CNIDARIA

Characteristics  Class Scyphozoa- Jellyfish- medusa form  Class Antozoa- corals, sea anemones- polyp form  Class Hydrozoa- Hydras  Tentacles  2 body plans:  Polyp- attached to ocean floor, mouth opens up, tentacles surround mouth

Characteristics  Medusa- free floating/swimming form, mouth opens down, tentacles trail down, bell-shaped  No organs  Movement- jellyfish swim, anemones move slowly along ocean floor

Anatomy  Gas exchange happens at cell level  No muscle cells, skeleton, or circulation  Nerve Net  Epidermis cells create “skin”  No excretory system

Anatomy  Tentacles have nematocysts – stinging cells  Central hollow body cavity  Radial symmetry  Acoelomates

Feeding  Uses stinging ability to capture food  Prey is stung and brought to mouth by tentacles  Digested in central body cavity  Niche: Predators, carnivores

Reproduction  Reproduction is both sexual and asexual  Asexual- budding by hydras, coral, sea anemones  Sexual- jellyfish have both sexes. Females produce eggs, males produce sperm

Life Cycle  Fertilized egg turns into larvae  Larvae settles on ocean floor  Polyp develops  Medusa buds off of polyp  Medusa reproduces sexually to form fertilized egg

Habitat  Marine/ Ocean habitat  Polyp form lives on ocean floor  Medusa form swims freely in open water  What are some biotic and abiotic factors?

Colony Life  Corals reefs- coral polyp attaches to rock or ocean floor, secretes calcium carbonate (CaCO 3 ) which is a hard skeleton. Then it reproduces asexually. Offspring attach on top of same hard skeleton and cycle goes on. This is how a coral reef is built

Colony Life  Portuguese Man-o- War  Is really over 1000 polyps living together  Some sting, some digest, some produce sex cells

Hydra  Stays in polyp form throughout life  Only freshwater cnidarians  Predators- prey on small invertebrates  Named after Greek mythology serpent-like creature with many heads

Adaptations  Regeneration of body parts  Anemones have strong adhesion in strong waves  Asexual reproduction – can colonize a large area quickly  Anemone can contract to a tight ball to prevent drying out in low tide