Fish vs. Amphibians — What's the Difference?

Fish are aquatic creatures that have specialized organs called gills, which they use to breathe underwater. Their bodies are designed for life in water, with streamlined shapes and fins for swimming. Fish reproduce in a variety of ways, but most lay eggs in the water. They are ectothermic, or cold-blooded, meaning their body temperature varies with the environment.

Amphibians, on the other hand, begin their life cycle in water and often move to land as they mature. They have lungs for breathing air as adults, although some species also use their skin for gas exchange. Amphibians typically undergo a metamorphosis from a larval stage to an adult form, changing their habitat and sometimes their diet. They are also ectothermic but rely on both water and land environments to complete their life cycle.

While fish are covered in scales that protect their bodies, amphibians have permeable skin that can absorb water and oxygen, which is why they often stay near moist environments. This skin requires them to live in habitats that will not dry them out, limiting their range compared to fish.

Fish have a wide variety of reproductive strategies, including laying eggs (oviparous), giving birth to live young (viviparous), and a combination of both (ovoviviparous). Their reproductive behavior can be quite complex, involving courtship and sometimes parental care of the eggs or young.

Amphibians usually lay their eggs in water, and these eggs are often unprotected by a hard shell, making them susceptible to dehydration. This necessitates a moist environment for successful reproduction. The transition from water to land as they develop allows for a unique life cycle that impacts their feeding, breeding, and habitat preferences.