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INVESTIGATING AEROBIC RESPIRATION
Need for Energy
Living cells are the site of a number of chemical reactions. Together these chemical reactions are called
metabolism. Some of these reactions release energy. Living cells need energy for:

Cell division e.g. growth & repair

Maintaining body temperature (birds & mammals)

Movement

Chemical reactions e.g. making enzymes, digesting food
RESPIRATION is the process by which cells release ENERGY from GLUCOSE. It happens in all
living cells (plant & animal) all the time.
Aerobic Respiration
Oxygen is required for aerobic respiration. Two waste products, water and carbon dioxide are
made.
Equation for aerobic respiration:
GLUCOSE + OXYGEN
WATER + CARBON DIOXIDE + ENERGY
Reactants
waste products
useful product
The carbon dioxide released can be detected by

Turning limewater milky

Turning bicarbonate indicator from red to yellow
Aerobic respiration occurs in many small steps, each controlled by an enzyme. This allows the
energy to be released in small amounts.
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The energy in food molecules such as glucose is CHEMICAL ENERGY. Green plants
capture LIGHT ENERGY and convert it into chemical energy in photosynthesis (Error!
Bookmark not defined.). Animals obtain their food from plants (Error! Bookmark not
defined.).
The quantity of energy contained in foods can be found by burning a measured mass of food
and using the heat energy released to heat a measured volume of water.
The energy content of different foods differs:
Fats contain TWICE as much energy as proteins or carbohydrates (e.g. glucose & starch)
Respirometers
A
respirometer
can
be
used
to
measure
the
rate
of
respiration
The use of respirometers depends on three factors:

The volume of oxygen used up is equal to
the volume of carbon dioxide produced

The carbon dioxide can be absorbed by a
chemical (e.g. soda lime, potassium
hydroxide) and so the uptake of oxygen is
seen as a drop in the volume of air in the
respirometer

There is no change in the temperature of the
apparatus. (changes in temperature cause
changes in the volume of gases!)
In the apparatus above, the taps are closed at the start of the experiment. As the oxygen is
removed the volume of air in the tube decreases and this sucks the coloured liquid up the tube
towards the earthworm’s tube.
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The control should be a non respiring material (i.e. dead animal or glass beads) and of the
same volume as the respiring animal.
The syringe is used to return the volume back to its original level. In this way, the volume of
oxygen taken in can be measured and if the time taken to produce the change is known, the
rate of respiration (oxygen uptake per minute) can be calculated.
Energy release
During respiration some of the energy is released as heat energy. As a result in a confined
space the temperature of the surroundings is raised. The heat can be detected using an air
thermometer.
The heat released by the
respiring animal expands the air
in the tube and pushes the
coloured liquid. There is no
expansion in the control side.
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ANIMAL SURVIVAL
THE NEED FOR FOOD
Food provides energy and raw materials for growth.
Food contains 3 types of food molecule:
Food Molecule
Carbohydrates:
Fats
Proteins
Use in Body
Source of energy
Source of energy/ Store of energy/
Raw
materials for growth & repair
Insulation
Structure of Food Molecules:
Polymers (long chains)
to
carbon
sugar
give starch.
to give
cellulose
amino
20
acid
proteins.
nitrogen
fatty
acid
to form a fat molecule
hydrogen
glycerol
glycerol
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fatty
acid
units
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Parts of the Mammalian Alimentary Canal (gut)
Digestion
Food is made of large particles containing large, insoluble molecules. Large, insoluble
molecules cannot pass across the wall of the intestine. Food molecules can only be absorbed
if they are soluble.
Digestion is the process in which large, insoluble food particles are broken down into small soluble molecules,
which can pass across the wall of the small intestine.
Mechanical Digestion
This when the teeth are used to break large pieces of food into smaller pieces. This increases
the surface area of the food on which enzymes (Error! Bookmark not defined.) can act.
Teeth are specially adapted to suit the diet of the organisms:
Herbivore
Animal that eats only plants, e.g. Cow, sheep
Carnivore
Animal that eats only meat (other animals) e.g. Lion, dog
Omnivore
Animal that eats both plants and animals e.g. human, bear.
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(HERBIVORES)
(CARNIVORES)
(OMNIVORES)
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Chemical Digestion
Chemical digestion is carried out by enzymes in digestive juices. They are:
Digestive
Juice
Site of Production
Main Enzymes
Saliva
Salivary Glands
Salivary Amylase
Gastric juice
Stomach
Pepsin
Bile
Liver (stored in gall bladder)
Bile is not an enzyme, but helps in fat digestion.
Pancreatic
juice
Pancreas (secreted into small
intestine)
Pancreatic amylase; Lipase; Protease
Intestinal juice Wall of small intestine
Proteases
Action of digestive enzymes
A digestive enzyme is a chemical which speeds up the breakdown of food
ENZYME
Amylase
SITE PRODUCED
Saliva (salivary amylase)
Pancreas (into small intestine)
Pancreas (into small intestine)
Lipase
Proteases
e.g. pepsin—stomach
e.g. peptidase—pancreas
intestine)
SUBSTRATE
PRODUCT
STARCH
MALTOSE
FATS
(into
FATTY ACID &
GLYCEROL
PROTEINS PEPTIDES OR AMINO
small
ACIDS
Structure of the Small Intestine
The small intestine is where all soluble food molecules are absorbed. It is adapted to fulfil
this role:
It has a large surface area for absorption because:

It is very long

Its lining has finger-like projections (villi)
It can rapidly absorb digested food molecules by
Part of small
intestine
Thin
surface
layer
Blood
capillary
One villus
diffusion because:

The lining is very thin

Lots of blood vessels carry away absorbed food
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lacteal
Finger-like
projections—
called villi
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Absorption of Digested Foods
Feature
Function
Thin lining
Allows rapid diffusion of products of digestion
Blood capillaries
Absorption and transport of glucose and amino
acids
Lacteal
Absorption of products of fat digestion
Lymph vessels
Transports fats from villus
Role of the Large Intestine
- Reabsorption of water and elimination of undigested remains (FAECES)
Faeces are collected in the rectum and then passed out through the anus.
gut
Movement of Food along the Gut
PERISTALSIS = contractions of the muscular
wall of the gut pushing food along .
MECHANISM OF PERISTALSIS
Muscles behind
contract
Muscles behind contract
Muscles in front relax
Muscles in front relax
A wave of this muscular contraction and relaxation
sweeps down the gut, pushing the food ahead of it.
STOMACH CONTRACTIONS: Muscles in the stomach wall contract and relax, helping churn the food
with digestive juices, speeding up the digestion of food.
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REPRODUCTION
Asexual reproduction
- one parent, no sex organs, no sex cells
Sexual reproduction
- two parents, sex organs, sex cells (gametes) are made
Sex cells:
Sperm
Male sex cell
Head nucleus and tail
Can swim
Small
Sperm are attracted to egg cells
Egg
Female sex cell
Nucleus and food store
Cannot swim
Large
Fertilisation:
The nucleus of the male sex cell joins with the nucleus of the female sex cell
Fertilisation can be internal or external. External fertilisation takes place outside the body and
internal fertilisation occurs inside the female’s body. Sperm need to swim to the egg so
external fertilisation must take place in water. In internal fertilisation the sperm swim in the
semen. Internal fertilisation allows land living animals to reproduce without returning to the water.
External Fertilisation e.g trout, frog

Produce many sex cells*

Release sex cells into water

Have courtship rituals or
synchronise release of sex cells*
* This increases the chances of an egg
being fertilised.
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Internal Fertilisation e.g. human, and other
mammals
Produce few sex cells (especially eggs)
Male places sperm inside the female’s body. The
egg is fertilised in the OVIDUCT.
Immediately following fertilisation, a
FERTILISATION MEMBRANE forms around
the egg. This prevents a second sperm from entering the
egg. If a second sperm was to penetrate the egg, the
resulting zygote would have the wrong number of sperm
and so would not develop normally (see S4 notes).
The fertilised egg (ZYGOTE) develops into an
EMBRYO. It develops in the uterus.
Feeding/ Caring for the young
Fish
A fertilised fish egg consists of:
An embryo
A food store
A protective, flexible covering (jelly/ membrane)
A newly hatched trout
Feeds from yolk in the yolk sac
Receives no parental care and so looks after itself
Finds food for itself after its yolk sac is used up
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Mammalian Egg
 The egg is fertilised in the oviduct
 As it travels down the oviduct to the uterus, it divides many times, forming a ball of cells
 The ball of cells implants into the spongy wall of the uterus
 Here the embryo develops a placenta. It is connected to the placenta by the umbilical
cord
 The embryo grows inside a sac called the AMNION, filled with amniotic fluid. This
supports the embryo and protects it from bumps
STRUCTURE & FUNCTION OF THE PLACENTA
An embryo mammal develops a PLACENTA which is a flattened cushion-like organ.
A long twisted coil of blood vessel, called the umbilical cord, stretches from the embryo to the placenta. In the
placenta, the blood of the mother and embryo pass very close to each other but do not actually mix.
Passes from mother to embryo
Passes from embryo to mother
Oxygen
Carbon Dioxide
Glucose, Amino Acid (food)
Urea (& other wastes)
Harmful substances (e.g. drugs, alcohol, nicotine)
Mammals are born through the vagina. Once born, it suckles milk from its mother.
Mammals receive a large amount of care and protection from their parents.
Number of eggs and chances of survival
The more care offspring receive, the more likely they will survive to reproduce, so the fewer are produced e.g.
turtles lay many eggs, bury them & leave.
Many young lost due to predation.
polar bears produce two or three young, feed and protect them for around two years.
Most of them survive
Animals with INTERNAL fertilisation and much care of the young, need to produce very few eggs, as each
has a high chance of survival
Animals with EXTERNAL fertilisation and no parental care need to produce huige numbers of eggs as each
has such a low chance of survival .
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WATER & WASTE
Our bodies contain much water
This amount needs to be kept constant if we are to remain healthy
Water is lost or gained in a variety of ways
Daily water Gain
Daily water loss
DRINK
SWEAT BREATH
FOOD
URINE
CHEMICAL REACTIONS e.g
FAECES
aerobic respiration
WATER GAIN = WATER LOSS
The Human Urinary System
The functions of these parts of the urinary system are:
Part
Renal artery
Renal vein
Kidney
Ureter
Bladder
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Function
Carries blood TO the kidney
Carries blood FROM the kidney
Regulates water
Carries urine from kidney to bladder
Stores
urine
Removes
waste (urea) from the blood
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The kidneys
 are the main organs for regulating water content of blood
 change the VOLUME & CONCENTRATION of URINE
 remove poisonous waste, called urea*, from the blood
* Urea is produced from the breakdown of amino acids. This happens in the liver. The urea is then
transported, dissolved in the plasma of the blood to the kidney, where it is excreted.
How the Kidney works
The kidneys function by:
FILTRATION
REABSORPTION
FILTRATION occurs in the glomerulus, both poisonous and useful substances are filtered from the blood.
The glomerular filtrate is captured by the Bowman’s Capsule, and moves into the tubule.
In the tubule, useful substances, glucose, most of the water are reabsorbed, back into the blood. They go into the
blood capillary running alongside the tubule.
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The role of ADH in regulating Water Balance
ADH (Anti diuretic hormone)
 Hormone, made of protein
 Produced in the pituitary gland (at base of the brain)
 Increases permeability of tubule to water
 Causes more water to be reabsorbed (reduces volume/ increases concentration of urine)
If there is too little water in the blood*, the brain detects this and causes the pituitary gland to produce more
ADH. This causes the kidney to reabsorb more water from the glomerular filtrate and so reduces the volume of
urine produced. The concentration of urine is increased.
If there is too much water in the blood, the brain senses this and causes the pituitary gland to produce less
ADH. This causes the kidney tubule to reabsorb less water. The volume of urine is produced increases, the
concentration decreases.
* Too little water in the blood is caused by sweating a lot, not drinking enough or eating lots
of salt.
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If the kidneys become damaged (diseases, accident) then toxic wastes build up in the body.
This is fatal if left untreated. 2 treatments are possible.
 Kidney dialysis on a kidney machine
 Kidney transplant
In the kidney machine, only harmful substances are filtered out of the blood, useful
substances stay in the blood, so there is no need fro reabsorption.
Comparison of Machines and Transplants
Kidney Machine
Benefits
Drawbacks
Prevent death
Expensive
Restrictive (dialysis takes several hours, 2
or 3 times a week)
Transplant
Allows a normal life to be lead
Donor shortage
Possible rejection of kidney – so drugs
taken rest of life
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RESPONDING TO THE ENVIRONMENT
Animals need to respond to changes in their environment to ensure their survival e.g.
Animals
Stimulus
Response
Survival Value
Woodlouse
Dampness
Move towards it (high humidity)
Prevent drying out
Flatworms
Extract of
Moves towards it
Source of food
Moves away from it
Escapes predation/
liver
Earthworms Light
drying out
Euglena
Light
Moves towards it
Euglena
photosynthesises
Rhythmical Behaviour
Animal behaviour shows regular changes triggered by environmental changes. e.g. Light &
dark, long/ short days. Migration in geese is an annual rhythmical behaviour triggered by
changes in daylength. Activity in shore crabs is a TIDAL rhythm triggered by tidal
movements.
The main features of rhythmical behaviour are:
 Regular occurs at fixed intervals
 Triggered started by an external stimulus
 Persistent continues even if the trigger stimulus is absent (e.g. shore crabs show behaviour patterns
related to tidal changes even when placed in a non tidal tank
Rhythmical behaviour helps animals exploit regular changes in their environment. e.g. it makes sure
They have their young at a time when food is plentiful and weather is fine (daylength triggers mating in deer,
sheep & blue tits). This increases the chances of survival.
For shore crabs, being active during specific periods of the tide cycle allows them to obtain food as the tide comes
in and escape predation by hiding when the tide is receding.
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PROBLEM SOLVING
Percentage Calculations.
PERCENTAGE CALCULATIONS
3 Types of percentage calculation can be asked:
Percentage change (increase or decrease):
To find the
change
End value—start value
Percentage change =
X 100
To change to a
percentage
Start value
STEP 1
STEP 2
STEP 3
(use a calculator!!!!!):
Find the START Value (in the question)
Find the END value (in the question)
FIND OUT HOW MUCH IT HAS CHANGED
END VALUE – START VALUE
STEP 4
-
Divide this answer by the START VALUE
STEP 5
-
Multiply that answer by 100
If the answer is negative the factor has decreased, if it is positive the factor has increased
e.g. Calculate the percentage change in blood flow to the skeletal muscles during exercise, if it rises from 10 l/min to 30l /min.
Percentage change = 30-10 ÷ 10 X 100 = 20÷10 X 100 = 200% change (increase).
Percentage of:
To calculate the proportion the subset forms of the total
This asks what percentage a subset is of the total
Percentage of =
Size of subset
To change to a
percentage
X100
Total
e.g. What percent of the whole population has blood group AB?
Blood Group
A
B
AB
O
Number
24
45
33
86
Total = 24 + 45 + 33 + 86 = 188
Subset = 33
Percentage = 33 ÷ 188 X 100 = 17.6%%
How many, if the percentage is already given:
Total X Percentage
Number =
100
e.g. If 20% of a class of 40 have blue eyes, how many of the class has blue eyes?
Total =40
Number = 40 X 20 ÷ 100
= 800 ÷ 100 = 8
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Ratios
A ratio is a way of showing the relationship between two or more values.
For example a forest contains two types of deer, Roe deer and Fallow deer. The deer are counted and
360 Roe deer are found, but only 120 Fallow deer are present. To express this as a ratio a number of
steps can carried out.
 each by 120
1. Try to divide the large number by the small number 360 : 120
3:1 this is the simplest whole number ratio.
Second example.
The head teacher wishes to know the ratio of male staff to female staff in the school. There are 32
male staff and 56 female staff
1. Try to divide the large number by the small number 32: 56  each by 32
1:1.75, not a whole number ratio so move to next step
2. Divide both sides by the largest number which goes in evenly,
32:56
 each by 4
8: 14
 each by 2
4:7 This is the simplest whole number
ratio, the two numbers cannot be divided evenly by the same number!
Third example
The EU fishery minister suggested that the North Sea contained very little cod, but much more
herring. The survey shows that there were 175 cod, and 1,260 herring. What is the ratio of cod:
herring.
1. Try to divide the large number by the small number 175 : 1260
 each by 175
7.2:1, not a whole number so move to next step
2.Find a number that will divide evenly into both sides (the same number for each side)
175: 1260
 each by 5
35:252 can they be divided again?
35:252
5:36
 each by 7
This is the simplest whole
number ratio, the two numbers cannot be divided evenly by the same number!
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Chemical
Tests
TESTS
pH Scale (Acidity/ Alkalinity)
The pH Scale gives a measure of how acidic or alkaline a solution is:
1
COLOUR of
pH indicator
2
RED
3
4
5
6
7
GREE
pH
ORANG YELLOW
8
9
10
11
BLUE
12
13
14
PURPLE
pH is measured using pH indictor or paper
The pH falls (becomes more acidic) when fats are broken down to fatty acids (& glycerol), or protein
are broken down (to give amino acids)
Carbon Dioxide
Carbon dioxide is the gas used up in photosynthesis and produced in aerobic respiration in animals and
plants (along with water) and in anaerobic respiration in plants (along with alcohol). In experiments it
can be absorbed by soda lime or potassium hydroxide.
Carbon dioxide turns limewater milky.
Bicarbonate indicator can be used to tell how much carbon dioxide is present
Carbon Dioxide
Colour of Bicarbonate Indicator
Zero
Normal (0.03%
High
Purple
Red
Yellow
Experimental Design
In a scientific experiment a test is only fair if only one variable factor has been changed at a time.
Examples of variable factors are time, lengths, volumes, weights and concentrations. If more than one
is is
changed between experiments the test is not fair. A fair test is also a VALID test.
Experiments are repeated to make them more RELIABLE or REPRESENTATIVE. To make an
experiment more accurate better equipment must be used e.g. a more accurate balance or replace a
ruler having centimetre divisions with one having millimetre divisions.
Food Tests
Food Type
Reagent
Procedure
Positive result
Glucose (sugar)
Benedict’s
Heat with sample at 95°C
Turns from blue to orange
Starch
Iodine
Add to sample
Turns from orange to blue/
black
Protein
Biuret
Heat with sample
Turns from to violet
Fats
Alcohol and
water
Shake with sample.
Solution goes cloudy
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CHARTS
Charts/Graphs
In Biology two types of chart are used:
the BAR chart and the LINE GRAPH
Usually a question tells you which to draw.
BAR CHART
When data concerns the numbers in various groups, then a bar chart is used
Number
RED
37
40
BLUE
15
35
YELLOW
7
30
WHITE
3
GREEN
24
Number
Colour of Flower
25
20
15
10
Germination (%)
0
7
80
10
24
70
20
59
60
30
74
40
37
50
2
Germination (%)
Temperature (ºC)
GREEN
WHITE
YELLOW
BLUE
RED
Label; axes names and units (if any)
5
copy the column headings. The first set of
0
information goes on the horizontal axis, the
second on the vertical axis.
Devise a scale (divide the axis up evenly).
Find the highest value in your data.
37
Colour of Flower
Count the number of large squares on your vertical axis 8
Divide the highest value by the number of squares,
37/8 = 4.625
round your answer up to the nearest easy* number. i.e. 5 Each large square is worth 5
*easy numbers are usually 1, 2, 5, 10, 50, 100 etc.
Draw the bars (you should make each bar the same width and leave a gap between the bars (you won’t
lose marks if you don’t)
LINE GRAPH
Line graphs are used when both sets of data are numbers. A scale must be used on both axes.


50
40

30
20

10
Label axes by copying the column headings

(first 1st—horizontal, 2nd column—vertical)

0
Devise scales for both axes
0
10
20
30
40
50
Horizontal 50/10 = Each big box is worth 5 ºC
Temperature (ºC)
Vertical 74/8 = 9.25, Each big box is worth 10%
Plot the points and join with a straight line (Only join 0,0 if that point is in the data)
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ADH
Hormone which regulates water
Aerobic respiration
chemical reaction to release energy which requires oxygen
Amino acid
Basic unit of protein molecule
Amnotic sac
Membrane surrounding the developing foetus
Amylase
Enzyme which breaks down starch into simple sugars
Anus
Opening through which faeces are ejected
Bowman's capsule
End of the kidney tubule which collects the filtrate
Canine
Tooth used for ripping and tearing
Carbohydrate
Chemical containing carbon, hydrogen and oxygen
Carnivore
Meat-eater
Collecting duct
Tube which takes urine from the tubules to the ureter
Fat
Chemical containing carbon, hydrogen and oxygen
Fatty acid /Glycerol
Basic units of fats
Fertilisation
Fusion of an egg and a sperm cell
Gall bladder
Stores bile
Glomerulus
Knot of capillary blood vessels
Herbivore
Plant eater
Incisor Tooth
used for cutting
Lacteal
Small lymph vessel in the villus which absorbs the products of fat digestion
Large intestine
where water is absorbed
Lipase
An enzyme which breaks down fat into fatty acid and glycerol
Metabolism
all of the chemical activity taking place within an organism
Molar/Premolar
Tooth used for grinding and chewing
Nephron
Kidney filtration unit
Oesophagus (gullet)
Connects mouth to stomach
Omnivore
Eats plants and meat
Ovary
Site of production of ova (eggs)
Oviduct
Tube which carries the ova; site of fertilisation
Ovum (egg)
Female gamete
Pancreas
Makes digestive juices containing enzymes
Penis
Organ for transferring sperm into the female
Peristalsis
Muscular contractions which move food through the intestines
Placenta
Region of the uterus wall where materials are exchanged
Protease
An enzyme which breaks down protein into amino acids
Protein
Chemical containing carbon, hydrogen, oxygen and nitrogen
Rectum
Area of bowel for temporary storage of waste
Renal artery
Blood vessel carrying blood to the kidney
Renal vein
Blood vessel carrying blood away from the kidney
Rhythmical Behaviour
shown on a regular, predictable pattern
Salivary glands
Site of saliva production
Small intestine
Site of absorption of products of digestion
Sperm
Male gamete
Stimulus
Change in the environment
Stomach
Main site of chemical digestion
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Testes
Site of sperm production
Urea
Waste product from the breakdown of amino acids
Ureter
Tube which carries urine to bladder
Urethra
Tube which carries urine from bladder to outside the body
Uterus
Organ in which the foetus develops
Vagina
Organ in which sperm are deposited
Villus
Finger-like fold in the wall of the small intestine
Yolk sac
Food store used by fish embryo
Zygote
Fertilised egg
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