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 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)
“The moles nested in my cellar, nibbling every third potato, and making a snug bed even there of some hair left after plastering and of brown paper; for even the wildest animals love comfort and warmth as well as man, and they survive the winter only because they are so careful to secure them.”
—Henry David Thoreau (1817–1862)
“All animals are equal but some animals are more equal than others.”
—George Orwell (1903–1950)