AQA AS Biology Questions

Glycogen is an ❌ source for ❌. ❌ is an energy source of plants. ❌ is a structural molecule for plants.

Starch has ❌ chains and has a ❌ structure which means it is compact. You test for starch with the ❌ which uses ❌ solution. A positive result is ❌.

In DNA, the ❌ bases are adenine and guanine, and the ❌ bases are thymine and cytosine.

The ❌ Immune Response:
1) Phagocyte becomes an ❌ after it has destroyed the pathogen
2) The antigen presenting cell releases cytokines and the helper ❌ cell is activated
3) The helper T cell stimulates the production of ❌ T cells
4) Perforin is produced which cause ❌ of the cells infected with pathogens
5) Exposure to the specific antigen causes ❌ cells to be produced

❌ Immune Response:
1) The phagocyte becomes an ❌ after it destroys the pathogen
2) The antigen presenting cell stimulates the helper T cell by releasing ❌
3) The helper T cell stimulates the differentiation of ❌
4) Some B lymphocytes become ❌ cells which release large quantities of specific ❌
5) Some B lymphoctes become ❌ cells

Arteries have a ❌ muscular layer which can be constricted and dilated to control the volume of blood passing through them. They have a thick ❌ layer which helps to maintain blood pressure by stretching and ❌. The overall thickness of the artery help to prevent ❌. There are no ❌.

Veins have a ❌ muscular layer which can ❌ to control the flow of blood. They have a thin elastic layer. They have very thin walls since the pressure is ❌ and means they can be flattened easily to aid the flow of blood. There are valves throughout which ensure the blood doesn't flow ❌.

A genetic bottleneck will ❌ genetic diversity. It is an event which causes a big ❌ in the population so will reduce the number of ❌. The survivors will reprodue and the larger population is created from ❌ indiviuals.

Directional selection favours individuals with characteristics at the ❌ of the population whereas stabilising selection favours individuals in the ❌ of the range when the environment ❌ changing much.