Evolution of Animal Diversity

1. Evolution of Animal Diversity Chapter 18

2. Animal Evolution Basics • Animal Evolution was rapid, occurring ~ 600 million years ago (Precambrian Era) • Evidence suggests that animals have evolved from protists that lived as colonies of cells. • Colonies form when cells divide, but do not separate. • These cells differentiated and became specialized.

3. Protoanimals • Model of blastula and grastula used to represent these early animals. Sources: http://farm3.static.flickr.com/2372/2121294845_dab7667079.jpg?v=0; http://www.dkimages.com/discover/previews/800/912525.JPG

4. Cambrian Explosion (545 mya) • Time period in which all the major body plans seen today developed. • Occurred during a short, 10 million year period of time. • Why?? • Ecological (food), Geological (atmosphere), Genetic (reg. genes)

5. Animal Specs. • Multicellular, eukaryotes that are heterotrophic (utilize ingestion). • Animal cells lack cell walls, utilize intercellular junctions, proteins. • Utilize muscle cells for movement

6. Animal Reproduction • Reproduce sexually • Mitosis & Meiosis involved • Blastula -> Grastula -> Ectoderm (epidermis) -> Endoderm (lines digestive tract) -> Mesoderm (internal organs) • Larval stages & Metamorphosis sometimes present • Hox genes = reg genes that control development.

7. Invertebrates / Vertebrates • Invertebrates = lack vertebral column • Vertebrates = have vertebral column

8. Animal Ancestry • Ancient Choanoflagellates = ancestor of all animals species today. • Colonial protist. • Fig. 18.3 E

9. Radial Symmetry • Animal body parts are arranged in a pie-like shape (around central axis). • Ex: Phylum Cnidaria: jellyfish Phylum Porifera: Cylindrical sponges • Fig. 18.3 B

10. Sponge Nutrition (Phylum Porifera) • Suspension Feeders = animals that collect food particles from water passed through some type of food-trapping mechanism. • Choanocytes: Trap and obtain bacteria from water via mucus. • Amoebocytes: digest food packaged in vacuoles. • Package food via phagocytosis (engulfment)

11. Cnidarians • Have gastrovascular cavity • Incomplete digestion: undigested foods exit through mouth. • Classified as polyp or medusa • Ex: Sea anemones, jellies

12. Bilateral Symmetry • Animal can be divided equally by a single cut; left & right mirror image. • Anterior (Head) - houses brain, sensory organs, and mouth. • Posterior (Tail) • Dorsal (Back) • Ventral (Bottom) • Lateral (Side)

13. Bilateral Symmetry • Animals with this symmetry are very active and travel headfirst through its environment. • Most have complete digestive tract (mouth to anus) & a body cavity between digestive tract and body wall. • *Importance in evolution of animals*

14. Body Cavity • *Fluid-filled space between the digestive tract and the body wall was important in the evolution of animals* • Pseudocoelom = body cavity not completely lined by tissue derived from mesoderm. • Coelom (“sea-lum”) = body cavity completely lined by tissue derived from mesoderm (complete digestive tract)

15. Advantages to having a Body Cavity • Flexibility • Allows use of muscles by force derived from “hydroskeleton.” • Allows internal organs to develop and move independently of outer body wall. • Fluid aids in protecting internal organs. • Circulate nutrients and oxygen. • Aids in waste disposal

16. Complete Digestive Tract • Anterior portions of body churn and mix food with digestive enzymes. • Posterior portions of body absorb nutrients and dispose of wastes.

17. Circulatory System • An organ system that distributes nutrients and oxygen throughout the body.

18. Segmentation • Subdivision of the body along its length into a series of repeated parts. • Allows for grouping of specialized cells. • Flexibility = adaptation for movement • Ex: Earthworm - grooved rings (external), coelom partitioned by walls (internal) • Ex: Dragon fly (head, abdomen, & thorax) human (vertebrae & abdominal muscles)

19. Arthropods • Have an exoskeleton = hard external skeleton. • Consists of layers of protein and chitin (polysaccharide) • Serves as protection and points of attachment for muscles. • Shedding of exoskeleton = molting.

20. Echinoderms • Endoskeleton - hard internal skeleton.

21. Chordates • Have the following features: • Dorsal, hollow nerve chord • Notochord • Pharyngeal slits • Post-anal tail Vertebrate chordates Invertebrate chordates (tunicates & lancelets)

22. Vertebrates (Chordates) • Have the following features: • Skull & Backbone (encases brain and main parts of nervous system) • Endoskeleton (cartilage / hard bone) *Evolution of jaws were of great importance in fish development*

23. Amphibians • 1st terrestrial vertebrates • *Evolution of lungs and appendages were major evolutionary advances in fishes and allowed evolution of amphibians / adaptation to land* • Adapted to living in shallow aquatic habitats and water’s edge. • Proliferated during Carboniferous period.

24. Reptiles • Adaptations to living on land: • Skin with scales (keratin) • Eggs that retain water • Amniotic eggs = self-contained nourishment. • Exothermic = absorption of heat externally.

25. Reptiles • Dinosaurs: • Endothermic animals = use heat generated by metabolism to maintain constant body temperature. • Mass extinction ~65 mya • Evolution of Birds

26. Birds • Relationship to Reptiles: • Presence of amniotic eggs • Scales on legs of birds • Toenails of keratin • Similar body structuring to reptiles • Flight Structures: • No teeth, hollow shafted feathers, honeycombed bones (strong, but light)

27. Birds • High Metabolic Rate • Endothermic (feathers ensure insulation of body temperature) • Efficient circulatory system

28. Mammals • Evolved about 220 mya from reptiles. • Mass extinction of dinosaurs allowed for a proliferation of mammals • Exposure to greater resources & lack of predation) • Endothermic, high metabolic rate, presence of hair, and mammary glands.

29. Mammals • 3 Groups: • Monotremes – EX: duck-billed platypus (egg-laying). 2) Marsupials – EX: kangaroo (External pouch) 3) Eutherians – EX: dogs, cats, humans (Reptile Homologous structure = amniotic tissues)

30. Mammals • Placenta = structure joining mother & embryo within uterus (#2 & #3) • Placentas provide long-lasting association between mother and developing young.