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.