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Learning Goal: Describe the main characteristics of cnidarians Explain why coral reefs are important Warm up: What makes up a coral reef? Homework: Finish all questions on packet pages 6, 7, 8, & 9 TEST on Wednesday on Ch. 9 Sec 1 & 3 MONDAY 2/29/16 Cnidarians Chapter 9 Section3 Jellyfish, corals, and sea anemones Invertebrates that have stinging cells to capture food and protect themselves Take food into central body cavity Cnidarians Two different body plans (vase and bowl) Radial symmetry Central hollow cavity Tentacles containing stinging cells Cnidarians: Body Structure Radial symmetry - symmetry around a central axis, as in a starfish Vase-shaped body plan is a POLYP Sea anemone Mouth opens at top Tentacles spread out from around mouth Most are attached to underwater surface Body Structure: Polyp Bowl-shaped body plan is a MEDUSA Jellyfish Adapted for a swimming life Mouths open downward and tentacles trail down Body Structure: Medusa Use stinging cells to catch animals they eat (prey) Contains threadlike structure with spines Uses tentacles to pull prey to mouth Takes food into central body cavity Expels undigested food through mouth Obtaining Food Unlike adult sponges, many cnidarians move to escape danger and to obtain food Jellyfish ◦ Swim through the water ◦ Hydras turn slow somersaults Sea Anemones ◦ Stretch out, shrink down, bend slowly from side to side Movement Asexual Reproduction ◦ Hydras, corals, and sea anemones Sexual Reproduction ◦ Jellyfish Reproduction Colony ◦ a group of many individual animals Stony corals and Portuguese man-ofwar Life in a Colony a coral reef is built by cnidarians coral reefs are home to more species of fishes and invertebrates than any other environment on Earth Coral polyps produce hard, stony skeletons around their soft bodies Stony Coral Contains as many as 1,000 individuals that function together as one unit Top: gas filled chamber, allows colony to float Bottom: polyps with different functions drift below ◦ Some catch prey and help with digestion and reproduction Portuguese Man-of-War
