Animals
In animal development, the term zygote is also used more loosely to refer to the group of cells formed by the first few cell divisions, although this is properly referred to as a morula.
In mammalian reproduction, after fertilization has taken place the zygote travels down the fallopian tube, while dividing to form more cells without the zygote actually increasing in size. This cell division is mitotic, and is known as cleavage. All mammals go through the zygote stage of life. Mammalian zygotes eventually develop into a blastocyst, after which they are more generally termed an embryo, and then a fetus.
A human zygote exists for about four days, and becomes a blastocyst on the fifth day.
Read more about this topic: Zygote
Famous quotes containing the word animals:
“Researchers, with science as their authority, will be able to cut [animals] up, alive, into small pieces, drop them from a great height to see if they are shattered by the fall, or deprive them of sleep for sixteen days and nights continuously for the purposes of an iniquitous monograph.... “Animal trust, undeserved faith, when at last will you turn away from us? Shall we never tire of deceiving, betraying, tormenting animals before they cease to trust us?””
—Colette [Sidonie Gabrielle Colette] (1873–1954)
“About sacrifice and the offering of sacrifices, sacrificial animals think quite differently from those who look on: but they have never been allowed to have their say.”
—Friedrich Nietzsche (1844–1900)
“There is no instant of time when one creature is not being devoured by another. Over all these numerous races of animals man is placed, and his destructive hand spares nothing that lives. He kills to obtain food and he kills to clothe himself; he kills to adorn himself; he kills in order to attack and he kills to defend himself; he kills to instruct himself and he kills to amuse himself; he kills to kill. Proud and terrible king, he wants everything and nothing resists him.”
—Joseph De Maistre (1753–1821)