Kingdom Animalia: Phylum Porifera

Study Notes

Kingdom Animalia is divided into two groups: Parazoa (animals lacking tissues) and Eumetazoa (true animals with differentiated tissues)
Both groups likely evolved from a common ancestor that resembled modern-day choanoflagellates

Sponges are the simplest of all animals
They are aquatic, asymmetrical, and lack true tissues
Adults are sessile, but larvae have motility
Features:
- Osculum: opening for water expulsion
- Spongocoel: central cavity
- Choanocytes: collar cells that direct water through the sponge to trap and ingest food via phagocytosis
- Spicules: skeletal spikes of silica
Lack digestive, respiratory, circulatory, reproductive, or nervous system
Reproduction:
- Asexual: fragmentation or budding
- Sexual: differentiation of amboecytes; monoecious/hermaphroditic

Eumetazoa are divided into two major groups based on embryology:
- Radiata: radial symmetry (includes Cnidaria and Ctenophora)
- Bilateria: bilateral symmetry (includes all other animals)

Stinging animals
Eumetazoa, radiata
Features:
- Diploblastic
- Endoderm: lines digestive cavity
- Ectoderm: epidermis
- Primitive nervous system: nerve net
- Incomplete digestive system: gastrovascular cavity
- Cnidocytes: specialized cell type for stinging; contain nematocysts
Reproduction:
- Asexual: budding
- Sexual: release of gametes into the water
Carnivorous
Body plans:
- Polyp: sessile, asexual
- Medusa: dimorphic, sexual
Class names:
- Anthozoa: corals, sea anemones; polypoid
- Scyphozoa: marine jellies; medusa
- Cubozoa: box jellyfish; true eyes
- Hydrozoa: both polyp and medusa forms

Bilateria are divided into two major clades, also based on embryology:
- Protostomes: further divided into two major clades
  - Lophotrochozoa: either have a trochophore larva and/or lophophore (feeding structure)
  - Ecdysozoa: molt their exoskeleton (ecdysis); include Arthropoda and Nematoda
- Deuterostomes: include echinoderms and chordates