Embryo

From EvoWiki

See Embryo in Wikipedia, the free encyclopedia.

The life cycle of many multicellular organisms includes a developmental stage during which the organism is an Embryo. Embryos are usually dependent on a supply of nutrients provided by an egg or a placenta. Embryos provided some of the evidence for evolution that influenced Charles Darwin's thinking about natural selection. Some embryos have features that appear to be remnants of the body plans of ancestral organisms. Examples of this that are frequently mentioned are gill slit-like features and webbed digits of the embryos of land-dwelling animals. It should be noted that digits form from an initially solid limb bud and there is no way to avoid a developmental stage where there is tissue between the digits. In humans, prenatal development is traditionally divided into an early embryonic period and a later fetal period. Embryogenesis is characterized by cell differentiation and the initial formation of most of the specialized tissues and organs required for the organism to survive as an independent organism. Fetal development is characterized by the growth and maturation of organs.