embryolab final draft - 1 Introduction: For years...

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Introduction: For years scientists have been studying the development of life. More specifically they study the way in which an organism matures from the time an egg is fertilized by a sperm. In the first stage of development the organism is called a zygote. The first step in development is called cleavage. During this phase the cell divides from one cell into many smaller cells. In chick eggs, there is only a relatively small area of yolk-free cytoplasm that undergoes cleavage. This is because yolk is very thick and abundant in bird eggs. The process by which the yolk does not completely divide is called meroblastic cleavage. The division of the yolk-free part of the cell forms an area of cells known as the blastoderm. In the next stage of development, called gastrulation, the outer cells of the blastoderm begin to move towards the inside of the embryo. This process results in the formation of three embryonic layers, which will eventually form all of the chick’s organs and body parts (Campbell, 2005). The next part of development is called organogenesis. This is the phase in which all the chick’s organs and systems form. One of the first systems that form in the chick embryo is the nervous system. Features of this system can be seen by a microscope about one day after fertilization. The next observable structures are the heart and blood vessels, which can be seen after about two days. One of the main goals in this lab exercise was “to follow the course of development of the nervous and circulatory systems through the first stages of development, using live chick embryos, and prepared slides of fixed embryos”(Burpee, 2008). This means that we looked at slides of embryos during certain times of development in order to learn when different structures and systems form. The next goal of the lab was the see if temperature had any effect on the development of the embryos. To do this we examined embryos that were the same age but incubated at different temperatures. We then had to determine the relative temperature at which the embryos were incubated. The last goal of the lab was “to test the effect of caffeine on the heart rate of live chick embryos” (Burpee, 2008). Using former knowledge of embryology and other areas of science, certain
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This note was uploaded on 04/21/2008 for the course BIOL 240W taught by Professor Nelson,kimberlyn during the Spring '08 term at Pennsylvania State University, University Park.

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embryolab final draft - 1 Introduction: For years...

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