Chapter 32 - An Introduction to Animal Diversity

Chapter 32 - An Introduction to Animal Diversity - Chapter...

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Chapter 32 Class Notes – An Introduction to Animal Diversity – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 32 An Introduction to Animal Diversity Our Kingdom: Biologists have identified 1.3 million living species of animals, and estimates run to as many as 200 million. Distinguishing the Animal Kingdom: Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers. Five criteria comprise a reasonable definition of an animal… 1. Animals are multicellular ingestive heterotrophs a. Taking in organic molecules through ingestion (eating) 2. Animal cells lack cell walls that provide structural support for plants and fungi a. Multicellular bodies are held together by extracellular structural proteins (collagen) b. Animals have intercellular junctions: tight junctions, desmosomes, and gap junctions, that all hold tissues together and are comprised of structural proteins 3. Animals uniquely have nerve cells (impulse connection) and muscle cells (movement) 4. Most animals reproduce sexually, with a dominant diploid stage a. A small flagellated sperm fertilizes a nonmotile egg b. The zygote undergoes cleavage, a succession of mitotic cell divisions, leading to the formation of a multicellular hollow ball of cells: the blastula c. During gastrulation, part of the embryo folds inward, forming layers of embryonic tissues that will develop into adult body parts i. The resulting development stage is a gastrula d. Some animals have a distinct larval stage i. A larva is a sexually immature stage that is morphologically distinct from the adult, usually eats different foods, and may live in a different habitat than the adult ii. Animal larvae undergo metamorphosis and become adults 5. Animals share a unique homeobox-containing family of genes: Hox genes a. All eukaryotes have genes regulating the expression of other genes b. Many of these genes contain common homeobox DNA sequences c. All animals share the unique family of Hox genes d. Hox genes control cell division/differentiation, and produce different morphological features
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Chapter 32 Class Notes – An Introduction to Animal Diversity – Page 2 e. Hox genes in sponges regulate the formation of channels; in bilaterians, they regulate patterning of the anterior-posterior axis The history of animals: Animals began to diversify over a billion years ago, diverging from the ancestors of fungi as much as 1.5 billion years ago. The common ancestor was probably a colonial flagellated protist and may have resembled modern choanoflagellates. Neoproterozoic Era:
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 32 - An Introduction to Animal Diversity - Chapter...

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