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Evolution of animals Heterotrophs- obtain their food from the environment Multicellular (single-celled “animals” are p

Evolution of animals Heterotrophs- obtain their food from the environment Multicellular (single-celled “animals” are protists) Movement Cells have no walls and are organized in tissue. Sexual reproduction Sperm and eggs function as gametes; do not develop on their own

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Evolution of animals Heterotrophs- obtain their food from the environment Multicellular (single-celled “animals” are p

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  1. Evolution of animals Heterotrophs- obtain their food from the environment Multicellular (single-celled “animals” are protists) Movement Cells have no walls and are organized in tissue

  2. Sexual reproduction Sperm and eggs function as gametes; do not develop on their own Embryonic development several distinct stages

  3. Animal kingdom (like all kingdoms) • organized into phyla • About 36 phyla • Certain body features appeared as animal • evolution progressed • Multicelluar (sponges) • Symmetry (cnidarians)

  4. 3. Internal organs and bilateral symmetry (flatworms) 4. Body cavity (roundworms, rotifers) 5. Coelom (completely enclosed body cavity  organ systems (mollusks) 6. Segmentation (more complex structures can develop)-segmented worms

  5. 7. Jointed appendages, exoskeleton (limbs, mechanism for growth) arthropods 8. Internal skeleton, more complex embryonic development (deuterostome) echinoderms (sea stars) 9. Notochord (gives rise to nervous system, helps organize organs)-vertebrates

  6. Radial symmetry Arrangement of parts around a central axis Cnidarians and ctenophores

  7. Bilateral symmetry All animals more advanced than cnidarians Allows more more complex organization and more specialization Most have a head and tail end

  8. Sponges symmetric specialized cells- no tissues for protection to draw water in to be filtered food molecules taken in by endocytosis

  9. Cnidarians ectoderm and endoderm extracellular digestion sponges- individual cells take in food molecules and digest them these organisms have a “gut cavity” (so can break down and digest organisms larger than a cell) Examples: jellies, hydra, sea anemones, corals

  10. Solid worms (Platyhelminthes) Bilateral symmetry Distinct head and tail No interenal cavity other than digestive (acoelomate) Usually parasitic Usually hermaphroditic

  11. Evolution of the body cavity Helps fluids circulate through body (move nutrients and wastes) Make body more rigid (support and muscle-driven movement) Organs can function without being impacted by others

  12. Nematodes (roundworms) and rotifers: body cavity Have a one-way digestive system No true circulatory system C. elegans- first animal whose genome was sequenced Many are parasitic Separate sexes

  13. Mollusks- most primitive coelomates Head, central body area, foot Gastropods- snails and slugs Bivalves- clams, oysters, scallops Cephalopods- octopuses, squids

  14. Annelids- segmented worms Segments have different functions (sensory, digestive, reproductive) Distinct systems (circulatory, nervous) Segmentation seen in more advanced organisms too

  15. Arthropods Jointed appendages Exoskeleton- provides protection but keeps it small (except in water) Insects Arachnids Centipedes and millipedes Crustaceans

  16. Echinoderms (sea stars) Endoskeleton (internal skeleton) First deuterostome (other phyla described so far are protostomes) Deuterostomes: mouth and anus develop differently and in different order

  17. Vertebrate evolution All of the surviving groups of animals originated in the sea in the Paleozoic era (the Cambrian explosion) First vertebrates appeared about 470 mya -jawless fishes

  18. II. Invasion of the land plants arthropods shortly after plants (why did plants have to come first?) vertebrates amphibians reptiles birds mammals

  19. Vertebrates are members of the phylum Chordata Common characteristics: Nerve cord (brain and spinal cord Notochord (located between nerve cord and digestive tract Gill structures in pharynx Post-anal tail All chordates have these in the embryonic stage

  20. Human embryo

  21. Types of vertebrates (in order of appearance): • Fishes (early Cambrian) • -Jawless (lampreys) • -Cartilaginous (sharks and rays) • -Bony • most numerous • can breathe without swimming • ray-finned or lobe-finned

  22. II. Amphibians- adapted to land and water must lay eggs in water metamorphosis from water to land use moist skin for gas exchange first vertebrates to colonize land “tetrapods” Frogs and salamanders

  23. III. Reptiles- snakes, lizards, turtles, crocodiles, alligators Evolved from amphibians: keratin waterproofed skin (scaly) “amniotic egg”: shell enclosed water so egg could be laid on land “ectotherms” absorb heat from atmosphere (how do mammals stay warm?) Mesozoic era- Age of Reptiles

  24. IV. Birds- evolved from dinosaurs amniotic eggs scales on legs How do birds fly? honeycomb bone structure no teeth endotherms (generate heat from internal metabolism) feathers

  25. V. Mammals first appeared about 225 mya very small during dinosaur era; got bigger after dinosaurs extinct Some are aquatic Some fly Most are terrestrial Hair Mammary glands Four-chambered heart

  26. Three major groups of mammals Monotremes (egg-laying) duck-billed platypus, echidna Marsupials- pouched mammals Eutherian (placental) 95% of mammalian species

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