Animals
Segmentation in animals typically falls into three types characteristic of the different phyla: Arthropoda, Vertebrata, and Annelida. The three will be discussed here in using an example from each phyla, drosophila, zebrafish, and leech, respectively. Drosophila form segments from a field of equivalent cells based on transcription factor gradients. Zebrafish, and other vertebrates, use oscillating gene expression to define segments known as somites. Leech embryos, and other annelids, use smaller cells budded off from teloblast cells to define segments.
Read more about this topic: Segmentation (biology)
Famous quotes containing the word animals:
“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)
“who cooked rotten animals lung heart feet tailborscht & tortillas
dreaming of the pure vegetable kingdom,”
—Allen Ginsberg (b. 1926)
“Chinese civilisation is so systematic that wild animals have been abolished on principle.”
—Aleister Crowley (1875–1947)