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A mutation can occur, causing the formation of an antibiotic resistant gene within a bacteria. This bacteria will then survive the course of antibiotics and reproduce, passing on the gene by vertical gene...

The smooth muscle contracts, causing vasoconstriction. Vasoconstriction is the narrowing of the vessel lumen.

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...

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...