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EdExcel Triple Science
Biology Unit B3
N Smith
St Aidan’s
Topic 1 – Control Systems
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The Urinary System
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Metabolism in cells causes us to produce waste products such as carbon
dioxide and urea. Urea is formed by the breaking down of amino acids in
the liver and kidneys are responsible for removing it.
Renal artery
Renal vein
Ureter (tube that takes
urine down to bladder)
Bladder and urethra
Dialysis
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Sometimes kidneys can fail due to infections, toxic substances
or genetic reasons. One possible answer is to use a dialysis
machine:
Partially permeable membranes
Sugar
Dialysis fluid
Sugar
Blood
Dialysis fluid
Urea
Urea
Urea and salt diffuse out of the blood into the dialysis fluid.
Also, the dialysis fluid contains the same concentration of
sugar and minerals as the blood so these don’t diffuse.
Kidney transplants
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Instead of dialysis a kidney could be transplanted into the
patient.
This option is cheaper than _____ but it requires
a _______ (a normal person can still function
with one kidney). This donor must have a similar
______ type to the patient. Also, the new
kidney might be rejected by the body’s ______
system which will try to destroy the new organ
by using _______ to attack the antigens on the
surface of the kidney. To work around this
problem the patient can take “immunosuppresant
___” which suppress the immune system.
Words – dialysis, donor, immune, tissue, drugs, antibodies
Kidneys
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Kidneys work in 3 stages:
Blood vessel
1. ULTRAFILTRATION - Lots of water and
products of digestion are squeezed out of
the blood and into tubules under pressure.
2. SELECTIVE REABSORPTION – the blood
takes back the things it wants (e.g. glucose
and ions) even though this means going
against a concentration gradient.
3. WASTE – excess water, excess ions and
any urea are now removed through the
ureter
Tubule
Kidney structure
1) Ultrafiltration
happens in the
glomerulus and
Bowman’s capsule
2) Selective
reabsorption
happens in the
convoluted
tubules
3) Excretion
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Controlling Water Content – “Negative Feedback”
Low blood water level causes a high
salt concentration
Receptors in the hypothalamus
detect the high salt content
More ADH is secreted into the blood
The kidney becomes more permeable
to water so more is absorbed.
The bladder fills with a small
quantity of urine
Normal blood water level is
achieved.
Controlling Water Content 2
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High blood water level causes a low
salt concentration
Receptors in the hypothalamus
detect the low salt content
Less ADH is secreted into the blood
The kidney becomes less permeable
to water so more is absorbed.
The bladder fills with a large
quantity of urine
Normal blood water level is
achieved.
Fertility
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The amount of glucose in our blood is an example of a process
controlled by hormones. Hormones are “chemical
messengers”, produced by glands and transported by blood.
Another example of a process controlled by hormones is the
menstrual cycle, where hormones can...
1) …stimulate the release of eggs
2) …inhibit the release of eggs
In normal circumstances natural
hormones are responsible for releasing
the egg and for thickening the lining of
the womb. These hormones are
produced by the pituitary gland in the
brain and in the ovaries.
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The 4 stages of the menstrual cycle:
Day 1: Bleeding starts when the lining of the uterus breaks down and
passes out the vagina – “Having a period”
Day 4: The lining starts to build up again and thickens into a spongy layer
of blood cells
Day 14 (approx): An egg is released and lasts for around 3 days
Day 28: The lining stays thick awaiting the arrival of a fertilised egg. If
one doesn’t come then the lining breaks down again.
Thickness of
uterus lining
Day 0
Day 4
Day 14
Day 21
Day 28
Fertility
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4 hormones are involved in the menstrual cycle: oestrogen, progesterone,
LH and FSH. Here’s how:
Step 1: FSH
produced by the
pituitary gland causes
both a follicle (an egg
and its surrounding
cells) to mature and
the ovaries to start
producing oestrogen
Step 2: The rising levels of
oestrogen cause the uterus lining
to thicken and the pituitary
gland to stop producing FSH and
produce LH instead
Step 3: LH
stimulates the
release of the
mature egg at day
14. The remains
of the follicle
develop into a
structure called a
“corpus luteum”
which then
secretes
progesterone
Step 4: The progesterone then maintains the lining of the uterus and inhibits
production of FSH and LH. When the level of progesterone falls (and there’s a low
oestrogen level) the lining breaks down. This allows FSH to be produced and the
process starts again. If the woman is pregnant then progesterone levels stay high.
Thickness of
uterus lining
Day 0
The Menstrual Cycle
Day 7
Hormone
concentration
Oestrogen – produced
in the _______ and
causes the lining of
the uterus to ______
Day 14
Day 21
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Day 28
Progesterone – produced by the empty
________ and maintains the ______.
If egg is _______ progesterone
continues to be produced to maintain
the lining for the fertilised egg
Words – follicle, lining, ovaries, thicken, fertilised
Eggs
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The female egg cell is an example of a gamete:
Nucleus
The egg cell is basically an
enlarged cell with massive
_______ reserves in the
cytoplasm
The nucleus in the egg cell is a “_______”, meaning it only
contains one set of _______ material and isn’t complete until
it is ______. When this happens the egg’s membrane changes
its structure to stop any more _______ getting in.
Words – nutrients, sperm, fertilised, haploid, genetic
Sperm
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The sperm cell is also specialised:
Haploid nucleus
A middle section with
lots of ________ to
produce a lot of
_______
The head has an
acrosome packed
with “enzymes” to
______ its way
through the egg’s
________
Strong tail for
________
Words – swimming, energy, mitochondria, digest, membrane
IVF
Some couples cannot have children naturally. In-vitro
fertilisation (IVF) can help. Here’s how it works:
1. Eggs are removed from
the womb and placed in a
solution of oxygen and
water to keep them alive
2. Sperm is added
3. The fertlised egg is allowed to grow
into an embryo (a group of 4-8 cells)
4. Usually 3 of these embryos are
transferred back into the uterus
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Other fertility treatments
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Artificial insemination – this is used when the sperm count is
low or if a woman’s oviducts are blocked. Sperm is put directly
into the uterus and oviducts to increase the chance of
fertilisation.
Egg donation – if the woman cannot produce eggs herself eggs
can be donated by another woman which are then fertilised
using IVF treatment (see next slide)
Ovary transplants – these are used if a woman’s ovaries do not
function
Surrogacy – this is when an embryo produced through IVF is
implanted into a surrogate mother who then carries the baby.
When the baby is born he/she is given to the biological
parents.
Boy or Girl?
X
Girl
Y
XX
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X
XY
Boy
Mother
Boy or Girl?
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Son
Father
Daughter
Genetic Diagrams
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Here’s what happens (genetically) when an egg is fertilised:
Mother
Father
xx
xy
x
x
x
y
xx
xy
xx
xy
Equal (50%)
chance of
being a boy or
a girl
Genetic Diagrams
Here’s another way of drawing it:
Father
Mother
x
x
x
y
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Inheriting colour blindness and haemophilia
Colour blindness and haemophilia are two “sex-linked” genetic disorders they are caused by faulty alleles located on sex chromosomes.
For example, here’s a female who carries the recessive allele for colour
blindness crossed with a “normal” male:
Parents:
X
XNXn
Xn Y
XN = Normal colour
vision allele
Xn = faulty colour
vision allele
Gametes:
XN
Xn
Xn
Y
(FOIL)
N
N n
Offspring: X X X Y
Carrier
female
Normal
male
XnXn XnY
Normal Colour
female blind male
Bacteria revision
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In unit B2 we met bacteria:
Bacteria grow VERY fast. For
example, if a certain bacteria
doubles itself every 5 minutes
calculate how many bacteria you
would have after one hour.
Bacteria – containing
cytoplasm and a membrane
surrounded by a cell wall.
The genes are NOT in a
distinct nucleus.
No. of bacteria
Time
How our bodies fight bacteria
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You’re going
down
Step 1: The lymphocyte “sees” the
pathogen (bacteria)
Step 2: The cell produces
antibodies to “fit” the pathogen
Step 3: The antibodies fit onto the
pathogens and cause them to “clump”
Step 4: The pathogens are
“eaten” by the white blood cells
Vaccinations
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Vaccinations work by doing the following:
1) A harmless ________ or antigenic material is
introduced
2) The antigens trigger an ________ response
which causes the production of _________
3) The antigens also trigger the production of
“_______ lymphocytes” that “_______” the
illness in case your body is exposed to the real
pathogen in the future.
Vaccinations can also cause concerns, such as the recent controversy over
the _____ vaccine.
Words – remember, pathogen, immune, MMR, memory, antibodies
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The Development of Vaccinations
Hi. I was a doctor in England and in the late
18th Century I discovered that you can
vaccinate people against smallpox:
Edward Jenner,
1749-1823
In 1796 Jenner took bits of scab from a girl who had
______ (a less deadly disease than smallpox). He then
put them into a cut in the arm of a boy and then
exposed the boy to ________ and discovered that the
boy was ______ to it.
The vaccination worked because the cowpox _____ triggered the boy’s Blymphocytes to produce _______. Smallpox has the same antigens as
cowpox so when the boy was exposed to smallpox his body quickly made
antibodies for it.
Words – smallpox, cowpox, antibodies, antigens, immune
Specific antibodies
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Microbe
Antigen
Antibodies are specific – they will neutralise the microbe
they have been made for. They do this by recognising
the antigen on the surface of the microbe.
Once the body has made the antibody “memory cells” can
make it again very quickly if needed, which protects you
from catching the disease again.
Immunity to later infections
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When the person catches the
disease again at a later time the
body responds much quicker
Concentration of
antibody in the blood
When this person first
catches a disease the
response takes time
Time
Memory lymphocytes
then stay in the body
for a long time
Vaccinations
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Some people argue that the MMR vaccine is a good idea,
others think it is a bad idea. Briefly summarise each side of
the argument:
For
Against
MMR vaccine
Vaccination Policies
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Is the
infection a
big risk?
Is the
vaccine
safe?
Factors to consider
about vaccinations
How much
does it
cost?
Who is at
risk?
Monoclonal Antibodies
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Monoclonal antibodies are basically “identical antibodies” that can be made
to bind to anything you want. They are the same because they are made
from the same parent cell. Here’s how:
Step 1: Take an animal (e.g. mouse) and inject
it with an antigen
Step 2: Extract the B-lymphocytes that the
mouse makes in reaction to the antigen
Step 3: Fuse this lymphocyte with fastgrowing tumour cells to make a “hybridoma”
(a cell that produces lots of antibodies)
Step 4: The hybridoma then divides really
quickly (due to it being made from a tumour
cell) which gives you lots of identical
antibodies called monoclonal antibodies
Eek!
Uses of Monoclonal Antibodies
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Diagnosis of
cancer and
the location
of cancerous
cells
Pregnancy
testing
What are monoclonal
antibodies used for?
Treating cancer
by targeting
specific
cancerous cells
Task: Find out how monoclonal
antibodies are used in each of the
above uses.
Louis Pasteur
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I did a lot of work on germs in the 1850s.
The process of “pasteurising milk” is named
after me.
Pasteur,
1822 - 1895
Pasteur took two flasks and put some boiled broth in each one.
One of the flasks had a curve in it, the other one didn’t. He
observed the fact that the broth in the non-curved flask went
bad but the one with the curved neck didn’t – what was his
conclusion?
Drugs from Plants
Plants produce chemicals to defend
themselves against pests:
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Back off
Some of these chemicals can be used
as drugs to treat human diseases or
to relieve pain symptoms. Some
examples:
1) Aspirin – made from a chemical found in the leaves and
bark of a willow tree
2) Taxol – an anti-cancer drug from the bark of the Pacific
yew tree
3) Quinine – used for treating malaria, it comes from the
South American cinchona tree
Plant Diseases and Pests
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Plant disease
Damage by
pests
How might these factors
affect the availability
and price of food?
Weeds
Bad weather
Periodicity in Plants and Animals
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Many plants and animals show various forms of periodicity. For example:
1) Plants show “photoperiodicity” – this means
that they respond to changes in the length of
a day. For example, many plants only flower
at the start of the summer season whereas
other plants only flower in autumn. Doing this
means that they flower when the right insects
for pollination are around.
2) Animals, plants and microorganisms show
“Circadian Rhythms” – rhythms that follow a
24-hour cycle. For example, sleep patterns
are affected by hormonal reaction to light
and the body’s production of urine also slows
down overnight. Plants control their stomata
using similar rhythms.
Topic 2 - Behaviour
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Mating Patterns
Here’s a random selection of animals:
This is my harem!
Animals have many different mating
strategies – some will have one mate for life,
others will have one mate for each mating
season while others have many mates.
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Behavioural Strategies
Most animals engage in some sort
of display that advertises their
qualities…
Some animals, particularly birds
and mammals, have developed
special behaviours for looking
after their young (which can
sometimes endanger the parents):
These behavioural adaptations
can increase the chances of
survival and increase the chance
of the parental genes being
passed on.
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Types of Animal Behaviour
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1) Innate behaviour – this is when an animal
does something almost by instinct, e.g.
feeding from a bottle.
2) Learned behaviour – this is when an
animal learns from a previous experience
and changes its behaviour accordingly.
Having a lot of learned behaviour can lead
to “habituation” – the animal learns not to
respond to something.
3) Imprinting – this is when an animal
recognises its parents and instinctively
follows them around, a combination of
learned behaviour and innate behaviour.
Whatever
Classical Conditioning - Pavlov’s Dog
I won the Nobel Prize in 1904 and am
most famous for investigating
“conditioned responses”:
Ivan Pavlov,
1849-1936
1) Steak + dog = saliva
2) Steak + bell + dog = saliva
3) Bell + dog = saliva
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Operant Conditioning – Skinner’s Box
Conditioning is a form of learned behaviour and there are two
main types:
Operant conditioning is when an animal
learns a behaviour by trial and error, i.e.
by learning that some behaviours give a
reward whereas others don’t. For
example, consider my Skinner Box:
Burrhus Skinner,
1904-1990
Combinations of
classical and operant
conditioning are used
to train animals such
as police horses,
sniffer dogs and
dolphins. How?
Signals in Animals
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Animals use a variety of ways to communicate with each other,
such as:
Squawk
Sound signals:
Chemical signals
(pheromones):
Visual signals (e.g. gestures
and body language):
Studying Behaviour in Animals
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Task: summarise the work of the following ethologists:
1)
2)
3)
4)
Tinbergen, who studied innate behaviour in gulls
Fossey, who studied social behaviour in gorillas
Goodall, who studied social behaviour in chimpanzees
Lorenz, who studied imprinting in geese
For each of these people find out how
they studied this behaviour and some
of their main observations and
conclusions.
Signals in Plants
As we’ve said before, plants can
use chemicals to warn off
unwanted insects:
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Back off
They can also use chemicals to
attract insects, such as bees to
help them pollinate.
Plants can also release chemicals to warn other plants of
predators:
Yum
My friend is
in danger –
I’m going to
harden my
leaves
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Co-Evolution in Plants and Animals
Co-evolution is when two organisms
evolve in ________ to each other.
For example, consider an orchid:
Orchids have a very deep store of
_____ so only certain types of ____
can reach it. This may mean that
this type of moth will probably only
pollinate other ______.
Some plants are also poisonous to most insects. This means
that the ones who can eat it have an evolutionary ________
over other insects while the plant in question has evolved a
defence mechanism to help it protect itself.
Words – advantage, response, orchids, moth, nectar
Human Evolution
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Task: Find out how the following famous fossil
hominids have provided evidence for human
evolution:
1) Ardi (4.4 million years old)
2) Lucy (3.2 million years old)
3) Various fossil hominids found by Leakey (1.6 million years
old)
For each fossil find suitable images and explain how these
images show human development over the last few million
years.
Then find images to show the development of tools over the
last 2 million years and how these tools show human evolution.
Mitochondrial DNA
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Recall our basic animal cell:
These are mitochondria and they have a small
piece of DNA inside them
Mitochondrial DNA is only inherited from your
mother. Everyone on Earth has similar mitochondrial
DNA but it also has a high mutation rate. Scientists
have used the mutation rate and the fact that it is
only passed down by the mother to come to this
conclusion:
Everyone on Earth has descended from ONE WOMAN – scientists call her
“Mitochondrial Eve” or “African Eve” and she lived in Africa around
200,000 years ago.
Scientists can also use Nuclear DNA to study human evolution and
migration. However, mitochondrial DNA is more useful as there are lots of
mitochondria in one cell and mitochondrial DNA degrades less over time.
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Climate Change and Human Behaviour
As humans migrated out of Africa they would have moved to a
different climate. How would they have had to adapt their
behaviour to this new climate?
Changes in diet
Hunting methods
Changes in human
behaviour due to a
different climate
Getting food
from trees/fish
Use of
tools/clothes
The Effect of the Ice Age
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Ice ages are very long periods of time where the climate goes
very cold and ice sheets and glaciers spread across most of
the Earth. To survive the last ice age what would early humans
have had to do? Think about the following:
1) Where they would live
2) What they would do for heating
3) How their clothing would change
4) How their hunting patterns changed
5) Use of tools
6) How their cooperation and communication might have had
to change
Topic 3 - Biotechnology
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Growing micro organisms
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Method:
1) Sterilise the
inoculating loop
2) Dip the loop in the bacteria
and spread it across the agar
3) Secure (but don’t
seal) the lid with tape
Questions:
1) Why are you sterilising the loop?
2) What does the agar do?
3) Why is the lid not sealed all the way around?
4) Why would you not want to culture your bacteria at 37OC?
Fermenters
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A fermenter is a controlled environment (i.e.
a large device) that provides ideal conditions
for micro organisms to grow and feed.
Micro organisms
Water
cooled
jacket
Temperature
sensor
pH sensor
Outlet tap
Sterile air
supply
More about Fermenters
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Using your knowledge of microbe growth explain why the
following features of a fermenter are important:
1) Aseptic
precautions
2) The use of
nutrients
3) An optimum
temperature
4) The right pH
5) A good air supply
6) Agitation
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Fusarium fungus and Mycoprotein
Fusarium sp is a fungus used to make mycoprotein (a
_______-rich food suitable for _________). The fungus is
grown on glucose ______ under ________ conditions and the
biomass is harvested and ________.
Words – aerobic, protein, vegetarian, syrup, purified
Using Microorganisms for food
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The human population is
growing exponentially:
Population
Time
Microorganisms are a useful way to feed the population.
Ease of
manipulation
Food can be produced
regardless of climate
Other
advantages of
using
microorganisms
The process can use
waste products from
other industrial
processes
Micro organisms
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Micro organisms are tiny living organisms such as bacteria,
viruses and fungi.
Cell wall
Bacteria is used for making yoghurts and
cheese.
Nucleus
Yeast is a single-celled organism used in
making alcoholic drinks and bread.
Cytoplasm
The difference between these two processes is whether the
yeast respires aerobically or anaerobically:
Aerobic respiration:
Sugar
Water + carbon dioxide
Anaerobic respiration
(fermentation):
Sugar
Alcohol + carbon dioxide
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Using micro organisms to make food
In yoghurt production bacteria is added
to warm ____. The _____ ferments the
sugar in the milk (lactose) to produce
______ ____. The lactic acid causes
the milk to ___ and turn into yoghurt.
Words – clot, milk, bacteria, lactic acid
Industrial uses of enzymes
1) Enzymes are used in washing powders
to help digest fats and proteins in food
stains. Biological washing powders will
only work on 400C or lower.
2) Chymosin is an enzyme produced by
genetically modified microorganisms,
used in the manufacture of vegetarian
cheese.
3) Invertase (sucrase) is produced by
yeast and used in the manufacture of
sweets
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Genetic engineering - Insulin
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“Sticky ends”
Step 1: Using RESTRICTION
ENZYMES “cut out” the part of
the human chromosome that is
responsible for producing insulin.
Step 2: Using another restriction
enzyme cut open a ring of bacterial
DNA (a “plasmid”). The enzyme
ligase is then used to insert the
piece of human DNA into the plasmid.
Step 3: Place the plasmid into a bacterium
which will start to divide rapidly. As it
divides it will replicate the plasmid and
make millions of them, each with the
instruction to produce insulin. Commercial
quantities of insulin can then be produced.
Feeding a Growing Population
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As we’ve said before, the
human population is growing
exponentially:
Population
Time
This population (and a lot of other factors) can cause a lack of
“food security” (where people go without food).
Using selective
breeding to select
and reproduce the
best plants
Genetically modifying
plants to be insectresistant
Using crop rotation
Ways to
increase food
security
Reducing the number of
pests by introducing
insects that eat pests
but not plants
Genetically Modified Plants
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Here’s a cotton plant:
Plants like cotton and corn can be genetically
modified by using a bacterium called bacillus
thuringiensis (Bt). Bt produces a toxin that kills
insect larvae so scientists can insert the gene for
the Bt toxin into crops like corn and cotton.
However, there are two problems with this:
1) Although Bt is considered harmless to humans, its long term effects
haven’t yet been discovered
2) Insects may develop resistance to it
Scientists have also used genetic modification to
introduce “flavonoids” (molecules that have antioxidant
effects and are useful in protecting against cancer) into
“purple tomatoes”.
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How plants are genetically modified
Plants are genetically modified using the bacterium agrobacterium
tumefaciens. This is basically a pathogen that invades plant cells and puts
its genes into the plant’s DNA. The bacterium acts as a “vector” (a carrier
that’s used to transfer DNA into other organisms):
Step 1: Take the genes you want (e.g.
herbicide resistance) from the
plant’s nucleus
Step 2: Cut open part of the
bacteria’s DNA and insert the
desired gene:
Step 3: Allow the GM bacteria to
infect the target plant:
Step 4: The bacteria will insert their GM genes
into the plant’s DNA. Put these cells into a medium
containing the herbicide – the non-resistant cells
will die, leaving the GM cells behind.
Biofuels
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One of the reasons deforestation happens is so that crops can be used to
grow biofuels. Biofuels are fuels that are “made” biologically. For
example:
•
Manure or other waste that can be used to
release _______ (biogas)
•
Corn or sugar cane that can undergo
anaerobic respiration in a fermenter and then
distilled to produce ______ like bio-ethanol.
Biofuels have two main advantages over
traditional fuels – they are ______ and
________ but growing crops can also take up
valuable land.
Words – alcohols, cleaner, burnt,
renewable, methane