Lecture 13 (3/31/26): Form and function in plants and animals

Porifera

Sponges; an animal phylum characterized by few cell types, no well-defined tissue

Cnidaria

A phylum characterized by radial symmetry, two germ tissues in the embryo, a closed internal gastric cavity, and well-developed tissues but not organs; includes jellyfish, sea anemones, and corals.

Bilateria

The monophyletic group of animals with bilateral symmetry.

diploblastic.

Describes animals in which the embryo has two germ layers, the endoderm and the ectoderm, from which the adult tissues develop.

triploblastic

Describes animals in which the embryo has three germ layers, with the mesoderm between the endoderm and ectoderm.

protostomes

A bilaterian in which the blastopore, the first opening to the internal cavity of the developing embryo, becomes the mouth. The taxonomic name is Protostomia, and the group includes mollusks and arthropods.

deuterostomes

A bilaterian in which the blastopore, the first opening to the internal cavity of the developing embryo, becomes the anus. The taxonomic name is Deuterostomia and includes humans and other chordates.

coelom

A body cavity surrounding the gut.

homeostasis

The active regulation and maintenance of a stable internal physiological state in the face of a changing external environment.

negative feedback

A process in which the output or product of a pathway opposes the initial stimulus, so that steady conditions are maintained. Negative feedback often underlies homeostasis in a cell or organism.

set point

A steady-state value in homeostatic regulation.