1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 18 Sponges and Corals

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.4 The body plans of animals can be used to build phylogenetic trees One hypothesis of animal phylogeny –Is based on morphological comparisons Ancestral colonial protist No true tissuesTrue tissues Bilateral symmetry Radial symmetry Eumetazoans Bilaterians Protostomes Deuterostomes Sponges Cnidarians Echinoderms Chordates Flatworms MolluscsAnnelids Arthropods Nematodes Figure 18.4

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.5 Sponges have a relatively simple, porous body Sponges, phylum Porifera –Are the simplest animals and have no true tissues. Are also sessile. INVERTEBRATES Figure 18.5A–C

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What is a Sponge? Sponges are classified as animals because they are : –multicellular –heterotrophic –have no cell walls –contain a few specialized cells

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges How do sponges carry out essential functions?

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges –Sponges do not have a mouth or gut, and they have no tissues or organ systems.

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Body Plan –Sponges are asymmetrical; they have no front or back ends, no left or right sides.

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges The body of a sponge forms a wall around a large central cavity through which water is circulated continually. Central cavity

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Water enters through pores located in the body wall and leaves through the large hole at the top of the sponge. Water flow Osculum Pores

10. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Choanocytes are specialized cells that use flagella to move a steady current of water through the sponge. Pore Choanocyte

11. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges The movement of water through the sponge provides a simple mechanism for feeding, respiration, circulation, and excretion.

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Sponges have a simple skeleton. In harder sponges, the skeleton is made of spiny spicules. A spicule is a spike- shaped structure made of calcium carbonate or silica. Spicule

13. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Spicules are made by archaeocytes, which are specialized cells that move around within the walls of the sponge. Archaeocytes

14. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Feeding –Sponges are filter feeders. –As water moves through the sponge, food particles are trapped and engulfed by choanocytes that line the body cavity.

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges These particles are then digested or passed on to archaeocytes, who complete the digestive process and transport digested food throughout the sponge.

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Respiration, Circulation, and Excretion –Sponges rely on movement of water through their bodies to carry out body functions. –Oxygen dissolved in the water diffuses into the surrounding cells. –Carbon dioxide and other wastes, such as ammonia, diffuse into the water and are carried away.

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Response –Sponges do not have nervous systems that would allow them to respond to changes in their environment. –However, many sponges protect themselves by producing toxins that make them unpalatable or poisonous to potential predators.

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Reproduction –Sponges can reproduce sexually or asexually. –In most sponge species, a single sponge forms both eggs and sperm by meiosis. –The eggs are fertilized inside the sponge’s body, in a process called internal fertilization. Sperm are released into the water column and picked up by the choanocytes. Sponge uses sperm from a different individual for reproduction

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Sponges Sponges can reproduce asexually by budding or by producing gemmules. In budding, part of a sponge breaks off of the parent sponge, settles to the sea floor, and grows into a new sponge.

20. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ecology of Sponges –Sponges are important in aquatic ecology. –They provide habitats for marine animals such as snails, sea stars, and shrimp.

21. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.6 Cnidarians are radial animals with tentacles and stinging cells Cnidarians, phylum Cnidaria –Have true tissues and radial symmetry

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Their two body forms are –Polyps, such as hydra –Medusae, the jellies Figure 18.6A–C

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What is a Cnidarian? –Cnidarians are soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around their mouths. They are the simplest animals to have body symmetry and specialized tissues.

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What is a Cnidarian? Cnidarians get their name from the cnidocytes, or stinging cells, located along their tentacles. Cnidarians use cnidocytes for defense and to capture prey.

25. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What is a Cnidarian? Within each cnidocyte is a nematocyst—a poison-filled, stinging structure that contains a tightly coiled dart. See also fig 18.6d Filament Barb Nematocyte Trigger Filament

26. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What is a Cnidarian? When a shrimp or small fish brushes up against the tentacles, thousands of nematocysts explode, releasing enough poison to paralyze or kill the prey.

27. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Cnidarians are radially symmetrical. They have a central mouth surrounded by numerous tentacles that extend outward from the body.

28. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Cnidarian polyps and medusas each have a body wall that surrounds an internal space called a gastrovascular cavity. Gastrovascular cavity

29. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Feeding –A cnidarian pulls its food through its mouth and into its gastrovascular cavity, a digestive chamber with one opening. –Food enters and wastes leave the body through that same opening.

30. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians The digestion that occurs in the gastrovascular cavity is extracellular, meaning that it takes place outside of cells. Partially digested food is absorbed by the gastroderm, where digestion is completed. Any materials that cannot be digested are passed out of the body through the mouth.

31. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Respiration, Circulation and Excretion –Following digestion, nutrients are usually transported throughout the body by diffusion. –Cnidarians respire and eliminate the wastes of cellular metabolism by diffusion through their body walls.

32. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Response –Cnidarians gather information from their environment using specialized sensory cells. Both polyps and medusas have a nerve net, a loosely organized network of nerve cells.

33. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Movement –Sea anemones have a hydrostatic skeleton. –A hydrostatic skeleton consists of a layer of circular muscles and a layer of longitudinal muscles that, with the water in the gastrovascular cavity, enable the cnidarian to move.

34. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Cnidarians Reproduction –Most cnidarians reproduce both sexually and asexually. –Polyps can reproduce asexually by budding. –In most cnidarians, sexual reproduction takes place with external fertilization. External fertilization takes place outside the female's body.

35. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Groups of Cnidarians –Cnidarians include: jellyfishes hydras and their relatives sea anemones and corals

36. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ecology of Corals –Worldwide distribution of corals is determined by a few variables: temperature water depth light intensity

37. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ecology of Corals The corals that build coral reefs require high levels of light—these corals rely on algae that capture solar energy, recycle nutrients, and help corals lay down their calcium carbonate skeletons.

38. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ecology of Corals Symbionts (photosynthetic algae) provide as much as 60 percent of the energy corals need. This allows coral reefs to live in water that carries few nutrients.

39. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ecology of Corals Many coral reefs suffer from human activity: –Silt and sediments from logging, farming, mining, and construction smother corals. –Chemical fertilizers, insecticides, and industrial pollutants poison corals. –Overfishing upsets ecological balance. –Stresses that makes coral reefs susceptible to other threats.