Embryology is the branch of biology that studies the prenatal development of gametes, fertilization, and development of embryos and fetuses. 
The study of one type of evidence of evolution is called embryology, the study of embryos.
An embryo is an unborn (or unhatched) animal or human young in its earliest phases.
Embryos of many different kinds of animals: mammals, birds, reptiles, fish, etc. look very similar and it is often difficult to tell them apart.
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Comparative embryology. Comparative embryology is the branch of embryology that compares and contrasts embryos of different species. It is used to show how all animals are related. Many things are compared (such as whether or not the organism has a notochord or gill arches).
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula. ... Gastrulation is followed by organogenesis, when individual organs develop within the newly formed germ layers.
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