Cnidaria.ppt
- 2. General Characteristics • They are ________ symmetrical; oral end terminates in a ________ surrounded by __________ • They have 2 tissue layers • Outer layer of cells - the _____________ • Inner __________________, which lines the gut cavity or ______________________ cavity (gastrodermis secretes digestive juices into the gastrovascular cavity) • In between these tissue layers is a noncellular jelly-like material called ________________
- 3. Cnidarian Body Plans _________________ form • Tubular body, with the mouth directed ______________ • Around the mouth are a whorl of feeding ________________ • Only have a small amount of __________________ • _______________ _________________ form • ________________ or umbrella shaped body, and the mouth is directed ___________________. • Small tentacles, directed downward. • Possess a large amount of ____________ • _______, move by weak contractions of body
- 4. Soft Coral Polyp Worm Anterior end with brain, eyes, etc.
- 5. Conditions for growth • Requires a temperature of 70-85 F degrees to grow. • Water movement ___________ the supply of ___________ and of __________. • Clarity allows _____________ for critical plankton growth. • Ocean water is a source of __________ for their skeleton development.
- 6. Movement • Both the epidermis and the gastrodermis possess ____________ arranged in a loose network - nerve net (plexus), which innervate primitively developed muscle fibers that extend from the epidermal and gastrodermal cells • ______________ in one part will spread across the whole body via the network
- 7. Nutrition • Cnidarians are ________________ (hydras and corals eat _____________ and sea anenomes can eat ______________ • Tentacles capture ________ and direct it toward the mouth so that it can be digested in the ___________________ via secretions from gland cells (extracellular digestion); some food is phagocytized by special cells and digestion occurs ________cellularly • The gastrovascular cavity exists as ________________ for food intake and the elimination of waste • There is no system of internal transport, gas exchange or excretion; all these processes take place via _________________
- 8. Stinging Organelles • Prey is captured by stinging cells called ____________ located in the outer epidermis. • The cnidocyte is armed with a stinging structure called a ______________. • The nematocyst is a long coiled thread that is _________ to release by touch or chemicals • Some entangle the prey; others harpoon prey and inject a paralyzing _____________
- 10. Reproduction •Some ________________ lost parts • Asexual reproduction is common with new individuals being produced by ______________ • They are _________________ (sexually distinct as males and females) • Fertilization is ______________, with the zygote becoming a elongated, ciliated, radially symmetrical larva - __________________ •The Larva is ____________________ (plankton for a while) until it drops to the ocean floor and grows into a ____________ Planula larva
- 11. Class ____________________ • Includes the solitary freshwater _____; most are colonial and marine • Typical life cycle may include both asexual polyps and sexual medusa stages Solitary Hydras • Freshwater hydras are found in ponds and streams on the underside of vegetation •Mouth opens to the gastrovascular cavity • The life cycle is simple: eggs and sperm are shed into the water and form fertilized _____; ____________ is passed and hatches into young hydras • Asexual reproduction via ____________
- 12. Colonial Hydrozoans - e.g., Obelia •All polyps in the colony are usually __________________________ • Two different kinds of individuals that comprise the colony: - __________ polyps or gastrozooids (C) and - - ______________ polyps or gonozooids (B)
- 13. Class Hydrozoa cont. Other Hydrozoans •____________________: Single gas-filled float with tentacles •______________ house the polyps and modified medusae of the colony • _________________
- 14. Class __________________ _______________ • The medusae are _______________ and contain massive amounts of mesoglea •Possess four ____________ pouches lined with ____________; these are connected with the mouth and the gastrovascular system
- 15. • Gametes develop in gastrodermis of gastric pouches; eggs and sperm are shed through mouth • Fertilized eggs develop into a ___________; settles on substrate and develops into a ___________ • The polyp releases free swimming _________ jellyfish •The jellyfish make _______ and continue the cycle Scyphozoan Life Cycle - Aurelia
- 16. Class __________________ • Exclusively ____________; there is no _______________ stage • At end of the mouth is a ciliated groove that generates a water current and brings food to the gastrovascular cavity • Possess a well developed ________________ •The gastrovascular cavity is large and petitioned by septa or mesenteries that increase the surface area for digestion or support
- 17. Class Anthozoa cont. • Most anthozoans are ____________ (e.g. corals) and secrete external skeletons composed of _____________________________ • Corals obtain much of their energy from microscopic photosynthetic green algae (________________) or dinoflagellates that live __________________ inside the cells of the coral •Why live together? •Coral? •Zooxanthellae?
- 18. Ctenophora – _______________ • 100 species up to _______________! • Swim with eight rows of ______ that beat in waves. • ____________ with big appetites eating fish larvae and ______________.