Difference Between Fish and Reptiles

By: | Updated: Jan-15, 2022
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There are many kinds of living things that exist on this planet. The best way to identify the difference between these living things is by looking at their physical appearance. We can also classify them by their origin and habitat. The other way to identify the difference between these living things is by looking at their internal organs. However, this method is not always effective because some of them are too small to be seen with the naked eye.

Summary Table

Fish Reptile
Use fins and tails to move Use legs and tails to move
Live underwater only Live in the forest, lakes, rivers, or ocean
Eat mainly fish and plankton Mostly carnivores

Difference Between Fish and Reptiles

There are animals that live in water, in the air, and on land. Animals are categorized into different types. There are animals that are aquatic, amphibious, and others. Animals are also categorized according to their physical appearance. Some of them have been grouped into the following types:

– Fish

– Reptiles

– Amphibians

– Birds and Mammals.

Different animals can be identified by their physical appearance. For example, a reptile can be identified by its long body, short legs, and four limbs. A bird has a long neck, beak, and wings. Birds are also categorized according to their origin. For example, some birds are aquatic birds and others are terrestrial birds. Animals that live in water can usually be identified by their external appearance. They may have fins, scales, or gills. They may also have a shell.

While there are reptiles that live in water, not all of them are aquatic. Thus, there are differences between fishes and reptiles. In this article, we will be discussing the difference between fishes and reptiles. We will take a look at the characteristics of fishes and reptiles, and their physical appearance.

So, let’s get started!

What is a Fish?

Fishes are warm-blooded, air-breathing vertebrates that can be found in freshwater, brackish water and sea. The classification of fishes are divided into three categories according to their size: freshwater fish, marine fish and anadromous fish. They live in freshwater streams, rivers and lakes as well as the ocean.

Fishes have fins. They have gills for respiration. The fins are found on the sides of the body and the tail fin is on top of it. Fishes can be classified into fish families based on their fins, gills and scales. However, there are also mammals that live under water. Therefore, the classification of fishes into families is not completely accurate. Fishes are further divided into three groups based on their fins: teleosts, bony fish and cartilaginous fish.

Dolphins, whales, manatees and porpoises are classified as cetaceans. Cetaceans are mammals that live in the ocean. They are warm-blooded, air-breathing vertebrates. Cetaceans have flippers and have a dorsal fin located on their back. Fishes are usually not considered to be mammals. However, fishes are related to mammals.

What is a Reptile?

Reptiles are cold-blooded animals. Cold-blooded animals do not have a special system that regulates their body temperature. Thus, the reptiles’ body temperature is very stable, and it does not change throughout the day or night.

In addition to being cold-blooded, reptiles are also soft-bodied animals. Their skin is covered with scales and their skeletons consist of calcium carbonate plates or bone. These characteristics make them able to live in any environment; however, they are generally found in moist places.

Reptiles are animals that have a lizard-like appearance. The following is a list of the most common reptiles: snakes, lizards, turtles and crocodiles. These animals have the same characteristics as fish and mammals but some of them are even more complex than other animals.

How are They Related?

Fishes and reptiles are related to each other because they both share the same ancestor. Fishes and reptiles are also different from one another because they evolved separately from the same ancestral species.

Fishes are aquatic animals. The majority of them live in water. Most fishes have gills to breathe oxygen and use their fins for movement and feeding. They have a tail fin that aids them in swimming. Fishes have evolved into various forms, but the basic structure of their body remains the same. Fishes can be classified into different types, such as freshwater fishes, saltwater fishes, and even deep sea fishes.

Reptiles are terrestrial animals that spend most of their time on land. They breathe air and do not have gills to extract oxygen from water. However, most reptiles live in water and can swim. Reptiles have limbs that enable them to move about, just like fishes.

What are the Differences?

Although there are some similarities between fishes and reptiles, there are also differences. Here are some of the differences between fishes and reptiles.


The first difference between fishes and reptiles is the appearance. Fishes have fins while reptiles do not. The fins of fishes help them swim faster and move easily in the water. Fishes also have tails, which is a fin that is present on the back of their bodies.

Fishes also have scales, which are also known as scutes. These scales help fishes to stay warm in the water. The scales of fishes also act as protection against water predators.

Reptiles also have scales, but their scales are usually soft and do not have any function. They are usually just for the purpose of camouflage. They have tails for the same reason as fishes, but they mostly move using their legs.


The second difference between fishes and reptiles is the habitat. Reptiles are mostly found in forests, but some of them can also be found in deserts. Fishes are usually found in water bodies, such as lakes, rivers, oceans and seas.


The third difference between fishes and reptiles is the diet. Fishes eat mainly fish, but some of them also eat plants and plankton. Reptiles are carnivores and they feed on other animals such as birds, lizards, snakes and mammals. They mostly do not have any known plant-eating habit like fishes do.

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