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Variation and Evolution - Coggle Diagram
Variation and Evolution
Allele Frequency
The number of times an allele appears at a particular locus in a population, expressed as a proportion or a percentage
Allopatric Speciation
A form of speciation that occurs when two populations become geographically isolated.
Behavioural Isolation
The reproductive isolation of two populations due to differences in their behaviour, e.g. mating rituals.
Continuous Variation
A type of variation that cannot be categorised, e.g. skin colour. It produces a continuous range in which a characteristic can take any value. Multiple genes influence this and it is often significantly affected by environmental factors.
Evolution
The gradual change in allele frequencies within a population over time due to natural selection.
Founder Effect
A type of genetic drift in which a few individuals of a species break off from the population and form a new colony. This results in smaller gene pools and an increased frequency of rare alleles.
Discontinuous Variation
A type of variation that can be categorised, e.g. blood group. A characteristic can only appear in discrete values. One or two genes influence this and environmental factors have little effect.
Gene Pool
All of the different versions of genes (alleles) in the individuals that makes up a population.
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Geographical Isolation
A physical barrier, e.g. river or mountain, separates two populations of the same species.
Hardy-Weinberg Principle
A model that predicts the ratio of dominant and recessive alleles in a population and will remain constant between generations if five conditions are met. It provides a formula for calculating the frequencies of alleles: p2 + 2pq + q2 = 1.0
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Hybrid Fertility
The formation of fertile hybrid offspring, e.g. wheat, due to hybridisation combined with polyploidy which doubles the chromosome number, enabling meiosis.
Hybrid Sterility
The formation of sterile hybrid offspring, e.g. mule, from the reproduction of individuals of different species; the chromosome sets from each parent differ so are unable to pair up during meiosis.
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Morphological Isolation
The reproductive isolation of two populations due to the incompatibility of their reproductive systems.
Natural Selection
The process by which the frequency of beneficial alleles gradually increases in a population's gene pool over time. This theory was developed by Charles Darwin.
Non-Heritable Variation
Acquired differences in the phenotypes of individuals that cannot be inherited.
Reproductive Isolation
The inability of two populations of the same species to interbreed due to behavioural, morphological or seasonal barriers.
Seasonal Isolation
The reproductive isolation of two populations due to differences in their breeding seasons.
Selection Pressures
Environmental factors that drive evolution by natural selection and limit population sizes, e.g. competition, disease and predation. They can change the frequency of alleles in a population.
Speciation
The formation of new species due to the evolution of two reproductively separated populations. Two forms; allopatric and sympatric speciation.
Species
A group of similar organisms that are able to breed with one another to produce living, fertile offspring.
Student's T-Test
A statistical test used to determine whether there is a statistically significant difference between the means of two data sets that show normal distribution.
Variation
The differences between individuals due to genes, the environment or a combination of both.
Sympatric Speciation
A form of speciation that occurs when two populations within the same area become reproductively isolated.