Evolution and Structure
All sexually reproducing life, including both plants and animals, produces gametes. The male gamete cell, sperm, is usually motile whereas the female gamete cell, the ovum, is generally larger and sessile. The male and female gametes combine to produce the zygote cell. In multicellular organisms the zygote subsequently divides in an organised manner into smaller more specialised cells, so that this new individual develops into an embryo. In most animals the embryo is the sessile initial stage of the individual life cycle, and is followed by the emergence (that is, the hatching) of a motile stage. The zygote, the sessile organic vessel containing the developing embryo, or even the ova itself may be called the egg.
Read more about this topic: Egg (biology)
Famous quotes containing the words evolution and/or structure:
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)
“A structure becomes architectural, and not sculptural, when its elements no longer have their justification in nature.”
—Guillaume Apollinaire (1880–1918)