Animal Kingdom and Basic Invertebrate Infauna

Kingdom Animalia

A kingdom consisting of all multicellular eukaryotic heterotrophs.

Heterotrophic

Organisms that obtain their food by hunting or consuming other organisms.

Invertebrate

An animal without a backbone (dorsal support); 95% of Animalia.

Phylum Porifera

A phylum including sponges, characterized by being sessile filter feeders with a porous structure.

Ostia

Pores in sponges through which water enters.

Choanocytes

Collar cells in sponges that create water currents and collect food.

Amoebocytes

Cells in sponges that can differentiate into any cell type and are involved in digestion.

Spicules

Rigid skeletal elements of sponges, composed of calcium carbonate or silica.

Acoelomate

Organisms that lack a true body cavity; e.g., sponges.

Asymmetrical

Lacking symmetry; a characteristic of sponges.

Calcarea

A class of sponges that have calcareous spicules with 1-4 rays.

Hexactinellida

Class of sponges known as glass sponges, characterized by silica spicules with 6 rays.

Demospongiae

Largest class of sponges that typically have spongin and can be leuconoid.

Protoplasmic organization

The level of organization seen in simple eukaryotic organisms like protozoans.

Cellular organization

A level of organization in sponges where cells serve specific functions.

Tissue organization

Cells grouped together for specific functions as seen in Cnidarians.

Bilateral symmetry

Body plan with left and right mirror images, typical of directional-moving animals.

Radial symmetry

Body plan where parts radiate from a central axis; seen in sessile or free-floating organisms.

Cleavage

The rapid cell division that occurs after fertilization in the development of an embryo.

Morula

A solid ball stage of embryonic development after the zygote.

Blastula

A hollow ball stage of embryonic development after the morula.

Gastrula

The stage of embryonic development that involves the folding of the blastula and formation of germ layers.

Diploblastic

Organisms with two germ layers: ectoderm and endoderm, such as Cnidarians.

Triploblastic

Organisms with three germ layers: ectoderm, mesoderm, and endoderm; includes all bilateral animals.

Protostome

An organism where the mouth forms first; includes most animals.

Deuterostome

An organism where the anus forms first; includes Echinoderms and Chordates.

Acoelomate

Triploblastic animals without a true body cavity.

Pseudocoelomate

A body cavity between the mesoderm and endoderm.

Coelomate

An organism with a true body cavity derived from the mesoderm.

Cnidocytes

Specialized stinging cells found in Cnidarians, containing nematocysts.

Nematocyst

An organelle in cnidocytes that functions in defense and prey capture by stinging.

Polyp

A sessile body form of Cnidarians with tentacles facing up.

Medusae

A free-swimming body form of Cnidarians with tentacles facing down.

Hypostatic skeleton

The gastrovascular cavity that functions as a skeleton in Cnidarians.