PSY 302 Chapter Notes - Chapter 2: Amniotic Fluid, Amniotic Sac, Umbilical Cord
30 Jan 2016
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Document Summary
Aristotle posed the fundamental question about prenatal development that was to underlie. He rejected the idea of preformation in favor of what he termed epigenesist-the emergence of new structures and functions during development. The idea of preformation persisted long after aristotle, degenerating into a dispute about whether the miniature, preformed human was lodged inside the mother"s egg or father"s sperm. A single cell resulted from the union of two highly specialized cells-a sperm from a father and an egg from our mother. These gametes contain one half of the genetic material found in other cells. They are produced through a special type of cell division in which the eggs and sperm receive only one member from each of the 46 chromosome pairs contained in all other cells of the body. The reduction to 23 chromosomes in each gamete is necessary since the union of egg and sperm must contain the normal amount of genetic material.
