2. Animal Evolution – The Invertebrates

3. Characteristics of Animals Multicelled heterotrophic eukaryotes Require O 2 for respiration Sexual & perhaps asexual reproduction Motile at some stage Develop from embryos

4. Here’s Something New:Symmetry! Radial Bilateral

5. The Gut Region where food is digested and then absorbed Saclike gut –One opening for taking in food and expelling waste Complete digestive system –Opening at both ends; mouth and anus

6. Body Cavities – Acoelomate (no coelom) epidermis gut cavity no body cavity; region between gut and body wall packed with organs

7. Body Cavities – Pseudocoel (false coelom) epidermis gut cavity unlined body cavity (pseudocoel) around gut

8. Body Cavities - Coelom gut cavity peritoneum lined body cavity (coelom)

9. Segmentation Repeating series of body units Units may or may not be similar to one another Earthworms - segments appear similar Insects - segments may be fused and/or have specialized functions

10. Animal Origins Originated during the Precambrian (1.2 billion - 670 million years ago) From what? Two hypotheses: –Multinucleated ciliate became compartmentalized –Cells in a colonial flagellate became specialized

11. Sponges No symmetry No tissues No organs Reproduce sexually Microscopic swimming-larval stage

12. Nematocyst before triggering After triggering, nematocyst pierces prey Cnidarians (jellyfish) Only animals that produce nematocysts (stinging cells) Nerve net Hydrostatic skeleton Saclike gut

13. Flatworms Acoelomate, bilateral, cephalized animals All have simple or complex organ systems Most are hermaphrodites

14. Three Classes Turbellarians (planarians) pharynx Flukes Tapeworms

15. Segmented worms Have digestive, nervous, excretory, and circulatory systems Annelids

16. Polychaetes (Bristleworms) Most are marine Bristles extend from paired, fleshy parapods on each segment Head end is specialized

17. Predators and parasites Less obvious body segmentation Most have sharp jaws Leeches

18. Bilateral, soft-bodied coelomate Most have a shell Mantle drapes over body and secretes shell Most have a fleshy foot Many have a radula for shredding food Mollusks

19. Gastropods Bivalves Cephalopods Molluscan Diversity

20. Cephalopods Only the nautilus retains external shell Other cephalopods are streamlined, active swimmers All move by jet propulsion –Water is forced out of mantle cavity through a funnel-shaped siphon Have large brains relative to body size

21. Cuttlefish Body Plan Closed circulatory system with heart and accessory heart anus siphon gill heart accessory heart shell brain reproductive organ stomach digestive gland radula

22. Roundworms False coelom Complete digestive system gonadpharynxintestine false coelom eggs in uterusanus muscularized body wall

23. The phylum with the greatest number of species Four lineages: –Trilobites (all extinct) –Crustaceans (crabs, shrimps, barnacles) –Chelicerates (spiders, mites, scorpions) –Uniramians (insects, centipedes, millipedes) Arthropods

24. Adaptations for Success Hardened exoskeleton Jointed appendages Fused and modified segments Respiratory structures Specialized sensory structures Division of labor

25. Most are marine, some freshwater, a few terrestrial Head has two pairs of antenna, three pairs of food-handling appendages Crustaceans Copepods Crayfish Barnacles Lobsters Shrimps Crabs Isopods (pillbugs)

26. Crab Life Cycle Larval and juvenile stages molt repeatedly and grow in size

27. Originated in seas A few are still marine: horseshoe crabs, sea spiders The arachnids are all terrestrial Spiders Mites Scorpions Chiggers “Daddy longlegs” Ticks Chelicerates

28. Insect Diversity Insects are the only winged invertebrates There are more than 800,000 known species Most successful species are small in size and have a great reproductive capacity

29. Insect Body Plan Thorax usually has three pairs of legs and one or two pairs of wings Abdomen contains most internal organs and specialized structure for reproduction Three-part gut Malpighian tubules attach to midgut and serve in elimination of wastes

30. Insect Headparts antenna labrum palps maxilla labium mandible Grasshopper Butterfly Fly Mosquito

31. adult youngegg nymphsegg larvaeegg Growth and molting Incomplete metamorphosis Complete metamorphosis Types of Insect Development

32. Echinoderms Deuterostomes Almost all are marine Body wall has spines or plates of calcium carbonate No brain Adults are radial with bilateral features

33. Echinoderm Diversity Crinoids (sea lilies and feather stars) Sea stars Brittle stars Sea urchins, heart urchins, sand dollars Sea cucumbers

34. Water Vascular System: Sea Star sieve plate ring canal ampulla part of the water-vascular system

35. Animal Evolution – The Vertebrates Chapter 23

36. Chordates Most are coelomate, bilateral animals All share four features: –Notochord supports body –Nervous system develops from dorsal nerve cord –Embryos have pharynx with slits –Embryos have tail that extends past anus

37. Lancelet Body Plan NOTOCHORD PHARYNX WITH GILL SLITS TAIL EXTENDING PAST ANUS DORSAL, TUBULAR NERVE CORD

38. Invertebrate Chordates Many of the animals that preceded vertebrates were like the simplest chordates – the urochordates –Sea squirts –Other tunicates

39. Larval Form of a Sea Squirt nerve cord gut notochord

40. Adult Tunicate pharynx with gill slits oral opening (water in) atrial opening (water out)

41. Cephalochordates Lancelets Fish-shaped filter feeders that lie buried in sediments Chordate characteristics of adult: –Notochord lies under dorsal nerve cord –Pharynx has gill slits –Tail extends past anus

42. Hagfish Body Plan tentaclesgill slits (twelve pairs)mucus glands

43. Trends in the Evolution of Vertebrates Shift from notochord to vertebral column Nerve cord expanded into brain Evolution of jaws Paired fins evolved, gave rise to limbs Gills evolved, gave rise to lungs

44. Craniates Cranium is a chamber of cartilage or bone that encloses all or part of a brain First craniates evolved by 530 million years ago

45. Evolution of Jaws First fishes lacked jaws Jaws are modifications of the anterior gill supports

46. tunicateslanceletshagfisheslampreys cartilaginous fishes ray-finned fishes lobe-finned fishes lungfishes amphibians“reptiles”birdsmammals lungs or swim bladder amniotes tetrapods jawed vertebrates vertebrates craniates ancestral chordates Evolution of Fishes

47. Jawed Fishes Most diverse and numerous group of vertebrates Two classes: –Cartilaginous fishes –Bony fishes

48. Cartilaginous Fishes Most are marine predators Cartilaginous skeleton Main groups: –Skates and rays –Sharks –Chimaeras (ratfishes)

49. Bony Fishes Includes 96 percent of living fish species Three subclasses: –Ray-finned fishes –Lobe-finned fishes –Lung fishes