Survey of the Animal Kingdom: Phyla Porifera and Cnidaria

These flashcards cover the vocabulary and key concepts regarding Phyla Porifera and Cnidaria, including cellular structures, classification, and life cycles.

Heterotroph

An organism that derives its energy from organic molecules made by other organisms.

Diploblastic

Animals whose tissues arise from two germ layers: the outer ectoderm and the inner endoderm.

Mesenchyme

The nonliving matrix located between the ectoderm and endoderm in sponges.

Mesoglea

The nonliving matrix located between the ectoderm and endoderm in jellies (Cnidaria).

Triploblastic

Animals whose tissues arise from three germ layers: the ectoderm, the endoderm, and a middle mesoderm comprised of cells.

Phylum Porifera

A phylum comprising approximately $5,150$ species of sponges, characterized as sessile, asymmetrical assemblages of cells lacking true tissues and organs.

Choanocytes

Flagellated "collar cells" that line the internal cavity of sponges and create a water current to trap food particles.

Spongocoel

The central cavity within a sponge.

Osculum

The large hole through which filtered water exits the sponge body.

Asconoid system

The simplest sponge structural organization, featuring pores but no incurrent or flagellated canals.

Sycon system

A sponge structural organization featuring incurrent canals open to the outside and flagellated canals that open to the spongocoel.

Leucon system

A sponge structural organization featuring flagellated chambers where food is absorbed.

Mesohyl

The nonliving matrix between the outer and inner cellular layers of a sponge, where the simple skeleton is located.

Spicules

Crystalline structures that make up the simple skeleton of a sponge, used as a basis for classification.

Class Calcarea

A class of sponges characterized by spicules made of calcium carbonate.

Class Hexactinellida

A class of sponges characterized by $6$-rayed (hexactinal) siliceous spicules.

Class Demospongiae

A class of sponges that may contain $1$- or $4$-rayed siliceous spicules, spongin protein, or both.

Amoebocytes

Creeping, motile cells within the sponge walls (mesohyl) that function in digestion and can differentiate into other cell types.

Sclerocytes

Cells derived from amoebocytes that are responsible for producing spicules.

Gemmules

Stress-resistant aggregates of amoebocytes used for asexual reproduction in sponges.

Phylum Cnidaria

A phylum of approximately $10,000$ species characterized by radial symmetry, stinging cells called cnidocytes, and a single digestive opening.

Cnidocytes

Stinging cells found in cnidarians that contain barbed, harpoonlike structures called nematocysts.

Nematocysts

Sharp, barbed harpoonlike structures within cnidocytes used to capture prey and for defense.

Polyp

A cnidarian body form where the mouth and tentacles are pointed upward.

Medusa

A cnidarian body form where the mouth and tentacles are pointed downward.

Gastrovascular cavity (GVC)

A digestive cavity with a single opening where both extracellular and intracellular digestion occur.

Class Hydrozoa

A class of cnidarians, such as Hydra, where the polyp stage usually dominates the life cycle.

Gastrozooids

Specialized feeding polyps found in colonial hydrozoans like Obelia.

Gonozooids

Specialized reproductive polyps found in colonial hydrozoans like Obelia.

Velum

A structure containing muscle fibers found in some hydrozoan medusae, like Gonionemus, that aids in locomotion.

Class Scyphozoa

A class of cnidarians, commonly called sea jellies, where the gelatinous medusa stage dominates the life cycle.

Class Anthozoa

The largest class of cnidarians ($>6,000$ species), including anemones and corals, which exist only as polyps with no medusa stage.

Acontia

Threads of tissue in sea anemones that bear dense batteries of cnidocytes and can protrude through the mouth or body pores.

Coral bleaching

A process where rising water temperatures cause coral polyps to expel their symbiotic algae and die.

Class Cubozoa

A class of cnidarians characterized by box-shaped medusae and potentially fatal stings, such as Chironex fleckeri.