Animals

1. Animals

2. What is an Animal? • Animal – multicellular eukaryotic heterotrophs whose cells lack walls • 95% of all animal species are invertebrates (no backbone or vertebral column

3. Embryology • Embryology – early development • Zygote undergoes series of divisions to become a blastula • Blastula - Hollow ball of cells • Gastrula - Blastula folds on itself, forming a single opening (blastopore) and the gastrula. • Blastopore leads into a central tube that runs the length of the developing embryo. Tube becomes the digestive tract.

4. The Fertilized Egg & Cleavage • Yolk~ nutrients stored in the egg • Vegetal pole~ side of egg with high yolk concentration • Animal pole ~ side of egg with low yolk concentration • Blastula~hollow ball stage of development

5. Gastrulation • Gastrula~ 2 layered, cup-shaped embryonic stage • 3 Embryonic germ layers: • Ectoderm~ outer layer; epidermis; nervous system, etc. • Endoderm~ inner layer; digestive tract and associated organs; respiratory, etc. • Mesoderm~skeletal; muscular; excretory, etc. • Invagination~ gastrula buckling process to create the... • Archenteron~ primitive gut • Blastopore~ open end of archenteron

6. Protostomes and Deuterostomes • Protosomes – an animal whose mouth is formed by the blastopore (most invertebrates) • Deuterosomes – an animal whose anus is formed by the blastopore ( echinoderms and all vertebrates)

7. Animal Embryology • Protostome-Deuterostome dichotomy among coelomates: protostomes (mollusks, annelids, arthropods); deuterostomes (echinoderms, chordates) • a) cleavage: protostomes~ spiral and determinate; deuterotomes~ radial and indeterminate • b) coelom (body cavity) formation: protostomes~ schizocoelous; deuterostomes~ enterocoelous • c) blastopore fate: protostomes~ mouth from blastopore; deuterostomes~ anus from blastopore

8. Body Cavity • Body cavity (coelom) formation – fluid filled space that lies between the digestive tract and the body wall. • Allow internal organs to be suspended – helpful during movement. • Provide room for internal organs to specialize and enlarge.

9. Body Symmetry • Asymmetrical – no symmetry (sponge) • Radial – like a bicycle wheel, no matter how you divide the animal with imaginary planes you get two equal halves (jellyfish) • Bilateral – a single imaginary plane can split the animal in half (crayfish, human) • Cephalization – animals with bilateral symmetry have concentrated sense organs and nerve cells at the front end of the body (head)

11. Binomial Nomenclature • The Linnaeus System works by placing each organism into a layered hierarchy of groups. Each group at a given layer is composed of a set of groups from the layer directly below. Simply knowing the two-part scientific name makes it possible to determine the other six layers.

12. Linnaeus System • The groupings (taxa) of taxonomy from most general to most specific are: • Kingdom • Phylum (animals) or Division (plants) • Class • Order • Family • Genus • Species

14. DOMAIN Eukarya KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Felidae GENUS Felis SPECIES Felis catus Fig. 23-1, p. 485

15. Domain Comparison

16. Modern Evolutionary Classification • If you lived in the time of Linnaeus, how would you have classified dolphins? Barnacles and crabs? • Phylogeny – study of evolutionary relationships o Species in a genus have a common ancestor o Genuses in a family have a common ancestor, etc. o Conclusion: the higher the taxon, the further back the common ancestor

17. Phylum: Porifera(“pore bearer”) • Sponges • Asymmetrical; no coelom; no organs • Sessile (attached to bottom) • Spongocoel (central cavity) • Osculum (large opening) • Choanocytes (flagellated collar cells) • Hermaphroditic (produce both sperm and eggs)

19. Phylum: Cnidaria • hydra, jellies, sea anemones, corals • Radial symmetry; no coelom • No mesoderm; gastrovascular cavity (GVC) (sac with a central digestive cavity) • Hydrostatic skeleton (fluid held under pressure) • Polyps and medusa forms • Cnidocytes (cells used for defense and prey capture) • Nematocysts (stinging capsule)

21. Phylum: Platyhelminthes • flatworms, flukes, tapeworms • Bilateral; no coelom • Predators, scavengers, parasites • Triplobastic; mesoderm but, GVC with only one opening • Some cephalization • Many pathogens (Schistosoma, Cestodidias)

23. Phylum: Nemotoda • roundworms • Very widespread group of animals (900,000 sp. ?) • Cuticle (tough exoskeleton) • Decomposition and nutrient cycling • Complete digestive track; no circulatory system • Trichinella spiralis

25. Phylum: Mollusca • snails, slugs, squid, octopus, clams, oysters, chiton • True coelom • Soft body protected by a hard shell of calcium carbonate • Foot (movement), visceral mass (internal organs); mantle (secretes shell); radula (rasp-like scraping organ) • Ciliated trochophore larvae (related to Annelida?)

28. Phylum: Annelida • earthworms, leeches, marine worms • True body segmentation (specialization of body regions) • Closed circulatory system • Metanephridia: excretory tubes • “Brainlike” cerebral ganglia • Hermaphrodites, but cross- fertilize

29. Phylum: Arthropoda • trilobites (extinct); crustaceans (crabs, lobsters, shrimps); spiders, scorpions, ticks (arachnids); insects (entomology) • 2 out of every 3 organisms (most successful of all phyla) • Segmentation, hard exoskeleton (cuticle)~ molting, jointed appendages; open circulatory system (hemolymph); extensive cephalization

33. Arthropoda: Insect characteristics • Outnumber all other forms of life combined • Malpighian tubules: outpocketings of the digestive tract (excretion) • Tracheal system: branched tubes that infiltrate the body (gas exchange) • Metamorphosis…... • •incomplete: young resemble adults, then molt into adulthood (grasshoppers) • •complete: larval stages (looks different than adult); larva to adult through pupal stage

34. Phylum: Echinodermata • sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, sea daisies • Deuterostomes • Spiny skin; sessile or slow moving • Often pentaradial • Water vascular system by hydraulic canals (tube feet)

35. Chordates • Notochord: longitudinal, flexible rod located between the digestive and the nerve cord • Dorsal, hollow nerve cord; eventually develops into the brain and spinal cord • Pharyngeal slits; become modified for gas exchange, jaw support, and/or hearing • Muscular, postanal tail

36. Invertebrate chordates • Both suspension feeders….. • Subphy: Urochordata (tunicates; sea squirt); mostly sessile & marine • Subphy: Cephalochordata (lancelets); marine, sand dwellers • Importance: vertebrates closest relatives; in the fossil record, appear 50 million years before first vertebrate

38. Subphylum: Vertebrata • Retain chordate characteristics with specializations…. • Neural crest: group of embryonic cells near dorsal margins of closing neural tube • Pronounced cephalization: concentration of sensory and neural equipment in the head • Cranium and vertebral column • Closed circulatory system with a ventral chambered heart

39. Vertebrate diversity • Phy: Chordata • Subphy: Vertebrata • Superclass: Agnatha~ jawless vertebrates (hagfish, lampreys) • Superclass: • Gnathostomata~jawed vertebrates with 2 sets of paired appendages; including tetrapods (‘4-footed’) and amniotes (shelled egg)

40. Superclass Agnatha • Jawless vertebrates • Most primitive, living vertebrates • lamprey and hagfish • Lack paired appendages; cartilaginous skeleton; notochord throughout life; rasping mouth

41. Superclass Gnathostomata, I • Class: Chondrichthyes~ Sharks, skates, rays • Cartilaginous fishes; well developed jaws and paired fins; continual water flow over gills (gas exchange); lateral line system (water pressure changes) • Life cycles: • Oviparous- eggs hatch outside mother’s body • Ovoviviparous- retain fertilized eggs; nourished by egg yolk; young born live • Viviparous- young develop within uterus; nourished by placenta

42. Superclass Gnathostomata, II • Class: Osteichthyes • Ossified (bony) endoskeleton; scales operculum(gill covering); swim bladder (buoyancy) • Most numerous vertebrate • Ray-fined (fins supported by long, flexible rays): bass, trout, perch, tuna, herring • Lobe-finned (fins supported by body skeleton extensions): coelocanth • Lungfishes (gills and lungs): Australian lungfish (aestivation)

43. Superclass Gnathostomata, III • Class: Amphibia • 1st tetrapods on land • Frogs, toads, salamanders, caecilians • Metamorphosis; lack shelled egg; moist skin for gas exchange

44. Superclass Gnathostomata, IV • Class: Reptilia • Lizards, snakes, turtles, and crocodilians • Amniote (shelled) egg with extraembryonic membranes (gas exchange, waste storage, nutrient transfer); absence of feathers, hair, and mammary glands; ectothermic; scales with protein keratin (waterproof); lungs; ectothermic (dinosaurs endothermic?)

45. Superclass Gnathostomata, V • Class: Aves • Birds • Flight adaptations: wings (honeycombed bone); feathers (keratin); toothless; one ovary • Evolved from reptiles (amniote egg and leg scales); endothermic (4-chambered heart) • Archaeopteryx (stemmed from an ancestor that gave rise to birds)

46. Superclass Gnathostomata, VI • Class: Mammalia • Mammary glands; hair (keratin); endothermic; 4-chambered heart; large brains; teeth differentiation • Evolved from reptilian stock before birds • Monotremes (egg-laying): platypus • Marsupials (pouch): opossums, kangaroos, koalas • Eutherian (placenta): all other mammals