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:
“The struggle alone pleases us, not the victory. We love to see animals fighting, not the victor raving over the vanquished.... It is the same in gambling, and the same in the search for truth.... We never seek things for themselves—what we seek is the very seeking of things.”
—Blaise Pascal (1623–1662)
“Shall we never have done with that cliché, so stupid that it could only be human, about the sympathy of animals for man when he is unhappy? Animals love happiness almost as much as we do. A fit of crying disturbs them, they’ll sometimes imitate sobbing, and for a moment they’ll reflect our sadness. But they flee unhappiness as they flee fever, and I believe that in the long run they are capable of boycotting it.”
—Colette [Sidonie Gabrielle Colette] (1873–1954)
“We know what the animals do, what are the needs of the beaver, the bear, the salmon, and other creatures, because long ago men married them and acquired this knowledge from their animal wives. Today the priests say we lie, but we know better.”
—native American belief, quoted by D. Jenness in “The Carrier Indians of the Bulkley River,” Bulletin no. 133, Bureau of American Ethnology (1943)