BIOL 1002 Chapter : Chapter 23 Study Guide
Document Summary
Chapter 23-study guide: describe basic characteristics of animals. Most animal phyla that currently populate earth were present by the cambrian period (544 million years ago). The scarcity of pre-cambrian fossils led systematists to search for clues about the evolutionary history of animals by examining the features of anatomy, embryological development, and dna sequence. Certain features represent evolutionary milestones, and mark major branching points on the animal evolutionary tree. These include the appearance of tissues, the appearance of body symmetry, and protostome and deuterostome development: describe each of the following, sponges, sponges have a simple body plan. Sponges belong to the phylum porifera and are found in most marine and aquatic environments. Sponges do not move, but occur in a variety of sizes and shapes. They may reproduce asexually by budding, where the adult produces miniature versions of itself that drop off and assume an independent existence. They may reproduce sexually through fusion of sperm and eggs.
