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11 Cards in this Set
- Front
- Back
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Evolution |
Cumulative change in the heritable characteristics of a population |
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Selective breeding |
Form of artificial selection, where man intervenes in the breeding of animals to produce desired traits in offspring. (e.g. speed in horses) |
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Homologous structures |
Comparative anatomy of groups of animals or plants show certain structural features are basically similar, implying common ancestry |
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Adaptive radiation (divergent evolution) |
Similar basic plan has been adapted to suit various environmental niches |
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Malthusian dilemma |
Populations tend to multiply geometrically, while food sources multiply arithmetically - populations tend to produce more offspring than the environment can support |
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Members of a species show variation 1. Discontinuous Variation 2. Continuous Variation |
1. Controlled by a single gene, leads to distinct classes (e.g. A/B/O blood group in humans)
2. Controlled by many genes, leads to a range of characters (e.g. pigmentation of skin) |
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Variation has 3 main vehicles 1. Gene mutations 2. Gene flow 3. Sexual reproduction |
1. permanent change to the genetic composition of an individual 2. movement of genes from one population to another via immigration/emigration 3. combination of genetic materials from 2 parental sources |
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Sexual reproduction introduces variation 3 ways 1. Independent assortment 2. Crossing over 3. Random fertilisation |
Metaphase I: homologous chromosomes line up at the equator, paired chromosomes arrange themselves in one of two orientations (paternal left/maternal right vice versa). Separation at Anaphase I = final gametes differ depending on whether they got maternal/paternal chromosome |
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Sexual reproduction introduces variation 3 ways 1. Independent assortment 2. Crossing over 3. Random fertilisation |
Prophase I: homologous chromosomes pair up as bivalents, undergo crossing over where parts of the homologues break off and are integrated into the sister chromatid |
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Sexual reproduction introduces variation 3 ways 1. Independent assortment 2. Crossing over 3. Random fertilisation |
Fertilisation results from the fusion of gametes from a paternal and maternal source. Offspring receives different combinations of traits every time because the exact gametes that fuse are random. |
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Natural selection leads to evolution |
1. Genetic variation in a population is inheritable 2. Competition for survival is inevitable (Malthusian dilemma) 3. Environmental selective pressures lead to differential reproduction 4. Organisms with beneficial adaptations more suited to the environment are more likely to survive and pass on their genes. 5. Over generations, there will be a change in allele frequency within a population. |
