Animal Evolution The Invertebrates. Chapter 25 Part 2

Transcription

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 branching gut pharynx; protrudes onto food, then retracts into the body between feedings rudimentary brain (pair of large ganglia in head) pair of nerve cords that have lateral branchings ovary testis oviduct genital pore pair of highly branched tubules that adjust water and solute levels in body flame cell nucleus cilia fluid filters through membrane folds opening at body surface Fig , 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 , 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 , 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 D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts. 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. Fig , 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 D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts. 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. Stepped Art Fig , 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 a, p. 414

18 jaws toothlike structures pharynx (everted) antenna palp (food handling) tentacle eyes chemicalsensing pit parapod Fig a, p. 414

19 Fig b, p. 414

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

21 before feeding Fig a, p. 414

22 after feeding Fig b, 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 a, p. 415

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

27 Fig b, p. 415

28 anus clitellum head Fig b, p. 415

29 Animation: Earthworm body plan

30 How Earthworms Move

31 bristles used in locomotion Fig , 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 a, p. 416

36 Fig b, p. 416

37 Fig c, p. 416

38 Fig d, p. 416

39 Gastropod Body Plan

40 Fig a, p. 416

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

42 Fig b, p. 416

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

44 Animation: Snail body plan

45 Animation: Torsion in gastropods

46 Variations on the Gastropod Body Plan

47 Fig a, p. 417

48 Fig b, p. 417

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

50 Fig c, p. 417

51 Bivalve Body Plan: Clam

52 adductor muscle (cut) mouth left mantle adductor muscle (cut) Water flows out through exhalant siphon Water flows in through inhalant siphon foot palps left gill shell Fig , p. 417

53 Animation: Clam body plan

54 25.9 Cephalopods Fast and Brainy Cephalopod ( head foot ) Tentacles attached to the head are evolutionary modifications of the foot; they surround the mouth, which has a hard, horny beak Include the fastest (squids), biggest (giant squid), and smartest (octopuses) invertebrates Jet propulsion, complex eyes, closed circulatory system, complex behavior

55 Cephalopods

56 Fig a, p. 418

57 Fig b, p. 418

58 Fig c, p. 418

59 Fig d, p. 418

60 arm beak radula internal mantle shell tentacle siphon anus ink sac heart gill accessory heart reproductive organ Fig d, p. 418

61 Fig e, p. 418

62 Animation: Cuttlefish body plan

63 25.10 Rotifers and Tardigrades Tiny and Tough Rotifers (phylum Rotifera) and tardigrades (phylum Tardigrada) are tiny bilateral animals Rotifers have a pseudocoelom, but are genetically closest to annelids and mollusks Tardigrades have a coelom and molt, and are probably relatives of roundworms and insects

64 Rotifer Body Plan

65 ciliated lobe mouth brain with eyespots protonephridium stomach intestine anus one of two toes Fig , p. 419

66 Tardigrades

67 tardigrade s mouth roundworm prey Fig a, p. 419

68 Animation: Blood fluke life-cycle

69 Animation: Feeding leech

70 Animation: Marine polychaetes

71 Animation: Molluscan classes