Phylum Porifera and Cnidaria Overview

Study Notes

Comprises the simplest invertebrates, primarily classified as sponges.
Defines cells called choanocytes, which are pivotal for water movement and feeding.
Over 5,000 species of sponges recognized, distinguished by specific body structures aids in transporting water for essential functions like feeding and gas exchange.
Asexual reproduction methods include fragmentation, budding, and gemmule formation, in addition to sexual reproduction.
Sponges are hermaphroditic, possessing both male and female reproductive structures.

Spongocoel: Central cavity lined with choanocytes facilitating water circulation.
Ostia: Pores on the sponge's surface that allow water intake into the spongocoel.
Osculum: Large opening for water to exit after passing through the spongocoel.
Spicules: Structural components that provide support, made of silica or calcium carbonate.
Spongin: A protein that forms flexible structures in some sponges.

Divided into four classes based on spicule composition:
- Calcarea: Sponges with calcareous spicules.
- Hexactinellida: Characterized by six-rayed siliceous spicules.
- Demospongiae: Contains siliceous spicules, spongin, or both.
- Sclerospongiae: Coraline sponges with multilayered calcium carbonate skeletons.

Three canal system types allow for optimal water movement:
- Ascon: Simplest form, facilitating basic water flow.
- Sycon: More complex, provides increased surface area for filtration.
- Leucon: Most advanced, highly efficient in water processing and nutrient absorption.

Exhibits radial or biradial symmetry, incorporating diverse aquatic life forms.
Cnidocytes, or stinging cells, used for capturing prey or defense.
Possesses two main body plans: polyp (attached form) and medusa (free-swimming form).
Gastrovascular cavity functions in both digestion and circulation, with gas exchange occurring through diffusion.
Approximately 10,000 species identified.

Four primary classes:
- Hydrozoa: Over 3,200 species, both marine and freshwater; includes notable structures like tentacles and hydranth.
- Scyphozoa: Known as true jellyfishes; around 200 species, exclusively marine, dominate in medusa form.
- Cubozoa: Includes box jellyfishes, known for their solitariness and potent venom; reduced polyp stage.
- Anthozoa: Comprised of around 6,100 species; only polyp form, inhabiting marine environments, can be solitary or colonial.