Marine Science 2016 Edition

Marine Invertebrates (1) Page 281 Figure 281.1 Soft coral Bob Moffatt Figure 281.3 Sea fan (Murray Waite) Corals The only living thing that can be seen from outer space is the Great Barrier Reef. This reef is made by individual coral polyps that secrete a calcium carbonate base when they grow. When the animal dies, this is left behind for new coral polyps to grow on, so coral reefs are made of dead coral with a thin veneer of living corals and animals on the outside. Corals need specific requirements for growth and scientists from the Great Barrier Reef Marine Park Authority have identified the following four main requirements: • clear water so they can get necessary light, • low nutrients, • stable salinity and • hard surface to grow on. Few reefs grow next to the mainland because the water quality is too poor caused by high sediment runoff and other pollutants from land. There are two types of coral — hard and soft. Soft corals and sea fans Soft corals lack a hard skeleton and protect themselves by secreting chemicals called terpenes. These make them toxic to predators. Soft corals have eight fringing tentacles with each tentacle having side branches giving it a feathery appearance (Figure 281.1). Sea fans Sea fans are like soft corals but the coral polyps are supported by an substance called gorgonium. They often protrude out from coral bommies like the ones shown in Figure 281.2. Hard corals Tourist operators commonly classify hard corals by their appearance as either boulder, branching, plate, table, vase, or solitary — see Figures 282.1 - 7 over. Questions 1. Make a table of the structural characteristics that separate the protozoa, porifera and cnidaria. 2. Give example of animals from each of the phyla mentioned above. 3. Distinguish between corals and sea anemones. 4. Describe the life cycle of an animal from the class scyphozoa. 5. How does a sponge get its food? 6. Describe the special relationship between the clownfish and the anemone. 7. What's the treatment for a box jelly fish sting? 8. What's the signs and symptoms of an Irukandji sting and what treatment would you recommend to a tourist if stung? 9. How do corals reproduce? 10. Draw a diagram of a cross-section of a sponge showing the relationships between the various cellular layers. 11. Distinguish between the medusa and polyp stage of a cnidarian giving an example. 12. Discuss possible reasons for considering the Protozoa as the most basic form of life. 13. What is phagocytosis and how is it important to the Protozoa? 14. Compare and contrast the digestive processes of sponges and jellyfish. 15. Mutualism is one form of symbiosis - name two others (see chapter 15). Figure 281.2 Hard coral Bob Moffatt