19Development of Animals

Multicellular organisms are not a simple aggregate of homogenous cells, but consist of specified cells with different morphologies and functions. Populations of specified cells form tissues and organs, which in turn form an individual organism while working cooperatively with each other and maintaining a balance. The development of animals begins with a fertilized egg that consists of one cell. This cell divides repeatedly and becomes multicellular. Eventually, it differentiates to form a body similar to the parent’s body which consists of various specified cells. This chapter focuses on the basic mechanisms of animal development, while referring to some specific examples.

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