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:
“Russian forests crash down under the axe, billions of trees are dying, the habitations of animals and birds are layed waste, rivers grow shallow and dry up, marvelous landscapes are disappearing forever.... Man is endowed with creativity in order to multiply that which has been given him; he has not created, but destroyed. There are fewer and fewer forests, rivers are drying up, wildlife has become extinct, the climate is ruined, and the earth is becoming ever poorer and uglier.”
—Anton Pavlovich Chekhov (1860–1904)
“Feet are considered a delicacy among certain animals, you know.... In fact, there are certain man-eating animals who will eat only the feet, leave everything else, will not touch one other thing.”
—Blake Edwards (b. 1922)
“The greatness of man is so evident that it is even proved by his wretchedness. For what in animals is nature, we call in man wretchedness—by which we recognize that, his nature being now like that of animals, he has fallen from a better nature which once was his.”
—Blaise Pascal (1623–1662)