GCSE Biology - Revision Notes

Includes B1a, B1b and B2 from the AQA specification. Does NOT have any B3 notes.

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  • Created on: 09-04-12 11:03
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BIOLOGY NOTES Christmas 2011 Mocks
The Nervous System Reflexes
· The sensory organs detect stimuli, your · Help prevent injury, and are automatic responses to
sensory organs are your nose, ears, eyes, certain stimuli e.g. a bright light will cause your pupils
skin and tongue to automatically dilate
· A stimulus is a change in your environment · The reflex arc :
· The sensory organs contain receptors, these · Stimulus
are groups of cells that are sensitive to · Receptor
stimuli. They can change stimulus energy · Sensory Neurone
e.g. light energy into electrical impulses · Relay neurone
· Stimulus can be light, sound, touch, · Motor Neurone
pressure, chemical or a change in position · Effector
or temperature · Response
· An example of a sensory organ is the eye, · Synapses connect the neurones
while it contains light receptors · They are where the nerve signal is transferred by
· Sensory Neurone - they are the nerve cells chemicals which diffuse across the gap
that carry electrical impulses from · These chemical signals then then set off new electrical
receptors in the sense organs to the CNS signals in the next neurones
(central nervous system) Hormones
· Motor Neurone - The nerve cells that carry · They are chemical messengers which travel in the blood
signals to the effector muscles or glands to start target cells
· Effectors - These muscles or glands are · These chemicals are carried in the blood plasma, they
known as effectors and respond in different control things in organs that need constant adjustment
ways to stimuli muscles contract while for example insulin levels
glands secrete hormones · Hormones are produced and secreted by glands and
· The CNS tend to have longer lasting effects (they travel at the
· The Central Nervous system is where the speed of blood)
information form the sense organs is sent · The pituitary gland - FSH, LH, ADH
and where the reflex actions are · Ovaries - oestrogen
coordinated · Testes - Testosterone
· The central nervous system consists of the · Pancreas - Insulin
brain and the spinal cord
· Instructions from the CNS are sent to the · Hormones are slow and nerves are fast
effector muscles or glands · Hormones last for a long time nerves act for a very
short time
· Hormones are more general while nerves are very
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The Menstrual Cycle
· Stage 1 - day 1, the uterus lining breaks down
· Stage 2 - days 4 - 14 the uterus lining builds back up
· Stage 3 - day 14 a developed egg is released from the ovary
· Stage 4 - The wall is maintained from days 14-28 if there is no fertilized egg by day 28 the whole cycles starts again
· The are 3 main hormones involved:
· FSH (follicle stimulating hormone), causes egg…read more

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· The balance between sweat and urine depends on the activities you are doing on the day for example on a cold day
when you are not exercising you don't sweat much and produce more urine (paler as diluted)
· However on a hot day when we are exercising you sweat a lot, this means that we will produce less urine and it will
be more concentrated. You will also lose more water through your breath as you breath faster.…read more

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· Another risk factor of heart disease is hypertension or high blood pressure
· Eating too much salt may cause high blood pressure for about 30% of the British population
· Many are derived from natural substances found in plants
· Some chemical changes due to a drug can lead to addiction and when we try to stop taking them we face
withdrawal symptoms, some examples of addictive drugs are heroine, cocaine, nicotine and caffeine
· Drugs today must be…read more

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· Produce Antibodies, every invading cell has unique molecules called
antigens on its surface, when white blood cells come across foreign antigen
they will produce proteins call antibodies to find and kill the invading cells.
These antibodies are specific and lock onto only that molecule. Antibodies
are then produced rapidly to wipe out the pathogen. If the same pathogen
attacks again the body will be ready to produce more antibodies and wont
get ill, also known as `naturally immune' .…read more

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· Plants compete for light, water, nutrients
· Animals compete for space or territory, food, water and mates
· Infectious diseases can wipe out species or control the number of organisms in an area
· Predation, some species will not increase in population due to the predators in the area
· There are 2 main types of variation genetic and environmental
· Genetic variation is where you receive characteristics from your parents and you are unable to change them an…read more

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· We can now add, remove or change an organisms genes and alter its characteristics
· The basic idea involves moving more useful genes from one organisms chromosomes into another
· A modern day example is when we use restricting enzymes to take the insulin gene out of our pancreas. We then
put it inside the DNA of a bacteria, as the bacteria grows more insulin is produced, this can be useful for some
people who have diabetes.…read more

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· Human activity produces load of carbon dioxide, we do this by simply breathing, and by burning fossil fuels for
energy and using machinery. By cutting down loads of trees we also reduce the amount of carbon dioxide taken out
of the atmosphere during photosynthesis.…read more

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· Red blood cells, they are adapted to carry as much oxygen as possible, they have a concave surface area to absorb
as much oxygen as possible and also pass through capillaries easily
· They are packed with hemoglobin so that they can absorb more oxygen, they have no nucleus to make more space
for oxygen
· Sperm and egg cells are specialized for reproduction, the main function is to carry the DNA and the female gamete
must nourish the egg…read more

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Rate of Photosynthesis
12.…read more


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