Lecture 16,17, 18, 19 - Lecture 16 Animal Forms and Tissue...

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Lecture 16: Animal Forms and Tissue Characteristics of Animals: Multicellular, heterotrophic (chemo-aka must consume other organisms for both mass and energy purposes), internal digestion, motility, have muscles and nervous system (evolved to coordinate muscles), no cell wall (specialized cell junctions) Closest group to out group is the choanoflagellate, which resembles sponge cells (closest non-animal ancestor) o Is an opsitonkont, has single posterior flagella o How we got from colonial choanoflagellate to multicellular animal: More rigid adherence of cells, Cells in an animal are arranged into tissues, the cells adhere in a specific way, which evolved specialization To evolution of molecules which allow cells to “stick” was an important evolutionary development o Two important ones: o CAMs (cell adhesion molecules)-two molecules- one on one cell the other on the other cell which bind specifically to each other o Integrins-they attach cell cytoskeleton to collagen and other proteins in the ECM, these are important in connective tissue. They have to change shape if cell is moving. Cell (functional) specialization Further differentiation of cell types Cell coordination/communication Increase in size of animals Increase in complexity of animals Animal Body plan components: o Symmetry, digestive system, may or may not have body cavity (coelom), segmentation, appendages Symmetry: Types- o Spherical (ONLY FOUND IN PROTISTS) o Animals generally have either: o Radial Have single axis that goes through the body. Top and bottom o Bilateral Has greater land mobility usually Digestive system Very few parasites lack digestive system Most have two designs:
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o Sac design- has one opening, serves as both mouth and anus. Take in food and regurgitate waste. The sac also is in involved in circulation, gas exchange, and hydrostatic skeleton since it does so many things, it doesn’t have many specialized regions remain small and thin Mostly found in Hydras! o Tube design- Us Known as gut, tube that runs fro mouth to anus Sometimes used for purposes other than digestion (some fish do gas exchange through it) Associated with more complex forms, greater size, but it requires additional exchange system Body cavity No coelom, acoelomate Have coelom, pseduoelomates (roundworm) o If there is any endoderm that sticks out, then its this! Have coelom, coelomates (earthworm and us) Segmentation Most animals are segmented Sometimes segments are just repeats (called mers) This allows rapid evolution and specialization of body regions and changes in shape These are the result of hox genes and changes in their expression Allows radiation of arthropods (allowed them to be the most successful species) Appendages Ex. Feet (locomotion), hands (grasping), antennae (sense organs), Claws (eating), appendages for transfer of sperm or egg incubations Cell junctions: o
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