Fish: Reptiles or Amphibians?
Fish are considered neither reptiles nor amphibians, as they are their own distinct group of animals. Found in nearly every aquatic biome on the planet, fish are the most diverse group of vertebrates on the planet, with over 33,000 known species.
Evolutionary Differences
Fish diverged from their tetrapod ancestors, reptiles and amphibians, more than 400 million years ago. These evolutionary differences have resulted in numerous key physiological differences between the three groups.
Fish
Fish possess numerous adaptations that make them uniquely suited to life in water:
- Gills: Fish are able to extract oxygen out of water using modified organs known as gills
- Fins: Fins provide fish with propulsion and help them to steer themselves in water
- Scales: Fish are covered in scales, which are the first line of defense against potential predators
Reptiles and Amphibians
Reptiles and amphibians are unable to complete life in water on their own. They possess adaptations that allow them to breath both underwater and on land, whereas fish are unable to breathe on land and must remain in water.
Summary
Fish, reptiles, and amphibians represent three distinct types of animals that have developed their own individual and unique adaptations over millions of years of evolution. Although they share common ancestors, they each possess the adaptations necessary to survive in their particular environments. Fish are best adapted to aquatic living and are unable to breathe on land, whereas reptiles and amphibians can breathe both underwater and on land.
Therefore, the answer to the question of “Are fish reptiles or amphibians?” is neither, as fish are a unique group of vertebrates that are distinct from both reptiles and amphibians.
