Week 8 | Animalia 1 | Porifera, Cnidaria, Platyhelminthes

Animal characteristics

• Multicellular

• Eukaryotes

• Heterotrophs

• O₂ consumer

• Motile or sessile

• Descended from single celled colonia flagellate

Grantia (Phylum Porifera) apomorphies

• Aquatic, marine

• Asymmetrical

• Basket with spongocoel

• Budding

• Sessile

Monoecious

Having both the male and female reproductive organs in the same individual

Dioecious

Having male and female reproductive organs on separate individuals

Spongocoel - central cavity

Choanocytes - filter water, phagocytosis

Spicule - structural support

Amoebocytes - nutrient transport, waste removal

Obelia & Hydra (Phylum Cnidaria) apomorphies

• Aquatic/marine

• Radial symmetry

• Incomplete gut

• Diploblastic

• Hydrostatic skeleton

• Can be mono or dioecious & budding

• Both sessile & mobile

• Nematocysts

Feeding polyps - hairy structure

Reproductive polyps - buds

Hydra whole mount

Hydra cross-section

Obelia medusa cross-section

Planaria (Phylum Platyhelminthes) apomorphies

• Aquatic, mostly terrestrial

• Bilateral, cephalization

• Incomplete gut, acoelomate

• Triploblastic; excretory & nervous system w brain

• Muscle

• Monoecious with internal fertilization

Planaria whole mount

Planaria cross-section

Nematocyst

A specialized cell in the tentacles of cnidaria species containing a barbed or venomous coiled thread that can be projected in self-defense or to capture prey