Biology AQA GCSE Unit 1

These are the notes i made for Unit 1 biology. I got an A* on Unit 1 and i really hope that these notes help you guys too! :) 

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  • Created by: niharie
  • Created on: 05-05-12 12:55
Preview of Biology AQA GCSE Unit 1

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Co-ordination and control.
Hormones are chemical messengers which travel in the blood to activate target cells.
The nervous system uses electric impulses to enable you to react to your surroundings
and co-ordinate what you do. A stimulus is a change in your environment which you may need
to react to. Receptors are group of cells which are sensitive to a stimulus.
How you nervous system work?
Once a sensory receptor detects a stimulus, the information passes along
special cells called neurones. The impulse travels along the neuron until it
reaches the central nervous system (CNS)
The CNS is made up of the brain and the spinal cord. The motor neurones carry
information from the CNS to the rest of the body. They carry impulses to make
the right bits of your body- the effectors organs ­ respond. Effectors organs
are muscles or glands.
Some responses to stimuli are automatic and rapid and are called reflex action.
The neurones in reflex arcs go through the spinal cord. When a stimulus is
detected by receptors, an impulse is sent along a sensory neurone to the spinal
cord. In the spinal cord the sensory neurone passes on the message to another type of
neurone ­ a relay neurone. The relay neurone sends the impulse to the motor neurone. The
impulse then travels along the motor neurone to the effector. And then a response takes
How synapses work?
When an impulse arrives at the junction between two neurones, there is a tiny gap called a
synapse. Signals cross this gap using chemicals. One neurone releases the chemical into
the gap. The chemical diffuses across the gap and makes the next neurone transmit an
electrical signal.
The menstrual cycle

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Each month the lining of the womb thickens ready to support a developing baby. At the
same times an egg starts maturing in the ovary.
Ovulation is when the egg is released from the ovary (14 day)
I f the egg is not fertilised, the lining of the womb and the dead egg are shed from the body,
called a period.
How the menstrual cycle work
FSH: secreted by the pituitary gland. It makes eggs
mature in the ovaries.…read more

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The eggs are checked to make sure they have been fertilised and the early embryos
are developed properly
6) The embryos are then placed in the uterus of the mother.
Humans need to maintain a constant internal environment, controlling levels of
water, ions, blood, sugar and blood.
Ion (Na) are taken into the body in food, then absorbed into the blood. If the food contains
too much of any kind of ion then the excess ions need to be removed.…read more

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You need energy to fuel the chemical reactions in the body that keep you alive. These
reactions are called your metabolism, and the speed at which they occur is your
metabolic rate. Muscle needs more energy than fatty tissue, which means people with
higher proportion of muscle to fat in their bodies will have a higher metabolic rate.…read more

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A drug is a substance that alters the way in which you body works. Drugs change the
chemical processes in your body, so you become addicted to them. Recreational drug is
a drug used non-medically for personal enjoyment .
What is an addiction?
Some drugs change the chemical processes in your body so that you may become addicted
to them. Once addicted, you need more and more of the drug. When addicts try to stop
using drugs they usually feel very unwell.…read more

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Nicotine gums or patches are given to help stop smoking. This gradually reduced the dose
of the nicotine that the body is craving for.
Infectious diseases are cause by microorganisms. Microorganisms which cause disease
are called pathogens. Common pathogens are bacteria and viruses.
Bacteria are very small cells which can reproduce rapidly inside your
They make you feel ill by doing two things: damaging your cells or
producing toxins (poisons)
Viruses are not cells. They are tiny.…read more

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Some medicines relieve the symptoms of disease but do not kill the pathogens:
Antibiotics cure bacterial diseases by killing the bacteria
Antibodies can't destroy viruses, because they reproduce rapidly using your own body cells.
Changing Pathogens
In the 1940s Antibiotics treated killer diseases.
Unfortunately they were over used and the bacteria had evolved
(adapted to the environment). If antibiotics are taken to deal
with an infection, not all the bacteria are killed.…read more

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You can be immunised against a disease by injecting a small amount of dead pathogens.
They carry antigens, which cause your body to produce antibodies. Then your body will
respond rapidly to future infection by the same pathogens by making the correct antibody.
You become immune to the disease. Vaccinations `wear off' over time- so you will need
booster injections
Thalidomide was developed as a sleeping pill and was found to prevent morning sickness
in early pregnancy.…read more

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slit-like nostrils and two rows of eyelashes to help keep the sand out
Desert plants
Cacti are well adapted for survival in the desert. They have:
stems that can store water
widespread root systems that can collect water from a large area
In addition, cacti have spines instead of leaves. These minimise the surface area and so
reduce water loss by transpiration. The spines also protect the cacti from animals that might
eat them.…read more

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Sexual reproduction:
2 parents are needed
Offspring will have "pairs" of chromosomes
This will cause genetic variation
Asexual reproduction:
Only 1 parent needed (no gametes)
Off springs are genetically identical to parent ("clones")
An alternative form of genes is called alleles.
For example, there are genes which decided whether:
You have dimples or not
Your thumb is straight or curved
Your earlobes are attached or not
A clone is an individual which has been produced asexually from its parent.…read more


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