Lecture 15

Lecture 15 - Lecture 15Diversity trends through the...

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Lecture 15- Diversity trends through the Phanerozoic; Life invades the Land A. Arthropods- Lobster, crabs, spiders, scorpions, hexapods (insects), myriapods (centipedes and millipedes), and Trilobites (extinct) e Most diverse clade on Earth- 1.2 million species e There are four main groups that are living- o 1. Crustaceans (shrimp, crabs, lobsters, etc.) o 2. Chelicerates (spiders, scorpions, horseshoe crabs) o 3. Hexapods (insects) o 4. Myriapods (centipedes and millipedes) e There is also one distinct groups of arthropods- trilobites B. Trilobites- three ‘lobes’ e Dominated Cambrian diversity- the most diverse extinct group, and it extinct by the end of the Paleozoic C. Echinoderms- Sea Star, Brittle stars, Crinoids, sea urchins, sand dollar, sea cucumbers e Water vascular system- operates tube feet e Ambulacra: grooves associated with the tube feet e Brittle stars- arms distinct from central disc, mobile- with detachable arms e Crinoids (sea lilies) o Looks like a flower: a stem and ‘petals’ and attached suspension feeders D. Sepkoski’s Diversity Curve- developed by Jack Sepkoski e Consulted literature on fossil animal species then compiled a database, plotted diversity along a growth curve e Perservational bias toward depositional environments E. Three Evolutionary Faunas- Cambrian fauna, Paleozoic fauna, and Modern fauna F. Sepkoski’s Diversity Curve- e Cambrian radiation- within the first 20 or 30 million years of the Cambrian all
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Lecture 15 - Lecture 15Diversity trends through the...

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