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:
“Only the most acute and active animals are capable of boredom.—A theme for a great poet would be God’s boredom on the seventh day of creation.”
—Friedrich Nietzsche (1844–1900)
“Old women snore violently. They are like bodies into which bizarre animals have crept at night; the animals are vicious, bawdy, noisy. How they snore! There is no shame to their snoring. Old women turn into old men.”
—Joyce Carol Oates (b. 1938)
“From the oyster to the eagle, from the swine to the tiger, all animals are to be found in men and each of them exists in some man, sometimes several at the time. Animals are nothing but the portrayal of our virtues and vices made manifest to our eyes, the visible reflections of our souls. God displays them to us to give us food for thought.”
—Victor Hugo (1802–1885)