Practice question

Cleavage patterns classify based on yolk content and distribution affecting division planes. Meroblastic cleavage restricts division to small cap of cytoplasm atop large yolk mass, so only part of egg contributes to embryo while remainder serves nutritive function. Characterized as discoidal meroblastic in birds, reptiles, bony fish, and superficial meroblastic in insects centrolecithal eggs. Holoblastic cleavage completely bisects egg forming blastomeres comprising entire embryo. Meroblastic pattern allows evolution of large yolky eggs supporting external development without placenta, demonstrating adaptation linking egg architecture to embryonic cleavage strategy.