Animal development Flashcards
Cell determination
It is a series of molecular events that lead to cell differentiation in which a cell becomes specialized and carries out specific functions.
Morphogenesis
The develop of form occurs through pattern formation, a series of events in which cells may communicate by signalign, migrate, undergo changes in shape and undergo apoptosis.
Nuclear equivalence
No genetic changes occur in cell determination and cell differentiation. Instead, various types of differentiated cells express different subsets of their genes.
Cleavage
A series of rapid cell divisions without a growth phase. The main effect of cleavage is to partition the zygote into many small blastomeres. It also forms a solid ball of cells called morula and then usually a hollow ball of cells caled blastula.
Isolecithal eggs
They have evenly distributed yolk. They undergo holoblastic cleavage, which involves division of the entire egg.
Telolecithal eggs
A concentration of yolk at the vegetal pole slows cleavage so that only a few large cells form there compared with a large number of cells at the animal pole. They undergo meroblastic cleavage, which is restricted to the blastodisc.
Gastrulation
The basic body plan is laid down as three germ layers form: the outer ectoderm, the inner endoderm and the mesoderm between them.
Organogenesis
It is the process of organ formation. Ectoderm becomes the nervous system, sense organs, and the outer layer of skin. Mesoderm becomes the notochord, skeleton, muscles, circulatory system, and inner layer of skin. Endoderm becomes the lining of the digestive tube.
Chorion
It is used in gas exchange.
The amnion
It is a fluid-filled sac that surrounds the embryo and keeps it moist. It also acts as a shock absorber.
The allantois
It stores nitrogenous wastes.
Yolk sac
It makes food available to the embryo.
