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Macroevolution (Development genes (major changes in body form are usually…
Macroevolution
Development genes
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dev. genes control the embryonic and post-embryonic development of an organism which influences rate, timing, and spatial pattern of form
dev. genes tend to be highly conserbed (identical or very highly similar) between species, even ones that are very distantly related
- changes that can occur to dev. genes include a change in gene sequence(mutation) through the process of duplication and divergence.
Hox genes are a great example of duplication and divergence-> more roughly correlates to more complex morphological structure
- change in gene regulation- through process of duplication and divergence- regulating when, where, and how long a gene is expressed and allowed to function
other changes can lead to morphology:
- heterochrony- evolutionary change in the rate or timing of developmental events
Macroevolution can tell us that speciation has been affected by both small scale factors and large scale factors
new forms arise by the slight modification of existing forms
can observe trends in the fossil record
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Adaptive Radiations
where new groups of organisms fill empty niches and diversify
- period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities
=niche- ecological role in the community
4 factors that promote adaptive radiations:
- mass extinction
- major evolutionary innovations
- diversification of another group of organisms (which can provide new sources of food)
- migration to new locations where few competitor species exist
example of adaptive radiation:
new organisms reach new location with relatively little competition. They diverge by natural selection. These are all descendants of an ancestral tarweed.
Fossil Record
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fossil record based mostly on sequence in which fossils accumulate in sedimentary rock layers (strata)
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