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Biology

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Definitions
Eukaryotic
Prokaryotic
Protoctists
Pathogen
Herbaceous
Legume
Mycelium
Hyphae
Chitin
Saprotrophic
Cell
differentiation
Organelle
Stem cell
Transpiration
Translocation
Dominant
Recessive
Homozygous
Heterozygous
Phenotype
Genotype
Codominance
Population
Community
Habitat
Ecosystem
Biodiversity
Abiotic
Biotic
Producers
Single-celled
Unicellular
Things that aren’t fungi, plants or animals
Something that causes disease
Herbs
Edible part of pea plant
Vegetative part of fungus
What makes up mycelium
Fibrous substance, makes up fungi’s cell wall
Saprotrophic nutrition is when enzymes are
secreted onto the food and broken down for the
nutrients to be absorbed.
How a normal cell becomes a specialised cell
A group of specialised cells
An undifferentiated cell
Evaporation of water on the surface of a plant
Movement of something
One allele is required for the phenotype
Two alleles are required for the phenotype
Two alleles of the same
Two different alleles
Physical trait
Genetic constitution
When both alleles are expressed in the phenotype
A community of animals or plants
The collection of animals or plants
Where a community lives
The habitat with the community, atmosphere etc.
Variety of living organisms in an ecosystem
Non-living factor
Living factor
An animal that produces its energy from the sun
Primary
consumers
Secondary
consumers
Tertiary
consumers
Decomposers
An animal that eats the producer
Eats primary consumer
Etc.
Organisms that break down dead/decaying
organisms
Characteristics of living organisms:
Organisms need:
1. Nutrition –provide them with energy and help grow and repair.
Nutrients are protein, fats, carbohydrates, vitamins, minerals.
2. Respiration – to release energy, uses food.
3. Excretion of waste – Waste products, such as carbon dioxide
and urine, must be removed via excretion.
4. Response to surroundings – react to changes in surroundings.
5. Movement – move to food, away from predators.
6. Control of internal conditions – temperature and water content
7. Reproduction – to produce offspring to survive
8. Growth and development – to become adult.
Variety of living organisms:
Cells can be eukaryotic, which includes all plant and animal cells, or
prokaryotic, such as bacteria.
A unicellular organism is one that consists of a single cell.
A multicellular organism is one that consists of many cells.
Plants
Multicellular organisms.
Flowering
Cells contain chloroplasts, so can carry out
plants, maize.
photosynthesis.
Herbaceous
Cell walls made of cellulose.
legumes, peas
Stores carbohydrates, such as starch or
or beans.
sucrose.
Animals
Multicellular organisms.
Mammals,
Cells don’t contain chloroplasts, no
humans.
photosynthesis.
No cell walls.
Respond rapidly to changes in environment
due to nervous co-ordination.
Can move from place to place.
Stores carbohydrates as glycogen
Fungi
Can’t photosynthesise.
Some have body organised into a mycelium
made from hyphae, which contain many
nuclei.
Some are unicellular.
Cell walls made of chitin.
Feed via saprotrophic nutrition, which is when
they secrete extracellular enzymes onto the
food to dissolve it, then absorb nutrients.
Can store carbohydrate as glycogen.
Protoctists Unicellular.
Some like animal cells, some like plant cells.
Insects,
houseflies or
mosquitos.
Bacteria
Unicellular.
Have cell wall, membrane, cytoplasm,
plasmids.
No nucleus, contain circular chromosome of
DNA.
Some photosynthesise, others feed off other
organisms.
Lactobacillus
bulgaricus, rodshaped, used in
milk
production.
Pneumococcus,
spherical,
causes
pneumonia.
Viruses
Not living, small particles, smaller than
bacteria.
Tobacco
mosaic virus,
Mucor, hyphal
structure.
Yeast,
unicellular.
Amoeba, like
animal cell.
Chlorella, like
plant cell
Parasitic, reproduce inside living cells.
Infect every living organisms.
Wide variety of shapes and sizes.
No cellular structure, protein coat, contain
DNA or RNA.
causes
discolouring of
tobacco plant
leaves.
Influenza,
causes flu and
HIV.
Cell structure:
A collection of organelles creates a cell.
A collection of cells creates a tissue.
A collection of tissues creates an organ.
A collection of organs creates an organ system.
Animal cell:
Animals are multicellular organisms.
Nucleus
Cell membrane
Cytoplasm
Ribosomes
Mitochondria
Plant cell:
Contains genetic material. Controls cell activity.
Controls the entrance and exit of substances.
Where the chemical reactions take place. Contains
enzymes that control the reactions.
Small organelles where proteins are made.
Small organelles where aerobic respiration takes place.
Plants are multicellular organisms.
Special features a plant cell has:
Chloroplasts Carries out photosynthesis, makes food, contains chlorophyll.
Vacuole
Large organelle, contains cell sap, helps support cell
Cell wall
Rigid, made of cellulose, surrounds cell membrane, supports
and strengthens cell.
Stem Cells:
Specialised cells, such as red and white blood cells, are created via
cell differentiation.
As the cells change, they develop different organelles and turn into
different types of cells.
Stem cells are undifferentiated cells, which can divide into many
more undifferentiated cells.
Embryonic stem cells are mostly found in early human embryos.
They are very useful since they can turn into any cell in the body.
Other types of stem cells can be found in the bone marrow of adults,
but they can’t turn into any cell type, only blood cells.
Adult stem cells are already being used to cure diseases associated
with the blood, but embryonic stem cells could be used to replace
faulty cells, such as insulin-producing cells in diabetes and nerve cells
for people who are paralysed.
However, there are risks involved.
Stem cells grown in a lab could become contaminated with a virus,
which could be passed onto the patient.
Some people are against stem cell research, since they feel human
embryos shouldn’t be used for experiments.
Other people believe that suffering patients are more important
than embryos.
Biological Molecules:
Carbohydrates
Elements Carbon, hydrogen,
oxygen
Examples Starch, glycogen
Proteins
carbon, nitrogen,
hydrogen, oxygen
Lipids/Fats
carbon, hydrogen,
oxygen
Chains
Made of smaller
units, e.g. glucose or
maltose.
Made of amino
acids.
Made of fatty acids
and glycerol.
How to make a food sample:
Add water and allow the
food to dissolve. Stir
and filter the solution to
get rid of the solid bits
Get food and grind with
pestle and mortar
Benedict’s test for glucose:
Add 10 drops of Benedict's
solution to test tube. Place
in water bath with tube
pointing away. Leave for 5
minutes.
Prepare food sample. Add
5cm3 to a test tube. Prepare
a water bath set to 75C.
Iodine solution for starch:
Add 5cm3 to a test
tube. Add drops of
iodine. Shake.
If contains starch,
change from
browny-orange to
black/blue-black
Biuret test for proteins:
Add 2cm3 to a test
tube. Add same
volume of biuret
solution.
Shake the test tube.
If contains protein,
change from blue to
pink or purple.
Sudan III test for Lipids:
Add 5cm3 of food. Add
2cm3 of ethanol. Shake
tube. Pour ethanol
layer into another test
tube.
Add 2cm3 of water. If
contains lipid, milky
emulsion.
If contains glucose, change
from blue to green/yellow
for low concentration,
brick-red for high
concentration
Enzymes:
Enzymes are biological catalysts produced by living things.
It speeds up a reaction without being changed or used up in the
reaction.
Each enzyme only speeds up one reaction since each has a specific
active site.
This is called the lock and key model.
Enzymes need specific conditions to work at their best. These are
called optimal conditions.
If the temperature is too hot, the bonds holding the enzymes
together break and the enzyme is said to be denatured.
This is the same with pH.
Investigating how temperature/pH affects enzyme
activity:
Mix starch and amylase
together and heat to
specific temperature.
Put a drop of iodine into
each depression on the
spotting tile. Every 10
seconds, add a drop of the
mixture into a depression.
Repeat with the water
bath at different
temperatures or add
different buffer solutions
to the mixture
When the iodine remains
browny-orange, meaning
there is no more starch,
stop the stopwatch.
Amylase catalyses the breakdown of starch into maltose.
When the iodine remains brown-orange, it means that the reaction is
complete.
When you change the temperatures, you can see which temperature
is optimal for the speed of the reaction, so you know what the
optimal temperature of the enzyme is.
Movement of substances in and out of cells:
Cell membranes only allow substances of a certain size to enter the
cell.
Factors affecting movement of substances:
1. Higher surface area to volume ratio = higher rate of movement
2. Shorter distance = higher rate, such as thin cell membranes
3. Higher temperature = higher rate, since more energy, move
faster.
4. Higher concentration gradient = higher rate of diffusion and
osmosis. Since they move from an area of high concentration to
low concentration.
Diffusion:
Diffusion is the net movement of particles from an area of higher
concentration to an area of lower concentration.
The particles move down the concentration gradient.
Diffusion doesn’t require energy. It happens in fluids.
The higher the concentration gradient, the faster the diffusion rate.
This happens in cells when glucose and amino acids go into them.
Investigating diffusion in a non-living system.
Make agar jelly by
mixing phenolphthalein
and sodium hydroxide.
Put hydrochloric acid in
a beaker. Put cubes of
jelly into beaker.
Cubes will eventually
turn colourless as acid
diffuses into agar jelly
and neutralises sodium
hydroxide
Phenolphthalein is pink in alkaline solutions and colourless in acidic
solutions.
Since the cube turns colourless, the hydrochloric acid must have
diffused into the jelly and neutralised the sodium hydroxide.
Osmosis:
Osmosis is the net movement of water molecules across a partially
permeable membrane from a region of higher water concentration
to a region of lower water concentration.
A partially permeable membrane is a membrane with small holes
thay only allow small molecules to pass through them.
This happens in cells when tissue fluid moves out of the capillaries
and into other cells to provide them with water.
Investigating osmosis using a living system:
Cut a potato into identical
cyclinders. Fill beakers with
different sugar
concentrations. One should
be pure water.
Measure length of cylinders
and leave 4 cylinders in each
beaker for 30 mins. Take
them out and measure
lengths again.
If the cylinders drew in
water, they will be longer. If
water has been drawn out,
they will be shorter.
The cylinders in the pure water will be longer since there will be a
higher concentration of water outside the cylinders.
Investigating osmosis using a non-living system:
Put visking tubing over
the end of a thisyle
funnel with sugar
solution. Put this in a
beaker of pure water.
Measure where the
sugar solution comes up
to on the glass tube.
Leave overnight and
measure again.
Water will be drawn in
through the visking
tubing by osmosis,
forcing solution up the
tube.
Visking tubing is a partially permeable membrane, so only allows
water through. Since there is a higher concentration of water outside
the tube, it moves into the funnel via osmosis across the partially
permeable membrane.
Active Transport:
Active transport is the movement of particles against a
concentration gradient, from an area of lower concentration to an
area of higher concentration, using energy released during
respiration.
This is used in cells when the digestive system gains nutrients from
the blood, or when minerals from the soil get into a plant’s root hair
cells.
Human Nutrition:
Nutrient
Carbohydrate
Lipids
Proteins
Source
Pasta, rice, sugar
Butter, oily fish
Meat, fish
Function
Energy
Energy, energy store, insulation
Growth and repair of tissue.
Energy in emergencies.
Vitamin A
Liver
Improve vision, keeps skin, hair
healthy
Vitamin C
Fruit
Prevents scurvy
Vitamin D
Eggs, sunlight
Calcium absorption
Calcium
Milk, cheese
Make bones and teeth
Iron
Red meat
Make haemoglobin
Water
Food, drink
Every bodily function. Constant
supply to replace water lost
through urinating, breathing,
sweating
Dietary Fibre bread, fruit
Aid food movement through gut
If you are more active, you need more energy, to keep up with this.
If you are a child or teenager, you need more energy to grow.
If you are pregnant, you need more energy to provide the energy for
the baby to develop.
Investigating energy content in a food sample:
Use dry food. Weight it and
skewer onto a needle. Add
a set volume of water to a
boiling tube.
Measure temperature of
the water and light the food
using a Bunsen burner.
Ensure the Bunsen burner
isn't near the tube.
If the food goes out, relight.
Continue until the food
can't catch fire. Measure
temperature of the water
again.
Use 𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑓𝑜𝑜𝑑 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 × 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 ×
4.2 to find the energy in food. The 4.2 is the amount of energy
needed to raise the temperature of 1g of water by 1C.
You can use 𝐸𝑛𝑒𝑟𝑔𝑦 𝑝𝑒𝑟 𝑔𝑟𝑎𝑚 =
𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑓𝑜𝑜𝑑
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑓𝑜𝑜𝑑
to find the energy
per gram.
This experiment isn’t perfect. Lots of energy is lost to the
surroundings, which is the results will be extremely incorrect. You
could insulate the boiling tube to minimise heat loss.
Digestive enzymes help to break down big molecules, such as starch,
into smaller ones, such as maltose or glucose.
Alimentary Canal:
Mouth
Oesophagus
Liver
Gall Bladder
Large
Intestine
Rectum
Stomach
Salivary glands produce amylase in saliva. Teeth break down food
Muscular tube, connects mouth and stomach
Bile produced
Bile stored
Colon, excess water absorbed
Last part of large intestine. Faeces stored.
Pummels food. Produces pepsin. Produces hydrochloric acid to kill
bacteria and give optimum pH for protease to work.
Pancreas
Produces protease, amylase, lipase. Releases these into small intestine.
Small
Produces protease, amylase and lipase. Where nutrients are absorbed
intestine
out of alimentary canal into body. First part=duodenum. Last part=ileum.
The bile stored in the gall bladder is released into the small intestine.
This is because the hydrochloric acid makes it too acidic, so the
enzymes can’t work.
The bile neutralises the acid and makes conditions alkaline.
It also emulsifies fats, breaking it down into smaller droplets, making
a larger surface area for lipase the work on, speeding up digestion.
Food is moved through the guy by peristalsis.
Peristalsis uses waves of circular muscle contractions to squeeze
boluses through the gut.
The small intestine is adapted for absorption:
 It is very long, so there is lots of time to break down and absorb
all the food before the end.
 Large surface area since the walls are covered with villi:
Each cell on the villi has their own microvilli, increasing the surface
area further.
They have a single permeable layer of surface cells and a very good
blood supply, assisting rapid absorption.
Plant Nutrition:
Photosynthesis produces glucose, which is food, in plants.
It occurs in the leaves of all green plants, inside the chloroplasts. The
chlorophyll absorbs sunlight and uses energy to convert carbon
dioxide and water into glucose and oxygen.
It converts light energy into chemical energy, stored in glucose,
which is released when broken down during respiration.
Carbon dioxide + water glucose + oxygen
6CO2
+ 6H2O C6H12O6 + 6O2
Limiting factors affecting the rate of photosynthesis:
A limiting factor is something that stops photosynthesis from
happening any faster. Light and carbon dioxide levels are limiting
factors for photosynthesis.
Factors affecting the rate of photosynthesis:
 Light – limiting factor. As light intensity increases, so does the
rate of photosynthesis, up to a certain point.
 Carbon dioxide – limiting factor. As carbon dioxide level
increases, so does rate of photosynthesis, up to a certain point.
 Temperature – As temperature increase, so does the rate of
photosynthesis, up to a certain point. After that, the
temperature is too high, so the enzymes become denatured.
Leaf adaptations for photosynthesis:




Leaves are broad, so large surface area
Most of chloroplasts found at top of leaf, closest to sunlight
Upper epidermis is transparent, so light can pass through
Network of vascular bundles transport water and nutrients to
every part of leaf and take away glucose. Also support leaf
structure
 Waxy cuticle reduces water loss by evaporation
 Stomata allow carbon dioxide to diffuse directly into the leaf
Testing a leaf for starch:
Dunk leaf in boiling
water. This stops any
chemical reactions.
Put leaf in boiling tube
with ethanol. Heat in
water bath until boils.
This rids any chlorophyll,
making leaf white-ish
Rinse leaf in cold water.
Add drops of iodine. If
starcg, leaf turns blueblack
This shows photosynthesis is taking place, since if a plant can’t
photosynthesise, it can’t make starch.
Investigating whether chlorophyll is needed for
photosynthesis:
Take variegated leaf
from plant that has been
exposed to light. Record
which bits are green and
which aren't
Test the leaf for starch,
see above. Only the
green bits turn blueblack.
This suggests only the
parts of the leaf that
contained chlorophyll
can photosynthesise and
produce starch
Investigating if carbon dioxide is needed for
photosynthesis:
Add plant to a sealed
bell jar with soda lime
in an evaporating dish.
The soda lime will
absorbs CO2 out of the
air. Leave the plant for
a week.
Investigating whether light is needed for
photosynthesis:
Put a plant in a dark room,
but ensure it is warm and
has enough carbon
dioxide.
Leave for 48 hours. Test a
leaf for starch. It won't
turn blue-black, since it
can't photosynthesise or
produce starch.
Test for starch. It won't
turn blue-black, since it
can't photosynthesise
or produce starch
Investigating the rate of photosynthesis by measuring
oxygen production:
Place a source of white light
at a specific distance from
the pondweed, that is in a
test tube with water and
sodium hydrogencarbonate
Leave to photosynthesise for
1 hour. Oxygen will be
collected in the capillary tube
as a bubble. Measure the
length of the bubble.
Repeat with lamp at different
distances, or vary
temperature by using a water
bath or pH by using buffer
solutions.
The length of the bubble is
proportional to the amount
of oxygen produced.
Plants need certain mineral ions to grow:
Mineral ion Makes
Nitrate
Contains nitrogen for amino acids and proteins
Phosphates Contains phosphorous for DNA and cell membranes
and needed for respiration and growth.
Potassium Helps enzymes for photosynthesis and respiration.
Magnesium Makes chlorophyll.
Respiration:
Respiration is the process of transferring energy from glucose. It
happens in every cell.
Some energy is transferred by heat. Most is stored in ATP.
When energy is needed, ATP molecules break down and energy is
released.
There are two types of respiration, aerobic and anaerobic.
Aerobic Respiration:
Uses oxygen. Most efficient way to transfer energy from glucose.
Produces 32 molecules of ATP per molecules of glucose.
Glucose + oxygen carbon dioxide + water (+ energy)
C6H12O6 + 6O2 6CO2 + 6H2O
Anaerobic Respiration:
doesn’t use oxygen. Not efficient. Produces 2 molecules of ATP per
molecule of glucose, since glucose is only partially broken down, and
lactic acid is produced.
When lactic acid builds up in muscles, it leads to cramp.
Glucose lactic acid (+energy)
Anaerobic respiration in plants produces ethanol and carbon dioxide,
rather than lactic acid:
Glucose ethanol + carbon dioxide (+energy)
Investigating the evolution of carbon dioxide and heat
from respiring seeds:
Prepare a set of germinating seeds
and boiling seeds, which will act as
the control.
Place the same amount of
hydrogen-carbonate indictaor in
two test tubes. Place a gauze
platform in each test tube and
place the beans on them.
Seal with a rubber bung and leave
for an hour. The germinating seeds
will turn the indicator yellow,
showing carbon dioxide is
produced. The boiled beans will
have no change.
The boiled seeds are dead, so respiration isn’t carried out, so no
carbon dioxide is produced, so the indicator stays the same.
The germinating seeds are respiring, so they produce carbon dioxide,
so the indicator turns yellow.
Gas exchange in plants:
Waste products, such as oxygen from photosynthesis and carbon
dioxide from respiration, diffuse out of the plant through little holes
at the bottom of the leaves, called stomata.
When a plant is photosynthesising, it uses lots of carbon dioxide, so
there is very little in the leaf. Due to diffusion, this makes the carbon
dioxide from the atmosphere diffuse into the leaf.
It also produces oxygen as a waste product, so there is lots in the
leaf. Due to diffusion, it diffuses out of the plant into the atmosphere
Photosynthesis only happens during the day, but plants respire all
the time.
During the day, plants make more oxygen by photosynthesis than
respiration, so they release oxygen. They also use more carbon
dioxide than produced, so they take in oxygen.
At night, this swaps around.
Leaf Adaptations for Efficient Gas Exchange:
 Broad, so large surface area for diffusion
 Thin, short distance to travel
 Air spaces, so gases can move easily between cells. Increases
surface area for gas exchange
 Stomata allow diffusion of gases and transpiration
Stomata:
Photosynthesis can’t happen in the dark, so carbon dioxide is no
longer required.
Because of this, the stomata close, so that water can’t escape, and
the plant doesn’t dry out.
Stomata also close when supplies of water begin to run out. This is
because they don’t want the plant to photosynthesis, since if it did, it
would use up the water, causing the plant to dry up and die.
The opening and closing of the stomata is controlled by the guard
cells surrounding them.
The guard cells can change their shape and volume to open and
close. An increase in volume opens the stomata. A decrease in
volume closes the stomata.
Investigating the effect of light on net gas exchange
from a leaf, using hydrogen-carbonate indicator:
Add same volume of
hydrogen-carbonate indicator
to four boiling tubes. Put same
size healthy-looking leaves into
3 tubes.
Seal with a rubber bung and
trap the stem of the leave with
the bung, so it doesnt touch
the indicator. Wrap one boiling
tube with tin foil, another with
gauze.
Place all the tubes in bright
light. Leave for an hour and
check colour of indicator.
There will be no change in the control tube since there was no
change in carbon dioxide levels.
The one wrapped in foil will turn yellow, since photosynthesis can’t
take place, but respiration can. Therefore, carbon dioxide is being
produced by respiration, but not used up by photosynthesis, so the
carbon dioxide levels will increase, turning the indicator yellow.
The one wrapped in gauze will stay roughly the same colour, since
the rate of photosynthesis and respiration will be similar.
The uncovered one turns purple, since the rate of photosynthesis is
higher than the rate of respiration, more carbon dioxide is being
used up than taken in, lowering carbon dioxide levels, turning
indicator purple.
Gas exchange in Humans:
Trachea
Bronchiole
Bronchus
Alveoli
Diaphragm
Windpipe. Connects mouth and nose to lungs
Connected to alveoli
Thick tube. Divides into bronchioles
Tiny air sacs where gas exchange takes place
Separates the thorax from the rest of the body. Sheet
of muscle that helps with breathing
Muscles between ribs to control it during breathing.
Intercostal
muscle
Rib
Protects everything within it
Pleural
Lubricates lung to reduce friction by sticking to the
membranes outside of lungs and inside of chest cavity. Lungs
follow chest movement.
Breathing:
Intercostal muscles and diaphragm contract.
Thorax volume increases.
Decreases pressure, draws air in.
Intercostal muscles and diaphragm
relax.
Thorax volume decreases, air
forced out.
Alveoli adaptations for gas exchange:

blood next to alveoli is very close, and there is
a high concentration gradient; the blood has a high
concentration of carbon dioxide and low conc of
oxygen.
 When blood reaches body cells, oxygen is
released from red blood cells. There is a high
concentration gradient between the blood and the
cells; the blood has a high conc of oxygen.
 Millions of alveoli, high surface area
 Moist lining for gases to dissolve in
 Walls of 1 cell thick, short diffusion distance
 Great bloody supply to maintain high
concentration gradient
 Walls are permeable, easy to diffuse.
Smoking problems:
Emphysema:
Smoking damages walls inside alveoli, reducing surface area, slowing
the rate of diffusion, reducing the amount of oxygen cells can
receive.
Smoker’s cough:
Tar in cigarettes damages cilia, which are meant to catch dust and
bacteria and mucus before they reach the lungs.
If they are damaged, dust, bacteria and mucus enter lungs, taking up
space of air, reducing the amount of oxygen. It could also lead to
infections.
Therefore, smokers cough to rid themselves of these foreign objects.
Bronchitis:
Tar irritates bronchi and bronchioles. More mucus is produced,
which can’t be removed due to the damaged cilia.
This causes chronic bronchitis.
Coronary Heart Disease:
Carbon monoxide irreversibly binds to haemoglobin, stopping
oxygen binding to it, so reducing the amount of oxygen the blood can
carry.
To make up for this heart rate increases, leading to higher blood
pressure.
High blood pressure damages artery walls, making blood clots more
likely, increasing the risk of coronary heart disease, or heart attacks.
Cancer:
Tobacco smoke contains carcinogens.
Investigating the effect of exercise on breathing rate:
Sit still for 5 minute.
Count the number of
breaths in one minute.
Do 4 minutes of exercise.
As soon as you stop, start
counging the number of
breaths in one minute.
Repeat and find average.
Use other people as well.
Breathing rate increases after exercise since your muscles respire
more during exercise, so more oxygen is need and more carbon
dioxide needs to be removed.
Investigating the release of carbon dioxide in breath:
Put the same volume of
limewater in 2 boiling
tubes. Set up the
experiment as shown.
Breathe in and out
several times with your
mouth around the
mouthpiece.
As you breathe in, air from the room is drawn in through boiling tube
A. This air contains very little carbon dioxide, so limewater remains
colourless.
When you breathe out, the air you exhale bubbles through the
limewater in boiling tube B. Since it turns cloudy, it proves that
carbon dioxide was produced during respiration.
Since the limewater in boiling tube A stays clear, you know the
carbon dioxide from the exhaled air was from respiration, since it
was inhaled through boiling tube A.
Transport:
Unicellular organisms don’t require a transport system since their
nutrients and gases can diffuse into them, since there is a short
diffusion distance.
Multicellular organisms require a transport system since without
one, direct diffusion would be too slow, and they wouldn’t get
enough nutrients or gases. Transport systems allow the substances
to move to and from individual cells quickly.
Transport in plants:
Plants have two systems transporting stuff to every part of the plant:
The xylem carries water and mineral salts from the roots up the
shoot to the leaves in the transpiration stream.
The phloem transports sugars, such as sucrose, and amino acids
from the leaves to every other part in the plant. This movement of
food substances is translocation.
Root hair cells absorb water:
The cells on plant roots grow into long
hairs, which stick out into the soil.
There are millions of these, giving the
plant a high surface for water
absorption.
There is a higher concentration of water
in the soil, so it is drawn in by osmosis.
Transpiration:
Transpiration is caused by the evaporation and diffusion of water
from a plant’s surface, usually the leaves.
This causes a slight shortage of water in the leaf, so more water is
drawn up through the xylem vessels.
This means more water is drawn up through the roots, causing a
constant transpiration stream.
Transpiration is an effect of how leaves are adapted for
photosynthesis. Since they have stomata, there is more water in the
plant than outside, so it escapes via diffusion.
Factors affecting transpiration:
 Brighter light, higher transpiration rate since stomata close in
dark and plants can’t photosynthesise. Stomata are closed, no
water can escape.
 Warmer, faster transpiration. When warm, water particles have
more energy to evaporate or diffuse out of the stomata.
 Faster wind speed, faster transpiration. If wind speed is low,
water vapour hangs around the leaf, so the concentration
gradient is small. If wind speed is high, little water particles
around leaf, so higher concentration gradient, so faster
diffusion of water.
 Lower humidity, faster transpiration. If humid, lots of water
around leaf, small concentration gradient. If dry air, almost no
water particles around leaf, high concentration gradient, fast
diffusion.
Investigating how environmental factors affect
transpiration rate, POTOMETER:
Cut a shoot underwater, to
prevent loss of air from xylem, at
a slant, to increase surface area.
Assemble the potometer in
water.
Remove apparatus from water,
keep end of capillary tube in
beaker of water. Check apparatus
is water and airtight. Dry leaves,
leave shoot to acclimatise and
shut the tap.
Remove end of capillary tube
from beaker until one air bubble
forms. Record starting position of
air bubble. Leave for an hour,
measure final position of bubble.
You can change the conditions around the plant:
 Light intensity – lamp to increase, put in cupboard to decrease
 Temperature – change temperature of surroundings
 Humidity – increase by spraying water in a bag and surrounding
the plant with said bag
 Wind – to increase, use a fan.
The further the bubble moves, the faster the transpiration rate, since
more water is being taken up by the xylem to replace the water lost
via transpiration.
Transport in Humans:
Blood is made of:
 Plasma
 Platelets
 Red Blood Cells
 White Blood Cells
Plasma:
Pale yellow liquid. Carries everything that needs to be transported
around the body, such as blood cells, platelets, carbon dioxide, urea,
hormones, heat, digested food products.
Red Blood Cells:
They transport oxygen from the lungs to all the cells in the body.
Adaptations:
 Biconcave shape gives it large surface area for absorption and
release of oxygen
 Contain haemoglobin, allows it to carry lots of oxygen.
 No nucleus, frees up space for more haemoglobin.
White Blood Cells:
Pathogens cause disease and can kill you if allowed to reproduce
rapidly.
The immune system and white blood cells, phagocytes and
lymphocytes, stop this.
Phagocytes:
They detect foreign objects and engulf and digest them. They aren’t
specific and will attack anything that isn’t meant to be there.
Lymphocytes:
Every pathogen has antigens on its surface.
When lymphocytes find a foreign antigen, it starts to produce
antibodies, which are proteins.
These antibodies lock on to the invading pathogens and mark them.
The antibodies produced are specific to that antigen.
Then, antibodies are produced rapidly and mark all other pathogens
of that kind.
Memory cells are also produced. These stay in the body and
remember a specific antigen.
If the same pathogen re-enters the body, this memory cell can
reproduce the antigen very quickly.
Therefore, you are immune to diseases if you already had it.
This is how vaccinations work.
Vaccinations:
Vaccines are dead/inactive pathogen that are injected into the body.
Your lymphocytes then produce the antigen required to combat this
pathogen and store it in a memory cell.
This means that if the active version of the pathogen infects your
body, the lymphocytes already know what antigen to produce, and
can produce it very quickly.
Blood Clotting:
When a blood vessel is damaged, the platelets clump together to
plug up the damaged area.
This is blood clotting and stops you losing too much blood and
prevents other bacteria entering the wound and causing an infection.
The platelets are held together by a mesh of fibrin. The clot also
requires clotting factors.
Blood vessels:
There are 3 different types of blood vessels:
 Arteries
 Capillaries
 Veins.
Arteries:
Blood flowing away from the heart runs through
this.
Therefore, the artery walls are strong and elastic
to withstand the high pressure. The elastic fibres
allow the arteries to expand.
The walls are thick compared to the lumen.
The largest artery in the body is the aorta.
Capillaries:
Arteries branch into capillaries, which are tiny.
They carry the blood very closely to every cell to
exchange substances.
They have permeable walls, so substances can
diffuse, such as waste products, like CO2.
They supply food and oxygen.
Their walls are 1 cell thick, reducing the diffusion
distance.
Veins:
Capillaries eventually join up to form
veins.
The blood is at a low pressure, since
it is travelling to the heart, so the
walls don’t need to be thick, like
arteries.
Bigger lumen to help blood flow.
Have valves to keep blood flowing in
the right direction. Largest vein is the
vena cava.
The Heart:
1. Right atrium receives deoxygenated blood through vena cava
2. Deoxygenated blood moves to right ventricle, which pumps it
to the lungs via the pulmonary artery.
3. Left atrium receives oxy blood from lungs, via pulmonary vein.
4. Oxygenated blood moves to left ventricle, which pumps it to
the whole body via the aorta
The left ventricle has much thicker wall than the right, since it pumps
blood to the whole body, whereas the right only pumps to the lungs.
Therefore, the blood is under higher pressure in the left ventricle.
The valves prevent the backflow of blood.
Exercise increase heart rate, muscles need more energy, so respire
more.
To respire more, you need more oxygen and less carbon dioxide, so
the blood is pumped around faster to give oxygen faster.
You can investigate this by measuring pulse before and after
exercise.
This all done by:
 Exercise increases the carbon dioxide level in the blood
 This is detected by receptors in the aorta and carotid artery
 The receptors send signals to the brain
 The brain sends signals to the heart, telling it to contract more
frequently and with more force.
Adrenaline can also affect heart rate:
If an organism is threated, the adrenal glands release adrenaline.
This binds to specific receptors in the heart and causes the cardiac
muscle to contract more frequently and with more force, so heart
rate increases and pumps more blood.
This increase oxygen supply to muscles, readying the body for action.
Circulation system:
Arteries carry oxygenated blood, except the
pulmonary artery.
Veins carry deoxygenated blood, except the
pulmonary vein.
Pulmonary = lungs
Hepatic = liver
Renal = kidneys
Factors leading to coronary heart disease:
Coronary heart disease is when the coronary arteries, that supply
blood to the heart muscle, get blocked by layers of fatty material.
This causes arteries to become narrow, so blood flow is restricted
and there is a lack of oxygen to the heart muscle, leading to a heart
attack.
Risk factors:
 High saturated fat – fatty deposits form inside arteries
 Smoking – increase blood pressure, causing damage to inside of
coronary arteries. Also, cigarette smoke causes damage that
makes it more likely for fatty deposits to form.
 Inactive – high blood pressure damages artery lining, making it
more likely for fatty deposits to form.
Excretion in Humans:
Kidneys:
Kidneys remove urea, which is produced in the liver
from excess amino acids from the blood.
Adjusts ion/salt levels in the blood.
Adjusts the water content of the blood.
This is all done by filtering stuff out of the blood
under high pressure, then reabsorbing the useful
stuff. The product of all this is urine.
Ultrafiltration:
1.
Blood from the
renal artery flows through
the glomerulus, which is a
bundle of capillaries at the
start of the nephron.
2.
High pressure is
built up, which squeezes
out water, urea, ions and
glucose out of the blood
and into the Bowman’s
capsule.
3.
Membranes
between the blood vessels
in the glomerulus and the
Bowman’s capsule act like
filters, so big molecules, like proteins, aren’t lost. The filtered
liquid in the Bowman’s capsule is known as glomerular filtrate.
Reabsorption and release of wastes:
1. As the filtrate flows through the nephron, useful substances are
reabsorbed.
2. All glucose is reabsorbed from the proximal convoluted tubule
via active transport.
3. Sufficient ions are reabsorbed, excess ions aren’t.
4. Sufficient water is reabsorbed from the collecting duct via
osmosis.
5. The remaining substances form urine, which continues out of
the nephron, through the ureter, into the bladder, where it is
stored until it is released through the urethra.
Osmoregulation:
The kidneys also adjust the body’s water content:
1. Water is taken in via food and drink and lost via sweating,
breathing and excretion.
2. The kidney can balance out the body’s water content by using a
hormone called ADH.
3. ADH makes the collecting ducts of nephrons more permeable,
so more water is reabsorbed.
4. If the body is low on water, lots of ADH is released, so more
water is reabsorbed.
Lung:
The lung excretes carbon dioxide as a waste product of aerobic
respiration during exhalation.
Skin:
The skin excretes excess water and salts through the sweat glands on
the skin producing sweat. This can also act as evaporative cooling.
Co-ordination and response:
Organisms can respond to changes in their external environment to
increase their chances of survival.
They can also respond to changes in their internal environment, to
ensure conditions are always right for their metabolism.
A change in environment is called a stimulus.
Receptors detect stimuli and effectors bring about a response to the
stimuli.
Effectors could be muscle cells or cells found in glands, they could
trigger a muscle to contract and secrete hormones.
Central Nervous System (CNS):
The nervous system consists of all the neurones in your body,
sensory neurones, relay neurones and motor neurones.
The CNS consists of the brain and spinal cord ONLY.
When receptors detect a stimulus, they send electrical impulses
along sensory neurons to the CNS.
The CNS sends electrical impulse to an effector, via motor
neurones. The effector responds.
The CNS coordinates the response. Coordinated responses
always require a stimulus, receptor and effector.
These are very rapid responses since the electrical impulses are
very quick.
Synapses:
The connection between two neurones is a synapse.
The nerve impulse reaches the synapse and
triggers a release of neurotransmitters, which
diffuse across the gap.
When the neurotransmitters reach the next
neurone, they trigger a new electrical signal.
Reflexes are automatic responses to certain stimuli, to remove your
body from danger and stopping it getting damaged. The reflex arc:
1.
In a reflex arc, the neurones
go through the spinal cord, an
unconscious part of the body.
2.
When a stimulus is detected,
an impulse is sent along a sensory
neurone to the CNS.
3.
In the CNS, the sensory
neurone passes on to a relay
neurone, which relays to a motor
neurone.
4.
The impulse travels along the
motor neurone to the effector.
These responses are very fast and don’t wait for you to realise what
is happening.
One example of this is when your finger goes near a hot object or
when a cat sees a predator.
The Eye:
Conjunctiva Lubricates and protects surface of eye
Sclera
Tough outer layer, protects eye
Cornea
Refracts light into eye. Transparent, no blood vessels.
Oxygen diffuses in from outer surface.
Iris
Controls diameter of pupil and how much light in the
eye
Pupil
Hole in the middle
Lens
Focuses light onto retina
Retina
Light sensitive. Covered in rods and cones, which are
light receptors.
Optic nerve Carries impulses from receptors to brain
Rods
More sensitive in dim light. Can’t sense colour
Cones
Sensitive to colour. Not good in dim light.
Fovea
Lots of cones here.
The Iris Reflex:
Very bright light can damage the retina, so there is a reflex to protect
it. Light receptors detect the light intensity and send a message
through the optic nerve, along a sensory neurone, to the brain.
The message continues to a relay neurone, then a motor neurone,
which tells the circular muscle to either contract or relax.
There is also a reflex when focusing on near and distant objects:
Distant Objects:
1. Ciliary muscles relax
2. Suspensory ligaments pull tight
3. Lens becomes thin
4. Refracts light less
Near Objects:
1. Ciliary muscles contract
2. Suspensory ligament slackens
3. Lens becomes fat
4. Light refracts more
Longsighted people can’t focus on near objects, since lens doesn’t
bend light enough, so glasses are used to refract the light more.
Short sighted people can’t focus on distant objects, since the lens
bends the light too much, so glasses are used to refract the light less.
Hormones:
Hormone
Adrenaline
Source
Adrenal
glands
Pancreas
Role
Readies body for
‘fight or flight’
Insulin
Helps control
blood sugar level
Testosterone Testes
Main male sex
hormone
Progesterone Ovaries Supports
pregnancy
Oestrogen
Ovaries Main female sex
hormone
ADH
Pituitary Controls water
gland
content
FSH
Pituitary Female sex
gland
hormone
LH
Pituitary Female sex
gland
hormone.
Effects
Increase heart rate, blood flow to muscles,
blood sugar level
Stimulates liver to turn glucose into
glycogen for storage
Promote male secondary sexual
characteristics
Maintains lining of the uterus
Controls menstrual cycle, promotes female
secondary sexual characteristics
Increase permeability of collecting ducts
Causes egg to mature in ovary. Stimulates
ovaries to produce oestrogen
Stimulates release of egg from ovary.
Differences between hormones and nerves:
Hormones
Nerves
Slower
Very fast
Act for long time
Act for very short time
Act in a general area Act in a precise area.
Homeostasis:
Homeostasis is the maintenance of a constant internal environment.
Homeostasis balances water content and body temperature.
Water content:
Water is taken in by food and drink and lost by sweating, breathing
and weeing.
We can look at urine to see whether you are losing lots of water.
On a hot day or during exercise, you sweat a lot.
You produce less urine, but it is more concentrated, so darker colour.
You lose more water in your breath since you breathe faster.
On a cold day or when you’re not exercising, you don’t sweat.
You produce more urine, which will be paler since it is more dilute.
Body Temperature:
All enzymes work best at a certain optimum temperature, usually
37C, so your body tries to keep it at this temperature.
A part of the brain is constantly receiving messages from
temperature receptors in the skin that provide information about
skin temperature. It is also sensitive to the blood temperature in the
brain.
Based on the signals, your CNS can activate necessary effectors to
maintain this body temperature. The skin helps to maintain body
temperature.
When you’re too hot:
1. Lots of sweat produced
2. Evaporates, transfer energy
from skin to environment, cooling
you down. This is evaporative
cooling.
3. Blood vessels wide, this is
vasodilation. Allows more blood to
flow near surface, so can transfer
more energy to surroundings
When you’re too cold:
1. Little sweat is produced
2. Blood vessels near surface constrict, this is
vasoconstriction. Less blood flows near surface,
less energy lost to surroundings
3. Shiver, increases rate of respiration, transfers
more energy to warm body.
4. Hairs stand on end to trap insulating layer of
air.
Coordination and response in plants:
Plants can also increase their chances of survival by responding to
changes in their environment.
They can sense the direction of light and grow towards it to
maximise light absorption for photosynthesis.
They can sense gravity, so their roots and shoot grow in the right
direction.
Climbing plants have a sense of touch so they can climb and reach
sunlight.
Plants can produce toxins to avoid being eaten.
Plants can produce certain proteins that stop the environment killing
them.
Auxins:
Auxins are growth hormones that control growth at the tips of the
roots and shoots.
They move through the plant dissolved in water.
It is produced in the tips and diffuses backwards to promote cell
elongation, which occurs just behind the tips.
Auxins promotes growth in the shoot but inhibits growth in the root.
Auxins are involved in phototropism and geotropism.
Shoots are positively phototropic:
This means they grow towards the light.
1.
When a shoot tip is exposed to light, the auxin
accumulates on the shaded side.
2.
This makes the cells grow faster on the shaded
side.
3.
This makes the shoot bend toward the light.
Shoots are negatively geotropic:
This means they grow in the opposite direction of gravity.
1. When a shoot grows sideways, gravity forces
the auxin on the lower side.
2. This causes the lower side to grow faster.
3. So, the plant bends upwards.
Roots are positively geotropic:
1. A root growing on its side will have auxin
on its lower side
2. In a root, the auxin inhibits growth, so
the cells on the top grow more than the
bottom, so the root bends downwards.
Roots are negatively phototropic:
1. If root is exposed to light, auxin
accumulates on shaded side.
2. Auxin inhibits cell elongation here, so
side with light grows more than shaded. This
means the light bends away from the light.
Reproduction and Inheritance:
The nucleus of a cell contains all the genetic material in the
form of chromosomes.
Chromosomes are long lengths of DNA coiled up.
A gene is a short section of DNA.
Human cells are diploid, so they have 2 copies of each chromosome,
arranged in pairs.
There are 46 chromosomes in a human cell nucleus. The diploid
number for a human is 46.
Genes:
DNA is a long list of instructions of how to make an organism and
make it work.
All the DNA of an organisms is its genome.
Each gene in a DNA molecule is a chemical instruction that codes for
a protein.
Proteins control most processes in the body and determine inherited
characteristics.
There can be different versions of the same gene, which give
different versions of a characteristic. The different versions of the
same gene are called alleles.
DNA:
A DNA molecule has two strands coiled together in a double helix.
The two strands are held together by bases:
 Adenine (A)
 Cytosine (C)
 Thymine (T)
 Guanine (G)
The bases are paired into A-T and C-G. This is complementary base
pairing.
Protein Synthesis:
Proteins are made of chains of amino acids. Each protein has a
number and order of amino acids.
Amino acid chains fold to give each protein a unique shape, so each
protein has a different function.
Each gene codes for a protein. The order of bases in a gene decides
the order of amino acids.
Each amino acid is coded by 3 bases. This is a codon. Some codons
code for the same amino acid.
Some regions of DNA don’t code for any amino acids but are still
used in protein synthesis.
Proteins are made in two stages:
 Transcription
 Translation
Transcription:
Proteins are made in the cytoplasm by ribosomes. DNA is in the
nucleus and can’t move out of it, since it is big.
To get the information from the DNA out, mRNA is used.
mRNA is also made up by a sequence of bases, but it is shorter, a
single strand and uses uracil (U) instead of thymine (T).
RNA polymerase is the enzyme that joins the base sequence to make
mRNA.
1.
RNA polymerase binds to a noncoding region of DNA in front of a gene
2.
The DNA strands unzip and the
enzyme move along one of the strands
3.
It uses the bases in the gene as a
template to make mRNA. Base pairing
between DNA and RNA ensures that mRNA
is complementary to the DNA’s bases.
4.
Once made, the mRNA moves out
of the nucleus and joins with a ribosome.
If the DNA had the base ATAGC, then the mRNA would have UAUCG.
This is because of the complementary base pairing and uracil (U) is
used instead of thymine (T).
Translation:
1. Amino acids are brought to the ribosome by tRNA
2. The order that the amino acids are brought matches the order
of codons.
3. Part of the tRNA structure is called an anticodon, it is
complementary to the codon for the amino acid. This pairing
ensures that the amino acids are brought in the correct order.
4. The amino acids are joined by the ribosome, making a protein.
Asexual reproduction and mitosis:
A cell can make a new cell by dividing in two. Both cells are
genetically identical, they both contain the same genetic
information. This is called mitosis.
Organisms that use mitosis to reproduce are said to asexually
reproduce.
Asexual reproduction involves only one parent. The offspring have
identical genes to the parent – so there’s no variation between
parent and offspring.
Mitosis is when a cell reproduces itself by splitting to form two cells
with identical sets of chromosomes.
If a diploid cell divides by mitosis, you get two diploid cells.
1.
DNA is spread out in long strings
2.
If the cell gets a signal to divide, it needs to
duplicate its DNA, so there is a copy for each new cell.
The DNA forms X-Shaped chromosomes. Each arm is
an exact duplicate of the other.
3.
The chromosomes line up at the centre of the
cell and cell fibres pull them apart. The two arms go to
opposite ends of the cell.
4.
Membranes form around each sets of
chromosomes. These become the nuclei of the two
cells.
5.
Finally, the cytoplasm divides. You now have
two new cells containing the same DNA – genetically
identical.
Sexual Reproduction:
Sexual reproduction is where genetic information from two
organisms (father and mother) is combined to produce offspring
which are genetically different to either parent.
Both parents produce gametes, father=sperm cell, mother=egg cell.
The gametes are haploid, so they have half the chromosomes in a
normal cell. In a human, the haploid number is 23.
Fertilisation:
The male gamete fuses with the female gamete to form a zygote,
which is a fertilised egg. The zygote ends up with a full set of
chromosomes, 1 half each from each gamete.
The zygote undergoes mitosis and develops into an embryo.
It has a mixture of chromosomes, so inherits features from both
embryos.
There is random fertilisation, making genetic variation in offspring.
Meiosis:
Meiosis is also cell division but doesn’t produce identical cells. It only
happens in the reproductive organs, ovaries and testes. Meiosis
produces four haploid cells with different chromosomes.
1.
Before it starts to divide, it duplicates its
DNA. One arm of each X-shaped chromosome is
the same as the other.
2.
In the first division, the chromosomes
line up. They are then pulled apart, so each new
cell only has one copy of each chromosome.
Some of the father’s chromosomes and some of
the mother’s chromosomes go into each new
cell.
3.
Each new cell has a mixture of the
mother’s and father’s chromosomes. This
creates genetic variation.
4.
In the second division, the chromosomes
line up again and the arms are pulled apart.
5.
This creates 4 haploid gametes, each
gamete only has one set of chromosomes, not
the normal two.
6.
All the gametes are genetically different.
Sexual Reproduction in Plants:
Pollination:
Pollination is the transfer of pollen from an anther to a stigma, so
that male gametes can fertilise the female gametes.
Cross pollination is when pollen is transferred from the anther of one
plant to stigma of another.
Plants that cross pollinate rely on insects or wind.
Insect Pollination:
1. They have brightly coloured
petals to attract insects. Also,
scented flowers and nectaries.
2. Plants produce big, sticky
pollen grains that stick to insects as
they go from plant to plant.
3. The stigma is also sticky, so any pollen picked up by insects on
other plants will stick to the stigma.
Wind Pollination:
1. Dull petals on plant, no need for insects.
No nectaries or strong scents
2. Lots of small and light pollen grains, so
can easily be carried by wind.
3. Long filaments hang anthers outside
flower, so lots of pollen gets blown away.
4. Large feathery stigma outside flower to
catch pollen.
Fertilisation in plants:
1. Pollen grain lands on stigma
2. Pollen tube grows out of pollen
grain and down through style to ovary
and into ovule
3. Nucleus from male gamete moves
down and fuses with female gamete.
4. The fertilised female gamete forms
a seed. The ovary develops into a fruit
around the seed.
Germination:
A seed will lie dormant until all the conditions are right:
 Water – to activate enzymes that break down food reserves in
seed
 Oxygen – for respiration
 Suitable temperature – for enzymes inside seed to work.
Germinating seeds get their energy from food stores, until they can
produce their own food:
1. developed seed contains any embryo and
store of food reserves, wrapped in a hard seed
coat, to protect it.
2. When germination begins, it gets glucose from
the food store, transferring the energy it needs
to grow.
3. Once the plant has grown enough to produce
green leaves, it can get its own food via
photosynthesis
Investigating the conditions needed for germination:
Boiled water
contains no
oxygen.
Put cotton wool at the bottom
of four boiling tubes. Put 10
seeds at the top of each
cotton wool. Set up the
boiling tubes as above.
Leave tubes for a few days.
and observe what happens.
There should only be
germination in Tube 1., since
all conditions are needed for
germination.
Asexual reproduction in plants:
Plants can reproduce asexually using natural methods, or we can
make them reproduce asexually using artificial methods.
Natural Method:
1. The plant sends out runners, which are fast growing stems that
grow out sideways, just above the ground.
2. The runners grow roots at various points and new plants start
to grow
3. The new plants are clones, so there is no genetic variation.
Artificial Method:
You can use cuttings to grow genetically identical copies of a plant.
Gardeners take cuttings from parent plants that they wish to be
cloned.
These plants can be produced quickly and cheaply.
Human Reproduction:
Male Reproductive system makes sperm cells:
Sperm mixes with a liquid to make semen, which is ejaculated into a
vagina during sexual intercourse.
Female Reproductive System makes ova/eggs:
One ovum is produced every 28 days form one of the ovaries.
It then passes through the Fallopian tube, where it might meet
sperm during sexual intercourse.
If it isn’t fertilised, the ovum will break up and pass out of the vagina.
If it is fertilised, the ovum begins to divide.
The new cells will travel down to the Fallopian tube to the uterus and
attach itself to the endometrium. A fertilised ovum will develop into
an embryo.
Sexual characteristics:
During puberty, your body starts to release sex hormones,
testosterone in mean and oestrogen in women.
These trigger secondary sexual characteristics:
Oestrogen:
 Extra hair on underarms and pubic area
 Widen hips
 Breast development
 Release of ovum and start of periods
Testosterone:
 Extra hair on face and body
 Develop muscles
 Penis and testicles enlarge
 Sperm production
 Voice deepening
Menstrual Cycle:
Stage 1 - menstruation
starts, uterus breaks down
for four days.
Stage 2 - uterus lining builds
up again, from day 4 to 14,
into thick spongy layer, full
of blood vessels, ready to
receive fertlised egg.
Stage 4 - wall is maintained
until day 28. If no fertilised
egg, spongy lining breaks
down and starts all over
again.
Stage 3 - Egg develops and
is released from ovary at
day 14. This is ovulation.
The menstrual cycle is controlled by four hormones:
FSH (Follicle
Stimulating
Hormone)
Oestrogen
LH
(luteinising
hormone)
Progesterone
1.
2.
3.
1.
2.
3.
4.
1.
2.
Produced in pituitary gland
Causes egg to mature in ovaries in a follicle
Stimulates ovaries to produce oestrogen
Produced in ovaries
Causes uterus lining to grow
Inhibits release of FSH
Stimulates release of LH
Produced in pituitary gland
Stimulates release of egg at day 14. This is
ovulation
1. Produced in ovaries, then by remains of follicle
after ovulation
2. Maintains uterus lining during second half of
cycle. When not enough progesterone, lining
breaks down.
3. Inhibits release of LH and FSH
Development of embryo during pregnancy:
Once an ovum is fertilised, it develops into an embryo and implants
itself in the uterus.
Once the embryo is implanted, the placenta develops. This allows the
blood of the embryo and mother to get very close to allow the
exchange of substances, such as food oxygen and waste.
Also, the amnion membrane forms, surrounding the embryo and is
full of amniotic fluid, which protects the embryo against knocks.
This eventually develops into a foetus.
Alleles and Inheritance:
Some characteristics are controlled by a single gene; however, most
are controlled by several genes interacting.
Most of the time, you have two copies of each gene, or two alleles.
If the alleles are different, you have instructions for two different
versions of the same allele, but you only show one version.
The version that is shown is said to be dominant, the other recessive
The recessive characteristic is shown if both alleles are recessive.
Some characteristics are caused by codominant alleles. Neither allele
is recessive, so you show characteristics from both alleles.
Genetic diagrams:
Family Pedigrees:
Family pedigrees require you to deduce what each person’s alleles
are from whether they are sufferers or carriers of a disease.
If someone is a carrier, then the disease is recessive, and they must
have the allele for the disease, but also an allele not for the disease.
Sufferers will have both alleles if recessive, one or both if dominant.
Neither carriers nor sufferers won’t have any of the alleles linked to
the disease.
Sex Determination:
The 23rd pair of chromosomes is labelled XX or XY.
Males have XY.
Females have XX.
There is an equal chance of having a boy or a girl.
All eggs have an X chromosome, but a sperm can have either X or Y,
so the sex of offspring depends on the sperm.
Genetic Variation:
All animals are slightly different due to their genes being slightly
different.
Most variation is caused by a mixture of genetic and environmental
factors.
Almost every aspect of life is affected by our environment.
Factors not affected by environment:
 Eye colour
 Hair colour
 Inherited disorders
 Blood group
Environment can affect many other characteristics, such as:
 Weight
 Height
 Health
Some characteristics are affected by both genes and environment:
 Intelligence
 Sporting ability
Huntington’s Disease:
Disorder of nervous system.
Caused by dominant allele.
Shows up when patient is around 30-40 years old, when they have
already had kids.
Cystic Fibrosis:
Disorder of cell membranes.
Causes lungs to produce sticky mucus, makes breathing difficult and
absorption of food difficult.
Caused by recessive allele.
Sickle-cell Anaemia:
Both alleles influence phenotype.
Red blood cells become sickle-shaped, since they contain an
abnormal amount of haemoglobin.
Common in Africa.
1 allele will give the trait, 2 gives the disease.
Haemophilia:
Part of sex chromosomes, on the X chromosome.
Men only need 1 to have it, since they only have 1 X chromosome.
Women need both to have it, since they have 2 X chromosomes.
Environmental variation in plants:
Environmental variation in plants is much greater, since they are
strongly affected by sunlight, moisture level, temperature, mineral
content, carbon dioxide level, oxygen level.
Plants could grow twice as big or twice as fast depending on
environment.
The organism in the environment:
Habitat – where an organism lives
Population – all the organisms of one species in a habitat
Community – all the different species of a habitat
Ecosystem – All organisms living in area and all non-living conditions.
Biodiversity –variety of different species of organisms on Earth, or
within ecosystem.
High biodiversity is important since it ensures ecosystems are stable
since species depend on each for shelter and food.
Many human actions are reducing biodiversity.
The environment can also affect habitats. changes caused by abiotic
and biotic factors.
Abiotic factors:
 Environmental– temperature, light intensity, moisture, soil pH.
 Toxic chemicals
Biotic factors:
 Availability of food
 Number of predators
 Competition
Investigating population size using quadrats:
Place quadrat on ground
at a random area within
first sample area, using a
random number
generator.
Count the number of the
organisms you are
investigating. Repeat steps
1 and 2 many times, then
find the average.
Repeat the whole process
in a new sample area.
Compare the two
averages.
You can then estimate the population size by multiplying the mean
per m2 by the total area in m2.
Investigating the distribution of organisms and
measuring biodiversity using quadrats:
Mark a line across your
area, e.g. hedge to middle
of field. Place quadrats
next to each and count
number of organism.
You could record other
data, such as average
height of the plant, or
temperature, or light
intensity.
Repeat the process,
counting for a different
organism, and find an
average number of
organisms.
Food Chains:
Food chains always start with a producer, which is something that
makes its own food using energy from the Sun.
Producers are eaten by primary consumers.
Primary consumers are eaten by secondary consumers.
Secondary consumers are eaten by tertiary consumers.
Each stage is called a trophic level:
Food Webs:
Food webs show how food chains are linked.
There are many different species in an environment, so there are
many different possible food chains. A food web shows all of them.
All the species are independent, meaning if one species changes, all
the others are affected.
An arrow points at the organism eating it.
Pyramid of number:
Pyramids of number show the number of an organism at one stage
of a food chain.
The producer is at the bottom, the tertiary consumer is at the top.
They aren’t always pyramid shaped, since 1 fox can feed 5000 fleas.
Pyramid of Biomass:
A pyramid of biomass shows the mass of living material at that stage
of the food chain.
Biomass pyramids are almost always pyramid shaped.
Pyramids of energy transfer:
Pyramids of energy show the energy transferred to each trophic level
in a food chain.
They are always pyramid shaped, since no energy can be gained, only
lost:
1. Energy from Sun is source of energy for producers
2. Plants uses this energy to make food during photosynthesis.
3. Only 90% of the energy is passed on to the next trophic level
due to many reasons.
4. Some parts, such as bones or roots, aren’t eaten, so energy
isn’t taken in. Some parts are indigestible, so pass through as
faeces.
5. A lot of energy is used in respiration.
6. Most energy is eventually transferred to surroundings as heat.
7. Only 10% becomes biomass.
The Carbon Cycle:
Material are constantly recycled. Carbon passes through living
organisms and other things, like air and rocks.
1. Carbon is used by plants in carbon dioxide during
photosynthesis.
2. Eating passes carbon in the plant to animals
3. Respiration releases carbon dioxide back to the air
4. Plants and animals eventually die and decompose via
microorganisms known as decomposers. These decomposers
release carbon dioxide into the air via respiration.
5. Some plants and animal products are burnt, which produces
carbon dioxide.
6. Decomposition returns nutrients to the soil.
Food Production – Crop Plants:
You can increase crop yield by making the optimal conditions for
photosynthesis.
You can do this by putting them in glasshouses, or polythene tunnels.
These:
 Keep plants enclosed, safe from pests and diseases
 Help farmers control water supplied
 Allow farmers to supply artificial light after the Sun sets
 Trap the sun’s heat to keep the plants warm.
 Allow farmers to increase carbon dioxide level
You can also use fertilisers to ensure the crops have enough
minerals, such as nitrogen, potassium and phosphorous.
You can also use pest control sprays to get rid of any chance of your
crop being eaten.
Pesticides are a form of pest control. They are poisonous to humans,
so must be used carefully with food. Some pesticides also harm other
wildlife.
Biological control is an alternative to using pesticides. It means using
other organisms to reduce the numbers of pests by encouraging wild
organisms or adding new ones.
The organisms added could be predators to the pest, or diseasecausing to the pest.
Biological control can have a longer-lasting effect and be less harmful
to wildlife.
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