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Evidence for evolution

Topic 5
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Biology SL

Artificial selection
➢ The science of breeding domesticated animals provides a good record of recent
changes in the heritage characteristics
➢ Artificial selection is when the farmers and breeders choose which animals will
reproduce and which will not
○

It’s not the driving force of evolution in natural ecosystems

➢ The breeders choos animals with specific characteristics
Homologous structures
➢ Homologous structures are similar anatomical structures that have been found in
seemingly dissimilar species
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Ex: pentadactyl limbs

➢ Similar bone structures with different function in modern animals point at a
common ancestor
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May be of a different size and morphology, but the basic shape and position
are the same

Adaptive radiation
➢ Adaptive radiation occurs when 2 or more populations of a species diverge and
evolve relatively rapidly forming a small number of species
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Happens as variations within a population allow certain members to exploit
a slightly different niche

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A niche is a position or role within a community of an ecosystem

➢ Can happen by natural selection and the presence of a barrier
➢ Madagascar has many different regions and due to this many species of lemurs are
adapted to different niches
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Ground, trees, rainforest, desert, diurnal, nocturnal

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They all share a common ancestor

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Fun fact! Lemurs are only found in Madagascar, but fossils have been found
elsewhere too
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When the latter become more common in fossil records, the former
becomes rarer

Gradual divergence
➢ Within a species that has a wide geographical distribution, there can be measurable
differences in DNA
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Evidence for evolution

Topic 5

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