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Adaptive Radiation

Adaptive Radiation. Cambrian Explosion. Cambrian Explosion. Fig. 25-10. 500. Sponges. Cnidarians. Molluscs. Annelids. Chordates. Arthropods. Brachiopods. Echinoderms. Early Paleozoic era (Cambrian period). Millions of years ago. 542. Late Proterozoic eon. Fig. 25-18.

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Adaptive Radiation

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  1. Adaptive Radiation

  2. Cambrian Explosion

  3. Cambrian Explosion

  4. Fig. 25-10 500 Sponges Cnidarians Molluscs Annelids Chordates Arthropods Brachiopods Echinoderms Early Paleozoic era (Cambrian period) Millions of years ago 542 Late Proterozoic eon

  5. Fig. 25-18 Close North American relative, the tarweed Carlquistia muirii 1.3 million years MOLOKAI KAUAI 5.1 million years Dubautia laxa MAUI OAHU 3.7 million years Argyroxiphiumsandwicense LANAI HAWAII 0.4 million years Dubautia waialealae Dubautia scabra Dubautia linearis

  6. Studying Hawaiian Drosophila Dawkins on Hawaiian Drosophila

  7. Melawi eye biter Scale-eating cichlid

  8. Placental and marsupial mammals radiated soon after dinosaur extinction, AND after many other mammal lineages also went extinct (see next slide)

  9. Radiation due to key character evolution?

  10. Russell 1968

  11. 4 genera appeared over a 2 my period Pappogeomys, Cratogeomys, and Orthogeomys diverged over 800,000 years Molecular data also support a relatively rapid radiation…

  12. From Korth 1994 Tertiary Record of Rodents of North America • The fossil record indicates rapid radiation leading to modern pocket gopher genera in the Blancan • Radiation corresponds with increase in hypsodonty and expansion of grassland

  13. Maybe expansion of Blancan grasslands was responsible for pocket gopher radiation?

  14. Replicated sister-group comparisons:allow a more refined approach to assessing “key characters” as causes of adaptive radiations Both clades of herbivorous insects are more taxonomically diverse than their sister groups This pattern was seen in 11 of 13 sister group comparisons of herbivorous vs. other

  15. Example radiation: Land plants are a monophyletic group that has evolved fit many ecological niches

  16. Waxy cuticle prevents water loss Stomata allow gas exchange through the waxy cuticle

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