1. Introduction to Animal Evolution Chapter 32

2. Origins All phyla form rather quickly in the “Precambrian explosion” Before 500 MYA Common ancestry with fungi in a colonial protistan similar to a choanoflagellate

3. Precambrian Explosion

4. Chaoanoflagellate Simple colonial Protist

5. WHAT IS AN ANIMAL?

6. Animals are multicellular eukaryotes I’ve got lots of cells and they all have a nucleus

7. Animals are heterotrophic by ingestion I just love to ingest. Store carbohydrate as Glycogen, or convert to fat

8. Animals have muscle and nervous tissues

9. Animal cells lack cell walls I’m all boxed in Not me

10. Have special cell to cell connections: Tight junctions – seals between cells Gap junctions – communication between cells Desmosomes -anchoring junctions Fig. 6.32 True tissues have these 4 Types of tissues

12. Animal Tissue types: Epithelial Muscle Nervous Connective- 3 parts – Cells, matrix and fibers

13. Most animals reproduce sexually Only have 1 lifecycle!! Mostly all diploid (2n) Except sperm and egg, with a few exceptions (e.g. drone bees etc.) Asexual reproduction does happen in some lineages, but it is not common (e.g. aphids)

14. Animals Undergo Embryonic Development Zygote – first new cell of animal – Diploid – Fertilized egg Cleavage – – repeated cell division without growth – Same amount of cytoplasm divides into – More, smaller cells

15. Figure 32.1 Early embryonic development (Layer 1)

16. Figure 32.1 Early embryonic development (Layer 2)

17. Animals Undergo Embryonic Development Blastula – hollow balls of cells not differentiated Gastrula – diploblastic – Blastopore – Opening to outside – Archenteron- new “gut” Cnidarians – Diploblastic & radially symmetrical

18. Embryonic tissue layers Ectoderm Endoderm Triploblastic animals also have: Mesoderm forms in between other two layers.

19. Origins of animals???

20. Figure 32.1 Early embryonic development (Layer 3)

21. Two Views of Animal Diversity The traditional view based on body plan and embryonic development. The new view is based primarily on molecular characteristics.

22. The Traditional View Parazoa vs Eumetazoa Parazoa lack true tissues (special cell connections) Eumetazoa are all the other animals

23. Traditional Phylogeny

24. The Traditional View Radiata vs Bilateria

25. Traditional View Continues Acoelomate - Pseudocoelomate vs Coelomate

26. Traditional View Continues Protostome vs Deuterostome

27. Fig. 21.37a

29. Protostomates Spiral and determinate cleavage- – Cell fate (specialization) starts during cleavage Mesoderm forms from a ball then splits open to form a cavity (ceolom) New opening forms an anus, blastopore becomes mouth. Proto (first) stomate (mouth)

30. Deuterostomates Radial and indeterminate cleavage- – Cell fate (differentiation) starts after cleavage – Identical twins Mesoderm forms from pockets in endoderm. Always has a gap or cavity in side New opening forms a mouth, blastopore becomes anus. Deutero (second) stomate (mouth)

31. Protostome vs Deuterostome I am a protostome. This opening will form my mouth I am a deuterostome. This opening will form my anus.

32. Traditional Phylogeny

33. Traditional Characters

34. Phylogeny based on SSU-rRNA

35. The New View Parazoa vs Eumetazoa - same Radial vs. Bilateral - same Protostomate vs. Deuterostomate – still significant Aceolomate and Pseudoceolomate traits not as significant. Considered simplified versions of ceolomates. Groups Nematodes with Arthropods in one branch and the rest of the protostomates in another branch.

36. Phylogeny Comparison

37. Molecular groupings

38. Metazoan phylogenies Adoutte A. et.al. PNAS 2000;97:4453-4456 ©2000 by The National Academy of Sciences

39. Lophotrochozoa Protostomate Have Trochophore larvae – – Bands of cilia Also include the Lophophore phyla – – Ciliated feeding structure Joins the Annelids – Mollusks onto the same clade

40. Larvae Juvenile ( pre – reproductive) phase Have simpler morphology than adult Often move, and feed differently than adults – Swims vs. crawls or flies Often live in different habitats to avoid competing with adults Often are the dispersal stage

41. Trochophore Larvae Annelida Mollusca

42. Lophophorate ectoprocts

43. Ecdysozoa Based on molecular data Joins Nematodes and Arthropods Both groups have hardened exoskeletons and undergo Ecdysis (Molting)

44. Molecular clades Includes some aceolomates and pseudocelomates into the different clades Not pre-ceolomates, but were rather simplified later.

45. THE END? WOW!!!!!!!!!!!! This is going to take a lot of study.