2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen.

ADH
Lack of water is detected by the hypothalamus in the brain, it causes the pituitary gland to produce Anti-diuretic hormone, or ADH. This makes the kidneys to reabsorb more water- so less is lost from the body.

Adrenaline
Produced in the adrenal glands in stressful situations. Heart rate quickens to increase the flow of blood to muscles- this means that they can respire more (as there is more oxygen available) to provide energy if you need to 'fight or flee'.

Insulin
Produced in the pancreas when there is too much glucose in the blood. It stimulates cells to convert the glucose into glycogen which is a from that can be stored. This means that you always have the right amount of glucose in your blood.

Testosterone
Produced in ovaries in girls and testicles in boys. Plays a key role in puberty, developing sex organs and inspiring hair growth.

Progesterone
Produced in the ovaries it maintains the lining ready for pregnancy, and continues to do so if the egg is fertilised.

Oestrogen
Produced in the ovaries, it is controls other hormones to regulate the menstrual cycle. It stops the production of FSH and starts the production of LH.

3.33 understand that the incidence of mutations can be increased by exposure to ionising radiation (for example gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (for example chemicals in tobacco).

There are things that make you more likely to have a mutated gene, these include: ionising radiation and chemical mutagens like some chemicals in tobacco.

3.32 understand that resistance to antibiotics can increase in bacterial populations, and appreciate how such an increase can lead to infections being difficult to control

Bacteria experience mutations (the reproduce very frequently so it is not rare.) These mutations can mean that they are no longer affected by a certain antibiotic, this makes it easier for them to survive. If bacteria evolve to be resistant to drugs we are treating them with then they are difficult to control; sometimes they can be stopped using a different antibiotic, but some are becoming resistant to all the drugs that we know of...

3.31 understand that many mutations are harmful but some are neutral and a few are beneficial

A lot of mutations are harmful, like genetic diseases; cystic fibrosis.
Some don't change the chances of survival: like having a different colour hair.
There are a few mutations which are beneficial, for example a insect pollinated plant becoming brighter.

3.30 describe the process of evolution by means of natural selection

Evolution is a change in species over a very long time (sometimes into different species.)
Natural selection is survival of the fittest.
What happens is:

• A mutation occurs
• If the mutation is beneficial, the animal will survive longer and reproduce more
• Some of its offspring will inherit the mutation
• These offspring will also have better chance of survival, meaning they live longer and reproduce more
• Over a long period of time this process is repeated and gradually the mutation becomes a common gene in a species and those with the mutation become the only ones, as those without cannot compete with those expressing the mutated gene

3.29 understand that mutation is a rare, random change in genetic material that can be inherited

A mutation is when a gene is copied incorrectly, this gene can be passed down. It doesn't happen very often or on purpose.

3.28 understand that variation within a species can be genetic, environmental, or a combination of both

Variation in a species is the differences between the members of a species.
Genetic is caused by what genes are inhereted.
Environmental is caused by some action after birth (e.g the sun giving you a tan.)
Some variation is a bit of both...