What is a Fish?

 

What is a Fish?

Body

Fish 

Fish are aquatic vertebrate animals that have gills but lack limbs with digits

 like fingers or toes. 

 Recall that vertebrates are animals with internal backbones. Most fish are streamlined in their general body form.

 

Bod

Defining a Fish 

Defining a fish is difficult because the term fish includes a very wide range of aquatic animals. more over, there are about as many species of fishes than there are of all other vertebrates combined (Fig. 4.4).

                                     Of the nearly 50,000 species of animals with backbones, approximately 4,500 are mammals, 9,700 are birds, 6,500 are reptiles, 4,000 are amphibians, and 25,000 are fishes. Although some  these numbers change as new species are discovered, new fishes are found more often than other new vertebrates are found.

                        As scientists make new discoveries, it is expected that the number of species of fishes will outnumber other vertebrates even more. Fishes also range in size from very small,  as like the tiny cyprinid in Indonesia, which grows to a maximum length of 10 mm (Fig. 4.5 A) to the large whale shark Rhincodon typus, which reaches 12 meters (Fig. 4.5 B),. 

                         And Fishes have a wide range of diets, including plankton, algae, fish, seals, and turtles. Some fishes are parasites, some are blind, some are venomous, and some can even produce electricity. and  With all of this amazing diversity, it is challenging to make a definition that describes all fishes.