Mammal fur and hair. Only mammals have hairs. Lots of hairs clumped together make up this tiger's fur. These hairs grow from the surface layer of the skin.

Terrestrial vertebrates use a pair of lungs to exchange oxygen and carbon dioxide between their tissues and the air.

Mammal fur and hair. Only mammals have hairs. Lots of hairs clumped together make up this tiger's fur. These hairs grow from the surface layer of the skin.

Reptiles have dry, scaly skin. But they don't need moisturizer! Their special covering actually helps them hold in moisture and lets them live in dry places. Reptile scales are not separate, detachable structures -- like fish scales.

Reptile Reproduction. Most reptiles reproduce sexually and have internal fertilization. Males have one or two penises that pass sperm from their cloaca to the cloaca of a female. Fertilization occurs within the cloaca, and fertilized eggs leave the female's body through the opening in the cloaca.

Sometimes more than a quarter of the oxygen they use is absorbed directly through their skin. Tadpoles and some aquatic amphibians have gills like fish that they use to breathe. There are a few amphibians that do not have lungs and only breathe through their skin.

Amphibians are cold-blooded animals, meaning they do not have a constant body temperature but instead take on the temperature of their environment. They have moist, scaleless skin that absorbs water and oxygen, but that also makes them vulnerable to dehydration (loss of bodily fluids).

Typically, frogs lay eggs. This process usually occurs through external fertilization, where the female releases her eggs from her body into water. Then, the male releases his sperm to fertilize them. However, a few species of frog use internal fertilization.

The beak, bill, or rostrum is an external anatomical structure of birds that is used for eating and for preening, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young.

While keratin also makes up snake and lizard scales, it is a slightly different compound in birds. The three main types of feathers are the filoplumes (sensory feathers), the contour feathers, and the down feathers (insulation).

Bird lungs do not expand or contract like the lungs of mammals. In mammalian lungs, the exchange of oxygen and carbon dioxide occurs in microscopic sacs in the lungs, called 'alveoli.' In the avian lung, the gas exchange occurs in the walls of microscopic tubules, called 'air capillaries.'

The ability to maintain a high and constant body temperature enables birds to exploit a remarkable range of habitats -- tropical, temperate, and polar. ... When heat-stressed, therefore, some birds, such as Black Vultures, excrete onto their unfeathered legs to increase heat loss by evaporation.

Most fish exchange gases like oxygen and carbon dioxide using gills on both sides of the pharynx. Gills are tissues that are like short threads, protein structures called filaments.

Mammals have hair or fur, birds have feathers, reptiles have dry scales, amphibians have soft, moist skin, and fish have wet, slimy scales.

The female usually lays the eggs, and the embryos in the eggs develop and hatch outside her body. These kind of fish are called 'oviparous' fish. Oviparous fish develop by obtaining food from the yolk in the egg. ... Some species of fish, such as various sharks, are viviparous.