Cnidarians -- Animals
Evolutionary Milestones
Cnidarians are the first animals to have tissues and the only animals to have radical symmetry.
Habitat
Cnidarians are marine animals.
Anatomical/Structural Features
Cnidarians have tentacles with stinging cells and a central mouth. They have no backbone, central nervous system, head, circulatory system, heart, or blood.
Symmetry
Cnidarians have radical symmetry, meaning they have multiple lines of symmetry.
How They Acquire Nutrients
Cnidarians are heterotrophs and carnivores.
What They Eat
Cnidarians use nematocyst (sticky or barbed capsule) to sting their prey, and then the prey is taken into the gastrovascular cavity to be digested. They eat small planktonic animals.
What Eats Them
Some specialist fish (such as parrot fish and butterfly fish) and sea stars eat coral polyps. Jellyfish are eaten by fish (such as sunfish) and turtles.
Mobility
The polyp stage is sessile (does not move), but the medusa stage is motile via tentacles.
Reproduction
Cnidarians can reproduce either sexually or asexually. If sexually, it occurs in the medusa stage as external fertilization (the male releases sperm and the female releases eggs into the water). If asexually, it occurs in the polyp stage as budding.
Development
Cnidarians can move back and forth between the polyp (adult) stage and the medusa (larvae) stage.
Examples
Some examples of cnidarians include jellyfish, sea anemones, hydra, and corals.
Other Information
There are three classes of cnidarians: hydrozoa, scyphozoan, and anthozoa.
Cnidarians provide homes for other organisms.
Cnidarians are the first animals to have tissues and the only animals to have radical symmetry.
Habitat
Cnidarians are marine animals.
Anatomical/Structural Features
Cnidarians have tentacles with stinging cells and a central mouth. They have no backbone, central nervous system, head, circulatory system, heart, or blood.
Symmetry
Cnidarians have radical symmetry, meaning they have multiple lines of symmetry.
How They Acquire Nutrients
Cnidarians are heterotrophs and carnivores.
What They Eat
Cnidarians use nematocyst (sticky or barbed capsule) to sting their prey, and then the prey is taken into the gastrovascular cavity to be digested. They eat small planktonic animals.
What Eats Them
Some specialist fish (such as parrot fish and butterfly fish) and sea stars eat coral polyps. Jellyfish are eaten by fish (such as sunfish) and turtles.
Mobility
The polyp stage is sessile (does not move), but the medusa stage is motile via tentacles.
Reproduction
Cnidarians can reproduce either sexually or asexually. If sexually, it occurs in the medusa stage as external fertilization (the male releases sperm and the female releases eggs into the water). If asexually, it occurs in the polyp stage as budding.
Development
Cnidarians can move back and forth between the polyp (adult) stage and the medusa (larvae) stage.
Examples
Some examples of cnidarians include jellyfish, sea anemones, hydra, and corals.
Other Information
There are three classes of cnidarians: hydrozoa, scyphozoan, and anthozoa.
Cnidarians provide homes for other organisms.