What Is a Reptile? Today there are 6,800 reptile species on earth; the major groups are alligators and crocodiles, turtles, lizards, and snakes. All reptiles are cold-blooded, which is why they warm themselves in the sun, and have bodies covered in dry, horny scales. Some reptiles lay eggs; others give birth to live young.
What Is an Amphibian? Like birds, reptiles, mammals, and fishes, amphibians are vertebrates –- that is, creatures with a backbone and an internal skeleton. Amphibians live part of their life in water and part on land. Even those species that lay eggs on land start life in a fluid-filled egg, breathing through gills.
What Is a Bird? Birds are warm-blooded creatures, like mammals, but they lay eggs, like most reptiles. All birds have feathers and wings, and most birds are able to fly. Birds are amazingly varied in their shapes, sizes, colors, and behavior patterns. There are more than 9,000 different species of birds in the world.
What Is an Insect? Insects and their relatives, including spiders and scorpions, belong to a huge group of animals called the arthropods. The main thing that all arthropods have in common is their hard outer coat, which is called an exoskeleton and protects their soft insides. The bodies of arthropods are divided into sections.
What Is an Insect? Insects and their relatives, including spiders and scorpions, belong to a huge group of animals called the arthropods. The main thing that all arthropods have in common is their hard outer coat, which is called an exoskeleton and protects their soft insides. The bodies of arthropods are divided into sections.
What Is a Fish? Fishes come in an amazing variety of shapes and colors, but they all have three important things in common: All fishes live in water, have fins, and use gills to get oxygen from the water. We have also included a few sea creatures -- some jellyfish and octopods -- in this category.
What Is a Mammal? Mammals live on land, at sea, in the air, and under the ground. All mammals, from bats to whales, share a number of important traits that make them different from other animals. Mammals are warm-blooded, they have fur or hair, and most mammals give birth to live young (rather than laying eggs).
What Makes a Bird a Bird? Feathers! Birds are the only creatures with feathers. ”Light as a feather” is no exaggeration. Feathers weigh very little, but birds could not live without them. Feathers allow flight, provide terrific insulation, and keep rain and snow away from the skin. They can be colorful as a rainbow or make a bird blend in perfectly with its surroundings.
Out with the Old Most birds replace their feathers every year, a few at a time, in a process called molting. A new feather grows out of the skin, inside a covering that looks like a straw; when it is fully grown, the cover peels away. Ducks and geese lose all their big wing feathers at once, so they are flightless for a few weeks in summer while the new ones grow in.
An Incredible Quantity of Feathers All the feathers on a bird’s body are called its plumage. A tiny Ruby-throated Hummingbird has about 1,000 feathers; a White-throated Sparrow has about 2,000. A scientist once counted every feather on a Tundra Swan, from the largest wing quills to the tiniest fluff of down, and came up with 25,216.