semester review
Answer Section
2011 – 12
Berkheimer
SHORT ANSWER
1. ANS:
Spallanzani had excluded air from his experimental sealed jar, and other scientists hypothesized that air was a
necessary factor in the process of generating life because air contained the “life force” needed to produce new
life.
2. ANS:
Pasteur’s flask was designed so that air was allowed to flow into the jar of broth, but protected the broth from
microorganisms.
3. ANS:
Answers can include any five of the following: molecules, cells, groups of cells, organism, population,
community, ecosystem, biosphere.
4. ANS:
Mass number is the sum of the protons and neutrons in the nucleus of an atom.
5. ANS:
Add some salt—the solute—to a container of water—the solvent—to produce a salt solution.
6. ANS:
The four groups are carbohydrates, lipids, nucleic acids, and proteins.
7. ANS:
RNA contains the sugar ribose, and DNA contains the sugar deoxyribose.
8. ANS:
Energy flows from the sun to the autotrophs, and from the autotrophs to the heterotrophs. Energy also flows
from the autotrophs and the heterotrophs to the decomposers.
9. ANS:
geographic distribution, density, growth rate, and age structure
10. ANS:
The population that has 25 pine trees per acre has the higher density because it has the same population size in
a smaller area than the population with 25 trees per kilometer.
11. ANS:
Deforestation, especially when accomplished by burning, removes plants that use carbon dioxide in
photosynthesis. Burning trees produces carbon dioxide, which leads to global warming.
12. ANS:
Models of enormous phenomena such as global warming help scientists make predictions. Global warming is
an abiotic factor that affects ecosystems and the geographic distribution of species.
13. ANS:
(A) rough endoplasmic reticulum; (B) cytoplasm; (C) smooth endoplasmic reticulum; (D) nucleolus; (E)
nucleus; (F) mitochondrion; (G) Golgi apparatus; (H) ribosome; (I) cell membrane
14. ANS:
When a blood cell is placed in a hypertonic solution, the water flows from the blood cell, through the cell
membrane, into the solution. As a result of losing water, the cell shrinks.
15. ANS:
Autotrophs are organisms, such as plants, that can make their own food, and heterotrophs, such as animals,
must use food made by other organisms to get energy.
16. ANS:
17. ANS:
The structure shown is a chloroplast. Its main function is to carry out photosynthesis.
18. ANS:
Sample answer: Both simultaneously absorb light. Each generates a high-energy product that is used to power
the Calvin cycle.
19. ANS:
The three stages are as follows: glycolysis (which occurs in the cytoplasm), the Krebs cycle (which occurs in
the mitochondria), and electron transport (which occurs in the mitochondria).
20. ANS:
Glycolysis requires an initial input of 2 ATPs and produces 4 ATPs, for a net gain of 2 ATPs.
21. ANS:
Citric acid is the first compound formed in the process.
22. ANS:
Cancer cells do not respond to the signals that control the growth of normal cells. As a result, cancer cells
form tumors and can spread throughout the body.
ESSAY
23. ANS:
Anything lacking one or more of the following characteristics of life is nonliving: made up of cells;
reproduces, based on a universal genetic code; grows and develops; obtains and uses materials and energy;
responds to its environment; maintains a stable, internal environment; and, taken as a group, changes over
time.
24. ANS:
Accept all reasonable answers. The biologist could be studying the population of wolves, a specific organism,
or even a group of cells, a particular type of cell, or molecules found in the wolves’ bodies. The biologist
could also be studying how the wolves fit into the community of organisms in the northern Minnesota forest.
25. ANS:
A compound light microscope is used to view living cells and organisms. A transmission electron microscope
(TEM) is used to view dead cells or organisms when greater magnifications are needed. A scanning electron
microscope (SEM) is used for three-dimensional, enlarged views of the surfaces of dead organisms.
26. ANS:
Cell culturing is used to obtain material to study by placing a single cell into a nutrient solution. A group of
cells then develops from the single original cell. Cell fractionation separates the different parts of a cell, which
allows the study of a particular cell part.
27. ANS:
Protons and neutrons are located in the nucleus, whereas electrons are located outside the nucleus. Electrons
have a negative charge, protons have a positive charge, and neutrons have no charge. Protons and neutrons
have approximately the same mass, which is 1840 times that of an electron.
28. ANS:
Isotopes of an element have the same number of protons but different numbers of neutrons. Because the mass
number is the sum of the atomic number (number of protons) and the number of neutrons, isotopes of the
same element have different mass numbers.
29. ANS:
In an ionic compound, valence electrons of atoms of one element have been transferred to the atoms of
another element. Thus, ionic bonding involves the gain and loss of electrons. In covalently bonded
compounds, atoms of different elements share electrons.
30. ANS:
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Both adhesion and cohesion are attractions. They are different in that adhesion is the force of attraction
between the molecules of two different substances, whereas cohesion is the force of attraction between
molecules of the same substance. Possible examples include capillary action, in which the adhesion between
water and glass causes the water to rise in a narrow tube against the force of gravity. Because of hydrogen
bonding, water is extremely cohesive. This causes molecules on the surface of water to be drawn inward,
which is why drops of water form beads on smooth surfaces.
ANS:
First, organic compounds contain carbon atoms, each of which has four valence electrons. Each electron can
join with an electron from another atom to form a covalent bond. Carbon can bond with many elements,
including hydrogen, oxygen, phosphorus, and nitrogen. Second, a carbon atom can bond to other carbon
atoms, which gives carbon the ability to form chains that are of great length. These carbon–carbon bonds can
be single, double, or triple bonds. Chains of carbon atoms can even close upon themselves to form rings and
loops. Carbon thus has the ability to form millions of different large and complex structures.
ANS:
In comparing the activity of enzymes to a lock and key, the lock symbolizes the active site of the enzyme and
the key symbolizes the substrate. A specific key can only fit into a specific lock; so too does a specific
substrate fit into the active site of a specific enzyme. Without a perfect match, the reaction cannot occur.
Likewise, without the right key, the lock cannot open.
ANS:
A food chain is a series of steps in which organisms transfer energy by eating and being eaten. A food web is
a feeding relationship among the various organisms in an ecosystem that forms a network of complex
interactions. A food web links all the food chains in an ecosystem together.
ANS:
An ecological pyramid is a diagram that shows the relative amounts of energy or matter contained within each
trophic level in a food chain or web. A biomass pyramid represents the amount of living tissue within each
trophic level. A pyramid of numbers shows the relative number of organisms at each trophic level.
ANS:
Certain types of bacteria are able to use nitrogen gas directly. These bacteria, which live in the soil and on the
roots of legumes, convert nitrogen gas to ammonia during the process of nitrogen fixation. Other bacteria in
the soil convert ammonia into nitrates and nitrites, which are also taken up directly by producers. Still other
soil bacteria convert nitrates into nitrogen gas during the process of denitrification, returning the nitrogen to
the atmosphere.
ANS:
Carbon is biologically significant because it is the key ingredient of all living organisms. Carbon is found in
several reservoirs within the biosphere. Carbon occurs in the atmosphere as carbon dioxide gas, in the oceans
as dissolved carbon dioxide, and in organisms, rocks, soil, and underground as coal, petroleum, and calcium
carbonate rock.
ANS:
Solar energy has an important effect on the temperature of the atmosphere. Atmospheric gases, such as
carbon dioxide, methane, and water vapor, do not allow heat energy to pass out of the atmosphere. This
natural situation in which heat is retained by these greenhouse gases is called the greenhouse effect. This
effect provides a natural insulating blanket around Earth and maintains its temperature range.
ANS:
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The three main classes of symbiotic relationships are mutualism, commensalism, and parasitism. In
mutualism, both species benefit from the relationship. For example, flowers depend on certain insects to
pollinate them. The flowers provide the insects with food in the form of nectar, pollen, or other substances. In
commensalism, one member of the association benefits and the other is neither helped nor harmed. Barnacles
attached to the skin of whales benefit from food particles in the water moving past the swimming whale, but
the whale is not affected. In parasitism, one member benefits by obtaining all its nutritional needs from the
host. The host can be damaged, but is usually not killed. Fleas, ticks, and lice are examples of parasites that
live on the bodies of mammals.
ANS:
Primary succession occurs on newly exposed surfaces, such as a fresh lava flow that destroys the previous
ecosystem. The first organisms to appear are plantlike lichens that colonize the newly formed volcanic
surfaces. Over several years, various species of plants including mosses and grasses establish themselves
among the rocks and then take root in the thin layer of soil. Eventually, tree seedlings and shrubs sprout
among the plant community. A characteristic ecological community may eventually dominate the area.
ANS:
A population will increase or decrease in size depending on how many individuals are added to it or removed
from it. There are two ways individuals can be added to a population. Individuals can be born into the
population or they can move into it from outside the population, or immigrate. There are two ways individuals
can be removed from a population. They can die or they can move out of the population, or emigrate.
ANS:
Exponential growth occurs when the individuals in a population reproduce at a constant rate. At first the size
of the population increases slowly, then it increases more and more rapidly until it approaches an infinitely
large size. Under ideal conditions with unlimited resources, a population will grow exponentially. Exponential
growth does not continue in natural populations for very long. As resources become less available as the
population grows, the rate of population growth slows down. Logistic growth occurs when a population’s
growth slows or stops following a period of exponential growth.
ANS:
Under ideal conditions, populations will continue to grow if there are no factors that limit their growth. Some
factors in a population’s environment that can limit growth are predation, competition, parasitism, and
disease. Other limiting factors are climate extremes and human activities.
ANS:
The predator/prey relationship is one of the best-known mechanisms of population control. As the predators
feed on the prey, the prey population falls. The decline in the prey population is followed, sooner or later, by a
decline in the predator population, because there is less for the predators to feed on. A decline in the predator
population means that the prey have fewer enemies, so the prey population rises again. This cycle of predator
and prey populations can be repeated indefinitely.
ANS:
Density-dependent limiting factors become limiting only when the population density—the number of
organisms in a given area—reaches a certain level. These factors include competition, predation, parasitism,
and disease. Density-independent limiting factors affect all populations in similar ways, regardless of
population size. These limiting factors include weather, natural disasters, and certain human activities, such as
damming rivers and clear-cutting forests.
ANS:
Many ecologists think that the growth of the human population must soon slow down. The rapid increase of
humans on the planet will make too many demands on the environment and could cause it permanent harm.
Many ecologists think the global economy could be harmed also. On the other hand, many economists think
that science and technology will find answers to solve the problem of negative impacts of a growing human
population.
ANS:
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Biodiversity is one of Earth’s greatest natural resources. Species of many kinds have provided us with foods,
industrial products, and medicines—including painkillers, antibiotics, heart drugs, antidepressants, and
anticancer drugs. For example, the rosy periwinkle plant is the source of substances used to treat certain
cancers. When biodiversity is lost, potential sources of material with significant value to the biosphere and to
humankind may be lost with it.
ANS:
One of the most important threats to biodiversity today comes from apparently harmless plants and animals
that humans transport around the world either accidentally or intentionally. Introduced into new habitats,
these organisms often become invasive species that reproduce rapidly and crowd out native species. Invasive
species increase their populations rapidly because their new habitat lacks the parasites and predators that
control their populations in their native environments.
ANS:
Damage to the ozone layer by chlorofluorocarbons has left a vast area over each of the polar regions that is
thin enough to allow higher than normal amounts of UV radiation to strike the Earth. UV radiation causes
sunburn, and excess exposure to UV can cause cancer, damage eyes, and decrease organisms’ resistance to
disease. Intense UV can damage tissue in plant leaves and phytoplankton. The United States and many other
nations have an international agreement to phase out the use of CFCs.
ANS:
The cell theory states that all living things are composed of cells. It also says that cells are the basic units of
life and new cells come from preexisting cells. The cell theory is significant to biology because all living
thing are made of cells. Differences in the structure and function of different life forms are reflected in
differences in their cell structures.
ANS:
Prokaryotes are generally simpler and smaller than eukaryotes. They have a cell membrane and cytoplasm,
but lack a nucleus. Eukaryotes have a nucleus and other specialized organelles. Bacteria and other cells that
lack a nucleus are prokaryotes. Plants, animals, fungi, and other microorganisms are eukaryotes.
ANS:
Microtubules are hollow tubes of protein that help maintain the shape of a cell and can serve as “tracks” along
which organelles are moved around inside the cell. Microtubules also make up cilia and flagella, which
function in cell movement. Microfilaments are long, thin fibers that are narrower than microtubules.
Microfilaments function in the movement and support of the cell.
ANS:
Like a piece of mosaic art, which is made of different tiles, the cell membrane is made up of many different
kinds of molecules. The background is a lipid bilayer. Within this bilayer are proteins that form channels and
pumps that help move materials from one side of the membrane to the other. Carbohydrates on the outer
surface of the membrane act like chemical identification cards and allow cells to identify one another.
ANS:
When sugar solutions of different concentrations are on opposite sides of a semipermeable membrane, the
molecules on both sides of the membrane flow across the membrane. However, there is a net flow of
molecules from the more concentrated solution into the less concentrated solution, until the concentrations are
equal. Once equilibrium is reached, roughly equal numbers of molecules move in each direction across the
membrane.
ANS:
Facilitated diffusion is the movement through a protein channel of molecules that could not otherwise cross
the membrane. Facilitated diffusion occurs only with a concentration difference and does not require
additional energy. Active transport is the movement of materials across a cell membrane against a
concentration difference and does require the addition of energy.
ANS:
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The levels of organization in a multicellular organism include cells, tissues, organs, and organ systems.
Similar cells are grouped into tissues; tissues that work together form organs; a group of organs that work
together make up an organ system. Unicellular organisms cannot have cell specialization. Instead, all the
activities of the organism must be carried out by the single cell.
ANS:
Heterotrophs depend on autotrophs to harvest energy from the sun. This energy is then passed on to
heterotrophs in the form of food. Without autotrophs, the sun’s energy would not be available to heterotrophs
and heterotrophs would eventually die out or find a new way of harvesting energy.
ANS:
A glucose molecule can store more than 90 times the energy as an ATP molecule. Glucose is used by cells to
store large amounts of energy for long periods of time. In contrast, ATP is used to store smaller amounts of
energy that will be used in the next few seconds. Cells can regenerate ATP from ADP as needed by using the
energy from glucose.
ANS:
Van Helmont measured the soil and water provided to a seedling over five years and concluded that trees gain
their mass from their intake of water alone. Priestley used a bell jar, a candle, and a plant to determine that
plants release a substance (oxygen) that can keep a candle burning. Ingenhousz discovered that water plants
release oxygen bubbles in the presence of light, but not in darkness. He concluded from this that plants
require sunlight to produce oxygen. From these and other experiments, we learned that plants convert carbon
dioxide and water into carbohydrates in the presence of sunlight, and they release oxygen.
ANS:
Electrons in the pigments in photosystem II absorb energy from light. These electrons then move through the
electron transport chain to photosystem I. H+ ions move from the stroma into the inner thylakoid membrane.
NADP+ becomes NADPH. The charge difference on either side of the thylakoid membrane provides the
energy to make ATP via ATP synthase.
ANS:
When energy from sunlight is absorbed by the electrons in chlorophyll, the electrons increase their energy
level and move on to the electron transport chain to photosystem I. The electrons in chlorophyll are
replenished by water molecules. Enzymes in the inner surface of the thylakoid membrane break up water
molecules into 2 electrons, 2 H+, and 1 O atom each. The electrons replace those that chlorophyll loses to the
electron transport chain.
ANS:
Three of the factors that affect the rate of photosynthesis are light intensity, temperature, and water. The rate
of photosynthesis increases with light intensity up to a certain point, then levels off. Photosynthesis slows at
extreme temperatures and usually has an optimal temperature for each kind of plant. Lack of water slows
down photosynthesis.
ANS:
Sample answer: Glycolysis is the breakdown of glucose into two molecules of pyruvic acid, producing 4 ATP
molecules. An initial input of 2 ATP molecules is required to start glycolysis; thus, there is a net gain of 2
ATP molecules. This process produces two high-energy electrons, which are passed to NAD+ to form NADH.
If oxygen is present, glycolysis leads to the Krebs cycle and the electron transport chain. If oxygen is not
present, glycolysis is followed by the rest of fermentation.
ANS:
Lactic acid fermentation occurs in animal muscle cells and in some microorganisms. Lactic acid fermentation
converts glucose into lactic acid. In yeast cells, alcoholic fermentation takes place. Unlike lactic acid
fermentation, alcoholic fermentation produces alcohol and carbon dioxide. Both types of fermentation result
in 2 ATP molecules.
ANS:
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Sample answer: During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of
energy-extracting reactions. Coenzyme A forms acetyl-CoA, which later becomes citric acid. Citric acid is
then broken down, CO2 is liberated, and electrons are transferred to energy carriers. The energy tally from one
molecule of pyruvic acid is 4 NADH, 1 FADH2, and 1 ATP.
ANS:
During intense or prolonged physical activity, muscle cells may use oxygen faster than it can be supplied by
the body. When the oxygen supply gets very low, the electron transport chain cannot function because oxygen
serves as its final electron acceptor. As a result, NADH and FADH2 accumulate in the mitochondria and are
not able to be recycled. This forces the Krebs cycle to stop. In this situation, the muscle cells continue to
produce ATP by means of lactic acid fermentation. The lactic acid will cause muscle pain and fatigue.
ANS:
Sample answer: Photosynthesis and cellular respiration are almost opposite processes. The reactants of
photosynthesis are the products of cellular respiration. The products of photosynthesis are the reactants of
cellular respiration. Whereas photosynthesis “deposits” energy, cellular respiration “withdraws” energy.
Photosynthesis removes carbon dioxide from and releases oxygen into the atmosphere. Cellular respiration
uses oxygen and gives off carbon dioxide.
ANS:
A cell’s volume increases more rapidly than does it surface area, causing its ratio of surface area to volume to
decrease with size (growth). As a cell’s ratio of surface area to volume decreases, it becomes more difficult
for a cell to move needed materials in and wastes out. Thus, a normal growing cell will usually divide into
two daughter cells before it becomes too large.
ANS:
As a cell grows, it functions less efficiently because it places more demands on its DNA and it is less able to
move materials to their proper destinations quickly. Cell division results in two daughter cells. Each cell has
its own copy of the parent cell’s DNA and has a size that allows it to efficiently exchange materials.
ANS:
Interphase consists of the G1 phase, S phase, and the G2 phase. During the G1 phase, the cell grows; during the
S phase, the DNA replicates; during the G2 phase, the cell prepares for mitosis. The M phase or cell division
includes mitosis and cytokinesis. Figures should approximate Figure 10-4 on page 245 of the student text.
ANS:
Prophase—the chromatin condenses into chromosomes, the centrioles separate (in animal cells), and the
nuclear membrane breaks down; Metaphase—the chromosomes line up across the midline of the cell and each
chromosome is attached to a spindle fiber and centromere; Anaphase—sister chromatids separate into
individual chromosomes; Telophase—chromosomes move to opposite sides of the dividing cell, and two new
nuclear envelopes form.
OTHER
71. ANS:
meter, centimeter, millimeter, kilometer
72. ANS:
The metric system is based on multiples of 10, whereas traditional English units have many different
conversion factors.
73. ANS:
The boiling point of water in degrees Celsius is 100 C.
74. ANS:
The prefix kilo- means 1000.
75. ANS:
Two L of water is equal to 2000 mL.
76. ANS:
12
77. ANS:
8
78. ANS:
13
79. ANS:
helium
80. ANS:
oxygen
81. ANS:
observing, experimenting, and modeling
82. ANS:
photosynthesis
83. ANS:
a chloroplast
84. ANS:
Oxygen gas, ATP, and NADPH are the products of the light-dependent reactions.
85. ANS:
sugars
86. ANS:
carbon dioxide
87. ANS:
The figure shows the electron transport chain.
88. ANS:
The electrons come from NADH and FADH2, electron carriers that come from the Krebs cycle.
89. ANS:
They join with 4 H+ and O2 to form water molecules.
90. ANS:
The H+ ions are mostly moving into the intermembrane space. This movement causes the intermembrane
space to become positively charged with respect to the matrix.
91. ANS:
Sample answer: ATP synthase converts ADP into ATP.
92. ANS:
It shows various stages of mitosis in an animal cell. We know this is an animal cell because of the presence of
centrioles and the shape of the cells.
93. ANS:
Four
94. ANS:
X is the centriole; Y is a spindle fiber.
95. ANS:
D, A, C, B
96. ANS:
The next step would be cytokinesis. It would show two daughter cells forming.