BI256 Lecture Notes - Lecture 1: Cambrian Explosion, Body Plan, Cnidaria
Document Summary
Have radial symmetry (wheel) and cell tissues grade of organization. Number of embryonic germ layers is important in architecture. Number of body cavities also determines architecture. All three of these things have to do with the complexity of the animal. Body plans is the layout of the organism. During this explosion groups of animals arose. Warm and shallow seas in this period. Light is penetrating to the bottom of the sea. Oxygen enriched environment in the warm shallow seas. 34 major phyla of living multicellular animals with a distinct body plan. Regular arrangement of body structures relative to axis of the body. Animals can be bisected along at least one plan. No body axis and no plane of symmetry. Sense/interact with environment from all directions: radial symmetry. Body has a general form of a cylinder. Radial can be divided in more then two planes. Biradial symmetry means that it can be divided in half.
