Ncea Biology Level 3 Speciation

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Natural Selection

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Process whereby the phenotype best adapted to their particular biological niche will be more likely to survive and pass their genes onto the next generation.

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Deme

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local population/subgroup where phenotypic variations reflect local environmental factors. There is limited gene flow between groups.

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Cline

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Geographical gradient in the phenotype of individuals of the same species. Often occurs in relation to changing altitude or latitude.

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Speciation

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The process leading to the development of new species.

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Reproductive Isolating Mechanisms

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Any factor that prevents two organisms from different species from mating and producing fertile offspring

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Convergent Evolution

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species with similar niches develop similar adaptations over time despite having different ancestors. This is due to similar selection pressures.

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Analogous Structures

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Organs that have the same basic structure and function but evolved independently from different ancestral organs in unrelated species. (Convergent Evolution)

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Ecological Equivalents

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Species with different origins develop similar adaptions because they occupy similar niches in different geographic areas. (Convergent Evolution)

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Divergent Evolution

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Occurs when two or more related groups develop different adaptions over time because they occupy different niches.

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Adaptive Radiation

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When a number of different species adapt from the same ancestor (divergent evolution)

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Homologous Organs

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Are found in related species that evolved from a common ancestral organ. They have different functions, but similar structures. (Divergent Evolution)

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Parallel Evolution

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Similar features evolve in species with a common ancestor. This is because they are subjected to similar selection pressures.

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Sequential Evolution

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This occurs when species change over time. This is can also be referred to as linear, serial or vertical evolution.

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Co-Evolution

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Reciprocal evolutionary effect two species can have on each other. Each species provides a natural selective influence on the other and they evolve together.

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Genetic Drift

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Describes the frequency of alleles can change over time due to chance events rather than selection pressures.

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Founders effect

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Occurs when a small number of individuals emigrate from a population or become geographically isolated from their original population.

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Bottleneck effect

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When a population becomes reduced to low numbers due to catastrophic environmental effects which reduce the genetic diversity.

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Evolution

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Evolution is a progressive change in genetic composition of a population.

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Directional Selection

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Selection against one end of a range of variation, resulting in a progressive change in allele frequency

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Directional Selection

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Selection against one end of a range of variation, resulting in a progressive change in allele frequency

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Stabilising selection

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Selection acting against the extremes of a range of variation

Prevents change

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Disruptive selection

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Selection acting against the middle of a range of variation

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Inbreeding

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When a population numbers fall to low levels inbreeding is more likely to occur. Related parents are more likely to carry the same recessive alleles