Contents
What are fish?
Fish are cold-blooded aquatic vertebrates with simple circulation.
These animals are provided with fins and scales, breathe through gills and reproduce through eggs.
The skeleton of the fish
The skeleton of fish can be of two types:
- Cartilaginous skeleton fish: These are those fish whose skeleton is made up of cartilage.
Cartilage is a resistant and elastic type of animal tissue, like the one we have in our nose and ears.
Cartilaginous fishes are sharks, rays, mantas, and other primitive fishes.
- Fish with skeleton bones: They are the group of fish that have a backbone made up of bone.
Bone is the solid and rigid tissue of animals made up of organic substance and mineral salts.
Bony fishes are breams, clownfish and many other evolved fish.
Fish skin
Fish have the body covered with skin like the rest of vertebrates. Fish skin is covered by scales.
Scales are the set of horny plates that cover the skin of these vertebrate animals and protect it from the outside environment.
Where do fish live?
Fish are aquatic animals because they all live in water.
These animals live in saltwater, such as seas or oceans, or in freshwater, such as rivers, lakes, swamps …
Saltwater fishes are sharks, tuna, sardines, hakes… Freshwater fishes are carps, barbels, angelfish, etc.
Fish adaptations
Fish are fully adapted to living in water. They do not have arms or legs like humans but rather have fins for swimming.
Fish bodies are specially shaped to facilitate swimming.
Fish breathing
Fish respiration is done through gills, in order to take up the dissolved oxygen in the water.
The gills are the respiratory organs of fish. With the gills, fish are able to extract the dissolved oxygen in the water and remove the carbon dioxide, a product of cellular respiration, to the water.
Fish feeding
- Many fish are carnivores, like sharks or, for example, tunas. Carnivorous fish eat worms, mollusks, aquatic insects, other fish…
- There are also omnivorous fish, such as carps. Omnivorous fish eat algae, aquatic plants and aquatic animals.
- A few fish are herbivores, such as salpas. Herbivorous fish do not eat any type of animal, but only eat algae and aquatic plants.
More information on other animals
