BI256 Lecture Notes - Lecture 1: Invagination, Archenteron, Blastocyst
Document Summary
New designs for living: cambrian explosion (500 mya) Body plans: animal symmetry: asymmetry, no body axis and no plane of symmetry, found in protozoan and poriferans (sponge, symmetry = balanced proportions, size/shape either side of a median plane, spherical symmetry. Infinite number of planes of symmetry: best suited for floating and rolling, rare, found only in protozoans (radiolarians), rarely found in any animals. Surfaces differentiate as dorsal (protection) and ventral (locomotion: major innovation: better suited for moving/sensing the environment, also good for feeding (better suited to directional (forward) movement) Five grades of organization within animals and animal-like groups: protoplasmic level of organization (cellular level of organization) Differentiated organelles that perform specific function: cellular level of organization (eg. volvex) Cells not organized into tissues: cell-tissue level of organization (eg. jellyfish) Aggregation of cells into tissues: tissue- organ level of organization (eg. flatworm) Organs made up of more than one kind of tissue.
