GCSE additional Biology

All males: Have an XY chromosome, the Y is dominant and causes the male characteristics.
All females: Have an X and X chormosome, the ** combination allows the female characteristics to develop.

The Dominant gene decides what the characteristics will be, also known as the 'bossy and loud gene' -(the Y in the male chromosome) and a Recessive gene is overpowered by the dominant gene, it will only show its characteristics when there is no dominant gene, also known as the 'shy and quiet gene'.

If either parent has a disorder, then there is a 50/50 chance that the offspring will have the disorder too. Cystic fibrosis is an example, the offspring could be healthy and not inherit the disorder or they could inherit the disorder, but they could inherit it that they get ill and it affects the cell membrane and the respiratory system or they could be a carrier, where they do not get affected at all.
                                          

The body uses enzymes to break down large food molecules into smaller molecules, for example;

• Amylase- breaks down starch into sugar
• Protease- breaks down protein into amino acids
• Lipase- breaks down fat into fatty acids and glycerol

Bile helps the digestion by breaking down fat into the small intestine, and bile is produced in the liver and stored in the gall bladder.

Enzymes are a biological catalysts which speed up reactions, and each has a certain shape, too high a temperature and the enzyme will change shape or it will stop working (destroyed). Enzymes can catalyse the build up of small molecules into large molecules or they can break down large molecules into smaller ones, enzymes lower the amount of energy for a reaction to take place, the 'activation' energy.

Homeostasis is a process in your body which makes sure that everything in your body is kept at a constant internal environment, for example; Body temperature
           If you get too hot, then your body responds to this by sweating- the sweat evaporates from the skin's surface which cools us down, and blood vessels moving to the surface of the skin- to let more blood flow through, and heat is lost by radiation. 
          If you get too cold, then your body responds to this by shivering- the muscles contract quickly which heats you up, and by the blood vessels moving away from the skin's surface, so less blood can flow through, so less heat is radiated.

Another example of homeostasis is the blood sugar levels in your body:

The pancreas keeps control of this, if there is too much sugar in the blood then the pancreas produces the hormone insulin which takes the excess sugar and stores it in the liver as glycogen.
Diebetics can not produce enough insulin, so they have to monitor the intake of sugar by diet or having to inject insulin into themselves, to make sure their blood sugar levels don't get too high.

A food web will demonstrate the feeding relationships in a habitat e.g woodland
A food chain is the individual feeding relationship of specific animals and plants

Energy is lost at each level of a food chain, energy is lost because of 'MRS.GREN', this is shown in a pyramid of biomass.

• Movement                                                           |Humans|
• Respiration                                                       | Crayfish  |
• Sensitivity                                                       |    Limpet     |
• Growth                                                       |    Seaweed    |
• Reproductions
• Excretion (poo/wee)
• Nutrition                                       Pyramid of Biomass; ( | word | ) - amount of energy lost at each level
    

A pyramid of number shows how many organisms are feeding from another organism in a food chain. This is not always shown a normal pyramid.

Lettuce----> Rabbit----> Fox                                | Fox |
10,000            20             1                             |    Rabbit   |
                                                                 |        Lettuce        |

Tree----> Aphid----> Ladybird                      |      Ladybird      |
   1         20,000          5000               |                  Aphid                  |
                                                                           | Tree |