Animal embryonic development

Animal Embryonic Development

Animal embryonic development, also known as embryogenesis, is the process by which the embryo forms and develops. It starts with the fertilization of an ovum, which is then followed by the formation of a zygote. The zygote undergoes rapid mitotic divisions with no significant growth, producing a blastula, which further develops into a gastrula.

Fertilization

Fertilization is the fusion of two gametes to form a zygote. The sperm and egg each contribute half the genetic material needed for the new individual. The process of fertilization and the formation of the zygote are the initiating events in the life history of the organism.

Cleavage

Following fertilization, the zygote begins to divide by mitosis in a process called cleavage. Cleavage is a series of rapid cell divisions that results in an increase in the number of cells but not their size. This process transforms the zygote into a small, multicellular organism, known as a blastula.

Gastrulation

Gastrulation is a significant phase in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.

Organogenesis

Organogenesis is the process by which the three germ layers formed from gastrulation develop into the internal organs of the organism. The cells interact and develop into complex tissues and organs, completing the formation of the three primary germ layers: ectoderm, mesoderm, and endoderm.

See also

• Embryo
• Zygote
• Blastula
• Gastrula
• Ectoderm
• Mesoderm
• Endoderm
• Organogenesis