1. Does a sea star have a digestive system? If so is it simple or complex?
2. What is the locomotion of a sponge? (Very short answer please)
2007-03-28 08:07:59 · 2 answers · asked by confidential 2 in Science & Mathematics ➔ Biology
Sea stars have a complete digestive system with two body openings.
Adult sponges are sessile, so they have no locomotion. Sponge larvae are motile, moving about by swimming with cilia.
2007-03-28 08:15:01 · answer #1 · answered by ecolink 7 · 1⤊ 0⤋
Starfish digestion is carried out in two separate stomachs. They are called the cardiac stomach and the pyloric stomach. The cardiac stomach, which is a sack like stomach located at the center of the body may be everted—pushed out of the organism's body and used to engulf and digest food. Some species take advantage of the great endurance of their water vascular systems to force open the shells of bivalve mollusks such as clams and mussels, and inject their stomachs into the shells. Once the stomach is inserted inside the shell it digests the mollusk in place. The cardiac stomach is then brought back inside the body, and the partially digested food is moved to the pyloric stomach. Further digestion occurs in the intestine and waste is excreted through the anus on the aboral side of the body.
Because of this ability to digest food outside of its body, the sea star is able to hunt prey that are much larger than its mouth would otherwise allow including arthropods, and even small fish in addition to mollusks.
Some echinoderms have been shown to live for several weeks without food under artificial conditions—it is believed that they may receive some nutrients from organic material dissolved in seawater.
2007-03-28 08:13:00 · answer #2 · answered by Anonymous · 0⤊ 1⤋