july13 - Tuesday Chapter 32*Overview-What is an animal*Theory re-protoanimal*Major branches in animal evolution(n=4 1 Parazoa Eumetazoa 2 Radiata

july13 - Tuesday Chapter 32*Overview-What is an...

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Tuesday, July 13, 2010 Chapter 32 *Overview -What is an animal *Theory re-protoanimal *Major branches in animal evolution (n=4) 1. Parazoa- Eumetazoa 2. Radiata- Bilateria 3. Acoelomate- Pseudocoelomate- Coelomate 4. Protostome- Deuterostome Chapter 33 Inverterbrate Animals *Overview *Lower Phyla -Porifera -Cnidaria -Platyhelminthes -Nematoda -Annelida -Mollusca Animal Characteristics - multicellular, heterotrophic, eukaryotes with tissues that develop from embroyonic layers -has exceptions to almost all criterion -several characteristics together define a group Reproduction and Development -most animals reproduce sexually with the diploid state usually dominating the life cycle -after a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage -cleavage leads to the formation of a blastula -the blastula undergoes gastrulation , forming a gastrula with different layers of embryonic tissue -all animals and only animals have Hox genes that regulate the development of body form -although the ox family of genes has been highly conserved, it can produce a wide diversity of animal morphology History of Animals -many span more than a billion years -animal kingdom includes not only great diversity of living species, but also the ever greater diversity of extinct ones -common ancestor of living animals may have lived 1.2 billion- 800 million years ago -may have resembled modern choanoflagellates - protists that are the closest living relatives of animals Neopaleozonic Era Paleozonic Era (542-251 million years ago)
-the Cambrian explodsion marks the earliest fossil appearance of many major groups of living animals Mesozoic Era (251-65.5 million years ago)

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