The New Childrens Encyclopedia

244

Evolution

Over long periods of time, all species of

organism slowly change. This gradual

change, called evolution, is driven by the

process of natural selection. This process

allows organisms that are best suited to their

environment to survive and reproduce.

The father of evolution

The English naturalist

Charles Darwin first

proposed the theory of

evolution after studying

hundreds of different

animals, plants, and fossils.

He realized that many

species were related and had

a common ancestor. Modern

DNA testing is now proving

that his theory was correct.

NATURAL SELECTION

Darwin observed that most animals and plants produce

more offspring than survive to become adults. He realized

that nature was selecting those with the characteristics

best adapted to their surroundings, allowing them to

pass on their characteristics to future generations.

 ADVANTAGE Having

a long neck allows the

giraffe to eat leaves that

other species cannot reach.

 SURVIVAL TACTICS

Frogs produce hundreds of

eggs but only a few grow

into adult frogs.

Adaptation Darwin’s theory can explain

why a giraffe has a long neck. In

the search for food, those that

could reach a little higher had

an advantage over those with

shorter necks. Over time, new

generations developed longer

and longer necks.

ARTIFICIAL SELECTION

In the wild, species evolve by natural

selection. However, humans have been

helping evolution by choosing animals and

plants with desirable characteristics and

breeding them to produce sheep with more

wool, cows that give more milk,

and crops that have better

yields. This process is

called artificial selection.

Cauliflower

(flowers)

Broccoli

(flowers)

Domestic dogs All dogs are

descended from wolves. Over

time, humans selectively bred

them for things like hunting

or herding ability, speed, and

size, so that we now have

hundreds of different species.

Gray wolf

These dogs all

have a little bit

of wolf in them.

Wild cabbage

SCIENCE