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:
“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)
“Lost at night in an immense forest, I only have a small light to guide me. A man appears who tells me: “My friend, blow out your candle in order to find your way.” This man is a theologian.
The sea, fluid garden filled with animals and plants.”
—Alfred Döblin (1878–1957)
“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)