Animal_Development_[1]

Animal_Development_[1] - Animal Development from Zygote to...

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Unformatted text preview: Animal Development from Zygote to Adult Animal Development Complexities of animal structure result from modifications of the patterns of embryonic development All animals share basic aspects of early development Modifications of features of early development are reflected in basic differences in body plans The evolution of body plans (evodevo) is a main theme in the study of animals as is the mechanisms that lead to differentiation from egg to adult Animal Development What we will discuss: Patterns of early development How a zygote becomes organized into the basic components of the organism to be Variations in this process, and how these variations are related to phylogeny Mechanisms controlling the development of organs and other structures How are complex animals assembled from one undifferentiated ovum? One early idea: Preformation Another idea: Epigenesis embryo gradually takes shape. Observational and experimental evidence supports this view Early development Three stages, after fertilization: Cleavage The orderly division of the zygote into smaller cells. These cells can move around, and can contain different complements of chemicals laid down in the ovum Formation of the blastula , a stage that is found, in one form or another, in essentially every animal embryo Gastrulation Invagination of the blastula, producing the basic organization of the embryo to be Early Embryonic Development Cleavage : -Orderly cell divisions -Simultaneous mitoses -Little cell growth -Little activity by genes in the nucleus! Each cell: a Blastomere Blastula Stage : -Small cells, which can be moved around. -Different kinds and amounts of material from cytoplasm of egg Gastrulation : -Invagination of the blastula, producing an embryo with at least two layers, and an opening from the outside to the inside. Sea urchin gastrulation Archenteron : Future gut Blastopore : Mouth or anus (or both), depending on the kind of animal Blastocoel : The space inside the blastula. It largely disappears in many animals, but persists in some....
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Animal_Development_[1] - Animal Development from Zygote to...

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