Animal Evolution and Body Complexity

1. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Kingdom: Animals Domain Eukarya

2. Animal Characteristics • Heterotrophs • must ingest others for nutrients • Multicellular • complex bodies • No cell walls • allows active movement • Sexual reproduction • no alternation of generations • no haploid gametophyte

3. Animal Evolution Cnidaria Nematoda Annelida Echinodermata Porifera Platyhelminthes Mollusca Arthropoda Chordata sponges jellyfish flatworms roundworms mollusks segmentedworms insectsspiders starfish vertebrates • body & brain size,  mobility backbone redundancy, specialization,  mobility segmentation  body size endoskeleton  digestive sys coelom radial • body complexity  digestive & repro sys body cavity bilateral symmetry distinct body plan; cephalization tissues specialized structure & function, muscle & nerve tissue specialization & body complexity multicellularity bilateral Ancestral Protist

4. pseudocoel coelom cavity acoelomate Body Cavity ectoderm mesoderm • Space for organ system development • increase digestive & reproductive systems • increase food capacity & digestion • increase gamete production • Coelem • mesoderm & endoderm interact during development • allows complex structures to develop in digestive system • ex. Stomach • CLICK FOR VIDEO endoderm pseudocoelomate ectoderm mesoderm endoderm coelomate ectoderm mesoderm endoderm protostome vs. deuterostome

5. What’s the most complex problem in biology?

6. The most complex problem How to get from here to there

7. Egg   zygote   morula

8. Egg   morula   blastula • Blastula formation • successive divisions result in a blastula • hollow single-layered sphere enclosing a space = blastocoel

10. Early embryonic stages • Morula • solid ball stage • Blastula • hollow fluid-filled ball stage • by time human embryo reaches uterus • Gastrula • development of primitive digestive tract (gut) & tissue layers

11. Gastrulation • zygote  blastula  gastrula How you looked as a blastula…

12. Gastrulation • zygote  blastula  gastrula • rearranges the blastula to form 3-layered embryo with a primitive gut

13. Gastrulation blastopore:forms at sperm penetration point archenteron:forms endodermembryonic gut mesoderm dorsal lip: organizing center for development tissue formation

14. Primary tissue or “germ” layers • ectoderm • external surfaces: skin • epidermis (skin); nails, hair & glands; tooth enamel; eye lens; epithelial lining of nose, mouth & rectum; nervous system • endoderm • internal lining • epithelial lining of digestive tract & respiratory systems; reproductive system & urinary tract; digestive organs • mesoderm • middle tissues: muscle, blood & bone • notochord; skeletal, muscular, circulatory, lymphatic, excretory & reproductive systems; lining of body cavity

15. Basic body plan • Archenteron becomes embryonic gut • mouth at one end • anus at the other • Protostomes • “1st mouth” • blastopore = mouth • invertebrates • Deuterostomes • “2nd mouth” • blastopore = anus • echinoderms & vertebrates

16. Invertebrate: Porifera food taken into each cell by endocytosis • Sponges • no distinct tissues or organs • do have specialized cells • no symmetry • sessile (as adults)

17. Invertebrate: Cnidaria • Jellyfish, hydra, sea anemone, coral • tissues, but no organs • two cell layers • radial symmetry • predators • tentacles surround gut opening • extracellular digestion • release enzymes into gut cavity • absorption by cellslining gut polyp medusa

18. mouth tentacles sensory cell discharged nematocyst stingingcell undischarged nematocyst hydra trigger stinging cell with nematocyst Stinging cells of Cnidarians

19. ectoderm mesoderm endoderm Invertebrate: Platyhelminthes • Flatworms • tapeworm, planaria • mostly parasitic • bilaterally symmetrical • have right & left & then have head (anterior) end & posterior end • cephalization =development of brain • concentration of sense organs in head • increase specialization in body plan Animals nowface the world head on! acoelomate

20. Invertebrate: Nematoda • Roundworms • bilaterally symmetrical • body cavity • pseudocoelom = simple body cavity • digestive system • tube running through length of body (mouth to anus) • many are parasitic • hookworm C. elegans

21. Invertebrate: Mollusca • Mollusks • slugs, snails, clams, squid • bilaterally symmetrical (with exceptions) • soft bodies, mostly protected by hard shells • true coelem • increases complexity & specialization of internal organs

22. Invertebrate: Annelida • Segmented worms • earthworms, leeches • segments • increase mobility • redundancy in body sections • bilaterally symmetrical • true coelem fan worm leech

23. Invertebrate: Arthropoda • Spiders, insects, crustaceans • most successful animal phylum • bilaterally symmetrical • segmented • specialized segments • allows jointed appendages • exoskeleton • chitin + protein

24. Arthropod groups arachnids 8 legs, 2 body parts spiders, ticks, scorpions crustaceans gills, 2 pairs antennae crab, lobster, barnacles, shrimp insects 6 legs, 3 body parts

25. Invertebrate: Echinodermata • Starfish, sea urchins, sea cucumber • radially symmetrical as adults • spiny endoskeleton • deuterostome loss of bilateral symmetry?

26. Invertebrate quick check… Invertebrates: Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata • Which group includes snails, clams, and squid? • Which group is the sponges? • Which are the flatworms? …segmented worms? …roundworms? • Which group has jointed appendages & an exoskeleton? • Which two groups have radial symmetry? • What is the adaptive advantage of bilateral symmetry? • Which group has no symmetry?

27. Chordata • Vertebrates • fish, amphibians, reptiles, birds, mammals • internal bony skeleton • backbone encasing spinal column • skull-encased brain • deuterostome hollow dorsal nerve cord becomes brain & spinal cord becomes gills or Eustachian tube pharyngeal pouches becomes vertebrae postanal tail becomes tail or tailbone notochord

28. 450 mya salmon, trout, sharks Vertebrates: Fish • Characteristics • body structure • bony & cartilaginous skeleton • jaws & paired appendages (fins) • scales • body function • gills for gas exchange • two-chambered heart; single loop blood circulation • ectotherms • reproduction • external fertilization • external development in aquatic egg body gills

29. Humerus Femur Ulna Pelvis Shoulder Tibia Radius Lobe-finned fish Fibula Femur Pelvis Humerus Shoulder Radius Tibia Ulna Fibula Early amphibian Transition to Land Evolution of tetrapods

30. lung buccal cavity glottis closed 350 mya frogs salamanders toads Vertebrates: Amphibian • Characteristics • body structure • legs (tetrapods) • moist skin • body function • lungs (positive pressure) & diffusion through skin for gas exchange • three-chambered heart;veins from lungs back to heart • ectotherms • reproduction • external fertilization • external development in aquatic egg • metamorphosis (tadpole to adult)

31. leathery shell embryo amnion chorion allantois yolk sac 250 mya dinosaurs, turtles lizards, snakes alligators, crocodile Vertebrates: Reptiles • Characteristics • body structure • dry skin, scales, armor • body function • lungs for gas exchange • thoracic breathing; negative pressure • three-chambered heart • ectotherms • reproduction • internal fertilization • external development in amniotic egg

32. lung trachea anterior air sacs posterior air sacs 150 mya finches, hawk ostrich, turkey Vertebrates: Birds (Aves) • Characteristics • body structure • feathers & wings • thin, hollow bone;flight skeleton • body function • very efficient lungs & air sacs • four-chambered heart • endotherms • reproduction • internal fertilization • external development in amniotic egg

33. muscles contract diaphragm contracts 220 mya / 65 mya mice, ferret elephants, batswhales, humans Vertebrates: Mammals • Characteristics • body structure • hair • specialized teeth • body function • lungs, diaphragm; negative pressure • four-chambered heart • endotherms • reproduction • internal fertilization • internal development in uterus • nourishment through placenta • birth live young • mammary glands make milk

34. Vertebrates: Mammals • Sub-groups • monotremes • egg-laying mammals • lack placenta & true nipples • duckbilled platypus, echidna • marsupials • pouched mammals • offspring feed from nipples in pouch • short-lived placenta • koala, kangaroo, opossum • placental • true placenta • nutrient & waste filter • shrews, bats, whales, humans

35. Vertebrate quick check… • Which vertebrates lay eggs with shells? • Which vertebrates are covered with scales? • What adaptations do birds have for flying? • What kind of symmetry do all vertebrates have? • Which vertebrates are ectothermic and which are endothermic • Why must amphibians live near water? • What reproductive adaptations made mammals very successful? • What characteristics distinguish the 3 sub-groups of mammals?

36. That’s the buzz! AnyQuestions?