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:
“Of all the animals with which this globe is peopled, there is none towards whom nature seems, at first sight, to have exercised more cruelty than towards man, in the numberless wants and necessities with which she has loaded him, and in the slender means which she affords to the relieving these necessities.”
—David Hume (1711–1776)
“In their sympathies, children feel nearer animals than adults. They frolic with animals, caress them, share with them feelings neither has words for. Have they ever stroked any adult with the love they bestow on a cat? Hugged any grownup with the ecstasy they feel when clasping a puppy?”
—Jessamyn West (1907–1984)
“The animals that depend on instinct have an inherent knowledge of the laws of economics and of how to apply them; Man, with his powers of reason, has reduced economics to the level of a farce which is at once funnier and more tragic than Tobacco Road.”
—James Thurber (1894–1961)