Sponges and Cnidarians

SPONGES

Sponges Phylum Porifera Have tiny openings, or pores, all over their bodies Sessile: they live their entire life attached to a single spot They are animals! Why…?

Sponges are Animals!!! Multicellular Heterotrophic No cell walls Contain a few specialized cells

Form and Function in Sponges Have nothing resembling a mouth or gut Have no tissues or organ systems Simple functions are carried out by a few specialized cells

Asymmetrical Have no front or back ends, no left and right sides A large, cylindrical water pump The body forms a wall around a large central cavity through which water flows continually

Feeding Filter feeders Sift microscopic food from the water Particles are engulfed by choanocytes that line the body cavity

Respiration, Circulation, & Excretion Rely on the movement of water through their bodies to carry out body functions As water moves through the cavity: Oxygen dissolved in the water diffuses into the surrounding cells Carbon dioxide and other wastes, diffuse into the water and are carried away

Response No nervous system Many sponges protect themselves by producing toxins that make them unpalatable or poisonous to potential predators

Reproduction Sexually or asexually A single spore forms both eggs and sperm; usually at different times

Ecology of Sponges Ideal habitats for marine animals such as snails, sea stars, sea cucumbers, and shrimp Mutually beneficial relationships with bacteria, algae and plant-like protists Many are green due to these organisms living in their tissues

Ecology of Sponges Attached to the seafloor and may receive little sunlight Some have spicules that look like cross-shaped antennae Like a lens or magnifying glass, they focus and direct incoming sunlight

CNIDARIANS

Cnidarians Phylum Cnidaria Hydras, jellies, sea anemones, and corals Soft-bodied Carnivorous Stinging tentacles arranged in circles around their mouths Simplest animals to have body symmetry and specialized cells

Form and Function in Cnidarians Only a few cells thick Simple body systems Most of their responses to the environment are carried out by specialized cells and tissues

Radially Symmetrical Central mouth surrounded by numerous tentacles that extend outward from the body Life cycles includes a polyp and a medusa stage

Body Plan Polyp: cylindrical body with arm-like tentacles; mouth points upward Medusa: motile, bell-shaped body; mouth on the bottom

Feeding Polyps and medusas have a body wall that surrounds an internal space: the gastrovascular cavity Gastrovascular cavity: a digestive chamber with one opening Food enters and wastes leave the body

Respiration, Circulation, & Excretion Following digestion, nutrients are usually transported throughout the body by diffusion Respire and eliminate wastes by diffusion through body walls

Response Specialized sensory cells are used to gather information from the environment Nerve net: loosely organized network of nerve cells that together allow cnidarians to detect stimuli Distributed uniformly throughout the body in most species In some species it is concentrated around the mouth or in rings around the body

Response Statocysts: groups of sensory cells that help determine the direction of gravity Ocelli: eyespots made of cells that detect light

Reproduction: Sexually and Asexually Polyps can reproduce asexually by budding External sexual reproduction The sexes are separate-each individual is either male or female Both egg and sperm are released into the water

Groups of Cnidarians Jellies (formerly jellyfishes) Hydras and their relatives Sea anemones Corals