Not everybody accepts the theory of evolution; but according to those who do, animal life (which includes fish, birds, and insects) began more than 500,000,000 years ago, after the earth's surface had cooled and the oceans were formed. Most scientists be have that there was life in the sea before There was any living thing on land. The land had no life for the next 160,000,000 years.
Then strange, fishlike creatures began to come out of the oceans on to the land. At first their movements were very awkward because they, had no legs. They had to use their fins like feet for a long time. After many generations, their fins became legs and feet. While these changes were taking place, the animals still laid their eggs and hatched their young in the water. These walking creatures, whose ancestors were fish-like, developed into "amphibians" (cold blooded animals that live part' of their lives on land after hatching from eggs laid in the water).
In time, some of the early amphibians no longer laid their eggs in the water. When this happened, the amphibians became "reptiles" (cold blooded animals that reproduce by laying their eggs on land).Reptiles ruled the earth for more than 100,000,000 years. Some of the reptiles developed feathers on their bodies, and their forelimbs became wings. In time they learned to fly, and birds came into being. Birds feathers are the result of changes that took place in the reptile scales.
Other reptiles ceased to lay eggs and became mammal-like animals that gave birth to their young. They also became warm-blooded and developed into true mammals.
Then strange, fishlike creatures began to come out of the oceans on to the land. At first their movements were very awkward because they, had no legs. They had to use their fins like feet for a long time. After many generations, their fins became legs and feet. While these changes were taking place, the animals still laid their eggs and hatched their young in the water. These walking creatures, whose ancestors were fish-like, developed into "amphibians" (cold blooded animals that live part' of their lives on land after hatching from eggs laid in the water).
In time, some of the early amphibians no longer laid their eggs in the water. When this happened, the amphibians became "reptiles" (cold blooded animals that reproduce by laying their eggs on land).Reptiles ruled the earth for more than 100,000,000 years. Some of the reptiles developed feathers on their bodies, and their forelimbs became wings. In time they learned to fly, and birds came into being. Birds feathers are the result of changes that took place in the reptile scales.
Other reptiles ceased to lay eggs and became mammal-like animals that gave birth to their young. They also became warm-blooded and developed into true mammals.
