Sponges and Cnidarians

1. Sponges and Cnidarians Chapter 21

2. The Animal Kingdom • Multicellular • Eukaryotic • Heterotrophs • Cells lack cell walls • 95% are invertebrates

3. Feeding Respiration Circulation Excretion Response Movement Reproduction What Animals Do to Survive

4. Trends in Animal Evolution • Cell specialization and levels of organization • Early development • Body symmetry • Cephalization • Body cavity formation

5. Embryo Developmet • Fertilized Egg—Egg fertilized by a sperm creates a zygote. • Cleavage—a series of rapid division that results in the formation of many cells. • Blastula—the cells from step 2 develop a fluid filled center called a blastula. -

6. 4. Gastrulation– Cells at one location on the blastula’s surface begin to move into the interior of the blastula. 5. Gastrula—During gastrula formation, cell layers develop that will later give rise to different tissues and organs in the organisms, this varies depending on the type of animal.

8. Vertebrates or Invertebrate • Vertebrates—have a backbone • Invertebrate—Lacking a backbone

10. SPONGES

11. Sponges • Phylum Porifera • Have tiny openings, or pores, all over their bodies • Sessile: they live their entire life attached to a single spot • They are animals

12. Sponges are Animals!!! • Multicellular • Heterotrophic • No cell walls • Contain a few specialized cells

13. Form and Function in Sponges • Have nothing resembling a mouth or gut • Have no tissues or organ systems • Simple functions are carried out by a few specialized cells

14. Asymmetrical • Have no front or back ends, no left and right sides • A large, cylindrical water pump • The body forms a wall around a large central cavity through which water flows continually

15. Choanocytes • Specialized cells that use flagella to move a steady current of water through the sponge • Filters several thousand liters/day

16. Osculum • A large hole at the top of the sponge, through which water exits • The movement of water provides a simple mechanism for feeding, respiration, circulation and excretion

17. Simple Skeleton • Spicule: a spike-shaped structure made of chalk-like calcium carbonate or glasslike silica in hard sponges • Archaeocytes: specialized cells that make spicules

18. Feeding • Filter feeders • Sift microscopic food from the water • Particles are engulfed by choanocytes that line the body cavity

19. Respiration, Circulation, & Excretion • Rely on the movement of water through their bodies to carry out body functions • As water moves through the cavity: • Oxygen dissolved in the water diffuses into the surrounding cells • Carbon dioxide and other wastes, diffuse into the water and are carried away

20. Response • No nervous system • Many sponges protect themselves by producing toxins that make them unpalatable or poisonous to potential predators

21. Reproduction • Sexually or asexually • A single spore forms both eggs and sperm; usually at different times

22. Sexual Reproduction • Internal fertilization: Eggs are fertilized inside the sponge’s body • Sperm are released from one sponge and carried by currents to the pores of another sponge

23. Asexual Reproduction • Budding • Gemmules: groups of archaeocytes surrounded by spicules

24. Ecology of Sponges • Ideal habitats for marine animals such as snails, sea stars, sea cucumbers, and shrimp • Mutually beneficial relationships with bacteria, algae and plant-like protists • Many are green due to these organisms living in their tissues

25. Ecology of Sponges • Attached to the seafloor and may receive little sunlight • Some have spicules that look like cross-shaped antennae • Like a lens or magnifying glass, they focus and direct incoming sunlight

26. CNIDARIANS

27. Cnidarians • Phylum Cnidaria • Hydras, jellies, sea anemones, and corals • Soft-bodied • Carnivorous • Stinging tentacles arranged in circles around their mouths • Simplest animals to have body symmetry and specialized cells

28. Cnidocytes • Stinging cells that are located on their tentacles • Used for defense and to capture prey

29. Nematocyst • A poison-filled, stinging structure that contains a tightly coiled dart • Found within cnidocytes

30. Form and Function in Cnidarians • Only a few cells thick • Simple body systems • Most of their responses to the environment are carried out by specialized cells and tissues

31. Radially Symmetrical • Central mouth surrounded by numerous tentacles that extend outward from the body • Life cycles includes a polyp and a medusa stage

32. Body Plan • Polyp: cylindrical body with arm-like tentacles; mouth points upward • Medusa: motile, bell-shaped body; mouth on the bottom

33. Feeding • Polyps and medusas have a body wall that surrounds an internal space: the gastrovascular cavity • Gastrovascular cavity: a digestive chamber with one opening • Food enters and wastes leave the body

34. Respiration, Circulation, & Excretion • Following digestion, nutrients are usually transported throughout the body by diffusion • Respire and eliminate wastes by diffusion through body walls

35. Response • Specialized sensory cells are used to gather information from the environment • Nerve net: loosely organized network of nerve cells that together allow cnidarians to detect stimuli • Distributed uniformly throughout the body in most species • In some species it is concentrated around the mouth or in rings around the body

36. Response • Statocysts: groups of sensory cells that help determine the direction of gravity • Ocelli: eyespots made of cells that detect light

37. Movement • Hydrostatic skeleton: a layer of circular muscles and a layer of longitudinal muscles that enable cnidarians to move

38. Reproduction: Sexually and Asexually • Polyps can reproduce asexually by budding • External sexual reproduction • The sexes are separate-each individual is either male or female • Both egg and sperm are released into the water

39. Groups of Cnidarians • Jellies (formerly jellyfishes) • Hydras and their relatives • Sea anemones • Corals

40. Ecology of Corals • The worldwide distribution is determined by: • Temperature • Water depth • Light intensity • Many suffer from human activity • Coral bleaching has become common • Global warming may add to the problem