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title: "5.1.1 Events before birth"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/288686119/5.1.1%20Events%20before%20birth"
format: markdown
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The life history of an animal starts with the fusion of an oocyte and a spermatozoid: the conception. What happened to these two before conception has an influence on their quality, and thus with the start-up conditions of the animal. The next important phase is that of development through embryonic and foetal phase to the birth of the animal. In mammals this phase occurs in the uterus and the mother has more or less continuous influence, in egg laying species it occurs in the egg and the mother’s influence mainly lays in the composition of the yolk and white components. During its time until birth, the animal encounters certain so-called windows of development: periods during which certain parts should develop. These windows often have a fixed time-frame. That means that the development has to take place during that time-frame. After the window closes again, development in that aspect is no longer possible. The development will depend on the genetics of the animal, but also on the environment. If that is not sufficient, the development will be sub-optimal.