Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Phylum Cnidaria Cnidarians Soft bodied animals with stinging cells on tentacles around the mouth Can live as individuals or in colonies Aquatic (fresh and marine) Sessile or motile (jellyfish, sea anemones) Some specialized tissue Specialized cells Body plan have two plans 1. Polyp o mostly sessile o has a long body tube with a mouth and tentacles at one end o ex) sea anemones 2. Medusa o motile o generally dome shaped with a mouth and tentacles in the underside (ventral) o ex) jelly fish P. 565 * Some Cnidarians go through stages in both body plans o Both body plans have similar features o one opening digestive system o mouth / anus o gastrovascular cavity o food enters by the mouth o digestion occurs in the gv cavity o undigested waste exits via the mouth the body wall has 3 layers I) Epidermis – outer layer II) Mesoglea – middle layer III) Gastroderm – inner digestive layer - around the mouth are tentacles on the tentacles are stinging cells called nematocysts each nematocyst is a poison filled sac containing a tightly coiled, spring loaded dart. Nematocysts are used to capture and immobilize prey Used also for defense Feeding / Digestion carnivores - capture small prey with tentacles and nematocysts some cnidarians have a relationship with photosynthetic protests to add to nutrition intake digestion is extracellular goes into the gastrovascular cavity, in a one opening system (Mouth/ Anus) Respiration - diffusion Internal Transport - diffusion Excretion - diffusion Responses Nerve network- net The nerve net is concentrated around the mouth For feeding Have chemoreceptors- detect chemicals Mostly medusas have receptors for balance Statocysts - balance Medusas have receptors for detecting light – ocelli Movement do not have muscle cells epidermal cells change shape to allow movement Reproduction Asexual o Mostly budding o Mostly polyps o However, a budding polyp can produce either polyps or medusa Sexual o Sperm and/or eggs are released into the water o Fertilization occurs in the water or in an egg carrying medusa o Zygote grows into a ciliated larva, which swim to a suitable living environment P. 567 3 Classes of Cnidarians 1. Class Scyphozoa o live most of its life as medusa ex) jellyfish o still have both body plans o most nematocysts are harmless to humans *exception – Australian box jelly – can cause death in 3-20 minutes 2. Class Hydrozoa o most of its life as a polyp ex) hydra, Portuguese man- of- war o most live in branching sessile colonies o in a colony specialized polyps will perform specialized functions o some hydrazoans are hermaphrodites – has both sex organs 3. Class Anthozoa o only polyps ex) sea anemones o can have symbiotic relationships ex) coral o build an exoskeleton to protect them either calcium carbonate or limestone ex) sea pens • colonies of polyps Importance of Cnidarians Symbiotic relationships Coral reefs – ecological homes Protect shorelines Studied for medical research