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Evolution of Animals (Metazoa)

Evolution of Animals (Metazoa). BIOL 1407. Animal Body Plan. Tissues Absent = Parazoa Present = Eumetazoa. Radial Symmetry. Encounter environment equally from all sides Sessile, sedentary or planktonic Sea Anemone Feeding Video http://www.mbayaq.org/efc/video_library/video_library.aspx

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Evolution of Animals (Metazoa)

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  1. Evolution of Animals (Metazoa) BIOL 1407

  2. Animal Body Plan • Tissues • Absent = Parazoa • Present = Eumetazoa

  3. Radial Symmetry • Encounter environment equally from all sides • Sessile, sedentary or planktonic • Sea Anemone Feeding Video • http://www.mbayaq.org/efc/video_library/video_library.aspx • Then click on “Anemone Feeding” • Jellyfish Swimming • http://www.youtube.com/watch?v=760lUxyle6I

  4. Bilateral Symmetry • Central nervous system in head • Active movers • Frilled lizard video • http://video.nationalgeographic.com/video/player/animals/reptiles-animals/lizards/lizard_frilled_ontherun.html?fs=animals.nationalgeographic.com • Crocodile gallop video • http://www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/images/cj-gallop2.mpg

  5. Number of Germ Layers • Diploblastic: has two germ layers • Endoderm • Ectoderm • Triploblastic: has three germ layers • Endoderm • Mesoderm • Ectoderm

  6. Question?

  7. Body Cavities • What is a body cavity? • Fluid-filled cavity separates digestive tract from body wall

  8. Body Cavities • Advantages: • Fluid cushions organs • Acts as hydrostatic skeleton • Allows internal organs to move independently of body wall • Allows internal organs space for folding

  9. Development • Protostome • Fate of blastopore • Type of cleavage: spiral and determinate • Coelom formation • Deuterostome • Fate of blastopore • Type of cleavage: radial and indeterminate • Coelom formation

  10. Animation of Spiral and Radial Cleavage http://worms.zoology.wisc.edu/urchins/rad_spir.html

  11. Schizocoelous Enterocoelous

  12. Sister Taxon

  13. Model of Early Animal Evolution

  14. Evolution of Animals • Earliest animal fossils • Fossilized embryos from China • 575 mya

  15. Ediacaran Fauna • 565-550 mya • Australia • Soft-bodied animal fossils • What type of symmetry?

  16. Ediacaran Fauna • Animal fossil • Many body segments • Head • What type of symmetry?

  17. Cambrian Explosion • 535-525 mya • Animal diversity ↑↑ • 50% extant animal phyla in fossil record

  18. Burgess Shale Fossils

  19. Cambrian Explosion • First animals with hard mineralized skeletons • 1st arthropods, chordates & echinoderms

  20. Hypotheses for Cambrian Explosion (1) Predator-prey coevolution (2) Rise in atmospheric oxygen levels  ↑ metabolic rate and body size (3) Evolution of Hox genes  developmental flexibility

  21. Traditional Phylogenetic Tree • Was based on body plans • Tissues absent or present • Type of symmetry • Types of body cavities • Protostomes versus deuterostomes

  22. Modern Phylogenetic Tree • Based on molecular data

  23. Modern Phylogenetic Tree • Reinforces some of traditional tree • Parazoa vs. Eumetazoa • Radial vs. Bilateral • Deuterostomes are a clade

  24. Modern Phylogenetic Tree • Radical affects on other parts • Body cavity characteristics are analogous • Two main lineages for most invertebrates • Lophotrochozoa • Ecdysozoa

  25. Lophotrochozoa • Clade named for presence of either a: • Lophophore (horse-shoe shaped ciliated feeding apparatus) • Trochophore larva

  26. Lophotrochozoa

  27. Ecdysozoa • Clade was named for presence of • Ecdysis = molting • Produce an exoskeleton • Must be shed as animal grows

  28. The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings. Slides 19 and 28 are from Campbell, et al. 2005. Biology, 7th ed.

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