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• There is genetic variation within the population of bacteria
• The variation has occurred due to random genetic mutations
• This variation means that a bacterium may have a mutation th...

the connections within the retina explain this. there is a different density and distribution of different types of cells in the retina - the fovea, in the centre of the eye, has a high density of cone ce...

Photosynthesis is the process that takes place in green plants to produce their energy. It is when light energy is converted into chemical energy. Carbon dioxide and water are taken in and used to make ox...

A test cross is used to discover the genotype of an individual by crossing two parents to see the phenoypic ratio of the offspring produced. A homozygous recessive individual (one with two recessive or sm...

Mark schemes for biology essays in AQA aren't like the six mark questions at GCSE. You have to cover the subject broadly at first and show that you have an overall understanding of the tpoic in question b...