
be at increased risk for dementia.
Not all fat is bad news, however. The brain is mostly fat—all those cell membranes and myelin coverings
require fatty acids—so it is important to eat certain fats, particularly omega-3 fats, which are found in fish, nuts and
seeds. Alzheimer’s disease, depression, schizophrenia and other disorders may be associated with low levels of
omega-3 fatty acids. It is especially important that babies get enough fat. Babies who don’t get enough of the stuff
have trouble creating the fatty myelin insulation that helps neurons transmit signals. Luckily for babies, breast milk
is 50 percent fat.
Fruits and vegetables also appear to be brain superfoods. Produce is high in substances called antioxidants,
which counteract atoms that can damage brain cells. Researchers have found that high-antioxidant diets keep
learning and memory sharp in aging rats and even reduce the brain damage caused by strokes. That’s food for
thought.
It’s not just what you eat that affects the brain. It’s also how much. Research has shown that laboratory
animals fed calorie-restricted diets—anywhere from 25 to 50 percent less than normal—live longer than other
animals do. And it turns out they also have improved brain function, performing better on tests of memory and
coordination. Rodents on calorie-restricted diets are also better able to resist the damage that accompanies
Alzheimer’s, Parkinson’s and Huntington’s disease.
METHOD 3: STIMULANTS
Stimulants are substances that rev up the nervous system, increasing heart rate, blood pressure, energy,
breathing and more. Caffeine is probably the most famous of the group. (It is actually the most widely used “drug”
in the world.) By activating the central nervous system, caffeine boosts arousal and alertness. Although high doses
of caffeine can undoubtedly have unpleasant effects (ranging from irritability, anxiety and insomnia to the most
unpleasant of all: death in rare cases), small to moderate amounts can boost our mental functioning in ways
researchers are now measuring. One study showed that the equivalent of two cups of coffee can boost short-term
memory and reaction time. Functional MRI scans taken during the study also revealed that volunteers who had
been given caffeine had increased activity in the brain regions involving attention. In addition, research suggests
caffeine can protect against age-related memory decline in older women. But try to limit yourself to fewer than 100
cups a day. That much coffee contains about 10 grams of caffeine, enough to cause fatal complications.
Cocaine and amphetamines are less benign. Although they work on the brain through different mechanisms,
they have similar effects. Taking them increases the release of some of the brain’s feel-good neurotransmitters—
including dopamine and serotonin—and produces a rush of euphoria. They also increase alertness and energy.
That all sounds pretty good, but cocaine and amphetamines are extremely addictive drugs and in high doses they
can cause psychosis and withdrawal. The withdrawal symptoms are nasty and can lead to depression, the opposite
of that euphoric feeling. And of course, an overdose can kill you.
METHOD 4: VIDEO GAMES
Video games could save your life. Surgeons who spend at least a few hours a week playing video games
make one-third fewer errors in the operating room than nongaming doctors do. Indeed, research has shown that
video games can improve mental dexterity, while boosting hand-eye coordination, depth perception and pattern
recognition. Gamers also have better attention spans and information-processing skills than the average Joe has.
When nongamers agree to spend a week playing video games (in the name of science, of course), their visualperception skills improve. And strike your notions of gamers as outcasts: one researcher found that white-collar
professionals who play video games are more confident and social.
Of course, we cannot talk about the effects of video games without mentioning the popular theory that they
are responsible for increasing real-world violence. A number of studies have reinforced this link. Young men who
play a lot of violent video games have brains that are less responsive to graphic images, suggesting that these
gamers have become desensitized to such depictions. Another study revealed that gamers had patterns of brain
activity consistent with aggression while playing first-person shooter games. This does not necessarily mean these
players will actually be violent in real life. The connections are worth exploring, but so far the data do not support
the idea that the rise of video games is responsible for increased youth violence.
23
METHOD 5: MUSIC
When you turn on Queen’s Greatest Hits, the auditory cortex analyzes the many components of the music:
volume, pitch, timbre, melody and rhythm. But there’s more to music’s interaction with the brain than just the raw
sound. Music can also activate your brain’s reward centers and depress activity in the amygdala, reducing fear and
other negative emotions. A highly publicized study suggested that listening to Mozart could boost cognitive
performance, inspiring parents everywhere to go out and buy classical CDs for their children. The idea of a “Mozart
effect” remains popular, but the original study has been somewhat discredited, and any intellectual boost that
comes from listening to music seems to be tiny and temporary. Nevertheless, music does seem to possess some
good vibrations. It can treat anxiety and insomnia, lower blood pressure, soothe patients with dementia, and help
premature babies to gain weight and leave the hospital sooner.
Music training can bolster the brain. The motor cortex, cerebellum and corpus callosum are all bigger in
musicians than in nonmusicians. And string players have more of their sensory cortices devoted to their fingers
than do those who don’t play the instruments. There is no agreement yet on whether musical training makes you
smarter, but some studies have indeed shown that music lessons can improve the spatial abilities of young kids.
METHOD 6: MEDITATION
Meditation, or the turning of the mind inward for contemplation and relaxation, seems to help all types of
conditions—anxiety disorders, sure, but it can also reduce pain and treat high blood pressure, asthma, insomnia,
diabetes, depression and even skin conditions. And regular meditators say they feel more at ease and more
creative than nonmeditators do. Researchers are now illuminating the actual brain changes caused by meditation
by sticking meditators into brain-imaging machines. For one, although the brain’s cells typically fire at all different
times, during meditation they fire in synchrony. Expert meditators also show spikes of brain activity in the left
prefrontal cortex, an area of the brain that has generally been associated with positive emotions. And those who
had the most activity in this area during meditation also had big boosts in immune system functioning.
Meditation can increase the thickness of the cerebral cortex, particularly in regions associated with attention
and sensation. (The growth does not seem to result from the cortex growing new neurons, though—it appears that
the neurons already there make more connections, the number of support cells increases, and blood vessels in that
area get bigger.) (From Scientific American, February, 2009)
Exercise 4. Do you agree with the recommendations given? Comment on each method suggested.
Exercise 5. Do you know any other methods that can help you to increase brainpower?
24
Unit 7. Sleep
Sleep covers a Man all over, Thoughts and all,
like a Cloak; ’tis Meat for the Hungry, Drink for
the Thirsty, Heat for the Cold, and Cold for the
Hot.
Miguel de Cervantes Don Quixote
Introduction.
Sleep remains one of the great mysteries of modern neuroscience. We spend nearly one-third of our lives
asleep, but the function of sleep still is not known. Fortunately, over the last few years researchers have made
great headway in understanding some of the brain circuitry that controls wake-sleep states. Scientists now
recognize that sleep consists of several different stages; that the choreography of a night’s sleep involves the
interplay of these stages, a process that depends upon a complex switching mechanism; and that the sleep stages
are accompanied by daily rhythms in bodily hormones, body temperature and other functions.
Sleep disorders are among the nation’s most common health problems, affecting up to 70 million people,
most of whom are undiagnosed and untreated. These disorders are one of the least recognized sources of
disease, disability and even death, costing an estimated $100 billion annually in lost productivity, medical bills and
industrial accidents. Research holds the promise for devising new treatments to allow millions of people to get a
good night’s sleep.
Exercise 1. What do you know about sleep?
1. What is sleep? What processes take place in human organism during sleep?
2. What processes take place in the human brain during sleep?
3. How long does sleep last? What stages does it include?
4. What sleep disorders do you know?
5. Are you an early bird or a night owl? What other sleep habits do you have?
Exercise 2. Is sleep primarily to benefit the body or the mind? Read the following text to find the answer.
Why Do We Sleep?
By C. Claiborne Ray
“Sleep has many functions, and most of us think the main functions are not for the body but for the brain,”
said Dr. Arthur Spielman, a sleep expert at City College of New York. “But,” he added, “you are talking to a brain
scientist, and it depends on whom you ask.’’
The reason sleep occurs in the first place is tied to both mental and physiological cycles that evolved on a
planet with a 24-hour cycle of light and dark, Dr. Spielman said. The internal biological clocks that developed in
living things, from single cells to humans, allow them to anticipate the transitions from light to dark and from dark to
light, so that they are ready for the functions appropriate to light, like metabolism and photosynthesis, and for those
suited to darkness. “A physiologist might say sleep was to avoid wasting metabolic energy in the dark,’’ he said.
“But a brain scientist would say that glycogen, the only fuel for the brain, is depleted during waking and restored
during sleep.”
Sleep is useful for restoring particular parts of the brain that are quiet during sleep and return to functioning
during waking, like the areas involved in attention, alertness and memory. Sleep is also important for regulating the
timing of hormones under the control of the brain, Dr. Spielman said, like cortisol, the stress-response hormone,
which is suppressed at the beginning of sleep and ramps up in anticipation of waking, and growth hormone, which
is secreted at night during sleep characterized by slow brain waves. (August 15, 2006 NY Times)
Exercise 3. Read the chapter about sleep taken from the book Brain Facts: a Primer on the Brain and
Nervous System, 2002 to check your answers in Exercise 1.
The Stuff of Sleep
Sleep appears to be a passive and restful time when the brain is less active. In fact, this state actually
involves a highly active and well-scripted interplay of brain circuits to produce the stages of sleeping.
The stages of sleep were discovered in the 1950s in experiments examining the human brain waves or
electroencephalogram (EEG) during sleep. Researchers also measured movements of the eyes and the limbs
during sleep. They found that over the course of the first hour or so of sleep each night, the brain progresses
through a series of stages during which the brain waves progressively slow down. The period of slow wave sleep is
accompanied by relaxation of the muscles and the eyes. Heart rate, blood pressure and body temperature all fall. If
awakened at this time, most people recall only a feeling or image, not an active dream.
Over the next half hour or so, the brain emerges from the deep slow wave sleep as the EEG waves become
progressively faster. Similar to during waking, rapid eye movements emerge, but the body’s muscles become
almost completely paralyzed (only the muscles that allow breathing remain active). This state is often called rapid
25
eye movement (REM) sleep. During REM sleep, there is active dreaming. Heart rate, blood pressure and body
temperature become much more variable. The first REM period usually lasts ten to 15 minutes.
Over the course of the night, these alternative cycles of slow wave and REM sleep alternate, with the slow
wave sleep becoming less deep, and the REM periods more prolonged, until waking occurs.
Over the course of a lifetime, the pattern of sleep cycles changes. Infants sleep up to 18 hours per day, and
they spend much more time in deep slow wave sleep. As children mature, they spend less time asleep, and less
time in deep slow wave sleep. Older adults may sleep only six to seven hours per night, often complain of early
wakening that they cannot avoid, and spend very little time in slow wave sleep.
Sleep disorders
The most common sleep disorder, and the one most people are familiar with, is insomnia. Some people have
difficulty falling asleep initially, but other people fall asleep, and then awaken part way through the night, and
cannot fall asleep again. Although there are a variety of short-acting sedatives and sedating antidepressant drugs
available to help, none of these produces a truly natural and restful sleep state because they tend to suppress the
deeper stages of slow wave sleep.
Excessive daytime sleepiness may have many causes. The most common are disorders that disrupt sleep
and result in inadequate amounts of sleep, particularly the deeper stages. These are usually diagnosed in the sleep
laboratory. Here, the EEG, eye movements and muscle tone are monitored electrically as the individual sleeps. In
addition, the heart, breathing, and oxygen content of the blood can be monitored.
Obstructive sleep apnea causes the airway muscles in the throat to collapse as sleep deepens. This
prevents breathing, which causes arousal, and prevents the sufferer from entering the deeper stages of slow wave
sleep. This condition can also cause high blood pressure and may increase the risk of heart attack. There is also
an increased risk of daytime accident, especially automobile accidents, which may prevent driving. Treatment is
complex and may include a variety of attempts to reduce airway collapse during sleep. While simple things like
losing weight, avoiding alcohol and sedating drugs prior to sleep, and avoiding sleeping on one’s back can
sometimes help, most people with sleep apnea require positive airway pressure to keep the airway open. This can
be provided by fitting a small mask over the nose that provides an air stream under pressure during sleep. In some
cases, surgery is needed to correct the airway anatomy.
Periodic limb movements of sleep are intermittent jerks of the legs or arms, which occur as the individual
enters slow wave sleep, and can cause arousal from sleep. Other people have episodes in which their muscles fail
to be paralyzed during REM sleep, and they act out their dreams. This REM behavior disorder can also be very
disruptive to a normal nights’ sleep. Both disorders are more common in people with Parkinson’s disease, and both
can be treated with drugs that treat Parkinson’s, or with an anti-epileptic drug called clonazepam.
Narcolepsy is a relatively uncommon condition (one case per 2,500 people) in which the switching
mechanism for REM sleep does not work properly. Narcoleptics have sleep attacks during the day, in which they
suddenly fall asleep. This is socially disruptive, as well as dangerous, for example, if they are driving. They tend to
enter REM sleep very quickly as well, and may even enter a dreaming state while still awake, a condition known as
hypnagogic hallucinations. They also have attacks during which they lose muscle tone, similar to what occurs
during REM sleep, but while they are awake. Often, this occurs while they are falling asleep or just waking up, but
attacks of paralysis known as cataplexy can be triggered by an emotional experience or even hearing a funny joke.
Recently, insights into the mechanism of narcolepsy have given major insights into the processes that control
these mysterious transitions between waking, slow wave and REM sleep states. (From Brain Facts: a Primer on the
Brain and Nervous System, 2002)
Exercise 4. Work in small groups. Write out from the text 15 key word combinations which will help you to
retell the text and explain your choice. Then together agree on the final list of word combinations.
Exercise 5. In the following text the paragraphs are mixed. Put them in the correct logical order. The first
and the last paragraphs are in their right places.
How long can humans stay awake?
J. Christian Gillin, a professor of psychiatry at the University of California, San Diego, conducts research on
sleep, chronobiology and mood disorders. He supplies the following answer.
(А) The easy experimental answer to this question is 264 hours (about 11 days). In 1965, Randy Gardner, a
17-year-old high school student, set this apparent world-record for a science fair. Several other normal research
subjects have remained awake for 8 to 10 days in carefully monitored experiments. None of these individuals
experienced serious medical, neurological, physiological or psychiatric problems. On the other hand, all of them
showed progressive and significant deficits in concentration, motivation, perception and other higher mental
processes as the duration of sleep deprivation increased. Nevertheless, all experimental subjects recovered to
relative normality within one or two nights of recovery sleep. Other anecdotal reports describe soldiers staying
awake for four days in battle, or unmedicated patients with mania going without sleep for three to four days.
(B) The more difficult answer to this question revolves around the definition of "awake." As mentioned above,
prolonged sleep deprivation in normal subjects induces altered states of consciousness (often described as
"microsleep"), numerous brief episodes of overwhelming sleep, and loss of cognitive and motor functions. We all
26
know about the dangerous, drowsy driver, and we have heard about sleep-deprived British pilots who crashed their
planes (having fallen asleep) while flying home from the war zone during World War II. Randy Gardner was
"awake" but basically cognitively dysfunctional at the end of his ordeal.
(C) In the case of rats, however, continuous sleep deprivation for about two weeks or more inevitably caused
death in experiments conducted in Allan Rechtschaffen’s sleep laboratory at the University of Chicago. Two
animals lived on a rotating disc over a pool of water, separated by a fixed wall. Brainwaves were recorded
continuously into a computer program that almost instantaneously recognized the onset of sleep. When the
experimental rat fell asleep, the disc was rotated to keep it awake by bumping it against the wall and threatening to
push the animal into the water. Control rats could sleep when the experimental rat was awake but were moved
equally whenever the experimental rat started to sleep. The cause of death was not proven but was associated with
whole body hypermetabolism.
(D) In certain rare human medical disorders, the question of how long people can remain awake raises other
surprising answers, and more questions. Morvan’s fibrillary chorea or Morvan’s syndrome is characterized by
muscle twitching, pain, excessive sweating, weight loss, periodic hallucinations, and severe loss of sleep
(agrypnia). Michel Jouvet and his colleagues in Lyon, France, studied a 27-year-old man with this disorder and
found he had virtually no sleep over a period of several months. During that time he did not feel sleepy or tired and
did not show any disorders of mood, memory, or anxiety. Nevertheless, nearly every night between 9:00 and 11:00
p.m., he experienced a 20 to 60-minute period of auditory, visual, olfactory, and somesthetic (sense of touch)
hallucinations, as well as pain and vasoconstriction in his fingers and toes. In recent investigations, Morvan’s
Syndrome has been attributed to serum antibodies directed against specific potassium (K+) channels in cell and
nerve membranes.
(E) Another rare disorder, Fatal Familial Insomnia (FFI), is an autosomal dominate disease that is invariably
fatal after about six to 30 months without sleep. FFI is probably misnamed because death results from multiple
organ failure rather than sleep deprivation. The pathological processes include degeneration of the thalamus and
other brain areas, over-activity of the sympathetic nervous system, hypertension, fever, tremors, stupor, weight
loss, and disruption of the body's endocrine systems. FFI belongs to a class of infectious prion diseases that
include Mad Cow Disease.
(F) To return to the original question, "How long can humans stay awake?" the ultimate answer remains
unclear. Despite the rat studies in Chicago, I am unaware of any reports that sleep deprivation per se has killed any
human (excluding accidents and so forth). Indeed, the U.S. Department of Defense has offered research funding
for the goal of sustaining a fully awake, fully functional "24/7" soldier, sailor, or airman. Future warriors will face
intense, around-the-clock fighting for weeks at a time. Will bioengineering eventually produce genetically-cloned
soldiers and citizens with a variant of Morvan’s syndrome who need no sleep but remain effective and happy? I
hope not. A good night’s sleep is one of life’s blessings. As Coleridge wrote years ago, "Oh sleep! It is a gentle
thing, beloved from pole to pole," and Wilse Webb, a prominent sleep researcher, more recently called sleep the
gentle tyrant: It can be delayed but not defeated.
Exercise 6. Are the following statements true or false, according to the text? Explain your answer.
1. A healthy person can survive without sleep no more than three days.
2. Sleep deprivation damages normal functioning of the organism.
3. Prolonged sleep deprivation produces no negative effect on health.
4. Sleep disorders may be a symptom of serious diseases.
5. Sleep disorders can be inherited.
6. Research of sleep has serious implications for economy and industry.
Exercise 7. Would you like to be able to live without sleep? Why? Why not?
Exercise 8. Summarize everything you know about sleep, its functions and sleep disorders into one report.
27
Unit 8. Coffee
In the cauldron boil and bake;
Eye of newt and toe of frog,
Wool of bat and tongue of dog,
Adder’s fork and blind-worm’s sting,
Lizard’s leg and howlet’s wing. . .
William Shakespeare, Macbeth
Exercise 1. What do you know about coffee?
1. What is coffee produced from?
2. In what regions of the world is coffee grown?
3. What do you know about coffee plants?
4. What is the main active ingredient of coffee?
5. How does caffeine affect the human body?
6. What are the risks of coffee overdose?
7. What other products contain caffeine?
8. How is the effect of coffee different from the effect of tea if caffeine is contained in both?
Exercise 2. Read the following facts about caffeine and coffee trees to check your answers in Exercise 1.
What is caffeine? An alkaloid found in coffee, cocoa beans, tea, kola nuts and guarana. Also added to
many fizzy drinks, energy drinks, pep pills and cold and flu remedies. For a single portion of espresso, 50 to 55
roasted coffee beans are required; a single imperfect bean will taint the whole sufficiently to be noticeable. This is
because human olfaction and taste senses originated as defense mechanisms that protected our ancestors from
rotten—hence, unhealthy—foods.
What does caffeine do? A stimulant of the central nervous system. Pure caffeine is a moderately powerful
drug and is sometimes passed off as amphetamine. In small doses, such as the 150 milligrams in a typical cup of
filter coffee, it increases alertness and promotes wakefulness. Caffeine also raises heart and respiration rate and
promotes urine production. Higher doses induce jitteriness and anxiety. The fatal dose is about 10 grams.
How does caffeine work? Caffeine blocks receptors for the neurotransmitter adenosine, which is generally
inhibitory and associated with the onset of sleep. Also raises dopamine levels, and stimulates the release of the
fight-or-flight hormone adrenalin (From Newscientist.com).
What is coffee? Raw coffee beans are the seeds of plants belonging to the Rubiaceae family, which
comprises at least 66 species of the genus Coffea. The two species that are commercially exploited are Coffea
arabica, which accounts for two thirds of world production, and C. canephora, often called robusta coffee, with one
third of global output. Robusta coffee plants and all wild coffee species have 22 chromosomes, whereas arabica
has 44. Therefore, arabica and other coffee species cannot be crossed to produce a hybrid plant.
Robusta is a high-yielding and disease-resistant tree standing up to 12 meters tall that grows best in warm,
humid climates. It produces a cup featuring substantial body, a relatively harsh, earthy aroma, and an elevated
caffeine content that ranges from 2.4 to 2.8 percent by weight. Although robusta is sold by many purveyors, it does
not give rise to the highest-quality coffee.
Arabica, which originated in the Ethiopian highlands, is a medium- to low-yielding, rather delicate tree from
five to six meters tall that requires a temperate climate and considerable growing care. Commercially grown coffee
bushes are pruned to a height of 1.5 to 2.0 meters. Coffee made from Arabica beans has an intense, intricate
aroma that can be reminiscent of flowers, fruit, honey, chocolate, caramel or toasted bread. Its caffeine content
never exceeds 1.5 percent by weight. Because of its superior quality and taste, arabica sells for a higher price than
its hardy, rougher cousin.
A good rainfall induces coffee plants to blossom, and some 210 days afterward red or yellow fruit called
cherries appear. Each cherry contains two oblong seeds—the coffee beans. The ultimate quality of the resulting
coffee beans depends on the genetics of the plant, the soil in which it grows and the microclimate, which
encompasses factors such as altitude, the amount of rainfall and sunlight, and daily temperature fluctuations. Along
with the roasting processes that are applied, these agricultural and geographical considerations are responsible for
the taste differences among the many varieties of coffee beans that suppliers combine to produce the various
distinctive blends one can purchase (From Scientific American, June 2002).
Exercise 3. Now read detailed explanation of the effects of caffeine provided by biologist Neal J. Smatresk,
Dean of the College of Science at the University of Texas at Arlington, and find answers to these
questions:
1. What is a neurotransmitter? What is a second messenger?
2. How does caffeine affect heart?
3. Does caffeine affect all animals?
28
How does caffeine affect the body?
Caffeine--the drug that gives coffee and cola its kick--has a number of physiological effects. At the cellular
level, caffeine blocks the action of a chemical called phosphodiesterase (PDE). Inside cells, PDE normally breaks
down the second chemical messenger cyclic adenosine monophosphate (cAMP). Many hormones and
neurotransmitters cannot cross the cell membrane, and so they exert their actions indirectly via such second
messengers; when they bind to a receptor on the surface of a cell, it initiates a chemical chain reaction called an
enzyme cascade that results in the formation of second messenger chemicals.
Historically, cAMP was the first second messenger ever described. Now, however, scientists have identified
several major classes of second messengers, which are generally formed in similar ways through a set of
molecules called G proteins. The advantage of such a complex system is that an extracellular signal can be greatly
amplified in the process, and so have a massive intracellular effect.
Thus, when caffeine stops the breakdown of cAMP, its effects are prolonged, and the response throughout
the body is effectively amplified. In the heart, this response prompts norepinephrine--also called noradrenalin--and
a related neurotransmitter, epinephrine, to increase the rate and force of the muscle's contractions. Although the
two act in concert, norepinephrine is released by sympathetic nerves near the pacemaker tissue of the heart,
whereas epinephrine is released primarily by the adrenal glands. These chemical messages lead to "fight or flight"
behavior. During stressful or emergency conditions, they raise the rate and force of the heart, thereby increasing
the blood pressure and delivering more oxygen to the brain and other tissues.
Caffeine would be expected to have this effect on any animals that used these neurotransmitters to regulate
their heartbeat. Generally speaking, the effects of caffeine are most pronounced in birds and mammals. Reptiles
have some response, and lower vertebrates and invertebrates have rather small or no responses. From an
evolutionary perspective, fish and amphibians don't show as strong a response to epinephrine and norepinephrine
as the higher vertebrates, and they lack a well-developed sympathetic (that is, stimulatory) enervation to heart.
Exercise 4. What positive and negative effects produced by coffee do you know? Choose from the list
below:
a. Coffee boosts attention, concentration and alertness.
b. Coffee improves mental performance.
c. Coffee increases life expectancy.
d. Coffee helps to fight infections.
e. Coffee prevents aging.
f. Coffee increases the risk of cardiovascular diseases.
g. Coffee can lead to a stroke.
h. Coffee protects against cancer.
Exercise 5. Read the article about health effects of coffee to check your answers in Exercise 4.
Coffee as a Health Drink? Studies Find Some Benefits
By Nickolas Bakalar
Coffee is not usually thought of as health food, but a number of recent studies suggest that it can be a highly
beneficial drink. Researchers have found strong evidence that coffee reduces the risk of several serious ailments,
including diabetes, heart disease and cirrhosis of the liver. Among them is a systematic review of studies published
last year in The Journal of the American Medical Association, which concluded that habitual coffee consumption
was consistently associated with a lower risk of Type 2 diabetes. Exactly why is not known, but the authors offered
several explanations.
Coffee contains antioxidants that help control the cell damage that can contribute to the development of the
disease. It is also a source of chlorogenic acid, which has been shown in animal experiments to reduce glucose
concentrations. Caffeine, perhaps coffee’s most famous component, seems to have little to do with it; studies that
looked at decaffeinated coffee alone found the same degree of risk reduction.
Larger quantities of coffee seem to be especially helpful in diabetes prevention. In a report that combined
statistical data from many studies, researchers found that people who drank four to six cups of coffee a day had a
28 percent reduced risk compared with people who drank two or fewer. Those who drank more than six had a 35
percent risk reduction.
Some studies show that cardiovascular risk also decreases with coffee consumption. Using data on more
than 27,000 women ages 55 to 69 in the Iowa Women’s Health Study who were followed for 15 years, Norwegian
researchers found that women who drank one to three cups a day reduced their risk of cardiovascular disease by
24 percent compared with those drinking no coffee at all. But as the quantity increased, the benefit decreased. At
more than six cups a day, the risk was not significantly reduced. Still, after controlling for age, smoking and alcohol
consumption, women who drank one to five cups a day — caffeinated or decaffeinated — reduced their risk of
death from all causes during the study by 15 to 19 percent compared with those who drank none.
29
The findings, which appeared in May in The American Journal of Clinical Nutrition, suggest that antioxidants
in coffee may dampen inflammation, reducing the risk of disorders related to it, like cardiovascular disease. Several
compounds in coffee may contribute to its antioxidant capacity, including phenols, volatile aroma compounds and
oxazoles that are efficiently absorbed. In another analysis, published in July in the same journal, researchers found
that a typical serving of coffee contains more antioxidants than typical servings of grape juice, blueberries,
raspberries and oranges. “We were surprised to learn that coffee quantitatively is the major contributor of
antioxidants in the diet both in Norway and in the U.S.A.,” said Rune Blomhoff, the senior author of both studies
and a professor of nutrition at the University of Oslo.
The same anti-inflammatory properties may explain why coffee appears to decrease the risk of alcoholrelated cirrhosis and liver cancer. This effect was first observed in 1992. Recent studies, published in June in The
Archives of Internal Medicine, confirmed the finding.
Still, some experts believe that coffee drinking, and particularly caffeine consumption, can have negative
health consequences. A study published in January in The Journal of the American College of Cardiology, for
example, suggests that the amount of caffeine in two cups of coffee significantly decreases blood flow to the heart,
particularly during exercise at high altitude.
Rob van Dam, a Harvard scientist and the lead author of The Journal of the American Medical Association
review, acknowledged that caffeine could increase blood pressure and slightly increase levels of the amino acid
homocysteine, possibly raising the risk for heart disease. “I wouldn’t advise people to increase their consumption of
coffee in order to lower their risk of disease,” Dr. van Dam said, “but the evidence is that for most people without
specific conditions, coffee is not detrimental to health. If people enjoy drinking it, it’s comforting to know that they
don’t have to be afraid of negative health effects.” (NY Times. August 15, 2006)
Exercise 6. In the following text the lines are mixed up. Put them in their proper order. The first and
the last lines are in their correct places.
Decaf Coffee Plants Developed
By Sarah Graham
For many coffee lovers, their precious beverage comes with an unwanted ingredient: caffeine. As a result,
which solvents flush caffeine from the beans. Their next step is to apply their technique to C. arabica plants, which
produce the high-quality Arabica coffee that accounts for 70 percent of the world market. Of course, it remains to
percent less caffeine than regular plants do.
Three enzymes are involved in making caffeine in coffee plants. Researchers at the Nara Institute of Science
the gene controlling one of these enzymes--theobromine synthase, or CaMXMT1--was repressed. Compared with
processes have been developed to remove the compound, although current methods are expensive and
regular plants, leaves from one-year-old GM plants exhibited a 50 to 70 percent reduction in caffeine content.
from the plant. Researchers report today in the journal Nature that their genetically modified coffee plants have 70
apart from their low caffeine content at maturity."
According to the report, "the transgenic plants described here should yield coffee beans that are essentially normal
The scientists note that their technique could sidestep some of the problems of industrial decaffeination, in
and Technology in Japan led by Shinjiro Ogita engineered seedlings of Coffea canephora in which expression of
sometimes compromise flavor. But scientists may have come up with a way to get decaffeinated coffee straight
be seen if java lovers will embrace "GM joe." (From Scientific American Online, June 19, 2003)
Exercise 7. Make up a list of the 10 key facts about coffee. Agree on the final list of facts with the
whole group. Then summarize everything you now know about coffee into one report.
30
Unit 9. Human Genetics and Diversity
I am the family face;
Flesh perishes, I live on,
Projecting trait and trace
Through time to times anon,
And leaping from place to place
Over oblivion.
Thomas Hardy
From a drop of water. . . a logician could infer the
possibility of an Atlantic or a Niagara without
having seen or heard of one or the other. So all life
is a great chain, the nature of which is known
whenever we are shown a single link of it.
Sir Arthur Conan Doyle A Study in Scarlet
Exercise 1. What do you know about genetics? Explain the following terms in English:
DNA, RNA
Ribosome
Phenotype
Selective breeding
Nucleic acid
Replication
Genotype
Hybrid
Gene
Transcription
Enhancer
Breeding (crossing)
Genome
Translation
Promoter
Inbreeding
Allele
Processing
Silencer
Pure line
Dominant / recessive gene
Splicing
Terminator
Exercise 2. Discuss the following questions about genetic diversity of humans:
1. What role does genetic diversity of humans play?
2. What genetic mechanisms control population diversity?
3. To what degree are different ethnic groups genetically different?
Exercise 3. Read the following two texts (Text A and Text B) about current genetic research of population
diversity to check your answers in Exercise 2.
Text A. How Our Genomes Control Diversity
Two research efforts have determined DNA recombination mechanisms that underlie population diversity, how it
happens and where in the genetic code it occurs
By Nikhil Swaminathan
Two recent discoveries have shed new light on the source of diversity in the human population. In one study,
scientists examined patterns in DNA recombination, the process by which a person's genome is consolidated into
one set of chromosomes to pass onto an offspring. In the other, a link was made between variants of a particular
gene and the extent to which DNA recombination occurs.
In human testes and ovaries, where sperm cells and egg cells, respectively, are manufactured, sections of
chromosomes inherited from a person's parents are shuffled together to create a collage of genetic material that is
passed to offspring. This process by which a new, unique set of chromosomes is created (with a mix of roughly half
the material coming from each parent) is called DNA recombination and is the source of variation in populations.
"Recombination impacts population diversity," says George Coop, a postdoctoral fellow in human genetics at the
University of Chicago and co-author of an article that details variation in the pattern in which genes are shuffled
from individual to individual. "Recombination is the way that you generate novel haplotypes, novel combinations of
mutations." (Haplotypes are combinations of different versions of genes on a single chromosome that are inherited
as a unit.)
Coop and colleagues in Science reveal the results of a high-resolution study designed to map the locations
where recombination occurs—where one parent's genes have been swapped out for another. Using a population of
725 Hutterites—communal farmers who settled in the Dakotas and Montana in the mid-19th century—the team
scanned genomes for 500,000 single-nucleotide polymorphisms (SNPs). SNPs mark points of genetic variation to
estimate where DNA shuffles occurred. Researchers can tell which part of a child's genetic code came from which
of its four grandparents by comparing variants in both.
The researchers noted nearly 25,000 total recombination events in analyses of 364 offspring. Excluding the
sex chromosomes, the team found that eggs typically showed 40 instances of recombination on each of their
chromosomes, whereas the chromosomes in sperm are typically made with 26 recombinational occurrences. The
University of Chicago team also noted that as women age, more recombination takes place during meiosis (the
cellular process that produces an egg). In men, there is no age effect. Further, they noted that such incidents
tended to focus on so-called "hot spots," locations where this crossover takes place often. Some turned out to be
gender specific, with females utilizing some recombination regions more often than males (and vice versa). The
31
usage of these zones of frequent recombination varied between individuals, but it seemed to be conserved among
families, indicating that the extent and pattern of recombination may be inherited.
Interestingly, a finding out of the Icelandic biotech firm deCODE genetics, also appearing in Science, sheds
light on that last observation. From a genome-wide analysis looking at 300,000 SNPs in 20,000 people, deCODE
scientists were able to find two locations on a gene found on chromosome 4 and link variations at those two locales
to the recombination rate. "What's interesting about the SNPs is that the variants have opposite effects on the
sexes," says deCODE's chief executive officer Kari Stefansson. According to the new study, one of the locations on
the gene, known as RNF212, is associated with high rates of recombination in men, but low rates in women; for the
other marker, the gender effect is reversed. "If you were going to design a mechanism to keep rates within [certain]
limits you would do exactly this," Stefansson explains about the gender paradigm. "For one generation, it leads to
higher recombination rate; for the next generation, it would lead to a lower recombination rate." Overall, the two
positions can account for 22 percent of the variability in a man's recombination rate and 6.5 percent of the
variability in a female's, the study says.
Chicago's Coop lauded the deCODE efforts, noting that this was the first mapping of a gene that influences
recombination in mammals. "I would imagine that the variation that we see in individuals is in part caused by these
SNPs," he says. "I think this represents a big step forward in determining the events of human recombination."
(From Scientific American Online, February 5, 2008)
Text B. Ethnic Differences Traced to Variable Gene Expression
Finding could explain why ethnic groups suffer from particular common diseases
By Nikhil Swaminathan
Tay-Sachs disease seems to favor Jews of Eastern European descent. Cystic fibrosis has an affinity for
Caucasians. Type 2 diabetes strikes Latin Americans and people of African descent more often than it does those
of other ethnic groups, appearing at rates of incidence that are 90 and 60 percent higher, respectively, than in
Caucasians. Researchers have been conducting studies such as the International HapMap Project--a global effort
to catalogue common single-nucleotide variations, such as the addition, deletion or substitution of a base in the
code of a gene--to get to the bottom of long-observed correlations between ethnicity and common complex
diseases.
But those efforts have borne little fruit, according to Vivian Cheung, a human geneticist at the University of
Pennsylvania School of Medicine. So, rather than characterize these individual nucleotide changes in genes,
Cheung and geneticist Richard Spielman employed microarray technology--essentially a genome chip that allows a
researcher to analyze the expression of many genes at once--to study across Chinese, Japanese and European
populations many different traits that are coded for in a type of white blood cell.
Their results, reported in this week's Nature Genetics, were that different ethnic groups not only carried
different genes, but there were greater disparities than previously believed in the degrees to which genes that were
the same among ethnic groups were expressed. Further, the genes themselves did not control the levels of their
own expression, rather noncoding regions adjacent to them determined whether to ratchet up or down the proteins
or other functional end products the genes encoded.
The authors of the new study note that large-scale changes to DNA--such as specific substitutions or
deletions of genetic material--almost certainly also contribute to differences between ethnic groups. But Cheung
says that expression levels likely can explain some of the ethnic underpinnings of Tay-Sachs and cystic fibrosis as
well as hypertension, which plagues those of Afro-Caribbean descent at a higher rate than other populations.
From its microarray, the team measured 4,197 genes expressed by cells. (After measuring expression levels
of those genes, Cheung, Spielman and their colleagues decided to lump the Japanese and Chinese groups
together due to similar results.) When the researchers then compared the Asian populations with the Caucasian
sampling, they noted that 1,097, more than 25 percent, of the genes had differing expression levels.
After analyzing some of the nearly 1,100 genes in detail, Cheung and Spielman believe that the expression
level discrepancies were due to nucleotide differences in noncoding regions around the genes, and not the genes
themselves. "We were able to pinpoint 11 genes where people have different forms of the regulator," Cheung
reveals, providing an example: "Let's say that among the Caucasian population, maybe the regulator that turns on
the gene more happens to be more frequent--overall the expression level of that gene will be higher. Whereas in
the Asian population, more people have the regulator that causes the expression level to be lower."
Steve McCarroll, a population and medical geneticist at the Massachusetts Institute of Technology's Broad
Institute says that with so many genetic variants out there, researchers need all the help they can get determining
which ones actually will affect cell function. "One of the things that's exciting about this work is that identifying the
genetic variants that account for gene expression differences could help the field to find those genetic variants that
affect disease risk," he says. (From Scientific American Online, January 9, 2007)
Exercise 4. Who are the following scientists mentioned in the articles? What studies have they carried out?
• Kari Stefansson
• George Coop
• Vivian Cheung and Richard Spielman
• Steve McCarroll
Exercise 5. Using the information from the texts prove that:
1. DNA recombination is the source of variation in populations.
32
2.
3.
4.
5.
DNA recombination is age and sex related.
Ethnic groups suffer from particular common diseases.
Not only different genes but difference in expression levels of these genes account for common diseases.
Noncoding regions are responsible for the degree of gene expression.
Exercise 6. Put the sentences given below (a-e) into their correct place in the text (1-5).
Ancient Europeans More Diverse, Genetically Speaking, than Modern Ones
Bubonic plague may be responsible for reducing the genetic diversity of present-day Britons
By David Biello
Modern Britons are a cosmopolitan bunch. Peoples from across the globe now make the island home,
bringing with them, theoretically, a diverse array of genes. (1) _____ Molecular ecologist Rus Hoelzel of Durham
University in England and his European colleagues compared the genetic make up of six English ancestors from
the Roman period, 25 from early in the Saxon conquest and 17 from the late Saxon period with the mitochondrial
DNA sequences of more than 6,000 modern Europeans and Middle Easterners. "We found higher mitochondrial
DNA diversity in ancient England (Roman to Saxon times) than in either modern England or in a combination of
northern European countries," Hoelzel says. (2) _______
Even when present-day Europeans were broken down into 10 smaller samples of 48 individuals each, they
still were less diverse than their ancestors. (3) ______ ; 6.3 percent of ancients carried it compared with nearly 22
percent of modern Britons and an average of nearly 19 percent of all Europeans.
The CRS haplotype imparts no known special traits in the humans who bear it, but the "black death" may
have played a role in increasing its abundance in the modern population. (4) _____ The dread disease could either
have increased the proportion of certain haplotypes somehow associated with increased survival or simply led to
the extinction of rare haplotypes in families or villages who had a particular susceptibility, Hoelzel says.
Only three small groups—modern peoples from Belarus, Palestine and Turkey—showed similar levels of
diversity to these early ancestors, though studies by others have shown that southern Europeans, such as Italians,
seem to retain a broader pool of genetic material. (5) ______ , according to researchers, the ancients possessed a
more robust array of differing genetic stocks. (From Scientific American Online, August 1, 2007)
(a) The 48 ancients bore 36 different haplotypes—a set of variations in the genetic code. But their
descendants more commonly carried one particular haplotype, known as Cambridge reference
sequence (CRS)
(b) It is unclear exactly why contemporary Europeans are less genetically diverse despite a continuing influx
of new populations but,
(c) This bubonic plague swept Britain (and all of Europe) in the 14th century, killing as much as half of the
population, before recurring again in London in the 17th century.
(d) “Modern human populations are highly diverse, just less so in northern Europe, at least, than the ancient
populations in England."
(e) But comparing the genetic material of more than 1,000 contemporary Englishmen with that of 48 of their
ancient peers reveals that the ancients had even more diverse genetic codes.
Exercise 7. In the following text the lines are mixed up. Put them in the correct order.
Genetic Study Reveals Similarities between Diverse Populations
By Sarah Graham
genetically very similar, researchers say. A report published today in the journal Science suggests that 93 to 95
from differences in a very small proportion of genetic traits."
people from several continents, suggesting that only a tiny fraction of genetic traits are distinctive to specific
percent of human genetic variation exists among individuals within populations, while differences among major
Marcus W. Feldman of Stanford University and his colleagues analyzed samples from 1,056 people belonging to
alone can provide enough information to group people by population.
52 populations. Specifically, they looked at 377 so-called microsatellites, short segments of DNA that occur in
Though they may speak different languages and eat distinct foods, people from far-flung geographical locations are
populations. This means that visible differences between human groups--such as skin color and skull shape--result
groups make up less than 5 percent of the variation. But the findings also reveal that even these tiny differences
specific patterns. "Each microsatellite had between four and 32 distinct types," Feldman says. "Most were found in
(From Scientific American Online, December 20, 2002)
Exercise 8. Summarize everything you know about population diversity and genetic mechanisms involved
into one report.
33
Unit 10. Animal Diversity
Nature proceeds little by little from things
lifeless to animal life in such a way that it is
impossible to determine the exact line of
demarcation, nor on which side thereof an
intermediate form should lie.
Aristotle
Exercise 1. What do you know about diversity of animals and their adaptations?
1. Why are animals classified into a separate Kingdom?
2. What are the basic taxonomic differences between the main classes of animals?
3. What basic adaptations have animals developed to different environments where animal live?
4. What environments can animals never adapt to? Why? Are there other organisms that can live there?
5. What is the role of species diversity in the stability of ecosystem?
6. What role do parasites and predators play in keeping biodiversity?
Exercise 2. You are going to read a text about bird migrations. The following figures will be used in the
text. What do you think they refer to?
• 30,000 km
• 100 hours
• 500 beats
• 9000 m
• 21 grams
Exercise 3. Now read the text to check your answers.
Have Wings, Will Travel: Avian Adaptations to Migration
By Mary Deinlein
Avian Aeronautics
Flight affords the utmost in mobility and has made possible the evolution of avian migration as a means of
exploiting distant food resources and avoiding the physiological stress associated with cold weather. Variations in
the patterns of migration are nearly as numerous as the birds that migrate. While some species move only a few
kilometers up and down mountain slopes, others will travel hundreds or even thousands of kilometers, often
traversing vast bodies of water or tracts of inhospitable terrain.
One record holder in long-distance travel is the Arctic Tern (Sterna paradisaea), which makes an annual
round-trip of about 30,000 kilometers between opposite ends of the globe, from Arctic breeding grounds to
Antarctic seas. This feat is possible because terns are adapted for feeding at sea, allowing them to refuel en route.
Even more amazing are the aerial voyages of the landbirds and shorebirds whose transoceanic flights must be
accomplished non-stop. The Pacific Golden-Plover (Pluvialis fulva) flies continuously for more than 100 hours to
travel the 5,000- to 7,000-kilometer distance from northern Siberia and Alaska to Hawaii and other islands in the
Pacific Ocean.
The Blackpoll Warbler's (Dendroica striata) over-water flight from the coast of New England or southern
Canada to South America keeps it aloft for 80 to 90 continuous hours over a distance of 3,000 to 4,000 kilometers,
an effort which researchers Tim and Janet Williams conclude "requires a degree of exertion not matched by any
other vertebrate; in man the metabolic equivalent would be to run a 4 minute mile for 80 hours. Even the tiny Rubythroated Hummingbird (Archilochus colubris), weighing only about as much as a penny, makes the 1,000-kilometer,
24-hour spring flight across the Gulf of Mexico from the Yucatan Peninsula to the southern coast of the United
States.
So how do they do it? What specialized adaptations allow birds to accomplish such prodigious feats of
endurance?
Bird Basics
To understand how superbly adapted birds are to their highly mobile way of life, one must first consider the
quintessential characteristics that distinguish birds from all other animals. Feathers, the trademark of the Class
Aves, provide the insulation necessary to maintain a high "engine" (body) temperature, ranging from 107 to 113
degrees F across species. Additionally the long feathers of the wings act as airfoils which help generate the lift
necessary for flight. Well-developed pectoral muscles power the flapping motion of the wings. A streamlined body
shape and a lightweight skeleton composed of hollow bones minimize air resistance and reduce the amount of
energy necessary to become and remain airborne.
Keeping the hard-running avian engine running smoothly requires super-efficient circulatory and respiratory
systems. Birds have a large, four-chambered heart which proportionately weighs six times more than a human
heart. This, combined with a rapid heartbeat (the resting heart rate of a small songbird is about 500 beats per
minute; that of a hummingbird is about 1,000 beats per minute) satisfies the rigorous metabolic demands of flight.
The avian respiratory system—the most efficient in the animal kingdom—consists of two lungs plus special air
sacs, and takes up 20% of a bird's volume compared to 5% in a human. Unlike mammalian or reptilian lungs, the
lungs of birds remain inflated at all times, with the air sacs acting as bellows to provide the lungs with a constant
supply of fresh air.
34
Migratory Mania
In addition to these general avian characteristics, migratory birds exhibit a suite of specialized traits. Migrants
generally have longer, more pointed wings than non-migratory species, a feature which further minimizes air
resistance. Also, the pectoral muscles of migrants tend to be larger and composed of fibers which are more richly
supplied with nutrient- and oxygen-carrying blood vessels and energy-producing mitochondria, making the pectoral
muscles of migrants especially efficient at energy production and use.
Many migrants face the additional challenge of flying at high altitudes. Most songbirds migrate at 500 to
2,000 meters, but some fly as high as 6,800 meters; swans have been recorded at 8,000 meters and Bar-headed
Geese (Anser indica) flying over the Himalayas at 9,000 meters. Accounting for their ability to withstand the low
levels of oxygen available at such altitudes, the blood of migratory birds is characterized by two specialized
adaptations. The oxygen-carrying capacity of the blood is enhanced by a high concentration of red blood cells.
Secondly, instead of one form of hemoglobin in the red blood cells as is typical in non-migrants and other classes
of vertebrates, some migratory birds possess two forms of hemoglobin which differ in their oxygen carrying and
releasing capacities. This guarantees an adequate oxygen supply over a wide range of altitudes and allows birds to
adapt rapidly to varying levels of oxygen availability.
Preparing for take-off
Migrants change rapidly into a "superbird state" in preparation for migration. This transformation is triggered
by an internal annual "clock," which is set by day length and weather.
When it comes to fueling migration, fat is where it's at. Fat is not only lighter and less bulky than
carbohydrates or protein, but also supplies twice as much energy. Not surprisingly, then, preparation for migration
entails a rapid weight gain program geared to increasing fat reserves. This program combines both behavioral and
physiological changes. A dramatic increase in appetite and food consumption, termed hyperphagia, begins about
two to three weeks before migration and persists throughout the migratory period. Accompanying this veritable
feeding frenzy is an increase in the efficiency of fat production and storage. As a result, a migratory bird can
increase its body weight through fat deposition by as much as 10% per day (usually 1-3%). Additionally, in birds
that are in migratory disposition, the pectoral muscles become larger and well supplied with enzymes necessary for
the oxidation, or "burning," of fat.
Longer migration distances require greater amounts of fat. Non-migratory passerines maintain a "fat load" of
about 3-5% of their lean body weight. In preparation for migration, short- and medium-distance migratory songbirds
attain a fat load of between 10 and 25%, while long-distance migrants reach fat loads of 40 to 100%. Maximum fat
loads are attained just prior to flights over major topographic barriers, such as deserts, high mountains, or large
bodies of water. A typical Blackpoll Warbler at the end of its breeding season weighs about 11 grams, equivalent to
the weight of four pennies. In preparing for its transatlantic trek, it may accumulate enough fat reserves to increase
its body weight to 21 grams.
Readiness for migration entails other behavioral modifications. Before migrating in the fall, many migrants
which ordinarily eat insects will switch to a diet of berries and other fruits. At this time when food intake needs are
increasing and insect numbers are decreasing, fruits are abundant and high in carbohydrates and lipids which are
readily converted to fat. Many migrants that typically are not gregarious will flock together prior to, or during,
migration. This social behavior may result in improved predator avoidance, food finding, and orientation. Some
species also fly in formation, a strategy that improves aerodynamics and reduces energy expenditure.
A radical shift from being active exclusively during the day to migrating at night occurs in many species
during migration, including most shorebirds and songbirds. Possible advantages to flying at night include
decreased vulnerability to predators, reduced threat of dehydration or overheating, a greater likelihood of
encountering favorable winds and a stable air mass (rising hot air and more variable wind directions occur during
the daytime), and time during the day to forage.
Migratory birds kept in captivity exhibit behavior termed Zugunruhe, or migratory restlessness. This behavior,
characterized by rapid fluttering of the wings while perching, begins at the same time that conspecifics (individuals
of the same species) in the wild are setting off on migration, and persists for the same length of time required for
the wild counterparts to complete their migration. The captive birds even orient themselves in the appropriate
direction in which they would be migrating. Over the past 15 years, this behavior has allowed researchers to
demonstrate experimentally that many of the important physical and behavioral correlates to migration are under at
least partial genetic control. For instance, when migratory Blackcaps (Sylvia atricapilla ) were mated with nonmigratory individuals of the same species, 30% of the offspring exhibited Zugunruhe. When individuals which
displayed high levels of Zugunruhe, consistent with their long migratory routes, were bred with conspecifics with
short migration routes, the offspring displayed intermediate levels of Zugunruhe. The results from these and other
cross-breeding experiments support the hypothesis that migration and its associated patterns—such as distance
and timing—are inherited traits, at least in some species. These experiments apply to species with relatively fixed
migration routes. Many species have facultative migration patterns, moving only when food supply is low, or when
weather turns bad. Research has shown that access to food for these species greatly affects Zugunruhe.
Despite this advanced understanding of some of the mechanisms behind avian migrations, the annual
odysseys of billions of birds remain one of the most mysterious and amazing phenomena in the animal world.
Exercise 4. What bird species are mentioned in the text? What facts are given about each of them?
35
Exercise 5. Give detailed answers to the following questions using the information from the text:
1. Why do birds migrate?
2. What adaptations allow birds to accomplish their migrations? Describe each in detail.
3. How are migratory birds different from non-migratory species?
4. How do birds prepare for the hardships of migration?
5. What is Zugunruhe?
Exercise 6. In the following text the paragraphs are mixed. Put them in the correct logical order. The first
paragraph is in its right place.
How do deep-diving sea creatures withstand huge pressure changes?
Paul J. Ponganis and Gerald L. Kooyman of the Center for Marine Biotechnology and Biomedicine at Scripps
Institution of Oceanography provide the following answer.
A sperm whale can dive down more than 2,000 meters and can stay submerged for up to an hour.
(A) Some sea creatures exploit great depths. The biggest physiological challenges in adapting to pressure
are probably faced by those animals that must routinely travel from the surface to great depth. Two such animals
are the sperm whale and the bottlenose whale. From the days of whaling, these animals have been recognized as
exceptional divers, with reports of dives lasting as long as two hours after they were harpooned. Today, with the
use of sonar tracking and attached time-depth recorders, dives as deep as 6,000 feet (more than a mile below the
surface of the ocean) have been measured. Routine dive depths are usually in the 1,500- to 3,000-foot range, and
dives can last between 20 minutes and an hour.
(B) Loss of gas exchange at depth has another important implication: the lungs of the deep diver cannot
serve as a source of oxygen during the dive. Instead deep-diving whales and seals rely on large oxygen stores in
their blood and muscle. Several adaptations enable this. First, these animals have mass specific blood volumes
that are three to four times those found in terrestrial mammals (i.e., 200 to 250 milliliters of blood per kilogram body
mass, in contrast to a human value of 70 milliliters blood per kilogram). Second, the concentration of hemoglobin
(the oxygen-transport protein in blood) is also elevated to a level about twice that found in humans. Third, the
concentration of myoglobin, the oxygen storage protein in muscle, is extremely elevated in these animals,
measuring about 10 times that in human muscle.
(C) In summary, the primary anatomical adaptations for pressure of a deep-diving mammal such as the
sperm whale center on air-containing spaces and the prevention of tissue barotrauma. Air cavities, when present,
are lined with venous plexuses, which are thought to fill at depth, obliterate the air space, and prevent "the
squeeze." The lungs collapse, which prevents lung rupture and (important with regard to physiology) blocks gas
exchange in the lung. Lack of nitrogen absorption at depth prevents the development of nitrogen narcosis and
decompression sickness. In addition, because the lungs do not serve as a source of oxygen at depth, deep divers
rely on enhanced oxygen stores in their blood and muscle.
(D) Diving to depth can result in mechanical distortion and tissue compression, especially in gas-filled spaces
in the body. Such spaces include the middle ear cavity, air sinuses in the head, and the lungs. Development of
even small pressure differentials between an air cavity and its surrounding tissue can result in tissue distortion and
disruption—a condition in human divers known as "the squeeze." In some species of cetaceans, the middle ear
cavity is lined with an extensive venous plexus, which is postulated to become engorged at depth and thus reduce
or obliterate the air space and prevent development of the squeeze. Cetaceans also have large Eustachian tubes
communicating with the tympanic cavity of the ear and the large pterygoid sinuses of the head. These air sinuses of
the head have an extensive vasculature, which is thought to function in a manner similar to that of the middle ear
and facilitate equilibration of air pressure within these spaces. Lastly, most marine mammals lack frontal cranial
sinuses like those present in terrestrial mammals.
(E) Collapse of the lungs forces air away from the alveoli, where gas exchange between the lungs and blood
occurs. This blunting of gas exchange is important in the deep diver because it prevents the absorption of nitrogen
into the blood and the subsequent development of high blood nitrogen levels. High blood nitrogen pressures can
exert a narcotic effect (so-called nitrogen narcosis) on the diver. It may also lead to nitrogen bubble formation
during ascent—a phenomenon known as decompression sickness or "the bends." Collapse of the lungs in the deep
diver avoids these two problems.
(F) Another organ susceptible to compression damage is the lung. In deep-diving whales and seals, the
peripheral airways are reinforced, and it is postulated that this allows the lungs to collapse during travel to depth.
Such collapse has been observed radiographically and confirmed with blood nitrogen analyses in the deep-diving
Weddell seal.
Exercise 7. Make up a list of the 10 key terms used in the text, then agree with the whole group on the final
list. Retell the article using these terms.
Exercise 8. Prepare your own report about adaptations of other species to their habitat and lifestyle.
36
Section 2. Recommended Report and Presentation Topics
1. Mental disorders.
2. Brain regions and their functions.
3. What exactly are dreams?
4. Dreams and nightmares.
5. Early bird or night owl?
6. Coffee – friend or foe? Health effects of coffee.
7. Decaffeinated coffee.
8. Tea or coffee?
9. Eugenics.
10. Gene therapy.
11. GM plants.
12. GM animals.
13. Engineered animals and natural populations.
14. Animal conservation.
15. Ecotourism.
37
Section 3.
Unit 11. Human Evolution
The species does not grow into perfection: the
weak again and again get the upper hand of the
strong,—their large number, and their greater
cunning are the cause of it.
Friedrich Nietzsche
Exercise 1. What is evolution?
1. Why is Africa considered the birthplace of Homo sapiens?
2. What is the difference between monocentrism and polycentrism?
3. What caused bipedalism (bipedal locomotion) and upright posture in humans?
4. Why do people living in the south tend to have dark skin colour, while people living in the north have fair
complexion?
5. How did human races originate?
6. What factors can speed up evolution?
Exercise 2. Explain the meaning of the following key terms connected with evolution:
natural selection
mutation
variation
atavism
heredity
norm of reaction
rudiment
selective breeding
species
divergence
competition
genotype
population
convergence
biological progress
phenotype
ecological niche
parallelism
biological regression
adaptation
Exercise 3. Now read the article to check some of your answers in Exercise 1.
Culture Speeds Up Human Evolution
Analysis of common patterns of genetic variation reveals that humans have been evolving faster in recent
history
By David Biello
Homo sapiens sapiens has spread across the globe and increased vastly in numbers over the past 50,000
years or so—from an estimated five million in 9000 B.C. to roughly 6.5 billion today. More people means more
opportunity for mutations to creep into the basic human genome and new research confirms that in the past 10,000
years a host of changes to everything from digestion to bones has been taking place.
"We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the
University of Utah, a member of the team that analyzed the 3.9 million DNA sequences* showing the most
variation. "Most are very recent, so much so that the rate of human evolution over the past few thousand years is
far greater than it has been over the past few million years." "We believe that this can be explained by an increase
in the strength of selection as people became agriculturalists—a major ecological change—and a vast increase in
the number of favorable mutations as agriculture led to increased population size," he adds.
Roughly 10,000 years ago, humanity made the transition from living off the land to actively raising crops and
domesticated animals. Because this concentrated populations, diseases such as malaria, smallpox and
tuberculosis, among others, became more virulent. At the same time, the new agriculturally based diet offered its
own challenges—including iron deficiency from lack of meat, cavities and, ultimately, shorter stature due to poor
nutrition, says anthropologist John Hawks of the University of Wisconsin–Madison, another team member. "Their
bodies and teeth shrank. Their brains shrank, too," he adds. "But they started to get new alleles that helped them
digest the food more efficiently. New protective alleles allowed a fraction of people to survive the dread illnesses
better."
By looking for wide swaths of genetic material that vary little from individual to individual within these sections
of great variation, the researchers identified regions that both originated recently and conferred some kind of
advantage (because they became common rapidly). For example, the gene known as LCT gave adults the ability to
digest milk and G6PD offered some protection against the malaria caused by Plasmodium falciparum parasite.
"Ten thousand years ago, no one on planet Earth had blue eyes," Hawks notes, because that gene—OCA2—had
not yet developed. "We are different from people who lived only 400 generations ago in ways that are very obvious;
that you can see with your eyes."
Comparing the amount of genetic differentiation between humans and our closest relatives, chimpanzees,
suggests that the pace of change has accelerated to 10 to 100 times the average long-term rate, the researchers
write in Proceedings of the National Academy of Sciences USA. Not all populations show the same evolutionary
speed. For example, Africans show a slightly lower mutation rate. "Africans haven't had to adapt to a fundamentally
new climate," because modern humanity evolved where they live, Cochran says. "Europeans and East Asians,
38
living in environments very different from those of their African ancestors and early adopters of agriculture, were
more maladapted, less fitted to their environments."
And this speedy pace of evolution will not slow until every possible beneficial mutation starts to happen—the
maximum rate of adaptation. This has already begun to occur in such areas as skin color in which different sets of
genes are responsible for the paler shades of Europeans and East Asians, according to the researchers.
The finding raises many questions. Among them: "the medical applications of this kind of knowledge [as well
as] exactly what most of the selected changes do and what drove their selection," Cochran says.
But the history of humanity is beginning to be read out from our genes, thanks to a detailed knowledge of the
thousands of them that have evolved recently. "We're going to be classifying these by functional categories and
looking for matches between genetic changes and historic and archaeological changes in diet, skeletal form,
disease and many other things," Hawks says. "We think we will be able to find some of the genetic changes that
drove human population growth and migrations—the broad causes of human history." (From Scientific American
Online, December 10, 2007)
*This article wrongly characterized the HapMap genotype dataset used for this analysis as "genes" rather
than "DNA sequences."
Exercise 4. Are the following statements true or false, according to the text? Explain your answer.
1. Homo Sapiens has demonstrated great biological progress over its history.
2. The rate of human evolution has slowed down due to vast numbers of people living.
3. Transition to agricultural lifestyle and domestication of animals provided a reliable source of food for
people.
4. It also helped to improve human health condition.
5. Different populations demonstrate different rates of evolutionary changes.
6. Humans have developed numerous adaptations and thus have achieved the maximum rate of
adaptation.
7. Genetic research sheds light on human evolution.
Exercise 5. Are humans still evolving? Discuss the following questions:
a. What changes have taken place since the emergence of Homo Sapiens? Give as many examples as you
can.
b. What adaptations to their environment and lifestyle have people developed?
Exercise 6. Read the text which provides some information about the changes of human phenotype.
Why are we getting taller as a species?
Humans increased in stature dramatically during the last 150 years, but we have now likely reached the
upper limit. The average height of a human man will probably never exceed that of basketball player Shaquille
O'Neal, who stands 7 feet and 1 inch tall.
This answer comes from Michael J. Dougherty, assistant director and senior staff biologist at Biologic Image:
SportsLine USA, Inc.
In fact, over the last 150 years the average height of people in industrialized nations has increased
approximately 10 centimeters (about four inches). Why this relatively sudden growth? Are we evolving to greater
heights? Before answering these questions, we need to remember that evolution requires two things: variation in
physical and/or behavioral traits among the individuals in a population; and a way of selecting some of those traits
as adaptations, or advantages to reproduction.
For example, finches that have large, powerful beaks also have an advantage cracking large, tough seeds
during periods when small, soft seeds are scarce. As a consequence, large-beaked birds are more likely to eat
better, survive longer and reproduce than small-beaked birds. Because beak shape is an inherited trait, more
successful reproduction by large beaked birds means that the genes predisposing finches to large beaks are
transmitted to the next generation in relatively larger numbers than those genes encoding small beaks. Thus, the
population of finches in the next generation will tend to have larger beaks than finches in their parent's generation.
Let's use this basic operating principle of evolution to predict, retrospectively, the direction of change in
human height if evolution were the cause of the change. We know from studies conducted in industrial England
that children born into lower socioeconomic classes were shorter, on average, than children born into wealthy
families. We also know that poorer families had larger numbers of children. Given those initial conditions, what
would evolution predict? The average population should have become shorter because the shorter individuals in
the population were, from an evolutionary fitness perspective, more successful in passing on their genes. But this
did not happen. Instead, all segments of the population--rich and poor, from small and large families--increased in
height. Thus, natural selection, the process whereby differences in reproductive success account for changes in the
traits of a population, does not explain why we are taller.
If evolution doesn't explain height increases, what does? Most geneticists believe that the improvement in
childhood nutrition has been the most important factor in allowing humans to increase so dramatically in stature.
The evidence for this argument is threefold:
39
First, the observed increase in height has not been continuous since the dawn of man; it began sometime
around the middle of the nineteenth century. In fact, examinations of skeletons show no significant differences in
height from the stone age through the early 1800s. Also, during World Wars I and II, when hunger was a frequent
companion of the German civilian population, the heights of the children actually declined. They only recovered
during the post-war years. Such data are consistent with recent research indicating that slow growth induced by
temporary malnourishment can usually be reversed. Chronic underfeeding during childhood, however, permanently
affects stature and other traits, including intelligence.
Second, the trend toward increasing height has largely leveled off, suggesting that there is an upper limit to
height beyond which our genes are not equipped to take us, regardless of environmental improvements.
Interestingly, the age of menarche, which is also influenced by nutrition, has shown a corresponding decrease over
this same time period. Some scientists believe that the increase in teenage and out-of-wedlock pregnancies in the
developed world may be an unanticipated consequence of improved nutrition.
Third, conditions of poor nutrition are well correlated to smaller stature. For example, the heights of all
classes of people, from factory workers to the rich, increased as food quality, production and distribution became
more reliable, although class differences still remain. Even more dramatic, the heights of vagrant London boys
declined from 1780 to1800 and then rose three inches in just 30 years--an increase that paralleled improving
conditions for the poor. Even today, height is used in some countries as an indicator of socioeconomic division, and
differences can reveal discrimination within social, ethnic, economic, occupational and geographic groups.
For those hoping that humans might someday shoot basketballs through 15-foot high hoops, the fact that the
increase in human height is leveling off no doubt will be disappointing. For those who understand, however, that
our genes are merely a blueprint that specifies what is possible given an optimal environment, a limit on height is
just one of many limitations in life, and certainly not the most constraining.
With environmental variables perhaps near their optimum, what are the prospects for evolutionary increases
in height as a consequence of changes to our genetic blueprints? Apply the methods of the thought experiment
above and see.
Exercise 7. Using the information from the text prove that:
1. Evolution doesn’t explain the increased height of people.
2. Improvement in childhood nutrition has been the most important factor in increasing the stature.
3. People will hardly increase their height any more.
Exercise 8. In the following text the paragraphs are mixed. Put them in the correct logical order. The first
and the last paragraphs are in their right places.
African Adaptation to Digesting Milk Is "Strongest Signal of Selection Ever"
East African cattle herding communities rapidly and independently evolved ability to digest lactose
By Nikhil Swaminathan
(A) For many adults in the world, the phrase "got milk?" is quickly followed by "got a nearby toilet?" Lactose,
the primary sugar in milk, is a universal favorite in infancy but into adulthood the level of lactase-phlorizin
hydrolase, the enzyme that metabolizes lactose in the small intestine, decreases and digestion of dairy products
becomes difficult. In some populations, however, such as those located in northern Europe, the ability to digest milk
remains most likely as a result of lifestyles based around cattle domestication. In 2002 Finnish scientists localized
the genetic mutation that conferred this trait in northern Europeans to two regions on chromosome 2.
(B) Tishkoff and her students tested 470 people representing over 43 ethnic fractions in the Sudan, Kenya
and northern Tanzania for lactose intolerance using glucose-monitoring kits, familiar to most diabetics. The team
then selected the 40 most lactose intolerant participants and the 69 most tolerant and sequenced parts of their
genomes around the two markers identified in the Finnish lactase persistence study. The researchers determined
there were 123 single nucleotide polymorphisms--SNPs, or changes to one base in the genetic code--associated
with digestibility. Of these, three SNPs were more promising than the others and one of them was very common
among Tanzanians and Kenyans, showing up in 40 to 50 percent of the sequences.
(C) Tishkoff believes that because she found so many markers associated with lactose tolerance in the
sequencing of her 109 subjects, evolution clearly develops multiple solutions when there is a strong selective force.
"There are some populations that can digest milk, and they don't have any of these mutations," she says. "There
are more out there." Dallas Swallow, a human geneticist at University College London, agrees with that
assessment. She released a study on a small Sudanese tribe in Human Genetics this past November, finding three
markers, two of which Tishkoff had isolated in her study. Oddly enough, Swallow found no data on the Maryland
study's primary variant. Tishkoff argues this disparity is due to geographic specificity of these mutations. Swallow,
for her part, notes that Tishkoff's dramatic results may be a result of "the relative relatedness" of her sample. "If you
have an ethnic group which is rather a small population in size but happens to migrate over geographic distances
then they might be more related to each other than the surrounding people," she points out.
(D) Working with this highly correlated locus, Tishkoff's team sequenced a broad region of the chromosome
around this nucleotide to determine whether it arose in concert with the European mutation. "It turns out they're on
completely different chromosome backgrounds," she explains. "So it had a completely different origin." Next, the
team tested to see if the mutation was positively selected, conferring a reproductive advantage and spreading
40
quickly through the population. People who had this particular SNP on both copies of chromosome 2 had identical
genetic scripts for the next two million base pairs--a phenomenon that occurs when there is a strong benefit to
having a particular trait." Because this section has been preserved intact without being mutated or broken up by
recombination, it indicates that it is very recent and very strong. In addition, Tishkoff's team determined the date
range when the mutation likely occurred: 3,000 to 7,000 years ago, which matches up well with the archaeological
record that places pastoralization coming to East Africa about 5,000 years ago. The European trait dates back
about 9,000 years.
(E) Now, the results of a four-year, international research project find that communities in East Africa leading
traditionally similar pastoral lives evolved their ability to drink milk rapidly and independently of the northern
Europeans. According to University of Maryland biologist Sarah Tishkoff, the lead author of a study appearing in
today's Nature Genetics, the mutation allowing them to "get milk" arose so quickly and was so advantageous that
"it is basically the strongest signal of selection ever observed in any genome, in any study, in any population in the
world."
(F) Nevertheless, both researchers are pleased that their studies found at least two genetic markers in
common. Swallow concedes: "It looks jolly well as though drinking milk as an adult was good for some of us at
some time in our history, that's for sure." (From Scientific American Online, December 11, 2006)
Exercise 9. Make up a list of the 10 key facts about human evolution discussed in this unit. Prove and
explain your choice. Then summarize all the information discussed into one report.
41
Unit 12. Alcohol
We drink one another’s health and spoil our own.
Jerome K. Jerome
Exercise 1. What do you know about alcohol?
1. What is its main active compound?
2. In what regions of the world is alcohol produced?
3. How does alcohol affect the human body?
4. What are the risks of alcohol overdose?
5. What causes hangover after drinking alcohol?
6. What is alcoholism? How quickly does it develop?
Exercise 2. Read the information about alcohol provided by NewScientist.com to check some of your
answers in Exercise 1.
What is it? Ethanol produced by the action of yeast on sugars.
What does it do? Ethanol is a biphasic drug: low doses have a different effect to high doses. Small amounts of
alcohol (one or two drinks) act as a stimulant, reducing inhibition and producing feelings of mild euphoria. Higher
doses depress the central nervous system, initially producing relaxation but then leading to drunkenness characterised by poor coordination, memory loss, cognitive impairment and blurred vision. Very high doses cause
vomiting, coma and death through respiratory failure. The fatal dose varies but is somewhere around 500
milligrams of ethanol per 100 millilitres of blood.
How does it work? At low doses (5 milligrams per 100 millilitres of blood), alcohol sensitises NMDA receptors in
the brain, making them more responsive to the excitatory neurotransmitter glutamate, so boosting brain activity.
These effects are most pronounced in areas associated with thinking, memory and pleasure. At higher doses it
desensitises the same receptors and also activates the inhibitory GABA system.
How long is its history?
4000BC - Wine and beer making in Egypt and Sumeria
3500BC - Bronze-age vessels show evidence of wine consumption in eastern Mediterranean
800BC - Distillation of spirits in India
AD625 - Mohammed orders his followers to abstain from alcohol
1850s - New York bartenders invent the cocktail
1920-33 - Prohibition in the US. Alcohol was also illegal in Finland from 1919 to 1932 and in various Canadian
provinces at various times between 1900 and 1948.
Exercise 3. Now read more detailed information about the effects of alcohol on the brain provided by
Anthony Dekker D.O., Director of Ambulatory Care and Community Health at Phoenix Indian Medical
Center.
What are the effects of alcohol on the brain?
The product of the oldest chemical reaction studied by man, alcohol, continues to challenge researchers.
Since the original work on alcohol's neurological effects in the early 20th century, new theories have regularly
emerged. What we have learned is that alcohol is a sedative-hypnotic in the acute intoxication phase for most
patients. But it diminishes the quality of sleep. Individuals with sleep apnea often experience longer and more
severe apneic episodes and hypoxia, or oxygen deprivation, after drinking alcohol.
In other individuals, though, alcohol may act as a stimulant. Indeed, its association with violent and selfabusive behavior is well documented. At intoxicating levels, alcohol is a vasodilator (it causes blood vessels to
relax and widen), but at even higher levels, it becomes a vasoconstrictor, shrinking the vessels and increasing
blood pressure, exacerbating such conditions as migraine headaches and frostbite. Researchers have also
thoroughly documented the effects of alcohol on the developing fetus. Approximately one third of all babies born to
alcoholic mothers will develop Fetal Alcohol Syndrome or Effects (FAS or FAE), causing central nervous system
dysfunctions including Attention Deficit Disorder (ADD) and impaired IQ. There are also growth and facial
abnormalities associated with these infants.
In the early 1900s, H. Meyer and Charles Ernest Overton originally theorized that the effect of alcohol was
achieved by altering the lipid environment of cell membranes. This theory, however, requires much higher
concentrations of alcohol than are clinically observed. A recent theory, supported by several researchers, pins
alcohol's effect on voltage and ligand-gated ion channels that control neuronal activity. Two distinct ligand-gated
channels have been identified, inhibitory ones (GABA receptors and strychnine-sensitive glycine receptors) and
excitatory ones (N-methyl-D-aspartate (NMDA) and non-NMDA glutamate-activated channels and the 5HT3
subtype of serotonin receptors).
The inhibitory aspect occurs due to a hyperpolarization of neurons, secondary to an influx of chloride ions.
The neuron becomes less likely to achieve the threshold membrane potential. The excitatory receptor is dependent
on the NMDA and non-NMDA glutamate receptors that control the influx of sodium and calcium, which bind to
42
endogenous neurotransmitters (glutamate or aspartate) and depolarize the neuronal membrane. The NMDA
receptor seems to have a high permiability to calcium, which acts as a catalyst to several intracellular events.
Chronic exposure to alcohol seems to alter the NMDA receptors and this may play a role in the clinical
symptoms of alcohol withdrawal. In vitro studies have demonstrated an increase in the binding sites for MK801
(dizocilpine) in neurons chronically exposed to alcohol. This rise may account for the acclimation process, in which
greater concentrations of alcohol are needed to cause experimental and clinical symptoms of intoxication. NMDA
can cause seizure activity. Mice that have been exposed to chronically elevated levels of alcohol reveal increased
numbers of NMDA receptors and NMDA related seizure activity. The NMDA antagonist MK801 has been shown to
decrease the severity of seizures in these mice during withdrawal. Through a complex process of cell membrane
ion pumps and neurotransmitter stimulation, the multi-faceted effects of alcohol and alcohol withdrawal are
becoming better understood.
Under the influence of alcohol, the brain experiences impairments in the following regions:
•Frontal Lobe - Loss of reason, caution, inhibitions, sociability, talkativeness and intelligence.
•Parietal Lobe - Loss of fine motor skills, slower reaction time, shaking.
•Temporal Lobe - Slurred speech, impaired hearing.
•Occipital Lobe - Blurred vision, poor distance judgement.
•Cerebellum - Lack of muscle coordination and balance.
•Brain Stem - Loss of vital functions.
Exercise 4. Do you agree with the statements below? Give reasons for your choice.
1. Alcohol may have sedative-hypnotic and stimulatory effect on people.
2. Alcohol affects circulatory system.
3. So far scientists have not completely uncovered the mechanism of its activity.
4. The effect of alcohol is most pronounced in the brain.
5. Chronic exposure to alcohol produces no changes of brain structures.
Exercise 5. Some scientists argue that alcohol can produce significant positive effect on one’s health. The
article below provides evidence for this point of view. Read the article and find answers to the questions:
1. What disorders can alcohol protect from?
2. What are the mechanisms involved?
Drink to Your Health?
By Arthur L. Klatsky
Three decades of research shows that drinking small to moderate amounts of alcohol has cardiovascular benefits.
A thorny issue for physicians is whether to recommend drinking to some patients.
America has always had trouble deciding whether alcohol is a bad thing or a good thing. Millions who
remember Prohibition, when all alcoholic beverages were illegal, now witness a constant stream of advertisements
from producers of alcoholic beverages encouraging people to drink. Despite alcohol’s popularity today, however,
many still consider abstinence a virtue. Certainly, heavy drinking and alcoholism deserve deep concern for the
terrible toll they take on alcohol abusers and society in general. But worry about the dangers of abuse often leads
to emotional denials that alcohol could have any medical benefits. Such denials ignore a growing body of evidence
indicating that moderate alcohol intake wards off certain cardiovascular conditions, most notably heart attacks and
ischemic strokes (those caused by blocked blood vessels). A few studies even show protection against dementia,
which can be related to cardiovascular problems.
The Alcohol Effect
A discussion of moderate drinking requires a working definition of “moderate.” Simple definitions of light,
moderate or heavy are somewhat arbitrary, but a consensus in the medical literature puts the upper limit for
moderate drinking at two standard-size drinks a day. Studies show that drinking above that level can be harmful to
overall health, although sex, age and other factors lower and raise the boundary for individuals.
The main medical benefit of reasonable alcohol use seems to be a lowering of the risk for coronary heart
disease (CHD), which results from the buildup of atherosclerosis (fatty plaque) in the arteries. Atherosclerosis
restricts blood flow to the heart and can promote the formation of vessel-blocking clots. It can thereby cause angina
(chest discomfort resulting from low oxygen levels in the heart muscles), heart attack (the death of heart tissue that
occurs when a blood clot or narrowing of the arteries prevents blood from reaching the heart) and death, often
without warning. The condition usually starts at a young age but takes decades to blossom into overt CHD. The
most common form of heart disease in developed countries, CHD causes about 60 percent of deaths from
cardiovascular ills and about 25 percent of all deaths in those nations.
Pathologists uncovered the first clues to the value of alcohol in the early 1900s, noting that the large arteries
of people who died of alcoholic liver cirrhosis seemed remarkably “clean”—that is, free of atherosclerosis. One
explanatory hypothesis assumed that alcohol was a nebulous solvent, essentially dissolving the buildup in the
arteries; another explanation held that heavier drinkers died before their atherosclerosis had a chance to develop.
Neither idea truly explained drinkers’ unblocked arteries, however.
43
A more telling hint emerged in the late 1960s, when Gary D. Friedman of the Kaiser Permanente Medical
Center in Oakland, Calif., came up with a novel idea: use computers to unearth unknown predictors of heart
attacks. The power of computing could first identify healthy people who had risk factors similar to heart attack
victims. Such factors include cigarette smoking, high blood pressure, diabetes, elevated levels of low-density
lipoprotein (LDL, or “bad”) cholesterol, low levels of high-density-lipoprotein (HDL, or “good”) cholesterol, male
gender, and a family history of CHD. Friedman then searched for predictors of heart attacks by comparing the
patients and the newly found controls in hundreds of ways—for example, their exercise and dietary habits and their
respective levels of various blood compounds. The computers spit out a surprising discovery: abstinence from
alcohol was associated with a higher risk of heart attack.
Since then, dozens of investigations in men and women of several racial groups in various countries have
correlated previous alcohol use with current health. These studies have firmly established that nondrinkers develop
both fatal and nonfatal CHD more often than do light to moderate drinkers. In addition, in 2000 Giovanni Corrao of
the University of Milan-Bicocca in Italy, Kari Poikolainen of the Järvenpää Addiction Hospital in Finland and their
colleagues combined the results of 28 previously published investigations on the relation between alcohol intake
and CHD. In this meta-analysis, they found that the risk of developing CHD went down as the amount of alcohol
consumed daily went up from zero to 25 grams. At 25 grams—the amount of alcohol in about two standard
drinks—an individual’s risk of a major CHD event, either heart attack or death—was 20 percent lower than it was
for someone who did not drink at all. New data about alcohol protecting against death from CHD are even more
impressive. At a meeting of the American Heart Association last November, it was announced that those who had
one or two alcoholic drinks a day had a 32 percent lower risk of dying from CHD than abstainers did.
The possible mechanisms by which alcohol has such an apparently profound effect on cardiovascular health
primarily involve cholesterol levels and blood clotting. Blood lipids play a central role in CHD. Numerous studies
show that moderate drinkers have 10 to 20 percent higher levels of heart-protecting HDL cholesterol. And people
with higher HDL levels, also known to be increased by exercise and some medications, have a lower risk of CHD.
That lower risk stems from HDL’s ability to usher LDL cholesterol back to the liver for recycling or elimination,
among other effects. Alcohol seems to have a greater influence on a different HDL subspecies (HDL3) than on the
type increased by exercise (HDL2), although both types are protective. (The biochemical pathways in the liver that
could account for alcohol’s ability to raise HDL levels remain incompletely known; it is thought that alcohol probably
affects liver enzymes involved in the production of HDL.) Three separate analyses aimed at determining specific
contributions of alcohol all suggest that the higher HDL levels of drinkers are responsible for about half of the
lowered CHD risk.
Alcohol may also disrupt the complex biochemical cascade behind blood clotting, which can cause heart
attacks when it occurs inappropriately, such as over atherosclerotic regions in coronary arteries. Blood platelets,
cellular components of clots, may become less “sticky” in the presence of alcohol and therefore less prone to
clumping, although data on this question remain ambiguous. Overall, alcohol’s anticlotting capacity is not as well
established as its HDL effect, and some effects, such as platelet clumping, may be reversed by heavy or binge
drinking. In addition, studies have shown a beneficial effect on CHD risk in people who have far fewer than two
drinks a day—say, three or four drinks a week. Anticlotting could be a major factor in the protection accorded by
alcohol in these small amounts, which seem insufficient to affect HDL levels greatly.
Before accepting alcohol’s benefits, an epidemiologist attempts to locate hidden factors possibly at work. For
instance, could lifelong abstainers differ from drinkers in psychological traits, dietary habits, physical exercise habits
or other ways that might account for their higher CHD risk without the need to invoke the absence of alcohol? Were
such traits to explain away alcohol’s apparent protection, they would need to be present in both sexes, various
countries and several racial groups. Considering that no such traits have been identified, the simpler and more
plausible explanation is that light to moderate alcohol drinking does indeed enhance cardiovascular health.
In fact, the available evidence satisfies most standard epidemiological criteria for establishing a causal
relation. The numerous studies examining light and moderate alcohol intake and health reach consistent
conclusions. The positives associated with alcohol can be attributed to biologically plausible mechanisms. Alcohol
offers specific enhancement of cardiovascular health, not general protection against all illness. And alcohol’s effect
can be identified independent of known “confounders,” other alcohol related factors that could be responsible for a
subject’s cardiovascular condition.
Because heavy drinking is not more protective than lighter drinking, this absence of a clear dose-response
relation is also a weakness. Nevertheless, the collected data make a strong case for the cardiac benefits of
controlled drinking.
To Drink or Not to Drink
Most people drink for reasons other than alcohol’s health benefits, and many of them are already using
alcohol in amounts that appear to promote cardiovascular health. But the accumulated research on alcohol’s
positive effects presents a challenge to physicians. On the one hand, mild to moderate drinking seems better for
heart health than abstinence for select people. On the other hand, heavy drinking is clearly dangerous. It can
contribute to noncardiovascular conditions such as liver cirrhosis, pancreatitis, certain cancers and degenerative
neurological disorders, and it plays a part in great numbers of accidents, homicides and suicides, as well as in fetal
alcohol syndrome. (No conclusive evidence links light to moderate drinking to any of these problems.)
Heavy drinking also contributes to cardiovascular disorders. Too much alcohol raises the risk of alcoholic
cardiomyopathy, in which the heart muscle becomes too weak to pump efficiently; high blood pressure (itself a risk
44
factor for CHD, stroke, heart failure and kidney failure); and hemorrhagic stroke, in which blood vessels rupture in
or on the surface of the brain. Alcohol overindulgence is also related to “holiday heart syndrome,” an electrical
signal disturbance that disrupts the heart rhythm. The name refers to its increased frequency around particular
holidays during which people engage in binge drinking.
Given the potential dangers of alcohol, how can individuals and their physicians make the decision as to
whether to include alcoholic beverages in their lives and, if so, in what amounts? The ability to predict accurately an
individual’s risk of a drinking problem would be a great boon; the least disputed possible consequence of moderate
drinking is problem drinking. Individual risk can be approximated using family and personal histories of alcoholrelated problems or conditions, such as liver disease or, of course, alcoholism. Even when known factors are taken
into account, however, unpredictable events late in life may result in deleterious drinking changes.
Exactly because of these dangers, public health concerns about alcohol until recently have been
appropriately focused solely on the reduction of the terrible social and medical consequences of heavy drinking.
And the correlation between total alcohol consumption in society and alcohol-related problems has been used to
justify pushes for abstinence. Ultimately, however, a more complex message is necessary. Merely recommending
abstinence is inappropriate health advice to people such as established light drinkers at high risk of CHD and at low
risk of alcohol-related problems—which describes a large proportion of the population. Of course, the most
important steps for this group are proper diet and exercise; effective treatment of obesity, diabetes, high blood
pressure and high cholesterol; and avoidance of tobacco. But there is a place on that list of beneficial activities for
light drinking. Most light to moderate drinkers are already imbibing the optimal amount of alcohol for cardiovascular
benefit, and they should continue doing what they are doing.
Abstainers should never be indiscriminately advised to drink for health; most have excellent reasons for not
drinking. Yet there are exceptions. One case is the person with CHD who “goes clean”—quits smoking, switches to
a spartan diet, starts exercising and, with good intentions, gives up the habit of a nightly bottle of beer or glass of
wine. This self-imposed prohibition should be repealed. In addition, a number of infrequent drinkers might think
about increasing their alcohol intake to one standard drink daily, especially men older than 40 and women older
than 50 at high risk of CHD and low risk of alcohol-related problems.
But women also have to consider one possible drawback of alcohol: several studies link heavy drinking—and
a few even link light drinking—to an increased risk of breast cancer, a less common condition than heart disease in
postmenopausal women but certainly quite a serious one. For young women, who are generally at low short-term
risk of CHD and therefore may not benefit greatly from alcohol’s positive cardiovascular effects, this possible breast
cancer link looms larger in estimating the overall risks and benefits of alcohol. And for all women, the upper limit on
moderate drinking should be considered one drink a day.
The only clear-cut message regarding alcohol and health, then, is that all heavy drinkers should reduce or
abstain, as should anyone with a special risk related to alcohol, such as a family or personal history of alcoholism
or preexisting liver disease. Beyond that, however, the potential risks and benefits of alcohol are best evaluated on
a case-by-case basis. I believe that it is possible to define a clear, safe limit for alcohol consumption that would
offer a probable benefit to a select segment of the population. The ancient Greeks urged “moderation in all things.”
Three decades of research shows that this adage is particularly appropriate when it comes to alcohol. (Feature
article, abridged. From Scientific American, February, 2003)
Exercise 6. Would you recommend moderate amounts of alcohol to the following groups of patients?
Why? Why not?
● heavy drinkers
● pregnant women
● diabetics
● patients with CHD
● people with family history of alcoholism
● young people
● obese people
● women older than 50
Exercise 7. You are going to interview your fellow-students. Make up 10 questions about the key facts
discussed in the article.
Exercise 8. Summarize all the information discussed in this unit and speak on the effects of alcohol on
human organism.
45
Unit 13. Sex and Gender
A woman is only a woman, but a good cigar is a
smoke.
Rudyard Kipling
Exercise 1. What do you know about the sexes?
1. What are the physiological differences between individuals of male and female gender? What organs and organ
systems differ between males and females?
2. What mechanisms and when determine the sex of the future individual?
3. What are the functions of reproductive hormones (sex hormones)?
4. What are the secondary sexual characteristics?
5. Why do women generally live longer than men?
6. Do men and women really have different patterns of mental activity and emotions? Are they genetically or
socially programmed?
Exercise 2. Read the text to check some of your answers in Exercise 1.
Why is life expectancy2 longer for women than it is for men?
Bertrand Desjardins, a researcher in the demography department of the University of Montreal, explains.
Men dying sooner than women makes sense biologically: because 105 males are born for every 100
females, it would assure that there are about the same number of men and women at reproductive ages. But even
though women showed a longer life expectancy in almost every human society in the last decade of the 20th
century, the size of the advantage varied greatly. For example, in the U.S. life expectancy was 73.4 years for males
and 80.1 years for females, a difference of 6.7 years, whereas in France it was 7.8 years and in the U.K., 5.3 years.
The discrepancy was much greater in some countries, with the difference in Russia reaching more than 12 years,
but in others, such as India (0.6 year) or Bangladesh (0.1 year), it was much less.
The diversity in worldwide longevity alone indicates that the difference in mortality between the sexes is not
purely biological and that there are intervening social factors. The current range of situations actually reflects
different stages of a three-part historical evolution. Women most probably have a biological advantage that allows
them to live longer, but in the past--and in several places, still today--the status and life conditions of women
nullified this benefit. Today, given the general progress in female life conditions, women have not only regained
their biological advantage, but have gone much beyond it, both because they tend to engage in fewer behaviors
that are bad for health than men do and because they better profit from current advances in health care and living
conditions.
The biological advantage that women have is taken as a certainty, because the mortality of males is higher
than that of females from the very outset of life: during the first year of life, in the absence of any outside influence
which could differentiate mortality between the sexes, male mortality is 25 to 30 percent greater than is female
mortality. The genetic advantage of females is evident. When a mutation of one of the genes of the X chromosome
occurs, females have a second X to compensate, whereas all genes of the unique X chromosome of males
express themselves, even if they are deleterious. More generally, the genetic difference between the sexes is
associated with a better resistance to biological aging. Furthermore, female hormones and the role of women in
reproduction have been linked to greater longevity. Estrogen, for example, facilitates the elimination of bad
cholesterol and thus may offer some protection against heart disease; testosterone, on the other hand, has been
linked to violence and risk taking. Finally, the female body has to make reserves to accommodate the needs of
pregnancy and breast feeding; this ability has been associated with a greater ability to cope with overeating and
eliminating excess food.
Even though many biological and genetic factors have been identified, their overall effect is impossible to
measure, especially given the influence of social factors on mortality. The extraordinary economic and social
progress, that has occurred since the 18th century, has been accompanied by a dramatic reduction of the social
differences between men and women and of the burden of motherhood, which had previously negated women's
biological advantage. But the recent mortality trends have gone much farther than the mere recovery of an original
advantage, creating instead a new advantage of greater magnitude for women. Observations indicate that the
growing excess male mortality in industrial countries could be explained by the rise of so-called "man-made
diseases," which are more typically male. These include exposure to the hazards of the workplace in an industrial
context, alcoholism, smoking and road accidents, which have indeed increased considerably throughout the 20th
century.
2
The measure of life expectancy at birth is a statistic that represents the expected duration of life for babies born during a given
time period, usually one calendar year. Calculated from death rates observed at every age, it is based on the critical assumption
that the age-specific risks of death observed during a given year will prevail for all babies born in that year, for the remainder of
their lives. In contrast, life span is the theoretical upper limit to life that would be observed if everyone in the population adopted
ideal lifestyles from birth to death and if external threats to life were eliminated. Some researchers believe that there is no
biologically determined life span per se, but rather a series of time-dependent physiological declines that may eventually be
subject to modification (Encyclopedia of Bioethics, 2004, p.98)
46
But if these diseases are the only explanation for longer female life expectancy, why has the gap continued
to grow even though male and female behavior and life conditions have been converging in recent years? Part of
the paradox can certainly be explained by the fact that this convergence is not absolute: male smokers tend to
smoke more cigarettes than female smokers do, and men drive more recklessly than female drivers do, for
instance.
French demographer Jacques Vallin has long been monitoring longevity in general and sex differences in
mortality in particular. He adds to the above an interesting explanation of women's current mortality advantage that
could explain the more recent trends: the dramatic increase in excess male mortality emerged as an equally
dramatic progress in the general health conditions of our societies was taking place. He thus argues that beyond
the negative behavioral or environmental factors that affect men more than they do women, there could be very
well be a more fundamental difference in lifestyles that allows women to better benefit from the general progress in
health. For example, although women now participate massively in the work force, their roles remain different and
their professional activities are, on average, less prejudicial to their health. In addition, women often relate to their
bodies, their health and their lives in general in a much different way than men do. To caricature, women seek
beauty, men seek strength and power; thus, a woman's body must remain young and healthy as long as possible,
whereas a man's body must be submitted to risks and challenges from an early age. The result is that women,
much more than men, are attentive to their bodies and their needs and often carry on deeper dialogs more easily
with their doctors. Hence, women, being more inclined to take care of their bodies and to prolong their lives, may
be better able to glean greater profit from modern medical and social advances by practicing activities that are
healthier and better protect their bodies. In this context, women's biological advantage now appears relatively minor
in the total mortality differences between the sexes.
Exercise 3. Are the following statements true or false, according to the text?
1. Equal numbers of boys and girls are born every year.
2. Different economies demonstrate great diversity in average life expectancy.
3. There are no social factors accounting for the difference in male and female longevity.
4. Y-chromosome gives men biological advantage and better survival chances.
5. Historically men have enjoyed a better social position than women.
6. Men are exposed to a greater number of risk factors than women.
7. Women make better use of medical services and modern progress in science.
Exercise 4. Sex Differences in the Brain.
Men and women display patterns of behavioral and cognitive differences that reflect varying hormonal
influences on brain development. Before reading the next text guess if the following statements generally
refer more to men or to women:
a. Men/Women, on average, have stronger verbal skills (especially in writing).
b. Men/Women generally are better at mentally manipulating objects.
c. Men/Women have better memory for events, words, objects, faces and activities.
d. Men/Women are better at performing certain quantitative tasks that rely on visual representations.
e. Men/Women can better recognize emotions and show higher levels of empathy.
Exercise 5. Read the following article to check some of your answers in Exercise 4.
Girl Brain, Boy Brain?
The two are not the same, but new work shows just how wrong it is to assume that all gender differences are
“hardwired”
By Lise Eliot
As MRI scanning grows ever more sophisticated, neuroscientists keep refining their search for male-female
brain differences that will answer the age-old question, “Why can’t a woman think like a man?” (and vice-versa).
Social cognition is one realm in which the search for brain sex differences should be especially fruitful. Females of
all ages outperform males on tests requiring the recognition of emotion or relationships among other people. Sex
differences in empathy emerge in infancy and persist throughout development, though the gap between adult
women and men is larger than between girls and boys. The early appearance of any sex difference suggests it is
innately programmed—selected for through evolution and fixed into our behavioral development through either
prenatal hormone exposure or early gene expression differences. On the other hand, sex differences that grow
larger through childhood are likely shaped by social learning, a consequence of the very different lifestyle, culture
and training that boys and girls experience in every human society.
At first glance, studies of the brain seem to offer a way out of this age-old nature/nurture dilemma. Any
difference in the structure or activation of male and female brains is indisputably biological. However, the
assumption that such differences are also innate or “hardwired” is invalid, given all we’ve learned about the
plasticity, or malleability of the brain. Simply put, experiences change our brains.
Recent research by Peg Nopoulos, Jessica Wood and colleagues at the University of Iowa illustrates just
how difficult it is to untangle nature and nurture, even at the level of brain structure. A first study, published in
47
March 2008 found that one subdivision of the ventral prefrontal cortex - an area involved in social cognition and
interpersonal judgment, known as the straight gyrus (SG), - is proportionally larger in women, compared to men.
(Men’s brains are about 10 percent larger than women’s, overall, so any comparison of specific brain regions must
be scaled in proportion to this difference.) Wood and colleagues found the SG to be about 10 percent larger in the
thirty women they studied, compared to thirty men. What’s more, they found that the size of the SG correlated with
a widely-used test of social cognition, so that individuals (both male and female) who scored higher in interpersonal
awareness also tended to have larger SGs.
In their article, Wood and colleagues speculate about the evolutionary basis for this sex difference. Perhaps,
since women are the primary child-rearers, their brains have become programmed to develop a larger SG, to
prepare them to be sensitive nurturers. Prenatal sex hormones are known to alter behavior and certain brain
structures in other mammals. Perhaps such hormones—or sex-specific genes—may enhance the development of
females’ SG (or dampen the development of males’) leading to inborn differences in social cognition.
The best way to test this hypothesis is to look at children. If the sex difference in the SG is present early in
life, this strengthens the idea that it is innately programmed. Wood and Nopoulos therefore conducted a second
study with colleague Vesna Murko, in which they measured the same frontal lobe areas in children between 7 and
17 years of age. But here the results were most unexpected: they found that the SG is actually larger in boys!
What’s more, the same test of interpersonal awareness showed that skill in this area correlated with smaller SG,
not larger, as in adults. The authors acknowledge that their findings are “complex,” and argue that the reversal
between childhood and adulthood reflects the later maturation of boys’ brains, compared to girls. (Adolescents’
brains undergo a substantial “pruning” or reduction in gray matter volume during adolescence, which happens
about two years earlier in girls, compared to boys.)
However, in both studies, Wood and colleagues added another test that reminds us to be cautious when
interpreting any finding about sex differences in the brain. Instead of simply dividing their subjects by biological sex,
they also gave each subject a test of psychological “gender:” a questionnaire that assesses each person’s degree
of masculinity vs. femininity—regardless of their biological sex—based on their interests, abilities and personality
type. And in both adults and children, this measure of “gender” also correlated with SG size, albeit in just as
complicated a way as the correlation between “sex” and SG size. (Larger SG correlated with more feminine
personality in adults but less feminine personality in children.)
In other words, there does seem to be a relationship between SG size and social perception, but it is not a
simple male-female difference. Rather, the SG appears to reflect a person’s “femininity” better than one’s biological
sex: women who are relatively less feminine show a correspondingly smaller SG compared to women who are
more feminine, and ditto for men.
This finding—that brain structure correlates as well or better with psychological “gender” than with simple
biological “sex”—is crucial to keep in mind when considering any comparisons of male and female brains. Yes,
men and women are psychologically different and yes, neuroscientists are uncovering many differences in brain
anatomy and physiology which seem to explain our behavioral differences. But just because a difference is
biological doesn’t mean it is “hard-wired.” Individuals’ gender traits—their preference for masculine or feminine
clothes, careers, hobbies and interpersonal styles—are inevitably shaped more by rearing and experience than is
their biological sex. Likewise, their brains, which are ultimately producing all this masculine or feminine behavior,
must be molded—at least to some degree—by the sum of their experiences as a boy or girl.
And so, any time scientists report a difference between male and female brains, especially in adults, it begs
the question, “Nature or nurture?” Is women’s larger SG the cause of their social sensitivity, or the consequence of
living some 30 years in a group that practices greater empathetic responding? Wood and colleagues are among
the few neuroscientists to analyze male-female brain differences for their relationship to gender type, as opposed to
strict biological sex. Their findings do not prove that social learning is the cause of male-female differences in the
brain, but they do challenge the idea that such brain differences are a simple product of the Y chromosome. (From
Scientific American Online, September 8, 2009)
Exercise 6. Answer the questions using the information from the text:
1. Why is social cognition regarded a fruitful area of investigation?
2. What is nature/nurture dilemma?
3. What is straight gyrus (SG) and what is it responsible for?
4. How do researchers explain larger SG in women from the evolutionary perspective?
5. How did the results of the second study contradict those of the first?
6. What correlation between SG size and sex/gender was finally established?
7. How can it be interpreted?
Exercise 7. Divide into two groups. Each group should read either Text A or Text B about differences
between the sexes. Then tell other students what you have read about.
Text A. Enzyme Lack Lowers Women's Alcohol Tolerance
By Harald Franzen
An international team of researchers may have found one of the reasons why alcohol harms women more
than men: women, it appears, are deficient in an enzyme that helps metabolize alcohol. The findings appear in the
48
April issue of Alcoholism: Clinical and Experimental Research. "It has been known for a long time that, in general,
both women and female animals are more susceptible to the negative or toxic effects of alcohol," team member
Steven Schenker of the University of Texas at San Antonio says. "This is true for the liver, heart muscle and
skeletal muscle, and it may be true for the pancreas and the brain. In other words, there is something about the
female gender that makes them more susceptible to toxic amounts of alcohol."
In the past scientists attributed this susceptibility to women's smaller body size and their relatively higher
percentage of fatty tissue. For this study, however, the researchers focused on what is known as first-pass
metabolism. Before alcohol reaches the blood stream, it goes through the stomach, where so-called gastric alcohol
dehydrogenase (ADH) isozymes break some of it down. "In an earlier study we found that women have less of this
ADH activity than men do," notes lead author Charles Lieber of the Mount Sinai School of Medicine. "Accordingly,
women have a lesser first-pass metabolism and, therefore, for a given dose of alcohol, their blood level is higher
than it is for men."
Following up on that research, the team recently turned their attention to the makeup of ADH. They found
that one of the enzyme's three components, glutathione-dependent fomaldehyde dehydrogenase (x-ADH), is
deficient in women, thus explaining their lower ADH activity levels. To Schenker, the take-home message is clear:
"Women simply need to be more cautious than males in terms of the amount of drinking they do." (From Scientific
American Online, April 16, 2001)
Text B. Data Trends Suggest Women Will Outrun Men in 2156
By Sarah Graham
Every four years, athletes from around the world travel to the Olympic Games to compete in the 100-meter
dash, hoping to earn title of fastest man or woman on Earth. A new statistical analysis suggests that in the year
2156, the winner of the women's event may finally outrun her male counterpart.
Andrew J. Tatem of the University of Oxford and his colleagues collected the finishing times in the men's
100-meter dash run in 1900 and from 1928 (when the women's race was first run) to 2004. The winning times for
both genders have been steadily decreasing, with female competitors improving at a slightly faster clip than the
males. By plotting the results against the year of competition and extrapolating the results, the team determined
that the fastest human on the planet could be a woman after the 2156 games. In today's issue of the journal
Nature, they report with a 5 percent margin of error that the event could take place as soon as 2064 or as late as
2788, however.
Tatem is the first to admit that the study represents a purely academic exercise. A disease researcher by
trade, he says the new study was a result of noticing a strong and interesting trend in sprinting. Indeed, the
relationship was surprisingly linear and no other model fit the data as well. “We decided to throw caution to the wind
and see if current trends continued, what would happen in the future,” he remarks. Potential confounding factors
that are not addressed in the new analysis include illegal drug use, environmental conditions on race day, national
boycotts and timing accuracy. In addition, some researchers contend that humans are hurtling toward the limits of
their potential and that the winning times predicted for 2156 (8.079 seconds for the female champion and 8.098
seconds for the male winner) are simply beyond our grasp. The next chance to check the trend comes in 2008 at
Beijing. (From Scientific American Online, September 30, 2004)
Exercise 8. Summarize all the information discussed in this unit and speak on the role of the sexes in
nature.
49
Unit 14. Aging
What makes old age hard to bear is not the failing
of one’s faculties, mental and physical but the
burden of one’s memories.
W. Somerset Maugham
The body is most fully developed from thirty to
thirty-five years of age, the mind at about fortynine.
Aristotle
Exercise 1. What do you know about aging?
1. What is aging?
2. What changes take place in human organism with age?
3. How does aging affect the human brain?
4. Is aging genetically programmed?
5. Can aging be stopped or avoided?
6. Do age-related diseases result from aging?
Exercise 2. Read the article below and find answers to the questions:
a. How does the text define and explain aging?
b. What is the relation between aging and diseases?
c. Do the authors agree that aging is genetically programmed? Why?
No Truth to the Fountain of Youth
What Aging Is... and Isn’t
By S. Jay Olshansky, Leonard Hayflick and Bruce A. Carnes
Any discussion of aging should first clarify its terms. Various definitions have been proposed, but we think of
aging as the accumulation of random damage to the building blocks of life—especially to DNA, certain proteins,
carbohydrates and lipids (fats)—that begins early in life and eventually exceeds the body’s self-repair capabilities.
This damage gradually impairs the functioning of cells, tissues, organs and organ systems, thereby increasing
vulnerability to disease and giving rise to the characteristic manifestations of aging, such as a loss of muscle and
bone mass, a decline in reaction time, compromised hearing and vision, and reduced elasticity of the skin.
This accretion of molecular damage comes from many sources, including, ironically, the life-sustaining
processes involved in converting the food we eat into usable energy. As the energy generators of cells
(mitochondria) operate, they emit destructive, oxidizing molecules known as free radicals. Most of the damage
caused by these reactive molecules gets repaired, but not all. Biologists suspect that the oxidative assaults
ultimately cause irreparable injury to the mitochondria, thereby impeding the cell’s ability to maintain the integrity of
the countless molecules needed to keep the body operating properly. The free radicals may also disrupt other
parts of cells directly.
Aging, in our view, makes us ever more susceptible to such ills as heart disease, Alzheimer’s disease,
stroke and cancer, but these age-related conditions are superimposed on aging, not equivalent to it. Therefore,
even if science could eliminate today’s leading killers of older individuals, aging would continue to occur, ensuring
that different maladies would take their place. In addition, it would guarantee that one crucial body component or
another—say, the cardiovascular system—would eventually experience a catastrophic failure. It is an inescapable
biological reality that once the engine of life switches on, the body inevitably sows the seeds of its own destruction.
Men and women in the developed world typically live longer now (75 and 80 years, respectively) than they
did throughout much of history (about 25 years) because human ingenuity—which brought us sanitation systems,
vaccines, antibiotics and so on—has had phenomenal success in thwarting the infectious and parasitic diseases
responsible for a great deal of premature death. We live longer now not because we have altered the way we age
but because we have altered the way we live.
Though inevitable, aging is not, as some might think, a genetically programmed process, playing itself out on
a rigidly predetermined time schedule. The way evolution works makes it impossible for us to possess genes that
are specifically designed to cause physiological decline with age or to control how long we live. Just as an
automobile does not have a built-in plan for decline written in its blueprints, we do not possess genetic instructions
that tell our bodies how to age or when to die.
The logic behind this assertion goes basically like this: Genes perpetuate themselves by orchestrating the
transformation of a fertilized egg into a sexually mature adult that produces offspring. Clearly, any genetic variant
that compromises this developmental process would be self-eliminating. Conversely, evolution is totally blind to the
consequences of gene action (whether good, bad or indifferent) after reproduction is achieved. Genes or genetic
variants that prove detrimental in the postreproductive part of the life span can become commonplace, but only if
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they participate in important processes early on. For example, several genes that contribute to cancer in the later
years are known to participate in growth and development early in life.
Without a doubt, a host of our genes influence aging, but they do so indirectly, as an inadvertent by-product
of processes involved in growth, development, and the maintenance of health and vigor. The lack of a specific
genetic program for aging and death means that there are no quick fixes that will permit us to treat aging as if it
were a disease. A single genetic intervention in an organism as complex as a human being would have little
chance of combating the probably vast array of genes and biological activities that play subtle, unpredictable parts
in the timing of our ultimate demise. (From Scientific American Online, December 29, 2008)
Exercise 3. You are going to read an article about centenarians – people who are more than 100 years old.
Before reading discuss the following questions:
1. Are there any biological limits to human life span?
2. Have people reached the upper limit of longevity?
3. How can average life expectancy be increased?
4. Would you like to live to be a hundred years old? Why? Why not?
Exercise 4. Read the text.
Is 100 the New 80?: Centenarians Studied to Find the Secret of Longevity
Healthy aging may be possible with some genetic help
By Barbara Juncosa
Centenarians—those who live past age 100—may help researchers find the key to living longer, healthier
lives. The reason, say scientists who study this elite group: centenarians may possess genes that protect them
from disease into old age. One in every 10,000 individuals in the U.S. reaches the age of 100. There are currently
an estimated 60,000 centenarians in the U.S. with up to 70 beyond the age of 110. For the past decade,
researchers have marveled at these folks who often live independently—and free of major disabilities—well into
their 90s, if not longer.
To better understand their exceptional longevity, scientists have recruited centenarians for extensive physical
and genetic screening. Of particular interest to researchers is that some of the oldsters have a history of obesity
and heavy smoking. But despite these risk factors, most centenarians remain healthy up to the last few months of
their lives and, in some cases, up until their dying breaths.
Although sheer luck no doubt plays a role, "there is also a striking family history that supports a genetic
component," says Nir Barzilai, a geneticist at the Albert Einstein College of Medicine in New York City. In fact, he
adds, the odds of centenarians having a relative who lived into old age is 20 times that of the average person. The
goal now is "to find the subtle genetic differences between individuals in the genes or families of genes associated
with longevity," says Judith Campisi, a senior scientist at the Lawrence Berkeley National Laboratory in California.
By understanding the underlying biology of aging, she notes, it may be possible to develop drugs in the future that
will promote healthy aging and delay age-related diseases such as some cancers, arthritis, diabetes, high blood
pressure and heart disease.
The first genetic clues for slowing aging emerged from animal models in which the effect of individual genes
on average life spans could be tested. From these early studies, it became clear that insulin (a hormone secreted
by the pancreas that signals cells to absorb sugar) and its receptors are critical for longevity in species from yeast
or fungi to humans. Insulin lies at the heart of the "biological pathway whose main function is to affect how
efficiently we process food into energy," says Bradley Willcox, a geriatrics specialist at the University of Hawaii. His
team recently found that a variant in the insulin-pathway gene, FOXO3A, in Japanese men over age 95 was
associated with improved energy usage and greater sensitivity to insulin. (Type 2 diabetes, marked by resistance to
insulin, now affects 24 million people in the U.S. alone.)
Examining the blood profiles of centenarians has also yielded tantalizing targets for further study. Barzilai
observed that centenarians had higher levels and larger particles of HDL—high-density lipoprotein, or the so-called
good cholesterol. Genetic screening later revealed that 24 percent of centenarians from Ashkenazi Jewish
populations carry a variant in the CETP gene—an enzyme important for cholesterol metabolism—that reduces the
level of the protein CETP in the blood and is linked to a lower prevalence of hypertension, cardiovascular disease
and memory loss.
CETP inhibitors have been sought by the pharmaceutical industry as a method for increasing HDL levels and
protecting patients against heart disease. But clinical trials of such a drug, Pfizer's Torcetrapib, were halted in 2006
when investigators discovered that it was associated with an increased risk of death from heart attack and other
complications, including cancers and infections.
Daniel Rader, a cardiologist at the University of Pennsylvania School of Medicine in Philadelphia, remains
optimistic, however, that other CETP inhibitors could work, because the failure of Torcetrapib was likely due to
"effects on blood pressure that were unrelated to CETP inhibition." Pharmaceutical giant Merck is currently testing
a new CETP inhibitor, Anacetrapib, but Rader cautions that any potential longevity benefits could simply stem from
the drug's ability to decrease the risk of heart disease—the number one killer in the U.S.
More expansive genetic studies are now underway as researchers "look at the rate of genetic variation
across the entire genome" of centenarians, says Thomas Perls, director of the New England Centenarian Study at
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Boston University. By examining over one million gene variations, scientists hope to find additional target genes for
longevity studies that may not be obvious from blood screening and animal testing.
Perls acknowledges that the research is controversial as critics insist that centenarians may be too
genetically diverse to pinpoint any common factors that promote healthy aging. But he points out that
supercentenarians (those living past age 110) share even more genetic factors than centenarians, possibly
improving the chances of finding protective gene variants. "We already know what it takes for the vast majority of
us to reach our late 80s in good health," Perls says. That is, stop smoking, exercise, eat a balanced diet and
manage stress. "The trick will be to get people from 88 to 100," Perls adds, "but there will never be a magic bullet."
(From Scientific American Online, October 28, 2008)
Exercise 4. Who are the following scientists mentioned in the article? What point of view do they
represent? What studies have they carried out?
• Daniel Rader
• Thomas Perls
• Nir Barzilai
• Bradley Willcox
• Judith Campisi
Exercise 5. Answer the questions:
1. Who are centenarians? What is so special about this group of people?
2. What gives scientists reasons to believe that there may be some genetic factors involved in the longevity
of centenarians?
3. What is the role of insulin in fighting aging?
4. Why are expansive genetic studies necessary to uncover the secrets of longevity?
Exercise 6. Read the chapter from the book Brain Facts: a Primer on the Brain and Nervous System, 2002.
What changes occur to the brain as people age?
Picasso, Georgia O’Keefe and Grandma Moses, artists. Louise Nevelson, sculptor. Albert Einstein, physicist.
Giuseppe Verdi, musician. Robert Frost, poet. Each of these great minds worked differently, but they all shared an
outstanding trait: they were creative and productive in old age. They defied the popular notion that aging always
leads to a pronounced decline and loss of cognitive ability.
Neuroscientists now believe that the brain can remain relatively healthy and fully functioning as it ages, and
that diseases are the causes of the most severe decline in memory, intelligence, verbal fluency and other tasks.
Researchers are investigating the normal changes that occur over time and the effect that these changes have on
reasoning and other intellectual activities.
It appears that the effects of age on brain function vary widely. The vast majority of people get only a bit
forgetful in old age, particularly in forming memories of recent events. For example, once you reach your 70s, you
may start to forget names or phone numbers, or respond more slowly to conflicting information. This is not disease.
However, other individuals develop senile dementia, the progressive and severe impairment in mental function that
interferes with daily living. The senile dementias include Alzheimer’s and cerebrovascular diseases and affect
about one percent of people younger than age 65, with the incidence increasing to nearly 50 percent in those older
than 85. In a small, third group, that includes the Picassos, Einsteins and others, mental functioning seems
unaffected by age. The oldest human, Jeanne Calment, was considered to have all her wits during her 122-year
lifespan. The wisdom and experience of older people often make up for deficits in performance.
The belief that pronounced and progressive mental decline is inevitable was and still is popular for several
reasons. For one, until the 20th century, few people lived to healthy old ages. In 1900, when life expectancy was
about 47 years, three million people, or four percent of the population, were older than age 65, and typically they
were ill. In 1990, when life expectancy was more than 75 years, 30 million people, or 12 percent of the population,
were older than age 65. A generation ago, frailty was seen among people in their 60s; today it is more typical
among those in their 80s. Moreover, few people challenged the notion that aging meant inevitable brain decline
because scientists knew little about the brain or the aging process.
Aging neurons
Today’s understanding of how the normal brain ages comes from studies of the nervous system that began
decades ago and are just now bearing results. Modern technologies now make it possible to explore the structure
and functions of the brain in more depth than ever before and to ask questions about what actually happens in its
aging cells. Thus, neuroscientists are increasingly able to distinguish between the processes of normal aging and
disease. While some changes do occur in normal aging, they are not as severe as scientists once thought.
All human behavior is determined by how well the brain’s communication systems work. Often a failure in the
cascade of one of these systems results in a disturbance of normal functions. Such a failure may be caused by an
abnormal biochemical process or by a loss of neurons.
The cause of brain aging still remains a mystery. Dozens of theories abound. One says that specific “aging
genes” are switched on at a certain time of life. Another points to genetic mutations or deletions. Other theories
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implicate hormonal influences, an immune system gone awry and the accumulation of damage caused by cell
byproducts that destroy fats and proteins vital to normal cell function.
The brain reaches its maximum weight near age 20 and slowly loses about 10 percent of its weight over a
lifetime. Subtle changes in the chemistry and structure of the brain begin at midlife in most people. During a
lifetime, the brain is at risk for losing some of its neurons, but neuron loss is not a normal process of aging. Brain
tissue can respond to damage or loss of neurons in Alzheimer’s disease or after stroke by expanding dendrites and
refining connections between neurons. A damaged brain neuron can readjust to damage only if its cell body
remains intact. If it does, regrowth can occur in dendrites and axons. When neurons are completely destroyed,
nearby surviving neurons can compensate, in part, by growing new dendrites and connections.
Intellectual capacity
In the first large studies to follow the same group of normal healthy humans for many years, scientists have
uncovered unexpected results. They report declines in some mental functions and improvements in others. In one
study, the speed of carrying out certain tasks became slower, but vocabulary improved. Several studies found less
severe declines in the type of intelligence relying on learned or stored information, compared with the type that
uses the ability to deal with new information.
This research is supported by animal studies in which scientists found that changes in mental function are
subtle. For example, in rodents and primates in which only minor brain abnormalities can be detected, certain
spatial tasks, such as navigating to find food, tend to become more difficult with age.
The aging brain is only as resilient as its circuitry. Scientists debate whether this circuitry is changed only by
neuron atrophy or whether some neuron loss over time also is inevitable. In any event, when the circuitry begins to
break down, remaining neurons can respond by expanding their roles.
Learning conditions may dictate what happens to brain cells. Studies of rats shed light on some of the
changes that occur in brain cells when the animals live in challenging and stimulating environments. In tests of
middle-aged rats exposed to these environments, researchers found that dendrites in the cerebral cortex, which is
responsible for all conscious activity, developed more and longer branches when compared with rats housed in
isolated conditions. Another study showed that brain cells in rats given acrobatic training had greater numbers of
synapses per cell than rats given only physical exercise or rats who were inactive. The scientists concluded that
motor learning generates new synapses. Physical exercise, however, improved blood circulation in the brain.
Other scientists report that rats reared in a stimulating environment made significantly fewer errors on a
maze test than did similar rats kept in an isolated environment. Moreover, the stimulated rats showed an increase
in brain weight and cortical thickness when compared with the control animals.
Older rats tend to form new dendrites and synapses as do younger animals in response to enriched
environments. But the response is more sluggish and not as large. Compared to younger rats, the older rats have
less growth of the new blood vessels that nourish neurons.
While much has been learned about the aging brain, many questions remain to be answered. For instance,
does the production of proteins decline with age in all brain neurons? In a given neuron, does atrophy cause a
higher likelihood of death? How does aging affect gene expression in the brain—the organ with the greatest
number of active genes? Are there gender differences in brain aging that may be due to hormonal changes at
menopause?
Neuroscientists speculate that certain genes may be linked to events leading to death in the nervous system.
By understanding the biology of the proteins produced by genes, scientists hope to be able to influence the survival
and degeneration of neurons. (From the book Brain Facts: a Primer on the Brain and Nervous System, 2002)
Exercise 7. Are the following statements true of false, according to the text? Explain your opinion, correct
the false statements.
1. Mental decline with age is caused by loss of neurons.
2. Healthy aging is accompanied by a considerable loss of memory.
3. Nerve cells can both age and regenerate with time.
4. Neurons respond very slowly to the change of environment and lifestyle.
5. Age can bring some improvement of mental activity.
Exercise 8. Summarize all the information about age-related transformations in the human organism
discussed in this unit and speak on aging and the current research in this sphere.
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Unit 15. Food
Then I commended mirth, because a man hath
no better thing under the sun, than to eat, and
to drink, and to be merry.
Ecclesiastes 8:15:
One should eat to live, not live to eat.
Cicero
There is no love sincerer than the love of food.
George Bernard Shaw
Exercise 1. What do you know about food?
1. What nutrients are necessary for human life?
2. Why are vitamins and minerals necessary?
3. How much food should people consume? What does the daily norm of food consumption depend on?
4. What is generally understood as “healthy diet”?
5. What food products are considered healthy and unhealthy? Why?
6. What factors can lead to overweight and obesity?
7. What role have dietary habits played in human evolution?
8. How did cooking food affect human physiology?
Exercise 2. The article below deals with the role of dietary habits in human evolution. As you read the text,
find answers to the questions:
1. What were the main dietary shifts in human evolution?
2. What changes have they led to?
Food for Thought
Dietary change was a driving force in human evolution
By William R. Leonard
We humans are strange primates. We walk on two legs, carry around enormous brains and have colonized
every corner of the globe. Anthropologists and biologists have long sought to understand how our lineage came to
differ so profoundly from the primate norm in these ways, and a growing body of evidence indicates that these
miscellaneous quirks of humanity in fact have a common thread: they are largely the result of natural selection
acting to maximize dietary quality and foraging efficiency. Changes in food availability over time, it seems, strongly
influenced our hominid ancestors. Thus, in an evolutionary sense, we are very much what we ate.
So when and how did our ancestors’ eating habits diverge from those of other primates? Further, to what
extent have modern humans departed from the ancestral dietary pattern?
To appreciate the role of diet in human evolution, we must remember that the search for food, its
consumption and, ultimately, how it is used for biological processes are all critical aspects of an organism’s
ecology. The energy dynamic between organisms and their environments—that is, energy expended in relation to
energy acquired—has important adaptive consequences for survival and reproduction. The type of environment a
creature inhabits will influence the distribution of energy into maintenance energy (which keeps an animal alive on
a day-to-day basis) and productive energy (which, on the other hand, is associated with producing and raising
offspring covering the increased costs that mothers incur during pregnancy and lactation). Thus, by looking at the
way animals go about obtaining and then allocating food energy, we can better discern how natural selection
produces evolutionary change.
Becoming Bipeds
Without exception, living nonhuman primates habitually move around on all fours, or quadrupedally, when
they are on the ground. Scientists generally assume therefore that the last common ancestor of humans and
chimpanzees (our closest living relative) was also a quadruped. Exactly when the last common ancestor lived is
unknown, but clear indications of bipedalism—the trait that distinguished ancient humans from other apes—are
evident in the oldest known species of Australopithecus, which lived in Africa roughly four million years ago. Ideas
about why bipedalism evolved abound in the paleoanthropological literature. C. Owen Lovejoy of Kent State
University proposed in 1981 that two-legged locomotion freed the arms to carry children and foraged goods. More
recently, Kevin D. Hunt of Indiana University has posited that bipedalism emerged as a feeding posture that
enabled access to foods that had previously been out of reach. Peter Wheeler of Liverpool John Moores University
submits that moving upright allowed early humans to better regulate their body temperature by exposing less
surface area to the blazing African sun.
The list goes on. In reality, a number of factors probably selected for this type of locomotion. My own
research, conducted in collaboration with my wife, Marcia L. Robertson, suggests that bipedalism evolved in our
ancestors at least in part because it is less energetically expensive than quadrupedalism. Our analyses of the
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energy costs of movement in living animals of all sizes have shown that, in general, the strongest predictors of cost
are the weight of the animal and the speed at which it travels. What is striking about human bipedal movement is
that it is notably more economical than quadrupedal locomotion at walking rates.
For hominids living between five million and 1.8 million years ago, during the Pliocene epoch, climate change
spurred this morphological revolution. As the African continent grew drier, forests gave way to grasslands, leaving
food resources patchily distributed. In this context, bipedalism can be viewed as one of the first strategies in human
nutritional evolution, a pattern of movement that would have substantially reduced the number of calories spent in
collecting increasingly dispersed food resources. Indeed, modern human hunter-gatherers living in these
environments, who provide us with the best available model of early human subsistence patterns, often travel six to
eight miles daily in search of food.
Big Brains and Hungry Hominids
No sooner had humans perfected their stride than the next pivotal event in human evolution—the dramatic
enlargement of the brain—began. According to the fossil record, the australopithecines never became much
brainier than living apes, showing only a modest increase in brain size, from around 400 cubic centimeters four
million years ago to 500 cubic centimeters two million years later. Homo brain sizes, in contrast, ballooned from
600 cubic centimeters in H. habilis some two million years ago up to 900 cubic centimeters in early H. erectus just
300,000 years later. The H. erectus brain did not attain modern human proportions (1,350 cubic centimeters on
average), but it exceeded that of living nonhuman primates.
From a nutritional perspective, what is extraordinary about our large brain is how much energy it
consumes—roughly 16 times as much as muscle tissue per unit weight. We therefore use a much greater share of
our daily energy budget to feed our voracious brains. In fact, at rest brain metabolism accounts for a whopping 20
to 25 percent of an adult human’s energy needs—far more than the 8 to 10 percent observed in nonhuman
primates, and more still than the 3 to 5 percent allotted to the brain by other mammals.
How did such an energetically costly brain evolve? One theory, developed by Dean Falk of Florida State
University, holds that bipedalism enabled hominids to cool their cranial blood, thereby freeing the heat-sensitive
brain of the temperature constraints that had kept its size in check. I suspect that, as with bipedalism, a number of
selective factors were probably at work. But brain expansion almost certainly could not have occurred until
hominids adopted a diet sufficiently rich in calories and nutrients to meet the associated costs.
Comparative studies of living animals support that assertion. Across all primates, species with bigger brains
dine on richer foods, and humans are the extreme example of this correlation, boasting the largest relative brain
size and the choicest diet. According to recent analyses by Loren Cordain of Colorado State University,
contemporary hunter-gatherers derive, on average, 40 to 60 percent of their dietary energy from animal foods
(meat, milk and other products). Modern chimps, in comparison, obtain only 5 to 7 percent of their calories from
these comestibles. Animal foods are far denser in calories and nutrients than most plant foods. It stands to reason,
then, that for early Homo, acquiring more gray matter meant seeking out more of the energy-dense fare.
Fossils, too, indicate that improvements to dietary quality accompanied evolutionary brain growth. All
australopithecines had skeletal and dental features built for processing tough, low-quality plant foods. The later,
robust australopithecines—a dead-end branch of the human family tree that lived alongside members of our own
genus—had especially pronounced adaptations for grinding up fibrous plant foods, including massive, dish-shaped
faces; heavily built mandibles; ridges, or sagittal crests, atop the skull for the attachment of powerful chewing
muscles; and huge, thickly enameled molar teeth. (This is not to say that australopithecines never ate meat. They
almost certainly did on occasion, just as chimps do today.) In contrast, early members of the genus Homo, which
descended from the gracile australopithecines, had much smaller faces, more delicate jaws, smaller molars and no
sagittal crests—despite being far larger in terms of overall body size than their predecessors. Together these
features suggest that early Homo was consuming less plant material and more animal foods.
As to what prompted Homo’s initial shift toward the higher-quality diet necessary for brain growth,
environmental change appears to have once more set the stage for evolutionary change. The continued
desiccation of the African landscape limited the amount and variety of edible plant foods available to hominids.
Those on the line leading to the robust australopithecines coped with this problem morphologically, evolving
anatomical specializations that enabled them to subsist on more widely available, difficult to chew foods. Homo
took a different path. As it turns out, the spread of grasslands also led to an increase in the relative abundance of
grazing mammals such as antelope and gazelle, creating opportunities for hominids capable of exploiting them. H.
erectus did just that, developing the first hunting-and-gathering economy in which game animals became a
significant part of the diet and resources were shared among members of the foraging groups. Signs of this
behavioral revolution are visible in the archaeological record, which shows an increase in animal bones at hominid
sites during this period, along with evidence that the beasts were butchered using stone tools.
These changes in diet and foraging behavior did not turn our ancestors into strict carnivores; however, the
addition of modest amounts of animal foods to the menu, combined with the sharing of resources that is typical of
hunter-gatherer groups, would have significantly increased the quality and stability of hominid diets. Improved
dietary quality alone cannot explain why hominid brains grew, but it appears to have played a critical role in
enabling that change. After the initial spurt in brain growth, diet and brain expansion probably interacted
synergistically: bigger brains produced more complex social behavior, which led to further shifts in foraging tactics
and improved diet, which in turn fostered additional brain evolution.
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A Movable Feast
The evolution of H. erectus in Africa 1.8 million years ago also marked a third turning point in human
evolution: the initial movement of hominids out of Africa. Until recently, the locations and ages of known fossil sites
suggested that early Homo stayed put for a few hundred thousand years before venturing out of the motherland
and slowly fanning out into the rest of the Old World. Earlier work hinted that improvements in tool technology
around 1.4 million years ago—namely, the advent of the Acheulean hand ax—allowed hominids to leave Africa. But
new discoveries indicate that H. erectus hit the ground running, so to speak. Rutgers University geochronologist
Carl Swisher III and his colleagues have shown that the earliest H. erectus sites outside of Africa, which are in
Indonesia and the Republic of Georgia, date to between 1.8 million and 1.7 million years ago. It seems that the first
appearance of H. erectus and its initial spread from Africa were almost simultaneous.
The impetus behind this newfound wanderlust again appears to be food. What an animal eats dictates to a
large extent how much territory it needs to survive. Carnivorous animals generally require far bigger home ranges
than do herbivores of comparable size because they have fewer total calories available to them per unit area.
Large-bodied and increasingly dependent on animal foods, H. erectus most likely needed much more turf than the
smaller, more vegetarian australopithecines did. Exactly how far beyond the continent that shift would have taken
H. erectus remains unclear, but migrating animal herds may have helped lead it to these distant lands.
Modern Quandaries
Just as pressures to improve dietary quality influenced early human evolution, so, too, have these factors
played a crucial role in the more recent increases in population size. Innovations such as cooking, agriculture and
even aspects of modern food technology can all be considered tactics for boosting the quality of the human diet.
Cooking, for one, augmented the energy available in wild plant foods. With the advent of agriculture, humans
began to manipulate marginal plant species to increase their productivity, digestibility and nutritional content—
essentially making plants more like animal foods. This kind of tinkering continues today, with genetic modification of
crop species to make “better” fruits, vegetables and grains. Similarly, the development of liquid nutritional
supplements and meal replacement bars is a continuation of the trend that our ancient ancestors started: gaining
as much nutritional return from our food in as little volume and with as little physical effort as possible.
Overall, that strategy has evidently worked: humans are here today and in record numbers to boot. But
perhaps the strongest testament to the importance of energy- and nutrient-rich foods in human evolution lies in the
observation that so many health concerns facing societies around the globe stem from deviations from the energy
dynamic that our ancestors established. For children in rural populations of the developing world, low quality diets
lead to poor physical growth, smaller weight and height and high rates of mortality during early life. In these cases,
the foods fed to youngsters during and after weaning are often not sufficiently dense in energy and nutrients to
meet the high nutritional needs associated with this period of rapid growth and development.
In the industrial world, we are facing the opposite problem: rates of childhood and adult obesity are rising
because the energy-rich foods we crave—notably those packed with fat and sugar—have become widely available
and relatively inexpensive. According to recent estimates, more than half of adult Americans are overweight or
obese. Obesity has also appeared in parts of the developing world where it was virtually unknown less than a
generation ago. This seeming paradox has emerged as people who grew up malnourished move from rural areas
to urban settings where food is more readily available. In some sense, obesity and other common diseases of the
modern world are continuations of a tenor that started millions of years ago. We are victims of our own evolutionary
success, having developed a calorie-packed diet while minimizing the amount of maintenance energy expended on
physical activity.
The magnitude of this imbalance becomes clear when we look at traditionally living human populations.
Studies of the Evenki reindeer herders that I have conducted in collaboration with Michael Crawford of the
University of Kansas and Ludmila Osipova of the Russian Academy of Sciences in Novosibirsk indicate that the
Evenki derive almost half their daily calories from meat, more than 2.5 times the amount consumed by the average
American. Yet when we compare Evenki men with their U.S. peers, they are 20 percent leaner and have
cholesterol levels that are 30 percent lower.
These differences partly reflect the compositions of the diets. Although the Evenki diet is high in meat, it is
relatively low in fat (about 20 percent of their dietary energy comes from fat, compared with 35 percent in the
average U.S. diet), because free-ranging animals such as reindeer have less body fat than cattle and other feedlot
animals do. The composition of the fat is also different in free-ranging animals, tending to be lower in saturated fats
and higher in the polyunsaturated fatty acids that protect against heart disease. More important, however, the
Evenki way of life necessitates a much higher level of energy expenditure.
Thus, it is not just changes in diet that have created many of our pervasive health problems but the
interaction of shifting diets and changing lifestyles. Too often modern health problems are portrayed as the result of
eating “bad” foods that are departures from the natural human diet. This is a fundamentally flawed approach to
assessing human nutritional needs. Our species was not designed to subsist on a single, optimal diet. What is
remarkable about human beings is the extraordinary variety of what we eat. We have been able to thrive in almost
every ecosystem on the earth, consuming diets ranging from almost all animal foods among populations of the
Arctic to primarily tubers and cereal grains among populations in the high Andes. Indeed, the hallmarks of human
evolution have been the diversity of strategies that we have developed to create diets that meet our distinctive
metabolic requirements and the ever increasing efficiency with which we extract energy and nutrients from the
environment. (Feature article, abridged. From Scientific American, December 2002)
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Exercise 3. Which is the best summary of the text? Why?
Can you suggest your own variant of the summary?
A. Scientific interest in the evolution of human nutritional requirements has a long history. Some scientists
argued that the prevalence in modern societies of many chronic diseases—obesity, hypertension, coronary
heart disease and diabetes, among them—is the consequence of a mismatch between modern dietary
patterns and the type of diet that our species evolved to eat as prehistoric hunter-gatherers. Since then,
however, understanding of the evolution of human nutritional needs has advanced considerably—thanks to
new comparative analyses of traditionally living human populations and other primates—and a more
nuanced picture has emerged. We now know that humans have evolved not to subsist on a single,
Paleolithic diet but to be flexible eaters, an insight that has important implications for the current debate
over what people today should eat in order to be healthy. The challenge our modern societies now face is
balancing the calories we consume with the calories we burn.
B. Contemporary human populations the world over have diets richer in calories and nutrients than those of
our cousins, the great apes. Differences in the settings in which humans and apes evolved may help
explain the variation in costs of movement. Chimps, gorillas and orangutans evolved in and continue to
occupy dense forests where only a mile or so of trekking over the course of the day is all that is needed to
find enough to eat. Much of early hominid evolution, on the other hand, took place in more open woodland
and grassland, where sustenance is harder to come by. Thus, for far-ranging foragers, cost-effective
walking saves many calories in maintenance energy needs—calories that can instead go toward
reproduction. Selection for energetically efficient locomotion is therefore likely to be more intense among
far-ranging animals because they have the most to gain.
Exercise 4. You are going to interview your fellow-students. Make up 15 questions about the key facts
discussed in the article.
Exercise 5. Fruits and vegetables in our diet.
Discuss the following questions:
1. What is the role of fruits and vegetables in a healthy diet?
2. Should we cook vegetables or eat them raw? Why?
3. Which cooking techniques allow to preserve healthy substances found in fruits and vegetables and which,
on the contrary, can produce negative effects on one’s health?
Exercise 6. Read the article below to check some of your answers in Exercise 5.
Raw veggies are healthier than cooked ones
Do vegetables lose their nutritional value when heated?
By Sushma Subramanian
Cooking is crucial to our diets. It helps us digest food without expending huge amounts of energy. It softens
food, such as cellulose fiber and raw meat, that our small teeth, weak jaws and digestive systems aren't equipped
to handle. And while we might hear from raw foodists that cooking kills vitamins and minerals in food (while also
denaturing enzymes that aid digestion), it turns out raw vegetables are not always healthier.
A study published in The British Journal of Nutrition last year found that a group of 198 subjects who followed
a strict raw food diet had normal levels of vitamin A and relatively high levels of beta-carotene (an antioxidant found
in dark green and yellow fruits and vegetables), but low levels of the antioxidant lycopene. Lycopene is a red
pigment found predominantly in tomatoes and other rosy fruits such as watermelon, pink guava, red bell pepper
and papaya. Several studies conducted in recent years (at Harvard Medical School, among others) have linked
high intake of lycopene with a lower risk of cancer and heart attacks. Rui Hai Liu, an associate professor of food
science at Cornell University who has researched lycopene, says that it may be an even more potent antioxidant
than vitamin C.
One 2002 study he did (published in the Journal of Agriculture and Food Chemistry) found that cooking
actually boosts the amount of lycopene in tomatoes. He reports that the level of one type of lycopene, cis-lycopene,
in tomatoes rose 35 percent after he cooked them for 30 minutes at 190.4 degrees Fahrenheit (88 degrees
Celsius). The reason, he says: the heat breaks down the plants' thick cell walls and aids the body's uptake of some
nutrients that are bound to those cell walls.
Cooked carrots, spinach, mushrooms, asparagus, cabbage, peppers and many other vegetables also supply
more antioxidants, such as carotenoids and ferulic acid, to the body than they do when raw, Liu says. At least, that
is, if they're boiled or steamed. A January 2008 report in the Journal of Agriculture and Food Chemistry said that
boiling and steaming better preserves antioxidants, particularly carotenoid, in carrots, zucchini and broccoli, than
frying, though boiling was deemed the best. The researchers studied the impact of the various cooking techniques
on compounds such as carotenoids, ascorbic acid and polyphenols.
Deep fried foods are notorious sources of free radicals, caused by oil being continuously oxidized when it is
heated at high temperatures. These radicals, which are highly reactive because they have at least one unpaired
57
electron, can injure cells in the body. The antioxidants in the oil and the vegetables get used up during frying in
stabilizing the cycle of oxidation.
Another study published in the Journal of Agricultural and Food Chemistry in 2002 showed that cooking
carrots increases their level of beta-carotene. Beta-carotene belongs to a group of antioxidant substances called
carotenoids, which give fruits and vegetables their red, yellow, and orange colorings. The body converts betacarotene into vitamin A, which plays an important role in vision, reproduction, bone growth and regulating the
immune system.
The downside of cooking veggies, Liu says: it can destroy the vitamin C in them. He found that vitamin C
levels declined by 10 percent in tomatoes cooked for two minutes—and 29 percent in tomatoes that were cooked
for half an hour at 190.4 degrees F (88 degrees C). The reason is that Vitamin C, which is highly unstable, is easily
degraded through oxidation, exposure to heat (it can increase the rate at which vitamin C reacts with oxygen in the
air) and through cooking in water (it dissolves in water). Liu notes, however, that the trade-off may be worth it since
vitamin C is prevalent in far more fruits and vegetables than is lycopene. Among them: broccoli, oranges,
cauliflower, kale and carrots. Besides, cooked vegetables retain some of their vitamin C content.
That said, research shows that some veggies, including broccoli, are healthier raw rather than cooked.
According to a study in the Journal of Agricultural and Food Chemistry in November 2007, heat damages the
enzyme myrosinase, which breaks down glucosinates (compounds derived from glucose and an amino acid) in
broccoli into a compound known as sulforaphane. Research published in the journal Carcinogenesis in December
2008 found that sulforaphane might block the proliferation of and kill precancerous cells. A 2002 study in The
Proceedings of the National Academy of Sciences also found that sulforaphane may help fight the bacterium
Helicobacter pylori, which causes ulcers and increases a person's risk of stomach cancer.
On the other hand, indole, an organic compound, is formed when certain plants, particularly cruciferous
vegetables such as broccoli, cauliflower and cabbage, are cooked. According to research in The Journal of
Nutrition in 2001, indole helps kill precancerous cells before they turn malignant. And while boiling carrots was
found to increase carotenoid levels, another study found that it leads to a total loss of polyphenols, a group of
chemicals found in raw carrots. Specific polyphenols have been shown to have antioxidant properties and to
reduce the risk of cardiovascular disease and cancer, according to a 2005 report in The American Journal of
Clinical Nutrition.
Comparing the healthfulness of raw and cooked food is complicated, and there are still many mysteries
surrounding how the different molecules in plants interact with the human body. The bottom line, says Liu, is to eat
your veggies and fruits no matter how they're prepared. "We cook them so they taste better," Liu says. "If they taste
better, we're more likely to eat them." And that's the whole idea. (From Scientific American Online, March 31, 2009)
Exercise 7. What fruits and vegetables are mentioned in the text? Speak about each one and give detailed
information about the healthy substances it contains and what happens to it after cooking.
Exercise 8. Divide into three groups. Each group should read one text (either Text A, B or C) about various
effects of diet on human health. Then tell other students what you have read about.
Text A. Diet Linked to Twin Births
By David Biello
Over the last 30 years, the number of twin births has nearly trebled. This rise seems to have followed the
introduction of in vitro fertilization and a preference for having children later in life. But in the mid-1990s, doctors
began limiting the number of embryos transferred in the course of in vitro fertilization and still the proportion of twin
births rose. Now new research seems to show that bovine growth hormone in the food supply may be responsible.
Using data obtained from mothers by way of questionnaire, physician Gary Steinman of the Long Island
Jewish Medical Center and his colleagues compared the number of twin births from moms who consumed meat
and/or milk and those who consumed no animal products at all. They found that the omnivores and vegetarians
were five times more likely to have fraternal twins than the vegans. In a report published in the current issue of the
Journal of Reproductive Medicine, Steinman argues that insulin-like growth factor, a protein released by the liver in
response to growth hormone, may be the reason. Studies have shown that the protein increases ovulation and that
it persists in the body after entering via digested food, particularly milk. Drinking a glass of milk a day over a 12week period raised levels of the protein in the body by 10 percent. Vegan women, it turns out, have 13 percent
lower concentrations of it in their blood.
Steinman observed in the May 6 issue of The Lancet that although the twinning rate in the U.K.--where
bovine growth hormone is banned--rose by 16 percent between 1992 and 2001, it increased by 32 percent in the
U.S., where the substance is not banned. Of the new work he says: "This study shows for the first time that the
chance of having twins is affected both by heredity and environment or, in other words, by both nature and
nurture." (From Scientific American Online, May 22, 2006)
Text B. Diet May Cut Cholesterol As Much As Drugs Do
By Sarah Graham
Eating a diet similar to that of our simian relatives can have as much of an effect on cholesterol levels as
modern medicine does, a new study suggests. Results published today in the Journal of the American Medical
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Association indicate that a strict, low-fat vegetarian diet high in specific plant products can lower levels of bad
cholesterol as much as widely prescribed statin drugs can.
A number of foods, soy protein and oats among them, have known cholesterol-lowering effects. David J. A.
Jenkins of the University of Toronto and his colleagues tested a specific vegetarian diet that combined many of
these food groups into one menu that contained high amounts of plant sterols, fiber, nuts and soy protein. Of the 46
patients with high cholesterol levels that the team studied, 16 ate this diet for a month. A second group of 16 ate a
regular low-fat vegetarian diet and 14 participants consumed the low-fat diet and took 20 milligrams of lovastatin, a
standard cholesterol-reducing drug. At the end of the study period, those patients who ate the special diet lowered
their levels of LDL cholesterol (the "bad" type associated with clogging coronary arteries) by 29 percent whereas
the patients taking lovastatin reduced their LDL levels by 31 percent. The low-fat dieters, in contrast, showed just
an 8 percent decrease in the amount of LDL present. "As we age, we tend to get raised cholesterol, which in turn
increases our risk of heart disease," Jenkins explains. "This study shows that people now have a dietary alternative
to drugs to control their cholesterol, at least initially."
The results are still preliminary, however. Writing in an accompanying commentary, James W. Anderson of
the University of Kentucky notes that if the findings are confirmed by larger and more rigorous studies, they could
have far-reaching implications for many patients suffering from cholesterol problems. He notes "those who are
motivated to adopt prudent diets might achieve meaningful lipid reductions without pharmacotherapy." (From
Scientific American Online, July 23, 2003)
Text C. Additive Might Fight Fast-Food Fat
By Sarah Graham
In recent years fast food has been linked to the country's rising obesity rates and the increased incidence of
diabetes. Findings presented yesterday at the annual meeting of the American Chemical Society in San Diego may
provide a means of tempering the cuisine's ill effects: an additive that can slow the absorption of fat to a healthier
rate.
Wallace H. Yokoyama of the United States Department of Agriculture and his colleagues fed a group of
hamsters a diet with a fat content similar to that of typical American fast food--that is, with about 38 percent of its
calories derived from fat--for four weeks. A second group of animals ate a low-fat diet with 11 percent of the total
calories coming from fat. At the end of the study period, the high-fat eaters developed insulin resistance--a
precursor to diabetes--whereas the control animals did not. The initial results corroborated previous findings in
similar studies. But when the scientists repeated the experiment with the addition of a cellulose derivative known as
hydroxypropylmethylcellulose (HPMC) to the high-fat food, the animals on that diet did not develop insulin
resistance.
HPMC is already used as a food additive to modify the texture of items such as fillings, sauces and glazes.
To achieve similar fat-fighting results in humans, much larger amounts (about five grams per serving) would be
required, the scientists propose. The mechanism for HPMC's beneficial effects remains unclear, although
Yokoyama posits that the compound works to slow down the absorption of fat by the digestive system. The results,
which are preliminary, are not a panacea for fast-food devotees, however. "Obviously, the less fat you eat, the
better off you are," Yokoyama says. "But if you're going to eat high-fat foods, then adding HPMC to it might help
limit the damage." (From Scientific American Online, March 16, 2005)
Exercise 9. Summarize all the information about the role of diet discussed in this unit and speak on the
effects of food on human organism.
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Section 3. Recommended Report and Presentation Topics
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
“Out of Africa” migration theory.
Hutchinson syndrome.
Alzheimer’s disease.
Parkinson’s disease.
Why do people in the Caucasus traditionally live longer?
Age-related transformations in the organism.
Anti-age industry.
Impaired vision.
Wrinkles.
Pheromones.
The evolutionary role of sexual reproduction.
Hermaphrodites.
Parthenogenesis.
Eating disorders – bulimia, anorexia.
Why does fast food taste so good?
Health effects of fast food.
Dieting.
Vegetarians and vegans.
Internal organs transformation and alcoholism.
Prohibition and legal control of drugs.
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