Biology 3338A/B Study Guide - Final Guide: Spindle Apparatus, Central Spindle, Germ Layer
Document Summary
Study notes egg activation and cleavage patterns. Fertilization activates molecules necessary to begin cell cleavage and gastrulation. Concepts: cell cleavage differs from other forms of cell division: the number of cells and nuclear mass increases with each successive subdivision, but the cytoplasmic mass does not increase. It is a hollow ball of single-layered cells which folds upon itself during gastrulation to form the embryo with three germ layers. Each germ layer differentiates into different organ systems. Part 3: types of cleavage: determinate cleavage = mosaic cleavage, determinate cleavage is in most protostomes, results in the developmental fate of cells being set early in the embryo development. Each blastomere produced by early embryonic cleavage does not have the capacity to develop into a complete embryo: indeterminate cleavage = regulative cleavage. In holoblastic eggs, the first cleavage is always along the vegetal-animal axis of the egg; the second cleavage is perpendicular to the first.
