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Jellyfish: Example of Cnidarian
What they are - biological definition
Cnidaria are relatively simple animals that live in aquatic environments, especially at sea (about 99% live in marine water and 1% in freshwater).
There are currently about 10,000 known cnidarian species.
Main characteristics of cnidaria:
- Epidermis composed of a layer of muscle fibers.
- They have no respiratory system. Breathing is aerobic, with each cell exchanging gas with the medium through the diffusion process.
- Have tentacles in the mouth, which is attached to a digestive cavity. Extra digestion occurs within the cell.
- Have radial symmetry.
- They have no circulatory system.
- They do not have excretory system. The elimination of waste (excreta) in water is done by cells through the diffusion process.
- The nervous system of the cnidaria is diffuse and composed of a network of nerve cells.
- In general, they can switch between polyp form and free form during their reproductive cycle.
- Cnidaria are carnivores. They capture their prey using the tentacles. They feed on sea worms, crabs, protists, fish and other cnidaria.
Examples of cnidaria:
- Sea Anemones
- Soft Corals
- Freshwater Hydras
Sea anemones: example of cnidarian animal.