Sponges and Cnidarians Biology 112

Sponges Phylum Porifera Multicellular and heterotrophic No cell wall and few specialized cells Live their entire life attached to a surface They eat by sifting microscopic food in water Choanocytes are specialized structures that help move water through their body cavity Water enters through pores and leaves through the osculum (a large hole at the top of the cavity)

Getting Everything it Needs Digestion is intracellular Takes place inside the cells Not only is food provided using this sifting action but also everything for respiration, circulation and excretion

Sponges and Reproduction Reproduce sexually and asexually Sexually Eggs are fertilized internally Zygote develops into a larva Larva is the immature stage of the organism that looks different from the adult They are motile Carried by the ocean to the floor and grow into an adult sponge Asexually By budding

cnidarians Phylum Cnidaria Soft-bodied carnivores that have stinging tentacles arranged in circles around their mouth Simplest animals that have body symmetry and specialized tissues Exhibit radial symmetry Central mouth with several tentacles

Two Distinct life stages Polyp Cylindrical body with arm-like tentacles and usually do not move Lives attached to the surface with its mouth pointing upward Medusa Bell-shaped body with a mouth at the bottom Free swimming

Cnidarians and digestion Possess a gastrovascular cavity Digestive chamber with one opening Foods and wastes enter and leave this opening Nutrients are transported throughout body by diffusion Oxygen and wastes are diffused through the body walls

Cnidarians and response to stimuli Gather information from their environment using specialized sensory cells nerve nets a network of nerve cells that together let cnidarians detect stimuli

Cnidarians and body structure Possess a hydrostatic skeleton Consists of layers of circular muscles as well as longitudinal muscles that, with the digestive cavity, allow it to move

Cnidarians and reproduction Asexual – by budding Sexual – external fertilization in water

Classification of cnidarians Jellyfish Live mostly as medusas Hydras Grow in branching colonies Ex. Portuguese man-of-war Sea Anemones and Corals Only have a polyp stage Colonial Polyps grow together in large numbers Secrete an underlying skeleton of calcium carbonate Form coral reefs

Portuguese man-of-war

Coral reefs