Animal Evolution –The Invertebrates

1. Animal Evolution –The Invertebrates Chapter 25 Part 2

2. 25.6 Flatworms—Simple Organ Systems • Flatworms (phylum Platyhelminthes) have a three-layer embryo that develops into an adult with many organ systems but no coelom • Three main classes: turbellarians, flukes (trematodes), and tapeworms (cestodes)

3. Turbellarians:Structure of a Free-Living Flatworm • Pharynx • Muscular tube connecting the mouth with the gut • Nerve cords • Two lines of communication along length of body • Ganglia • Cluster of nerve cell bodies (simple brain)

4. Flatworm Organ Systems

5. pair of highly branched tubules that adjust water and solute levels in body nucleus rudimentary brain (pair of large ganglia in head) cilia ovary branching gut testis fluid filters through membrane folds oviduct pharynx; protrudes onto food, then retracts into the body between feedings pair of nerve cords that have lateral branchings flame cell genital pore opening at body surface Fig. 25-15, p. 412

6. Animation: Planarian organ systems

7. Parasites: Flukes and Tapeworms • In blood flukes (Schistosoma), reproduction takes place in mammals – immature stages live in intermediate hosts (snails) • A tapeworm body consists of proglottids – repeating hermaphroditic body units that bud from a region behind the scolex

8. Fluke Life Cycle: Schistosoma

9. A A fluke matures and mates in a human host. F Larvae burrow into new human host, enter intestinal veins, and start a new cycle. B Fertilized eggs exit host in feces. E Fork-tailed, swimming larvae develop and leave the snail. C Eggs hatch as ciliated larvae. D Larvae burrow into an aquatic snail and multiply asexually. Fig. 25-16, p. 413

10. A A fluke matures and mates in a human host. F Larvae burrow into new human host, enter intestinal veins, and start a new cycle. B Fertilized eggs exit host in feces. E Fork-tailed, swimming larvae develop and leave the snail. C Eggs hatch as ciliated larvae. D Larvae burrow into an aquatic snail and multiply asexually. Stepped Art Fig. 25-16, p. 413

11. Beef Tapeworm Life Cycle

12. A Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle). proglottids scolex B A human, the definitive host, eats infected, undercooked beef, which is mainly skeletal muscle. scolex attached to wall of intestine one proglottid C Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave the host in feces, which may contaminate water and vegetation. D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts. Fig. 25-17, p. 413

13. A Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle). proglottids scolex B A human, the definitive host, eats infected, undercooked beef, which is mainly skeletal muscle. scolex attached to wall of intestine one proglottid C Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave the host in feces, which may contaminate water and vegetation. D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts. Stepped Art Fig. 25-17, p. 413

14. Animation: Tapeworm life cycle

15. 25.7 Annelids—Segmented Worms • Annelids (phylum Annelida) are bilateral worms with a coelom and a segmented body; typically with chaetae (chitin reinforced bristles) • Three main groups: marine worms (polychaetes), oligochaetes (including earthworms), and leeches

16. Marine Polychaetes

17. Fig. 25-18a, p. 414

18. “jaws” toothlike structures pharynx (everted) antenna palp (food handling) tentacle eyes chemical-sensing pit parapod Fig. 25-18a, p. 414

19. Fig. 25-18b, p. 414

20. Leeches – Bloodsuckers and Others • Leeches lack chaetae and have a sucker at either end

21. before feeding Fig. 25-19a, p. 414

22. after feeding Fig. 25-19b, p. 414

23. Oligochaetes • Example: earthworms • Exchange gases across body surfaces • Have five hearts and a closed circulatory system • Nephridia regulate coelomic fluid • Nervous system of ganglia and nerve cords • Hydrostatic skeleton • Hermaphroditic

24. Earthworm Body Plan

25. Fig. 25-20a, p. 415

26. anus nephridium dorsal blood vessel clitellum coelom intestine gizzard crop esophagus pharynx gut longitudinal muscle mouth ventral nerve cord circular muscle ventral nerve cord ventral blood vessel brain 2 of 5 hearts Fig. 25-20a, p. 415

27. Fig. 25-20b, p. 415

28. anus clitellum head Fig. 25-20b, p. 415

29. Animation: Earthworm body plan

30. How Earthworms Move

31. bristles used in locomotion Fig. 25-21, p. 415

32. 25.8 Mollusks—Animals With a Mantle • Mollusks (phylum Mollusca) • Bilaterally symmetrical with a reduced coelom • Mantle covers internal organs, secretes a shell • Feed using a hard radula • Have a complete digestive tract • Gills for respiration in aquatic species

33. Mollusk Diversity • Chitons • Eight overlapping plates • Gastropods (snails, slugs) • Undergo torsion during development • Bivalves (mussels, clams, oysters) • Hinged, two-part shell • Cephalopods (squids, octopuses) • Large, fast and smart; closed circulatory system

34. Mollusk Groups

35. Fig. 25-22a, p. 416

36. Fig. 25-22b, p. 416

37. Fig. 25-22c, p. 416

38. Fig. 25-22d, p. 416

39. Gastropod Body Plan

40. Fig. 25-23a, p. 416

41. gill anus excretory organ heart mantle cavity digestive gland stomach shell edge of mantle that covers organs foot radula Fig. 25-23a, p. 416

42. Fig. 25-23b, p. 416

43. after torsion: before torsion: mouth mouth mantle’s edge anus anus, which discharges wastes into mantle cavity Fig. 25-23b, p. 416

44. Animation: Snail body plan

45. Animation: Torsion in gastropods

46. Variations on the Gastropod Body Plan

47. Fig. 25-24a, p. 417

48. Fig. 25-24b, p. 417

49. mantle eye opening that leads to lung foot sensory tentacle Fig. 25-24b, p. 417

50. Fig. 25-24c, p. 417