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Porifera: Very Simple Animals...(?)
Water in, water outSponges bring water in through their pores and move it out through the large top opening. This current provides:-Food-Respiration-Excretion-Circulation-Reproduction
-No nervous system-Many produce toxins-Create many symbiotic relationships (mutualism and commensalism)
Sexual Reproduction-Sponges form both eggs and sperm-The sperm move on current to other sponges
Asexual Reproduction-A “bud” comes off the sponge and grows-Produce “gemmules” in times of stress
-Jellies-Hydra-Anemones-Corals
Cnidarians:-Soft-bodied carnivores
-Have tentacles with specialized cells called nematocysts that shoot poisonous darts into prey (p. 669)
-Radial symmetry with a central mouth surrounded by tentacles
-Have two stages in their life-cycle: a polyp and a medusa. (p.670)
-Cnidarians paralyze prey with poison, then pull it to their mouths and into the gastrovascular cavity where it is digested. http://www.youtube.com/watch?v=o1A5acWEERA&feature=related
-They have a nerve net of specialized cells that allow them to detect touch, light and gravity.
-Use a hydrostatic skeleton to contract muscles for movement. http://www.youtube.com/watch?v=760lUxyle6I
-Sexual reproduction occurs through external fertilization where the zygote is a free-swimming larva
-The larva attaches to a surface and forms a polyp.
-The polyp can reproduce asexually by budding young medusae.
The Jellyfish: Scyphozoa (the “cup animals”)-Range from tiny to almost 4 meters across-Some species are extremely venomous- The box jellyfish is the most venomous animal in the world and has killed over 5 500 people since the 1950s.
Hydra and their Relatives-Hydras belong to the class Hydrozoa-Most hydrozoans are colonies of polyps performing specialized functions (Portuguese Man O’ War)-Hydra are freshwater hydrozoans that don’t have a medusa stage. They only live as polyps.
Anemones and Corals-This is the class Anthozoa (“flower animal”)-Corals and anemones only have the polyp stage
-Anemones are solitary polyps
-Corals form colonies of polyps that look like tiny anemones.-Colonies grow over thousands of years producing calcium carbonate structures that build huge reefs that are threatened.-Corals form mutualistic relationships with algae.
-Anthozoans release clouds of sperm and eggs into the water where the zygote becomes a swimming larva before turning into a polyp.