Chapter 23 Part I

1. Chapter 23 Part I Animal Characteristics

2. Animal Characteristics • Multicellular • Eat other organisms • Can move • Break down food for energy and to build tissue • Cells have no cell walls

3. Food getting • Some animals hunt • Some animals are sessile and wait for food to come to them • Movement is directly related to method of getting food

4. Animal digestion • Some digest food internally • Some digest food inside individual cells • Digested food is stored as fat or glycogen and used for energy when food is scarce • Digestive cavities can have one opening (mouth) or two openings (mouth and anus)

5. Animal development • Blastula • Gastrula • Protostomes • Deuterostomes • Mesoderm

6. Blastula development • Most animals develop from a single fertilized egg (zygote) • Zygote undergoes cell division to produce a hollow ball of cells (blastula) • Blastula – a single layer of cells surrounding a fluid filled space • Develops about 10 hours after fertilization

7. Gastrula development • Cells on one side of the blastula fold inward to form the gastrula • Outer surface is ectoderm (develops into skin and nervous tissue) • Inner surface is the endoderm (develops into the digestive tract)

8. Protostomes • The indented space in the gastrula develops into the mouth • Have one opening in their digestive tract

9. Deuterostomes • The indented space in the gastrula develops into the anus; mouth develops from cells in another location • Complex animals • Two openings in the digestive tract

10. Mesoderm • Third layer of cells that develops between the endoderm and ectoderm • Develops into muscles, reproductive organs, and circulatory vessels

11. Body plans: symmetry • Asymmetry • Radial symmetry • Bilateral symmetry

12. Asymmetry • Irregular body shapes • Usually sessile organisms • Ex: sea sponge

13. Radial symmetry • Can be divided along any plane, through a central axis, and produce roughly equal right and left halves • Detect and capture prey from any direction • Ex: hydra, starfish

14. Bilateral symmetry • Divided down the length into right and left halves that form mirror images • Anterior is head • Posterior is tail • Dorsal is the back • Ventral is the belly • Find food/mates more efficiently due to better muscle control

15. Body Cavities • Acoelom • Pseudocoelom • coelom

16. Acoelom • Three cell layers (ectoderm, endoderm, mesoderm) • Digestive tract • NO body cavity • Organs embedded in tissues • Water/digested food travel through body by diffusion • Ex: flatworms

17. Pseudocoelom • Fluid-filled body cavity partially lined with mesoderm • Develops between endoderm and mesoderm • More efficient movement • Two openings in digestive tract • Ex: roundworms

18. Coelom • Body cavity completely lined with mesoderm • Internal organs suspended in fluid-filled space • Allows space for complex organs • Ex: humans

19. Adaptations • Exoskeleton • Endoskeleton

20. Exoskeleton • Hard, waxy covering on outside of the body • Provides support, protection • Prevents water loss • Place for muscle attachment in invertebrates

21. Endoskeleton • Internal skeleton found in vertebrates • Protects internal organs • Place for muscle attachment

22. 26.2 Sponges • Phylum Porifera • Sessile (attached to a single spot as adults) • Multicellular • Heterotrophic • No cell walls • Few specialized cells

23. Sponge body plan • No mouth, gut, tissues, or organs • Use only specialized cells • Asymmetrical • No dorsal, ventral, left or right sides • Body is tubular and arranged around a central opening through which water flows

24. Body plan cont. • Choanocytes (cells with flagella) keep steady current of water flowing • Water enters through pores in body wall but flows out through osculum (hole at top of sponge) • Movement of water through sponge allows feeding, respiration, circulation, and excretion • Spicules-structure made of CaCO3 or silica make up internal skeleton in some sponges

25. Sponge feeding • Filter feeders – sift microscopic food from water • Intercellular digestion occurs in choanocytes that take in the food and then pass it to archaeocytes that transport digested food throughout the sponge

26. Sponge response • No nervous system • Protect themselves with toxins that make them taste bad or make them poisonous to predators

27. Sponge reproduction • Sexual – figure 26-9 • Sperm release into water by one sponge are carried on currents to another sponge • Sperm are carried to egg by archeocytes • After fertilization, zygote develops into a larva (immature form; looks different) • Larva are motile (usually use flagella) so swimming and currents carry them to new areas on sea floor

28. Sponge reproduction cont • Asexual budding – a piece of a mature sponge breaks off, settles on sea floor, and develops into a new sponge • Asexual gemmules – groups of archeocytes surrounded with spicules; used to withstand unfavorable conditions; good conditions allow the gemmules to develop into a new sponge

29. Ecology • Sponges provide habitat for other organisms (commensalism) • Sponges pair up with photosynthetic organisms providing their habitat, while the photosynthetic organism gives food (mutualism); also helps productivity at coral reefs

30. 26.3 Cnidarians • Soft-bodied • Carnivorous • Stinging tentacles arranged in a circle around the mouth (cnidocytes- stinging cells that contain nematocysts or darts with poison to kill prey) • Simplest animals with symmetry and specialized tissues

31. Cnidarian body plan • Radial symmetry • Central mouth surrounded with tentacles • Life cycle includes the polyp (sessile) and medusa (motile) stages • Body wall surrounds the gastrovascular cavity (digestion occurs in gastroderm) • Outside layer is epidermis • Middle layer is meoglea

32. Cnidarian feeding • Paralyze prey before pulling it in to the gastrovascular cavity • Extracellular digestion (outside of cells) • Digested food is absorbed by gastroderm • Digestion completed inside cells of gastroderm • Undigested materials are expelled through the mouth

33. Cnidarian response • Use a nerve net – loosely organized network of nerve cells that allow detection of stimuli (touch) • Usually distributed evenly throughout body but can be centrally located around mouth • Statocysts help determine direction of gravity • Ocelli – are eyespots that help detect light

34. Cnidarian movement • Some use hydrostatic skeleton – layer of circular muscles and layer of longitudinal muscles, with water in gastrovascular cavity, enable movement • Medusas use jet propulsion – muscle contractions that force water out of the “bell” of the organism which pushes the organism forward

35. Cnidarian reproduction • Sexual – figure 26-15 • Eggs and sperm released into water by separate sexes • External fertilization occurs producing the zygote that grows into a free swimming larva • Larva eventually attaches to hard surface to develop into polyp • Polyp buds and releases the medusa

36. Cnidarian reproduction cont • Asexual – budding • Budding can occur in polyps, producing a genetically identical organism

37. Jellyfishes • Class Scyphozoa • Live primarily as medusas • Polyp is small larva stage that does NOT produce colonies • Reproduce sexually

38. Hydras and relatives • Class Hydrozoa • Polyps grow in branching colonies, can be specialized for specific functions • Portuguese man-of-war • One polyp produces the “balloon” or float • Others produce tentacles to catch prey • Some also undergo digestion • Hydras – freshwater, lack a medusa stage; solitary; reproduce both sexually and asexually and may have symbiotic relationship with photosynthetic protists

39. Sea anemones and corals • Class Anthozoa • Only a polyp stage • Central body surrounded by tentacles • Many are colonial • Sea anemones • Live at all depths • Usually solitary • Can by symbionts with photosynthetic organisms

40. Corals • Most colonial • Hard corals develop after a motile larva attaches to a solid surface • New polyps produced by budding • Produce skeleton of CaCO3 or limestone • Can live for hundreds-thousands of years • Sexual reproduction • External fertilization (eggs and sperm are released into water)

41. Ecology of corals • Distribution determined by temperature, water depth, light intensity • Hard corals need high levels of light • Rely on mutualistic relationships with algae (provide 60% of energy needed by corals) • Corals provide habitat to a variety of marine organisms (commensalism)

42. Damage to corals • Human activity • Logging • Divers that damage corals • Silt • Farming / mining • Release of chemicals • High temperatures • Kill algae and cause bleaching • May be due to global warming