Fish

       Fish. Among the vertebrates (back-boned animals), the fish are lowest in order of intelligence, but among the most important from an economic standpoint. From earliest historic times men have used the flesh of fish as food, and today there is hardly a country in the world whose people do not include it in their diet.

How to fish swim in harmony? by TED-Ed

19 Characteristics of Fish:

1. Fish constitute the class Pisces, which is divided into about 13,000 species. 
2. All are back-boned animals, living in water. 
3. Notwithstanding the numerous species, fishes show a remarkable uniformity in appearance, for the greater number have elongated, compressed bodies, tapering toward both ends, with paired fins to take the place of limbs. 
4. This form of body is well adapted to meet the pressure of water. 
5. The body is generally covered with scales or bony plates, though a few species lack such covering.
6. With the exception of a small family of fresh-water fish, which possess both lungs and gills, fish breathe wholly by means of gills, which are designed to extract oxygen from the water.
7. They have cold, red blood, which is pumped through the system after being purified by passage through the gills. 
8. The backbone is composed of vertebrae, and is so loosely jointed that the body can be turned and bent freely in all directions. 
9. Fish possess in their air bladder, or swim bladder, an organ peculiar to themselves, which they are able to fill or empty at will. This bladder enables the fish the ability to control their buoyancy.
10. The skeletons of some families of fishes are not of bone, but of a strong, thick cartilage.
11. Geological investigations show that there have been many thousands of species of fish now wholly extinct, but those that survive are distributed throughout almost all the waters of the earth. 
12. Those in temperate or tropical waters are more brilliantly colored and strikingly marked than the inhabitants of colder waters. 
13. In most species the colors increase in intensity and beauty during the breeding season, much as the plumage of a bird grows bright. 
14. Some fish feed on both animal and vegetable matter, others are flesh-eaters, and some eat only vegetable food. 
15. They reproduce by eggs, these being laid in shallow water. 
16. The eggs are usually left uncared for, though some species, like the stickleback, gather the eggs in nests and protect and care for their young. 
17. Millions of eggs are laid by a single fish, but the young are preyed upon by so many enemies that relatively few survive. 
18. In size fish vary from tiny minnows, an inch or so in adult length, to man-eating sharks thirty-five feet long. 
19. Whales (which see) are mammals, though they bear certain resemblances to fish. 

More About Fish from The Web:

• Wonders of Wildlife Aquarium
• Tennessee Aquarium
• St. Louis Aquarium
• Chicago Aquarium
• National Aquarium

More About Fish from Our Blogs:

• "F" is for fish" alphabet coloring page
• Color these fish in a bowl