Animal diversity and relationships

1. Animal diversity and relationships

2. Living forms At least 30 phyla But only x “important” ones Importance = numerous, ecologically important, and fit into our conceptions of evolution

3. Porifera = sponges Assymetrical, 2 cell layers , internal silica spicules = skeleton.

4. Cnideria, jellyfish, corals Radially symmetrical, 2 cell layers, one ended digestive system. Often with algae inside to provide nourishment Light sensitivity.

5. Ctenophora – comb jellies Bilateral, one ended gut, marine

6. Platyhelminthes = flat worms. Three cell layers, no body cavity, one ended digestive system, brain, nerves, many are parasitic.

7. Two ended digestive system Head and tail, have an internal cavity – not solid. Very numerous in soil.

8. Annelida = segmented worms; bigger most free living. Have nerves, three cell layers, true body cavity = coelom, circulatory system, excretory system. Skin breathing and many have legs. Some carnivorous, soil eaters or leaches – blood suckers

9. Mollusca: clams, snails, squid, octopus, slugs Two ended gut, nerves, circulation, filter feeders or carnivorous. Some (squid, octopus) with eyes, brain, etc. Remnants of segmentation – chitins.

10. Arthropods – joint leg = insects, crustacea Segmented, brain, sense organs, excretory system

11. Echinoderms – pentaradiate, Starfish, urchins, sea lillys.

12. Chordata, including vertebrata . Backboned organisms.

13. The fossil record How to determine relationships – try fossils first.

14. Burgess Shale in British Columbia, a unique preservation at the right age.

18. Segmented worms (with legs?)

19. arthropods

20. Chordate – similar to early members of this group

21. sponge

22. ????

24. Result of fossil record: all major groups plus some other odd ones appear almost simultaneously = no sequental appearance.

25. How to make sense out of diversitywithout fossils. Rules: simple to complex symmetry (assymetrical, radial, bilateral) Cell layers – 1 to 2 to 3 Embryology - (old ontogeny recapitulates phylogeny statement of Haeckel) Digestive system design; one ended to two ended

26. Ernst Haeckel, 1866; “ontogeny recapitulates phylogeny” = early stages of development mirror evolutionary changes. Note – gill clefts in all embryos, tail present, etc. Basis; development is often incremental – add new stages to old – harder to change the beginning stages.

27. Classic example of this, the aortic arches in vertebrates. Start with a complete set; need gill arches to deposit them. All embryos have gill clefts and a complete set of arches To get to adult stages, loose some of the arches.

28. Because of assymetry, doesn’t fit into any neat story – so viewed as a development separate from everything else. Phylum porifera; sponges. assymetrical

29. Symmetry, bilateral or radial

30. Radial symmetry plus one ended digestive system = primitive Jellyfish, corals, radial cnideria

31. Bilateral symmetry; all other groups.

32. Clues from development • Hollow ball of cells • Then 2 cell layers, one opening,radial symmetry= cnidaria • Then three cell layers – new opening • bilateral symmetry = all higher forms

33. Cell layers 2 vs 3. sponges and cnideria = 2

34. Digestive system – one ended vs. two ended

35. Flatworms – bilaterial but with one openning to digestive system

36. Other ‘worms’ – two ended digestive system.

37. So: 1 – no symmetry, followed by radial and then bilateral - porifera oldest then cnidaria, then everything else 2. one ended gut, followed by 2 ended. 3. 2 cell layers, followed by three

38. Now what? Use embryology – the great Protostome – Deuterostome split

39. First opening = mouth Determinate clevage Spiral clevage Mesoderm = 4d cell Schizocoel coelom First opening = anus Indeterminate clevage Radial clevage Mesoderm = infolding Endocoel coelom Protostomes vs deuterostomes

41. Classical method mesoderm – solid to pseudocoelom to true coelom one ended gut to two ended no segments to segments Protostomes – how to organize

42. Body cavity (coelom) in relation to mesoderm Solid mesoderm = no coelom = flatworms acoelomate Coelom partially lined with mesoderm = roundworms pseudocoele Coelom completely lines with mesoderm = Segmented worms, vertebrates, etc. true coelom

44. Result = Molluscs = chitin, segmented. Odd –legs?? Arthropods – trilobite = segmented and legs Seg. Worms (annelids) segments true coelom Round worms; two openings dig system pseudocoel Flatworms – one opening dig system, solid (acoelomate)

45. Trilobite = arthropoda Chitin = mollusca Marine worm = annelida All segmented.

46. Deuterostome, protostome split Protostomes groups by segmentation. Note: Classical classification ((it’s wrong)) Link segmentation together

47. Lophotrochozoans Filter feeders Ecdysozoans Shell shedders New phylogeny

48. Two phylogenies: left based on hypothesized relationships, right based on Both genetic similarity and time. Right is correct in that all major groups appear almost simultaneously (brushpile evolution)

50. Note: flatworms,mollusc and annelid together// no arthropods