Evolution: Variation

Mind Map by amy.hamilton, updated more than 1 year ago
Created by amy.hamilton about 5 years ago


AS Biology

Resource summary

Evolution: Variation
1 Differences within a species
2 Caused by: organisms genes or environment
3 Genetic Variation
3.1 Differences between organisms due to their genes
3.2 Alleles: differences in genes for particular characteristics.
3.2.1 Meiosis & fertilisation produce new combinations of alleles Possible to have completely new alleles form sometimes Happens when a mistake is made as DNA is being replicated e.g a missing nucleotide, an extra nucleotide or a nucleotide replacing another
4 In sexual reproduction, alleles are shuffled around, each time a new organism is produced there is more chance of variation (More than in a plant) because in principle any male gamete can fuse with any female gamete
4.2 Gives an almost infinite number of combinations of possible variations
5 Environmental Variation
5.1 Differences between organisms due to the environment
5.1.1 2 people with the same alleles to make them tall but have very different diets can be very different heights 2 plants with identical genes can be a different size due to one being in the shade & the other being in the sun
5.2 Can arise throughout the lifetime but can not be inherited as it is not caused by DNA
6 Discontinous Variation
6.1 Variation where each organism belongs to one of a few clearly defined groups
6.1.1 E.g Human ABO Blood Groups: A, B, AB, O. No in-betweens
6.1.2 Almost always caused by genes, with little or no environmental influence Usually just 1/2 genes involved each having only a few alleles e.g Human ABO blood groups are controlled by a single gene with 3 alleles
6.2 Continous Variation
6.2.1 Variation where there is a continuous range of values between 2 extremes E.g eye or human skin colour is impossible to categorise in clearly defined colours E.g Oxford Ragwort leaf length can range between 2mm to 180mm, any length between those values is possible
6.2.2 May be caused by genes, environment or both E.g human eye colour is genes Skin colour can be both due to how much exposure to sunlight Leaf length is environmental due to how much sunlight they get
6.2.3 Most variations in humans is continuous influenced by genes & environment
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