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25.1 Animal Origins

25.1 Animal Origins. What is an animal? Multicelled, heterotroph Most motile Reproduce sexually Unwalled Most have tissue and organs. Evolutionary Tree. Tissues. Key innovation in complexity: Ability to interact in functional units Epithelium Sheet like array

matthew-trujillo
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25.1 Animal Origins

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  1. 25.1 Animal Origins • What is an animal? • Multicelled, heterotroph • Most motile • Reproduce sexually • Unwalled • Most have tissue and organs

  2. Evolutionary Tree

  3. Tissues • Key innovation in complexity: • Ability to interact in functional units • Epithelium • Sheet like array • Functions: absorption, secretion, sensory • 1st epidermis • 2nd gastrodermis

  4. cont. • Connective tissue • All contain • Most have a matrix in which living cells and protein fibers (collagen) exist • Embryo forming – 2 primary tissue layers • Outer ectoderm • Inner endoderm • mesoderm

  5. Body Size • How to deal with increasing constraints of SA-V ratios of cells? • Pseudopds and microvilli in single cell species • Simple animals are sheets/ribbons • circulatory system in large animals

  6. Where did it all start? • Colonial Theory • 1st animals evolved from tiny colony of flagellated, amoeba like cells • Choanoflagellates • Share common ancestor with sponges

  7. 25.2 Basic Body Plans • Body Symmetry • Polarity – front to back axis, with anterior and posterior ends • Radial – organized around main axis, water

  8. Bilateral – right and left halves along a main axis Cephalization – distinct head region

  9. Gut and Body Cavity Complete gut Tubular 2 openings Mouth (specialized feeding structures) to anus • Incomplete gut • Sac-like • One opening • 1st to evolve

  10. Formation of Complete Gut Deuterostomes 1st opening becomes anus Echinoderms, chordates • Protostomes • 1st opening becomes mouth • Flatworms, mollusks, annelids, roundworms, arthropods

  11. epidermis gut cavity organs packed between gut and body wall No coelom (acoelomate animals) • None – flatworms, few invertebrates • Tissue and organs fill region between gut and body wall Fig. 25-6a, p.406

  12. gut cavity epidermis Pseudocoel (pseudocoelomate animals) unlined body cavity around gut • Pseudocoel – roundworms • In some protostomes coelom is reduced/lost Fig. 25-6b, p.406

  13. gut cavity epidermis Coelom (coelomate animals) peritoneum body cavity with lining that holds internal organs in place Fig. 25-6c, p.406

  14. Repeating Units • Favors regional specialization in structure and function • Segmentation – annelids, arthropods, vertebrates • Divide into a series of functionally connected units along main body axis

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