**Fishes** are aquatic vertebrates that are characterized by having paired fins, scales, and gills. The fins are used for locomotion, scales for protection, and gills for respiratory function.

**Jaws** made it possible to nibble on plants and munch on other animals. They also allowed for consumption of a wider variety of food. Fins allowed for more control of body movement. The tail fins gave fish greater thrust when swimming.

Here are the adaptations of fishes for aquatic life:

1. Fishes have acquired gills as an adaptation for living in an aquatic habitat. The gills facilitated in the gas exchange and allowed them to breathe underwater.

2. Since fishes tend to lose water due to osmosis because salt water is more concentrated, the kidneys of the fish help control the amount of water inside the body.

3. The paired fins of the fishes help them propel forward or in any direction as they swim.

4. Fishes have acquired a swim bladder which helps adjust their buoyancy in the water.

5. Fishes acquired various modes of feeding. Many fishes are classified as herbivores, carnivores, parasites, filter feeders, and detritivores.

Here are the adaptations of fishes for aquatic life:

1. Gills for respiration

2. Kidneys for controlling the amount of water inside the body

3. Fins for swimming

4. Swim bladder to help adjust their buoyancy in the water

5. Various modes of feeding

There are around 24,000 living species of fish in the marine environment. These are composed of diverse species that are grouped based on their body structures. There are thee major groups of fishes and they are– jawless fishes, cartilaginous fishes, and bony fishes.

1. **Jawless fishes** are fish species that to doe not have true teeth or jaw. Their skeletons are composed of fibers and cartilage, and they lack vertebral structure rather the notochord persists even though they are in the adult stage. Example: Lampreys and Hagfishes

2. **Cartilahginous fishes** – are fish species that have skeletons made up of cartilage rather than bones. The cartilage present in the body of these animals is very flexible similar to those cartilage found in our ears and nose. Example: Sharks

3. **Bony fishes** – are fish species that have skeletons made up of calcified tissue called *bone*. Almost all living bony fishes are grouped under a sub-group called *ray-finned* fishes, and only seven living bony fish organisms are classified under *lobe-finned fishes*.
Example: Peacock flounder (ray-finned fish) and lungfish (lobe-finned fish)

Water quality is important as fish intake oxygen-rich water and pushes oxygen-poor water out of the openings in the sides of the pharynx. If water quality is poor they can really not respire well as only a small amount of oxygen is present in the habitat, and this can cause suffocation.