BIOL211#9 - Chapter 32 Characteristics of Animals 1.3...

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1 Chapter 32 Intro to Animal Diversity Characteristics of Animals 1.3 million extant (living) species of animals have been identified Total number of species may be as high as 100 – 200 million Difficult to characterize all animals The history of animal life spans over 590 million years ago (mya), starting at the end of the Proterozoic Era, when marine invertebrates first appeared Paleozoic Era (543 – 248 mya) – Considerable diversification during the Cambrian Period (Cambrian explosion) – Several hypotheses Development of a favorable environment Evolution of the Hox gene complex New predator-prey relationships Mesozoic Era (248 – 65 mya) – Few new animal body plans emerged – Animals spread into new ecological habitats – First coral reefs formed – Dinosaurs and birds emerged – The first mammals appeared
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2 Cenozoic Era (65 mya – present) – Mass extinctions ushered in the Cenozoic Era – Dinosaurs disappeared – Mammals exploited vacated niches – Global climate gradually cooled Terrestrial animals faced problems with desiccation Adaptations included internal fertilization and the development of an amniotic egg Traditional Classification Common ancestor was most likely a
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This note was uploaded on 10/02/2011 for the course BIOL 211 taught by Professor Boury during the Spring '08 term at Iowa State.

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BIOL211#9 - Chapter 32 Characteristics of Animals 1.3...

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