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Alleles are different versions of a gene. Every person has two alleles for each gene (one from either parent). For example, the gene which determines eye colour can either have an allele ...

When the population of a species is separated, each group is put under different selection pressures due to differing environments. In each population there is genetic variation, and more offspring are...

Eutrophication is the loss of oxygen in a body of water (e.g. pond or lake). This is usually due to algal bloom caused by artificial fertilisers and other chemicals being washed into the water by rain.The...

Muscle cells are present in the stomach wall so that they can contract and move the food. This aids digestion and the action of enzymes

The movement of molecules from an area of high concentration to low concentration across a membrane using energy.