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BIOLOGY TEXTBOOK NOTES
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2 Bacteria and yeast
SEE FILE FOR NOTES (GREEN SHEET LABELLED 1
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3 Specialised cells
SEE FILE FOR NOTES (GREEN SHEET LABELLED 1
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4 Diffusion
SEE FILE FOR NOTES (GREEN SHEET LABELLED 1
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5 Osmosis
SEE FILE FOR NOTES (GREEN SHEET LABELLED 1
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6 Active transport
• What is active transport? Active transport is the
movement of substances against a concentration
gradient and/or across a cell membrane, using energy
• When is active transport used? When substances have
to be moved against the concentration gradient
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• Using active transport, cells can absorb ions from very
dilute solutions, and actively absorb substances such as
sugar and salt against a concentration gradient
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the rate
of respiration

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1 Cell division, growth and differentiation
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FOR FIRST PAGE (P20) SEE FOLDER NOTES…

Differentiation
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In the early development of animal and plant embryos, the cells are unspecialised
What is an unspecialised cell called? A stem cell
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Many plant cells
can differentiate throughout their life…
What is producing identical offspring called? Cloning
Why is it difficult to clone animals? Animal cells differentiate permanently early in embryo
development
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2 Cell division in sexual reproduction
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Where does meiosis take place? Only in reproductive organs of animals and plants, in
humans this is the ovaries and the testes
What does meiosis result in? Meiosis results in sex cells, called gametes, with only half the
original amount of chromosomes
Steps of meiosis?
o When a cell divides to form gametes, the chromosomes are copied so there are now
four sets of chromosomes instead of the normal two sets
o The cell then divides to form four gametes, each with a single set of chromosomes
o These chromosomes contain a random mixture of the original chromosome pairs
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3 Stem cells
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What’s a zygote? A single new cell formed by the fusion of
the egg and sperm cell
Embryonic stem cells (from human embryos) and adult
stem cells (from adult bone marrow) can be made to
differentiate into many different types of cell
Many embryonic stem cells come from aborted embryos
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This raises ethical issues…
Stem cells have the potential to treat previously incurable
conditions
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4 Cell growth and cancer
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What is the cell cycle in normal, healthy cells?
o There is a period of active cell division, when mitosis takes place and the number of
cells increases
o What is this followed by? It’s followed by a long period of non-division called
interphase
What does this long-period involve? Cells get bigger, increase their mass, carry out normal
cell activity and replace DNA for the division
What is a tumour the result of Tumours result from the abnormal, uncontrolled growth of
cells
What is a benign tumour? Benign tumours form in one place and do not spread to other
tissues
What is a malignant tumour? Malignant tumours invade healthy tissue and may spread to
other healthy tissues in the bloodstream to form secondary tumours
Malignant tumours invade healthy tissue and may spread to other healthy tissues in the
bloodstream to form secondary tumours
What are carcinogens? Carcinogens are caner-causing chemicals such as asbestos and the
tar found in tobacco smoke
Causes of cancer?
o most cancers are the result of mutations(changes in the genetic material of the cells)
o Ionising radiation such as UV light and X-rays can interrupt normal cell cycle and
cause tumours to form
o About 15% of human cancers are caused by virus infections

Two main ways of treating cancer?
o Radiotherapy – when cancer cells are destroyed by targeted doses of radiation
o Chemotherapy – where chemical are used to either stop the cancer cells dividing or
to make them ‘self-destruct
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They also tent to affect other rapidly
dividing cells
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An organ can contain several tissues, all
working together… for example stomach:
o Muscular tissue –churns round food and digestive juices of the stomach together
o Glandular tissue –produces the digestive juices that break down food
o Epithelial tissue – covers the inside and outside of the organ
Example of animal organs? Stomach and heart
Example of plant organs? Stems, roots and leaves

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Your body cannot
absorb and use these molecules; they need to be broken down or digested to form smaller,
soluble molecules
Digestive system?
o The digestive system is a muscular tube that squeezes food through it
o Starts at your mouth and finishes at your anus
o Glands such as the pancreas and salivary glands make and release digestive juices
containing enzymes to break down your
food
o The stomach and small intestine are the
main organs where food is digested…
o What happens at the small intestine?
Your small intestine is where soluble food
molecules are absorbed into your blood
o How is small intestine adapted to increase
diffusion and active transport from the
gut into the blood? It is covered in villi
which greatly increases its surface area
o What happens at the large intestine?
Water is absorbed from the undigested
food into your blood
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The function linked to the digestive system
is the production of bile, which helps digestion of
lipids
Other organ systems in the body? Circulatory system and respiratory system

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Glycerol is always the same, but the fatty acids vary
Lipid-rich foods? All the oils (olive oil etc) as well as butter, margarine, cheese and cream

Proteins
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What are proteins used for? Proteins are used for building up the cells and tissues of your
body as well as all your enzymes
What are they made up of? Caron, hydrogen, oxygen, and nitrogen
Protein-rich foods? Meat, fish, pulses and cheese
What’s the molecular structure? A protein molecule is made up of long chains of small units
called amino acids
The long chains of amino acids that make up a protein are folded, coiled and twisted to
make specific 3-D shapes
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Bonds that hold proteins in these 3-D shapes? The bonds are very sensitive to temperature
and pH, and can be easily broken
What happens if the bonds break? The shape of the protein is lost, and may not function any
more in the cells

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What do we call the ‘broken’ protein? We say the protein is denatured
Functions of proteins? They act as:
o Structural components of tissues such as muscles and tendons
o Hormones such as insulin
o Antibodies, which destroy pathogens and are part of the immune system
o Enzymes, which act as catalysts in the cells

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They are large
protein molecules…
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Why a special shape? The special shape allows other molecules (substrates) to fit into the
enzyme protein
What is this part of the enzyme called? The active site…
The shape of an enzyme is vital for the enzyme’s function (the way it works)
What are enzymes involved in?
o Building large molecules from lots of smaller ones
o Changing one molecule into another
o Breaking down large molecules into smaller ones
What do enzymes actually do? Enzymes lower the energy needed to break the bonds, so
reactions are faster because a higher proportion of molecules have sufficient energy to react
How do enzymes actually work?
o The substrate (reactant) of the reaction to be catalysed fits into the active site of the
enzyme
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Remember that enzymes can join small molecules together as well as break up larger ones

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This is why high temperatures when you are ill are so dangerous
What do high temperatures do? High temperatures denature the enzyme because the shape
of the active site is changed
Different enzymes work best at different pH levels
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Where do these enzymes work? These enzymes ork outside the body cells in the gut itself
So how are digestive enzymes different to most other enzymes? Unlike most other enzymes,
digestive enzymes work outside your cells…
Different areas of the digestive system have different pH levels which allow the enzymes in
that region to work as efficiently as possible eg mouth and small intestine are slightly
alkaline, whereas the stomach has a low acidic pH value

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Using enzymes to convert this plant starch into sweet sugar provides a
cheap source of sweetness for food manufactures
The enzyme isomerase is used to change glucose syrup into fructose syrup… Glucose and
fructose contain exactly the same amount of energy however fructose is much sweeter than
glucose, so much smaller amounts are needed to make food taste sweet… Fructose is widely
used in ‘slimming’ foods because the food can still taste sweet, but with fewer calories

Advantages and disadvantages of using enzymes

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Many of the reactions in the industrial world need high temperatures and pressures to make
them go fast enough to produce the products needed
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1 Breathing and gas exchange in the lungs
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Where are lungs? Protected by? Your lungs
are found in your chest, or thorax, and are
protected by your ribcage
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The lungs provide an efficient surface for
gas exchange in the alveoli

Moving air in and out of the lungs
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How does air move into your lungs?
o When you breathe in, your
intercostal muscles contract which
moves your ribs upwards and
outwards
o At the same time, the diaphragm
muscle contracts which makes it
flatten as opposed to its normal
domed shape
o These two movements increase the
volume of your thorax… the
pressure decreases… then air is
pushed in by atmospheric pressure
How does air move out of your lungs?
o When you breathe out, your
intercostal muscles relax so the ribs
move down and in
o As the diaphragm relaxes ,it curves
back up into your thorax, resuming
its domed shape
o This increases the pressure inside
the chest… the pressure increases…
air is squeezed and forced out

Adaptions of the alveoli
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What’s the job of the alveoli? The alveoli provide a very large surface area and a rich supply
of blood capillaries
Why? This means gases can diffuse in and out of the blood as efficiently as possible
Why do alveoli have a ‘rich supply’ of blood capillaries? This maintains a concentration
gradient in both directions… the blood coming to the lungs is always relatively low in oxygen
and high in carbon dioxide compared to the inhaled air
Thickness of layer of cells? The layer of cells between the air in the lungs and the lungs is
very thin, which means diffusion can take place over the shortest distance possible

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To
keep polio sufferers alive until their bodies recovered, an iron lung is used…
How does the iron lung work?
o Metal cylinder from neck to abdomen
o Air is pumped out of the chamber which lowers the pressure inside
o As a result, air is forced into the lungs
o The vacuum is then switched off automatically, the pressure increases again, and air
is forced out of the lungs
Positive pressure ventilators? A positive pressure ventilator forces a carefully measured
‘breath’ of air into the lungs under a positive pressure
Benefits of positive pressure breathing?
o Patients do not have to be placed inside an iron lung machine
o The equipment can be used at home and the patient can move about
o Patients can have some control over the machine; modern systems can link a
ventilator with computer systems, which help patients manage their own breathing
much more easily

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It is the most efficient way to release energy from glucose…
What happens during aerobic respiration? Glucose (a sugar) reacts with oxygen
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EQUATION?
Glucose + oxygen -> carbon dioxide + water (+ energy)
C6H12O6 + 6O2 -> 6CO2 + 6H2O (+ energy)
Where do most of the reactions in aerobic respiration take place? Inside the mitochondria
What are mitochondria? Mitochondria are tiny rod-shaped parts (organelles) that are found
in almost all plant and animal cells as well as in fungi and algal cells
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All muscular activities
use energy
Mammals and birds need energy to maintain a constant internal body temperature almost
regardless of the temperature of their surroundings
In plants, energy from respiration is used to move mineral ions such as nitrates from the soil
into root hair cells
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Glycogen? Glycogen can be converted rapidly back to glucose to use during exercise
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5 Anaerobic respiration
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Anaerobic respiration is respiration without oxygen
When does this need to happen? When exercising, sometimes your blood cannot supply
enough oxygen to the muscles fast enough
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What is produced? Lactic acid is produced instead of carbon dioxide and water
The anaerobic brea
Explain muscle fatigue
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One cause of this fatigue is the build-up of lactic acid, made by
anaerobic respiration in the muscle cells
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As a
result, when the exercise is over, lactic acid needs to be broken down… this needs oxygen…
So… what is oxygen debt? Oxygen debt is the amount of oxygen needed to break down the
lactic acid to carbon dioxide and water…
What happens to your body during oxygen debt?
o Your heart rate and breathing rate stay high to supply the extra oxygen needed
The bigger the oxygen debt, the longer you will ‘puff and pant!’
Oxygen debt equation:
Lactic acid + oxygen -> carbon dioxide + water

Anaerobic respiration in other organisms
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Plants and other organisms can also respire anaerobically…
However they don’t form lactic acid – what do they form? Carbon dioxide and ethanol
Microorganisms such as yeast are used in the production of alcoholic drinks
EQUATION?
Glucose -> ethanol + carbon dioxide
C6H12O6 -> 2C2H5OH + 2CO2

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What are the three main parts of the circulatory system?
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Heart (pumps blood round your body)
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One transport system carries blood from your heart to your lungs and back… This
allows oxygen and carbon dioxide to be exchanged with the air in the lungs
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It is made up
of 2 pumps that beat together about 70 times a minute
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Blood flows into the two atria from the vena cava and the pulmonary vein
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The ventricles contract, forcing the blood out of the heart, into the pulmonary artery
and the aorta
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2 Helping the heart
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What’s a pacemaker? Something biological or artificial that sets the basic rhythm of the
heart
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They are attached to your heart by two wires, and only
weigh between 20 and 50 grams
People fitted with pacemakers need regular medical check-ups throughout your life,
however most people feel that this is a small price to pay for the increase in the quality and
length of life that a pacemaker brings

Artificial hearts
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When an artificial pacemaker is not sufficient, an artificial heart needs to be installed…
Examples of when they are used?

o To keep people alive while they wait for a transplant
o For their heart to rest and recover

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Why only one cell think? This increases the rate of diffusion by decreasing the distance over
which it has to occur

Problems with blood flow through the heart
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What’s coronary heart disease? Coronary heart disease is the name for a heart disease
caused by problems with the coronary arteries that supply the heart muscle with
oxygenated blood, it’s usually as a result of blockages caused by fatty deposits
How problems are often solved? By using stents
What is a stent? A stent is a metal mesh that is placed in the artery
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The balloon is then deflated and removed but the stent remains in place, holding
the blood vessel open


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What could happen? The recipient’s antibodies may attack the antigens on the donor organ
as they do not recognise them
How is rejection by the recipient prevented?
o The match between the antigens of the donor and the recipient is made as close as
possible… eg
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6 NOTE IN FILE (THREE PAGE HAND WRITTEN NOTES…)
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The stomach produces
hydrochloric acid, which maintains a low pH
What does your stomach produce on its wall? A thick layer of mucus coats the stomach wall
to protect it from being digested by the acid and the enzyme
Where are enzymes for the small intestine produced? Some made in pancreas, some
Why is bile produced? The acidic liquid coming from your stomach needs to become an
alkaline mix in your small intestine
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What happens as food comes into the small intestine? Bile is squirted onto it through the
bile duct
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Why? This provides a much bigger surface area of fats for the lipase enzymes to act upon
What do lipases break the fats into? Fatty acids and glycerol
What can sometimes form and block the gall bladder and bile ducts? Gall stones
Size? Can range from a few millimetres to several centimetres
Can cause terrible pain
Effects of gallstones besides pain? They can stop bile bring released onto the food and
therefor reduce the efficiency of digestion











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They carry impulses to the right bits of your
body – the effector organs
What is the CNS made up of? The CNS is made up of the brain and the spinal cord
What are effector organs? Muscles or glands
How do muscles respond? They contract

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How do glands respond? They release chemical substances, for example your salivary glands
produce and release extra saliva when you smell food cooking
‘Equation?’…
Receptor -> sensory neurone -> coordinator (CNS) -> motor neurone -> effector


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It then passes
along a relay neurone (usually in the spinal chord) and
then straight back along the motor neurone where it
later arrives at the effector organ
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The chemical crosses the gap and sets off a new electrical signal in the
next neurone
Speed, efficiency? The transmission of a nervous impulse is very fast, but it is slowed down
at the synapse because the diffusion of chemicals across the gap takes time
REFLEX PATHWAY EQUATION?

STIMULUS -> RECEPTOR -> SENSORY NEURONE ->
RELAY NEURONE -> MOTOR NEURONE ->
EFFECTOR -> RESPONSE


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if an area at the back of the brain
was damaged by a stroke and the patient then went blind, you know that that area has
something to do with vision
How can the brain be electrically stimulated? The brain can be electrically stimulated by
pushing a tiny electrode into the tissue and giving it a small charge of electricity
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It can be used to show which areas of the brain have been
affected after, for example, someone suffers a stroke



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How? They are carried in the blood to other parts of the
body but only affect particular cells (called target cells) They
regulate the functions of many organs and cells
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At only a few degrees above or
below this, the reactions in your cells no longer work at the ideal speed and you may die
How does your body control your temperature?
o You sweat to cool down
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What happens if your body temperature goes above 40-42oC? Your enzymes and cells don’t
work properly, you could die of heat stroke or heat exhaustion

Controlling blood sugar
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How is the concentration of glucose in your blood kept constant? By hormones made in your
pancreas
What else naturally uses glucose? The normal metabolism of cells (RESPIRATION!)

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What hormone is produced? Insulin

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04%
Percentage in air you breathe out? 4%

Urea
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Where is urea produced? Urea is produced by your liver as excess amino acids are broken
down…
Urea is poisonous and if levels build up in your blood, it will cause a lot of damage
What filters out the urea from the blood? The kidneys
How does it pass out of your body? In your urine, along with any excess water and salt

Functions of liver
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Liver carried out many different functions in the body…
Liver cells grow and regenerate themselves very rapidly
There are a number of functions of the liver involved in homeostasis…:
o Deamination of excess amino acids to form urea
o Detoxifying poisonous substances such as the ethanol in alcoholic drinks, and
passing the breakdown products into the blood so they can be excreted in the urine
via the kidneys
o Breaking down old, worm out red blood cells and storing the iron until it is needed
to synthesise more red blood cells

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They move by diffusion down a concentration gradient
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If the blood becomes too concentrated, the pituitary gland releases lots of
ADH into the blood
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On the other hand, if the blood plasma is too dilute, less ADH is released into the blood
Urea is lost in your urine
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How does it move back into your blood? By diffusion down a concentration gradient

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A person’s
blood leaves their body and flows between a partially permeable membrane
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There is
no active transport
Disadvantages of dialysis?
o You have to follow a very carefully controlled diet
o You have to spend regular, long sessions connected to the machine
o Over many years, the balance of substances in the blood can become more difficult
to control, no matter how careful the dialysis
Even so, for many people with kidney failure, dialysis keeps them alive



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There is a risk that the donor organ will be rejected by the
recipient’s antigens because of this…
How can the chances of rejection be reduced?
o The antigen match of the donor and the recipient is made as close as possible
o The recipient is given drugs to supress the immune response (immunosuppressant
drugs) for the rest of their lives
Disadvantages of immunosuppressant drugs?

They prevent patients from dealing effectively with infectious diseases, so they have
to take care they don’t become ill…
o Transplanted organs don’t last forever… The average transplanted kidney works for
around nine years, although some last much longer…
What happens once the organ starts to fail? The patient must return to dialysis
Disadvantages of transplants?
o You have to take medicine every day of your life in case the kidney is rejected
o You need regular check-ups to see if your body has started to reject the organ
o You may never get the change of a transplant at all
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What does the thermoregulatory centre consist of? It contains receptors that are sensitive
to temperature changes in the blood flowing through the brain itself
What temperature difference can the receptors detect? As little as 0
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The extra sweat cools your body down as its water
evaporates from the skin, taking heat energy from the blood

Keeping warm
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What would happen to your enzymes if your core temperature dropped? The rate of the
enzyme-controlled reactions in your cells falls too low
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This vasodilation reduces the energy released by radiation through the
surface of the skin
o Sweat production is reduced, therefor less heat energy is released
o Your muscles contract and relax rapidly, causing you to shiver
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This raises your
body temperature
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7 Controlling blood glucose
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What monitors your blood glucose concentration? The pancreas
What is the pancreas? The pancreas is a small pink organ found underneath your stomach
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Name them? Insulin and glucagon
When is insulin released? When your blood glucose concentration rises
How does it work? Insulin allows glucose to move from the blood into the cells and to be
stored as glycogen in the liver and muscles
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Also most importantly, your body cells
stop responding to your own insulin
Common or uncommon? Common, gets more common as people get older, and is often
linked to obesity and lack of exercise

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This is genetically identical to natural human insulin and the supply is
constant

Curing type 1 diabetes
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Doctors can transplant a pancreas successfully however the operation is quite difficult and
risky… also not enough donors available… also patient still has to take immunosuppressants
Scientists hope that eventually they will be able to genetically engineer faulty human
pancreatic cells so they work properly; then they will be able to return them to the patient
with no rejection issues

Curing type 2 diabetes
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You can often deal with this without having to inject insulin… by?
o Eating a balanced diet with carefully controlled amounts of carbohydrates
o Loosing weight
o Doing regular exercise
If this doesn’t work , there are drugs that:
o Help insulin work better on the body cells
o Help your pancreas make more insulin
o Reduce the amount of glucose you absorb from your gut
Who does type 2 diabetes usually affect? Older people, however it is becoming more
common in young people who are very overweight
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1 Pathogens and disease

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We use them to
make food like yogurt and cheese, to treat sewage and make medicines
What are the minority of bacteria? Pathogen bacteria are the minority…
Viruses? Viruses are even smaller than bacteria
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Where can they cause disease? In every type of living organism

How pathogens cause disease
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Bacteria and viruses reproduce rapidly inside your body
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2 NOTES IN FOLDER

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4 Using drugs to treat disease
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What do painkillers do? They relieve the symptoms of a disease, but do not kill the
pathogens
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Fleming was rather careless, and his lab was quite untidy
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However he noticed a clear ring in the jelly around some of the spots of mould
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Fleming saw how important this was, and he called the mould ‘penicillin
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They damage the bacterial cells without harming your own cells

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Some antibiotics kill a wide range of bacteria, but others are very specific and only work
against very specific bacteria
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It is difficult to develop drugs that can destroy viruses without
damaging your body cells
Why must new antibiotics be developed? Because of the development of antibiotic
resistance



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1 Photosynthesis
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What do chloroplasts contain? A green substance called chlorophyll
What happens during photosynthesis? Light energy is absorbed by the chlorophyll in the
chloroplasts
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What does photosynthesis also produce? Oxygen, which is released into the air
EQUATION?
Carbon dioxide + Water ----(light energy)---> Glucose + Oxygen
6CO2 + 6H2O ----(light energy)---> C6H12O6 + 6O2
How is the glucose produced used by the plant?
o Some is used immediately by the cells of the plant for respiration
o However a lot of glucose is converted into insoluble starch and stored

Leaf adaptions
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How are the leaves of a plant adapted for
photosynthesis?
o Most leaves are broad, giving a big
surface area for the light to fall on
o They contain chlorophyll in the
chloroplasts to absorb the light
energy
o They have air spaces that allow
carbon dioxide to get to the cells,
and oxygen to leave them by
diffusion
o They have veins, which bring plenty of water in the xylem to the cells of the leaves
and remove the products of photosynthesis in the phloem
How are algae adapted for photosynthesis? Algae are aquatic
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2 Limiting factors
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What are limiting factors? Plants need light, warmth and carbon dioxide if they are going to
photosynthesize and grow as fast as they can
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This is
why they are called limiting factors
What can the rate of photosynthesis be limited by?
o A shortage of light
o Temperature levels
o Carbon dioxide levels

Light
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Light intensity if the most obvious factor affecting the rate of photosynthesis
In low light? Photosynthesis will stop, whatever the other conditions are around the plant
General rule concerning light? The brighter the light, the faster the rate of photosynthesis

Temperature
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Temperature affects all chemical reactions, including photosynthesis
General rule concerning temperature? As the temperature rises, the rate of photosynthesis
increases as the reaction speeds up
However…? Photosynthesis is controlled by enzymes… most enzymes are denatured once
the temperature rises to around 40-50 OC
So? If the temperature gets too high, the enzymes controlling photosynthesis will be
denatured and the rate of photosynthesis will fall

Carbon dioxide levels
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Atmosphere? The atmosphere is only about 0
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There

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will be increased rates of photosynthesis therefor increased yield of the crops compared
with an unalterable environment
Advantages and disadvantages of greenhouses?
o Costs a lot of money, however turnover is fast which means profits can be high
o Crops are clean and unspoilt
o No ploughing or preparing the land, crops can be grown where land is poor
o Fewer staff are needed
Limiting factors are a thing of the past in controlled greenhouse conditions!

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These may be used in the cells as an energy store, and also
sometimes used in the cell walls to make them stronger

Starch for storage
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Why do plants convert glucose to starch? Because glucose is soluble in water; if glucose
were stored in plant cells it could affect the way water moves in and out of the cell by
osmosis
Why starch? Starch is insoluble in water, so will have no effect on the water balance of the
plant
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It provides an energy store for when it is
dark, or when light levels are low
o Starch is also kept in special storage areas of a plant
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We often take advantage of these starch stores, found in
vegetables such as potatoes and onions, by eating them ourselves

Minerals, proteins and carnivorous plants
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How are carnivorous plants adapted to living in nutrient-poor soil? They take minerals from
the animals they catch and digest
Venus fly trap?
o The Venus flytrap has special ‘traps’ that contain sweet smelling nectar
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o Insects are attracted to the colour and the smell
o Inside the trap are many small, sensitive hairs
o As the insect moves about to find the nectar, it will brush against these hairs

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Once the hairs have been touched, the trap is triggered; it snaps shut and traps the
insect inside
Special enzymes then digest the insect inside the trap

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Leaves have a flat ,thin shape which
gives them a large surface area for diffusion
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It has only a short distance to move across the root to the xylem, where it is moved up and
around the plant
How does a plant take in mineral ions? By active transport
How is energy made for this? They have plenty of mitochondria to supply the energy they
need to take in minerals ions by active transport
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5 Evaporation and transpiration
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What is transpiration? Transpiration is the loss of water vapour from the surface of plant
leaves known as transpiration
Where is water mainly lost through? The stomata
Function of stomata? Open to let in carbon dioxide needed for photosynthesis
What is the transpiration stream? The movement of water through a plant from the roots to
the leaves as a result of the loss of water by evaporation from the surface of the leaves
Anything that affects the rate of evaporation will affect transpiration

The effect of the environment on transpiration
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Anything that increases the rate of photosynthesis will increase the rate of transpiration

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Why does this occur? More stomata are opened up to let carbon dioxide in, but in turn,
more water is lost by evaporation and then diffusion through the open stomata
What do windy conditions do?
o More water is evaporated from the cells in windy conditions, and diffusion increases
o Water vapour will diffuse more rapidly into dry air than humid air…
o So windy conditions also maintain a steep concentration gradient from the inside of
the leaf to the outside


Controlling water loss
•
•
•
•

•

What’s the cuticle? The cuticle is a waxy, waterproof layer on leaves to prevent uncontrolled
water loss
Where are stomata found on the leaf? Mostly on the underside of leaves
Why? This protects them from the direct light and energy from the sun, and also reduces the
time they are open
What drastic measures can a plant take if it starts to lose water faster than it is replaced by
the roots?
o The whole plant can wilt
...
The leaves all collapse and hang down which greatly reduces the surface area
available for water loss by evaporation
o The stomata close, which stops photosynthesis but risks overheating
...
6 Transport systems in plants
•

What are the two separate transport systems to move substances around a plant?
o Xylem
o Phloem

Phloem
•

•
•
•

What does the phloem tissue do? The phloem tissue transports the sugars made by
photosynthesis from the leaves to the rest of the plant
...
If too
many of them attack a plant, they can kill it by taking all of the food

Xylem
•
•

What does the xylem tissue do? The xylem tissue carries water and mineral ions from the
soil around the plant to the stem and the leaves
Where is the xylem and the phloem found in trees?
o Xylem makes up the bulk of the wood
o Phloem is found in a ring just underneath the bark

Why is transport so important?
•
•

•

It is vital to move the food made by photosynthesis around the plant
...
The pressure of
the cytoplasm against the cell walls gives support for young plants and for the
structure of the leaves
...
7 Plant responses
•
•
•
•
•
•
•

Plants are sensitive to? Light, moisture and gravity
What are the responses of plant roots to light, gravity
and moisture called? Tropisms or tropic responses
Response to light? Phototropism
Response to gravity? Gravitropism/Geotropism
Response to moisture? Hydrotropism
What’s the hormone that responds to these things
called? Auxin
When can phototropism clearly be seen? When a shoot
responds to light from one side only

•

•
•
•

•
•
•

How does it work? Auxin moves from the side of the shoot where the light is falling to the
unlit side of the shoot
...
High levels of auxin
make shoot cells grow more but inhabit growth of root cells
...
8 Making use of plant hormones
•
•
•
•

•

Plant growth hormones are widely used in…? Horticulture and Agriculture
Gardeners and horticulturists rely on taking cuttings to produce lots of identical plants
...
By dipping the cut end of a cutting into rooting powder,
the chances of success are greatly increased
...
If you spray
auxin solution onto the leaves of plants, the hormone is absorbed
...

What are selective herbicides? Selective herbicides are chemicals that affect only one type
of plant and not another

9
...

The ovary also often forms the fruit once the ovules are fertilised


Pollination
•

What is pollination? Pollination is the process whereby the pollen grain is transferred from
the anther of a flower to the stigma

Feature
Petals

Scent
Nectar
Stigma

Anthers
Pollen grains

Insect pollinated flowers
Large, brightly coloured; many
are patterned to guide insects
in
Often scented to attract insects
A sugary liquid made to attract
insects
Found inside the petals so
insects brush against it on way
to the nectar; may be sticky
Inside the petals so insects
brush past on way to nectar
Relatively few, large and sticky
to attach onto the insects that
visit the flower

Wind pollinated flowers
Small, usually brown or green

Not scented
No nectar
Large, feathery; hangs outside
the petals to collet pollen from
the air; may be sticky
Hang outside petals so pollen
blown away by wind
Many, small and light to float
easily in the wind


9
...
They are eaten by animal or birds which carry
the seeds away inside their gut and later deposit them in a pile of manure
Sometimes the ovary walls form wings which enable the seeds to be carried by the wind
In other cases, the ovary walls become hard and tough, and it may have hooks attached it to
the fur of animals
Sometimes the ovary walls become a sort of explosive pad which expels the seeds at speed




10
...

The nucleus contains chromosomes which carry the genes that control the characteristics of
your body
DNA? Deoxyribonucleic acid… They are long molecules made up of two strands twisted
together…

•
•
•
•

•

This spiral known as? Double helix
How many chromosomes in humans? 46 chromosomes… 23 pairs
...
2 Types of reproduction
•

•
•
•

•
•
•
•

What happens in asexual reproduction?
o There is no joining of gametes
o Only one parent
o There is no genetic variety
Offspring called? Clones – their genetic material is identical
Cells in your body reproduce? Asexually
What happens in sexual reproduction?
o Male and female gametes join
o This mixture of genetic information from two parents leads to genetic variety in the
offspring
Where are gametes for sexual reproduction found in plants? Within ovules and pollen
Where are they found in animals? Called ova (eggs) and sperm
Different forms of gene known as? Alleles
Why is sexual reproduction so important? The variety it produces is a great advantage in
making sure a species survives

10
...

How? You may have a genetic tendency to be overweight, however if you never have
enough to eat, you will be underweight

10
...
Characteristics in plants are determined by “inherited factors”
2
...
Inherited factors can be dominant or recessive

10
...
These are grouped into threes, and each group of three bases code for a
particular amino acid
A change or mutation in a single group of bases can be enough to change or disrupt the
whole protein structure

10
...

Dominant or recessive allele? It is caused by a dominant allele of a gene and can be inherited
from either parent

•
•
•

What’s a mutation? A mutation is a change in a gene… sometimes random, and can be
caused by radiation
Inherited diseases contagious or non-contagious? Non-contagious
If one parent has the (dominant diseased) allele…? There is a 50% chance of the child having
the disorder

Cystic fibrosis
•

•
•
•

What is cystic fibrosis? Cystic fibrosis is a genetic disorder of the cell membranes… It results
in the body producing a lot of sticky mucus in air passages, and in pancreas… some collects
in the lungs
Caused by recessive if dominant allele? Recessive allele… 1 in 25 people carry it…
Because its recessive, people of only one copy of the allele…? People with only one copy of
the allele won’t suffer from the disorder, but they are known as carriers
For a child to have the disorder, what must happen? Both parents must be either carriers or
sufferers

Genetic diagrams
•

What do we use genetic diagrams for? To predict how genetic disorders might be
inherited and predict the inheritance of genetic disease

10
...

Effects of this?
o These sickle-shaped red blood cells can’t carry oxygen effectively and so you feel
breathless, suffer from lack of energy and tiredness…
o Also, the sickle-shaped cells can block small blood vessels
...



Down’s syndrome
•
•

•
•

Example of an inherited condition caused by abnormal numbers of chromosomes? Down’s
syndrome…
What is Down’s syndrome? Down’s syndrome is an inherited genetic condition that can
cause a number of developmental problems in many different areas of the body, including
the brain, the heart and the muscles
What’s it caused by? It’s caused by an extra copy of chromosome number 21, so the body
has 47 chromosomes instead of 46…
Extra chromosome can come from? Either male or female sex cell… It’s created by accident
during cell division

10
...
DNA is isolated from the embryo cells
2
...
Gene probe is added to a mixture containing the DNA from embryo
4
...
1 Cloning
•

What is a clone? A clone is an individual that has been produced asexually and is genetically
identical to the parent

Cloning plants
•
•

What do tissue cultures allow us to do? It allows us to make thousands of new plants from
one tiny piece of plant tissue taken from the original plant
How does it work?
1
...
Tissue grown in agar, and forms a ‘big mass of tissue’
3
...
Tiny identical plantlets then grow


Cloning animals
•

•

Where is animal cloning used? Advantages?
o It has become quite common in farming,
particularly with transplanting cloned
cattle embryos…
o Cows normally produce only one or two
cattle at a time, but using embryo
cloning, your best cow can produce
many more each year
How does it work?
1
...
Fertilise with top quality bull sperm, either inside the cow then they are gently washed
out, or just fertilised in a test tube
3
...
The calf that is born has no relation to the surrogate mother

•

Why are animals and plants chosen to be cloned? Because of their high quality, eg
...
2 Adult cell cloning
•

•

•
•

Generally, what does adult cell cloning involve? You place the nucleus of one cell into the
empty egg cell of another animal of the same species… Then you place the resulting embryo
into the uterus of another adult female where it develops until it’s born
Steps in adult cell cloning
1
...
At the same time, the nucleus is taken from an adult body cell, for example a skin
cell, of another animal of the same species
3
...
New egg cell given tiny electric shock which stimulates it to start dividing
5
...
3 Genetic Engineering
•
•

•
•

What’s genetic engineering? Genetic engineering is changing the genes of an organism
How does it work?
1
...
This gene is inserted into a vector (usually a virus – it inserts its DNA into the
organism it infects) or a (bacterial plasmid – small ring of DNA that can be passed
between bacteria)
3
...
Most of these children live in
developing countries where rice is a staple diet

11
...
People are worried they may develop
allergies to the food – although there’s probably no more risk for this than eating usual
foods
A big concern is that transplanted genes may get out into the natural environment
On the plus side, GM crops can increase the yield of a crop, making more food

12
...
This enables them to float on
top of the water and make food by photosynthesis

Living in extreme environments
•
•
•

What are extremophiles?
Extremophiles are organisms that survive and reproduce in the most difficult conditions
Some live at very high temperatures… bacteria known as thermophiles can survive at
temperatures of over 45 degrees
o These bacteria have specially adapted enzymes that do not denature and so work at
these high temperatures

•

Why do most living organisms struggle to survive in a very salty environment? It causes
problems with the water balance of the cell

12
...

o Many Arctic mammals have plenty of insulation… inside they have blubber (a thick
layer of fat that builds up under the skin)… outside they have a thick fur coat that
provides very effective insulation…
o The fat layer also provides a food supply in the winter when there is little food
Example of camouflage?
o Arctic fox has a grey, or brown coat in summer, but in winter, the coat changes to
pure white to blend into its surroundings

Surviving in dry climates
•

•

Biggest challenges in the desert?
o Coping with lack of water
o Stopping your body temperatures from getting too high
How are desert animals adapted?
o Many animals are adapted to need little or nothing to drink; they get the water they
need from the food they eat
o Animals find ways other than sweating to cool down as this wastes water
o They have behaviour adaptions to keep cool, for example they are often most active
in the early morning and late evening, when it is not so hot
o During the cold nights and the hottest times of the day, they rest in burrows or
shady areas where temperature doesn’t fluctuate as much
o Many desert animals are small so their surface area is large compared to their
volume
...
3 Adaptations in plants
•

How do plants in hot, dry conditions adapt to loose less water?
o Reduce surface area

o

Store water in the tissues

Changing surface area
•
•

•

Why do some plants living in dry conditions have leaves with a very small surface area?
o This adaption cuts down the area from which water can be lost…
Other adaptions of plant leaves?
o Some plants have small fleshy leaves with a thick cuticle
o Cuticle is a waxy covering on the leaf to stop water evaporating
Examples of plant adaptions?
o Marram grass grows on sand dunes
...
Also these sharp
spines discourage animals from eating them
...

The fat green body of a cactus is its stem, which is full of water-storing tissue
...
4 Competition in animals
•

•

•
•
•

•

What do animals compete for?
o Food
o Territory
o Mates
Competition for food is common…herbivores that eat a wide range of plants are most likely
to be successful… carnivores have to compete with their own species for their prey as well as
with different species
What is a territory? A territory may simply be a place to build a nest, or it could be all the
space needed for an animal to find food and reproduce
...
In addition, it must be able
to breed successfully
How could animals be successful?
o Avoid competition with other species as much as possible

•

o Feed in a way no other local animals do
o Eat a type of food that other animals avoid
How can one plant feed many animals without direct competition?
o Caterpillars eat the leaves
o Greenfly drink the sap
o Butterflies such nectar from the flowers
o Beetles feed on pollen

12
...
They
also prevent light from reaching the plants beneath them, so the plants around
them need adaptions to help them to survive

Coping with competition
•

•

•

Example?
o Small plants found in woodlands often grow and flower very early in the year, when
plenty of light gets through the bare branches of the trees
...
The soil is also full of nutrients as the leaves from the
previous year have rotted
...

tomato, plum, raspberry, grape
Animal external – Fruits have hooks which attach them to the fur of passing animals
eg
...
6 Adaptations in parasites
•

What are parasites? Parasites are organisms that are adapted for living in or on a host
organism and feeding off it while it is still alive
...

o They do not feed of the body of the host, but deprive them of their digested food
How are they specially adapted?
o They have a head with hooks and/or suckers that are used to attach the tapeworm
firmly to the gut wall
o A tapeworm does not need a mate to fertilise its eggs… the eggs are eaten by
another animal such as a cow or pig and this is where their life cycle begins

Their long flattened shape provides a large surface area so they can absorb readily
digested, soluble food from their host
...
GAMETOCYTES
•
•
•

When a mosquito sucks blood from an animal with malaria, it takes up gametocytes
The gametocytes reproduce sexually inside the mosquito
In the mosquito’s salivary glands the gametocytes turn into a new form called sporozoites

2
...

The sporozoites pass through the blood to the liver, where they enter the liver cells
Inside the cells, the sporozoites rapidly divide asexually to produce a new form – merozoites

3
...
Instead they enter a sexual phase
of reproduction which results in gametocytes
...
And so the life cycle begins all over
again

4
...
Toxins are released too,
triggering the fever attacks that are associated with malaria
These merozoites go on to invade other red blood cells and the cycle is repeated
Infected red blood cells all tend to burst at the same time – the cycles of bursting cells
results in the cycles of fever attacks malaria victims get
...
1 Organisms in their environment
FACTORS AFFECTING LIVING ORGANISMS:
Temperature;
•
•

In cold climates, temperatures is always a limiting factor…
Example?
o The low temperatures, limited light levels and water, and harsh windy conditions
mean that Arctic plants are small…
o This effects the number of herbivores, which in turn effects the number of
carnivores

Availability of nutrients;
•
•

•

The level of mineral ions, for example nitrate ions, has a considerable impact on the
distribution of plants…
Carnivorous plants such as Venus flytraps thrive where nitrate levels are very low because
they can trap and digest animal prey
...

Most other plants would struggle to grow with low levels of mineral ions

Amount of light
•
•

•

Light limits photosynthesis, so it effects the distribution of plants and animals
How have some plants adapted to living in low light levels?
o More chlorophyll
o Bigger leaves
Example of light levels effecting distribution?
o Nettles growing in the shade of other bushes have leaves with a much bigger surface
area than nettles growing out in the open

Availability of water
•
•
•

If there’s no water, there will be little or no life
Plants and animals are relatively rare in a desert as the availability of water is limited
What happens after it rains however…?
o The distribution changes…
o A large number of plants grow, flower, and set seeds very quickly as water is
available

Availability of oxygen and carbon dioxide
•

•


The availability of oxygen has a huge impact on water-living organisms, however the
distribution of land organisms is not affected by oxygen levels as oxygen levels in the air vary
very little
Carbon dioxide levels act as a limiting factor on photosynthesis and therefore plant growth

THE PHYSICAL FACTORS THAT AFFECT THE DISTRIBUTION OF LIVING
ORGANISMS DO NOT WORK IN ISOLATION

Availability of nesting sites, shelter and appropriate habitats
•

•

An animal’s habitat has to provide…?
o What it needs to feed
o What it needs to reproduce successfully
o Shelter from the worst weather
If any of these factors is missing, the population of that animal will fall
...
2 Measuring the distribution of organisms REFER TO CGP P84
•

•

•

•
•

•

How can we collect data on the distribution of organisms?
o Random sampling with quadrats
o Sampling along a transect
Explain how a quadrat works…
o A quadrat is usually a square frame made of wood or metal that you lay on the
ground, and this outlines your sample area
What are they used for?
o Investigating the size and population of plants
o They can also be used for animals that move very slowly, such as snails
What is another way of measuring the distribution of organisms?
o Sampling along a transect
How does this work?
o You stretch a tape between two points, and you sample the organisms along that
line at regular intervals using a quadrat
What could you also measure along a transect?
o Physical factors, such as light levels and soil pH that could be affecting growth

13
...
what is the
population density of snails in this garden

Controlling variables
•
•

When you are working in a laboratory, you can control as many of the variables as possible
...
She
found the same pattern everywhere – penguin numbers were falling
What could be causing these changed?
o Primarily climate change seems to be significant
o There have been several breeding seasons where unusually heavy rainfall has
occurred
...
This is
in response to changes in water temperature, so there has been less food available
in some years
Other factors?
o Penguins are also affected by oil and waste from nearby shipping lane… around
20,000 penguins were killed by a major oil spill in 1991 alone
o Thousands of tourists visit the colony every year
...
4 Measuring environmental change REFER TO CGP P81
•

•

•

•

Non-living, physical factors affecting distribution of organisms?
o The average temperature…
o The average rainfall
o Light, pH and local climate
o (only in water) Oxygen levels
Living factors affecting distribution of organisms?
o A new predator may move into an area
o A disease-causing pathogen may appear
How can environmental change be measured?
o By measuring physical factors such as… average rainfall, temperature, oxygen levels,
pH and pollutant levels in water or in the air…
How can living organisms be used as indicators of environmental change and pollution?
o Lichens are very sensitive to air pollution, particularly levels of sulfer dioxide

o

When air is clean, many different types of lichen grow


13
...
They quickly get taller and grow more
vigorously than the bluebells
Other problems facing bluebells?
o Habitat loss
o Over-picking
o Trampling
o Cross-breeding with cultivated Spanish bluebells

14
...
Wherever people
farm, the natural animal and plant populations are destroyed
o The human population is draining resources of the Earth
o

•

•

•

Managing waste
•

•

•

Due to rapid growth of the human population, increasingly large amounts of waste are being
produced… where?
o Human bodily waste
o Rubbish from packaging uneaten food and disposable goods
o Industrial waste
Why is this increasing amount of waste a problem?
o The dumping of this waste is another way which we reduce the amount of land
available for any other life apart from scavengers
o If it is not handled properly, it can cause serious pollution…
o Our water may be polluted by sewage, by fertilisers from farms, and by toxic
chemicals from industry… can lead to eureophication
What is ecology?

Ecology is the scientific study of the relationships between living organisms and their environments







14
...
g
...
Nitrates and phosphates are sprayed onto fields as mineral fertilisers
2
...
The nitrates and other mineral ions stimulate the growth of algae and water plants, which
then grow rapidly
4
...
The dead plant matter provides more food for the microorganisms
6
...
Aerobic organisms like fish will start to die because of the reduced oxygen concentration
Eventually, the oxygen levels in the water fall so low that all aerobic aquatic animals die, and the
pond or stream becomes ‘dead
...
Water can be analysed to
show the levels of polluting chemicals such as pesticides or industrial waste
o Bioindicators – species such as salmon and bloodworms that can only be found in
very clean or very polluted water – can be used to monitor pollution

14
...
If this concentration gets too high, plants and animals may not be able to
survive
...
The sulfer dioxide and nitrogen oxides are carried high in the air by winds
...
4 Deforestation and peat destruction
•

Reasons for deforestation
1
...
The land may be used to rear more cattle for the beefburger market

•

3
...
Cows produce methane during
their digestive processes and release it at regular intervals
What are peat bogs?
o Peat bogs form over thousands of years, usually in marshy areas
...
Peat bogs act as massive carbon stores
o Peat bogs are often drained so that the area can be used as farmland, or the peat is
cut up and used as fuel
o When peat is burned or used in gardens, carbon dioxide is released into the
atmosphere and the carbon store is lost
...
5 Global warming
•
•
•

Carbon is present in the atmosphere as carbon dioxide (CO2)
An example of a process that releases CO2?
o Burning fossil fuels
Examples where CO2 is sequestered?
o Oceans, lakes and ponds
o Green plants where it is stored as carbon compounds
o Peat bogs

•
•

Why are these CO2 stores important?
o Because it means that CO2 is removed from the atmosphere
SO what’s going on?
o As a result of human activities like deforestation, levels of carbon dioxide in the
atmosphere are increasing

The Greenhouse effect
•
•

•
•

Energy from the Sun reaches the Earth, warming it up, and much of it is radiated back out
into space…
Gases such as carbon dioxide and methane (called greenhouse gases…) absorb this heat
that is on its way back out to space, and re-radiate it in all directions, including back in
Earth’s direction
The way they keep the surface of Earth warm is known as the greenhouse effect, and it is
vital for all life on Earth
Because of increasing levels of greenhouse gases, the Earth is gradually heating up and this
is global warming
...
This will cause sea levels to rise, and there is already evidence to show this
happening today
...

•

As sea temperatures rise, less carbon dioxide can be sequestered in the water, which
makes the situation worse
...
6 Analysing the evidence
•
•

•

•
•
•

To find out how our climate is changing, scientists are busy collecting data about the
environment
How?
o Satellites are being used to monitor snow and ice cover, and to measure the
temperature of the sea surface
o The temperature and speed of ocean currents is being recorded to detect changes
o Automatic weather stations are constantly recording atmospheric conditions
How can its validity be assured?
o Data must cover a wide area
o Data must go over a long enough time scale
Observations of a very small area aren’t useful
...
That’s why most governments around
the world are starting to take climate change seriously

15
...
When they breed, they pass on the genes for those useful
inherited characteristics to their offspring
...
2 Accepting Darwin’s ideas
•

What happened in 1859?
o Darwin published his book On the Origin of Species by Means of Natural Selection
which sold out on the first day of publication

•

Why wasn’t Darwin’s theory accepted?
o It conflicted with the widely held religious beliefs at the time in early Victorian
England that God made all the animals and plants on the Earth
o In spite of Darwin’s efforts, many scientists felt there was not enough evidence to
convince them of his theory
o There was no mechanism to explain how inheritance happened… Genes and
genetics were not known until 50 years after Darwin published his ideas…
o Because of this, Darwin’s theory was much harder for people to accept and
understand

15
...

o The alleles that have enabled these individuals to survive are then passed on to the
next generation
...

How do new forms of genes form?
o They are as a result of mutations
...
It produces an adaption that makes an
organism better suited to its environment, which makes it more likely to survive and
breed
...
4 Classification and evolution
•

•

What is classification?
o Classification is the organisation of living things into groups according to their
similarities
Describe the natural classification system?
o KINGDOMS – Kingdoms contain lots of organisms with many differences but a few
important similarities… eg
...
A species is a group of organisms that can
breed together and produce fertile offspring
Why classify organisms?
o It helps us to understand how they evolved
o

•

Classification and evolutionary relationships
•
•

•

What are evolutionary trees?
o They are models to look at the similarities and differences between organisms
How do scientists work out evolutionary relationships?
o Some organisms look very different, but are closely related, others look very similar
but come from very different groups
...
5 The origins of life on Earth
•
•

•

•

Roughly when did life on Earth begin?
o Between 3 and 4 billion years ago
What are fossils?
o Fossils are the remains of organisms from many hundreds of thousands or millions
of years ago that are found preserved in rocks, ice etc
o Fossils have revealed to use the world of dinosaurs
How can fossils be formed?
o They may be formed from the hard parts of an animal (they don’t decay easily) for
example bones, teeth, claws or shells
o Another type of fossil is formed when an animal or plant does not decay after it
died… this happens when one or more conditions needed for decay are not there for
example in ice… These fossils are very rare but they give a clear insight into what an
animal looked like, what it had been eating… Scientists are even able to extract the
DNA! Examples of conditions? Tar pits… glaciers… peat bogs…
o Many fossils are formed when harder parts of the animal are replaced by other
minerals and become part of the rock…
General stages of fossilisation?
1
...
The flesh rots, leaving the skeleton to be covered in sand or soil and clay before it is
damaged
3
...
The rocks shift in the earth with the fossil trapped inside
4
...
This is why scientists cannot be absolutely certain about how life
on Earth began
o Most organisms that died did not become fossilised – the right conditions for fossil
formation were rare
o There are many fossils still to be found
...
6 Exploring the fossil evidence
•

•
•

What can we learn from fossil records?
o We can learn how much or how little organisms have changed as life has developed
on Earth
What is extinction?
o Extinction is the permanent loss of all the members of a species
What does extinction always involve?
o Extinction always involves a change in the environment of an organism… like a
change in temperature, new predators, new disease… This change could be over
geological time, or a single catastrophic event such as volcanic eruptions

Organisms that cause extinction
•

Living organisms can change an environment, and cause extinction in several ways:

o

o
o

New predators can wipe out unsuspecting prey animals if the prey animals don’t
have adaptions to avoid them… new predators may evolve, or an existing species
may move into new territory
New diseases can bring a species to the point of extinction
...
New mutations can
give one type of organism a real advantage over another…

15
...
8 Isolation and the evolution of new species
•

How can new species arise?

The most common was is by geographical isolation
...
In Borneo, there are more than 25 unique species of mammals on the island
What is speciation?
o Speciation is the development of a new species
...
they may have different climates…
o Because the environment is different on each side, different characteristics will
become more common in each population due to natural selection
o Eventually, individuals from the different populations will have changed so much
that they won’t be able to breed with one another to produce fertile offspring… The
two groups will have become separate species
o

•

•

•









16
...

o This new material adds to the biomass
What is biomass?
o Biomass is the mass of living material in an animal or plant
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2 Energy transfers
Energy lost in waste
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Herbivores?
o Herbivores cannot digest all of the plant material they eat so some of it is passed out
in faeces…
Carnivores?
o Carnivores can eat less often and produce less waste as the meat they eat is easier
to digest than plants
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Most of the
energy is eventually lost to the surroundings as heat…
Movement uses a great deal of energy – the muscles use energy to contract and also get
hot, so the more an animal moves about, the more energy ( and biomass) it uses from its
food…

Keeping a constant body temperature
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Mammals and birds must keep their body at constant temperature, which is normally higher
than the surroundings… this is called homeostasis
What is the effect of this on how much mammals and birds need to eat compared with
species from other kingdoms?
o Mammals and birds need to eat far more food than animals such as fish and
amphibians to achieve the same increase in biomass

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The efficiency of food
production is improved by reducing the number of stages in a food chain

Artificially managed food production

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We know that energy is used up by the animal for moving around, and maintaining a
constant body temperature… farmers apply these ideas to food production to make it more
efficient, there are two main way they do this:
o Limiting the movement of animals – they won’t use much energy moving their
muscles therefore more biomass will be available from their food for growth
o Controlling the temperature of their surroundings - animals will not have to use as
much energy regulating body temperature, leaving more biomass spare for growth
Arguments against factory farming?
o Some people say that forcing animals to live in unnatural and uncomfortable
conditions is cruel
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This
often means using power from fossil fuels
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o This uses fuel, which increases the amount of carbon dioxide in the atmosphere
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4 Sustainable food production
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What is meant by sustainable food production
o Sustainable food production means producing foods in ways that can continue for
many years, involving things like:
§ Maintaining the health of the soil so plant crops grow well year after year
§ Looking at ways of producing food that reduces the stages in the food chain
as this will increase its efficiency
§ Taking care of the fish stocks in our oceans so they do not run out

Managing the oceans
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Fish stocks are declining because increasing commercial fishing fleets of large factory ships
has led to overfishing
How can fishing be sustainable?
o It is important to maintain fish stocks at a level where breeding continues
successfully – then it will avoid using resources faster than they renew
How can overfishing be tackled?
o FISHING QUOTAS – there are limits on the number, and size of fish that can be
caught in certain areas
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This is to reduce the number of ‘unwanted’ and discarded fish
(the ones that are accidently caught) eg
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o It is grown in cheap sugar syrup and in optimum conditions, it can double its mass
every five hours
o The fungal biomass is harvested, purified, dried then processed to make
mycoprotein
o It is a pale yellow solid, with a faint taste of mushrooms… it’s low fat, high protein
and is used by vegetarians and people who want to reduce the fat in their diet
o Mycoprotein is given a range of textures and flavours to make it similar to many
familiar foods such as chicken and beef
o Because the fungi uses cheap food from plants, and reproduces rapidly, this is a very
sustainable food source#

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How are these materials returned?
o They are returned after they die through the action of the decomposers
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They will slow down and may even stop if conditions are too cold
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The
moisture makes it easier for them to digest their food and also prevents them from
dying out
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Most microorganisms need oxygen to
release energy, grow and reproduce
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The sewage works
aim to provide the microorganisms with optimum conditions…
o COMPOST HEAP – Grass cuttings, vegetable peelings and weeds are put on a
compost heap
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It forms compost which can be used as a fertiliser

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This constant cycling of carbon is called the carbon
cycle
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o Carbon dioxide is produced as a waste product, and it is returned to the atmosphere
What happens when plants, animals and algae die?
o Their bodies are broken down by decomposers
o Animals which feed on dead bodies and waste are called detritus feeders… examples
are worms, centipedes and many insects
o When these microorganisms and organisms respire, carbon dioxide is released into
the atmosphere
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o Scientists fear that the carbon cycle may not cope as the levels of carbon dioxide in
our atmosphere increase, it may lead to climate change

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