Key events in development: fertilization to organogenesis

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Epigenesis: Idea that all the materials and nutrients required to produce the infant are already provided in the egg.

Preformation: Theory that an infant is already inside the egg or sperm.

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Key events in development:

Gametogenesis: Gamete Formation and Maturation; Spermiogenesis and Oogenesis

Fertilization: Sperm and Ovum Fuse together

Cleavage: Zygote subdivides, the cytoplasm is partitioned into blastomeres

Gastrulation: germ layers formed

Organogenesis: organs are formed, cells differentiate

Growth: Development; organs increase in size, the adult body formed

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Cell Specialization

Cells differentiate because of two reasons:

Cytoplasmic determinants (germplasm localization): including morphogens; this is an autonomous specification

Induction: this is a conditional specification

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Gamete formation processes

Spermiogenesis

Oogenesis

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Fertilization processes

Contact: The sperm enters the jelly coat of the egg.

Entry of the sperms nucleus

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Types of cleavage processes

Radial