How can fishes survive inside water?

Introduction:
Fishes are aquatic animals that have adapted to live and survive in water. They have several unique features and adaptations that allow them to thrive in their watery environment. One of the key factors in their survival is the presence of oxygen in dissolved form in water.

The presence of oxygen in dissolved form:
Water is composed of molecules made up of hydrogen and oxygen atoms. Oxygen gas (O2) is not easily soluble in water, but it can dissolve to a certain extent. This dissolved oxygen is essential for the survival of aquatic animals like fishes. Fishes have specialized organs called gills that allow them to extract this dissolved oxygen from water.

Gills and respiration:
Fishes respire through their gills, which are located on the sides of their bodies. The gills are made up of thin, filamentous structures that have a large surface area. As water passes over the gills, oxygen from the dissolved oxygen in the water diffuses into the bloodstream of the fish. At the same time, carbon dioxide, a waste product of respiration, is released from the fish's bloodstream into the water.

Adaptations for efficient respiration:
Fishes have several adaptations that enhance their ability to extract oxygen from water efficiently:

1. Gill Filaments: The gill filaments are lined with tiny projections called lamellae, which further increase the surface area available for oxygen exchange.

2. Countercurrent exchange: Blood flows through the gill filaments in the opposite direction to the water flow. This arrangement creates a concentration gradient that ensures efficient oxygen uptake and carbon dioxide removal.

3. Ventilation: Fishes use various methods to ensure a constant flow of water over their gills. Some species swim with their mouths open, while others have specialized structures like gill covers or pumps to facilitate water movement.

Conclusion:
Fishes have adapted to survive in water by utilizing the dissolved oxygen present in their aquatic environment. Through their gills, they efficiently extract oxygen from the water and release carbon dioxide. These adaptations allow fishes to respire and survive in their watery habitat.