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Created by rebeccachelsea almost 5 years ago


B1 Topic 1 - Variation notes

Resource summary

1 Genes
1.1 Characteristics are determined by the genes inherited from its parents, some from the mother and some from the father.
1.2 Combination of genetics causes variation so no two are genetically identical
1.3 It is also due to genetic mutations.
1.4 Some characteristics are determined solely by genetics (e.g. blood type and inherited disorders like cyctic fibrosis and haemophilia.
2 Environment
2.1 Occurs over a wise range of differences (e.g. sun tan or getting yellow leaves).
2.2 Factors include diet, exercise, temperature, light level and water volume.
3 Continuous
3.1 When the individuals within a population vary within a certain range with no distinct categories
3.2 For example humans mass, E. coli width or number of leaves on tree.
3.3 Graph takes the place of a normal distribution curve where the curve is symmetrical around the mean.
4 Discontinuous
4.1 Where there are 2 or more distinct categories and each individual only falls into one of the categories, there are no intermediates.
4.2 For example blood group, whether bacteria are antibiotic-resistant or not and courgette colour.
4.3 Graph is a bar graph (bars don't touch).
5 Most characteristics are determined by a mix or genetic and environmental factors (e.g. body weight, height, skin colour).
5.1 For example, a plant's maximum height is caused by genes but whether or not it reaches that height depends on the environment in which it grows.
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