Today I take you into the animal world to get to know the animals of various groups. Start with simple, inferior animals.
The body structure of coelenterates is relatively simple, and most of these species live in the ocean, such as jellyfish, anemones, jellyfish, polyps, etc.;
A few species live in freshwater, such as the hydra.
Through observation, it can be found that the body of the coelenterate can only be divided into upper and lower, can not be separated from the front and back, left and right and dorsal abdomen, through the longitudinal axis of the body can have multiple sections to divide the body into two parts of symmetry, this body shape is called radiation symmetry.
The main characteristics of coelenterates are: the body is radiatively symmetrical; the body surface has thorn cells; and the mouth does not have anus.
Thorn cells are a weapon of attack and defense peculiar to coelenterates, especially at the tentacles.
Among coelenterates, jellyfish are processed and edible, with high nutritional value; the calcareous substance secreted by polyps accumulates to form coral reefs. Coral reefs can form islands, reinforce coasts, and provide important habitats and shelters for marine life such as fish on the seafloor.
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