BIOL 110 Study Guide - Final Guide: Parazoa, Choanoflagellate, Motility
Document Summary
The first animals likely originated from a colonial protist similar to choanoflagellates: similar to parazoa. Animals first appear in the fossil record approximately 750 million years ago, but molecular data suggest that animals evolved much earlier: dichotomous: parazoa versus eumetazoa. Parazoans have no symmetry therefore does not go to 2nd dichotomous. A chordate"s nerve cord develops into the brain and spinal cord in adults: notochord long flexible rod that provides support. In vertebrates, it becomes part of the intervertebral discs in adults: pharyngeal slits are openings in the pharynx (part of the throat) of an animal, postnasal tail. Development is defined as those processes that are irreversible and occur from zygote formation to death. Cellular differentiation is defined as how a cell diverges from its early morphology into a more specialized morphology (shape), in an irreversible manner. Totipotency is the capability of certain embryonic cells to form any type of adult cell.
