Jellyfish is a representative of the coelenterates type, of which there are more than 9000 species. Most of them are common in the seas. There are both attached forms - polyps, and free-floating organisms - jellyfish.
Instructions
Step 1
All coelenterates, including jellyfish, are multicellular two-layer animals. They have an intestinal body cavity and radial (radial) symmetry. The intestinal cavity communicates with the environment only through the oral opening. The processes of nerve cells form the nerve plexus. Cnidarians live only in water, mainly in the seas, lead a predatory lifestyle, and use stinging cells to catch prey and protect against enemies.
Step 2
The gelatinous body of the jellyfish resembles an umbrella. On the lower side in the middle there is a mouth, and along the edges of the body there are movable tentacles. The movement of a jellyfish in the water column resembles "jet propulsion": it collects water into an umbrella, then sharply cuts it and throws water out, due to which it moves with the convex side forward.
Step 3
Along with all coelenterates, jellyfish are predators that kill their prey with poisonous stinging cells. In contact with some jellyfish (for example, the spider that lives in the Sea of Japan), a person can get burned.
Step 4
But such coelenterates, like polyps, do not swim in the water, but sit motionless in the gorges of the rocks. They are usually brightly colored and have several corollas of short, thick tentacles. Marine polyps lie in wait for the prey, staying in one place or slowly moving along the bottom. They are fed by sedentary animals, which are captured by predators with tentacles.
Step 5
Many marine coelenterates form colonies. A young polyp formed from a kidney does not separate from the mother's body, as in a freshwater hydra, but remains attached to it. Soon, he himself begins to sprout new polyps. In the colony formed in this way, the intestinal cavities of the animals communicate with each other, and the food caught by one of the polyps is assimilated by everyone. Colonial polyps often become covered with a calcareous skeleton.
Step 6
In tropical seas in shallow waters, colonial polyps can form dense settlements - coral reefs. These colonies, covered with a strong calcareous skeleton, severely impede navigation.
Step 7
Often these corals settle along the island shores. When the seabed descends and the island is immersed in the water, coelenterates, continuing to grow, stay at the surface. Subsequently, characteristic rings are formed from them - atolls.
