Porifera & Cnidaria + Ocean Acidification

Porifera

Simplest multicellular animals with no tissues or organs

Choanocytes

Collar cells that create water flow and capture food

Spicules

Hard support structures that protect the sponge

Osculum

Large opening where water exits a sponge

Spongocoel

Central cavity inside a sponge

Filter feeding (Porifera)

Pumping water through pores to capture food

Ecological role of sponges

Filter water and provide habitat

Cnidaria

Animals with radial symmetry and stinging cells

Nematocysts

Stinging cells used to capture prey and defend

Tentacles

Arms that contain nematocysts and bring prey to the mouth

Gastrovascular cavity

One opening used for digestion

Medusa

Free-swimming form of cnidarians

Polyp

Sessile (attached) form of cnidarians

Coral

Colonial cnidarians that build calcium carbonate skeletons

Zooxanthellae

Photosynthetic algae living inside coral

Coral–zooxanthellae relationship

Mutualistic; both organisms benefit

What zooxanthellae give coral

Food (glucose) and oxygen

What coral gives zooxanthellae

A safe home and carbon dioxide

Coral bleaching

Loss of zooxanthellae due to stress (heat or acidity)

Ocean acidification

CO₂ dissolving in seawater forming carbonic acid

Carbonic acid

Weak acid that lowers ocean pH

Effect of low pH on shells

Dissolves calcium carbonate and weakens skeletons

Calcium carbonate

Material that makes up shells and coral skeletons

Causes of ocean acidification

Burning fossil fuels, increased atmospheric CO₂

Effects of ocean acidification

Weakens shells, harms corals, reduces biodiversity

Porifera vs Cnidaria

Sponges have no tissues; cnidarians have tissues and stinging cells