Animal Diversity II Lecture 2

These flashcards cover key concepts related to animal origins, evolution, and the distinctions between protostomes and deuterostomes.

Monophyletic Group

A group of organisms that consists of all the descendants of a common ancestor.

Polytomy

A node on a phylogeny where more than two lineages descend from a single ancestral lineage.

Protostomes

Animals in which the blastopore becomes the mouth → anus during development. (mollusks, roundworms, flatworms)

Deuterostomes

Animals in which the blastopore becomes the anus → mouth during development. (Echinoderms, Hemichordates, and Vertebrates)

Ectoderm

The outermost of the three primary germ layers, which develops into the skin and nervous system.

Mesoderm

The middle primary germ layer, which develops into muscles and bones.

Endoderm

The innermost primary germ layer, which develops into the digestive tract and lungs.

Ctenophore

A group of marine animals known as comb jellies that possess muscles and nerves.

Sponge

A simple multicellular animal that lacks nerves, muscles, and a gut.

Gastrulation

A phase early in embryonic development where the blastula reorganizes into a multilayered structure.

Triploblastic

Animals whose embryos have three germ layers: ectoderm, mesoderm, and endoderm.

Diploblastic

Animals whose embryos have only two germ layers: ectoderm and endoderm.

Nerve Cord

A structure that serves to transmit signals throughout the nervous system.