Biology
Evolution
Why do animals and plants look the way they do? Because species change over very long stretches of time.
What you need first
The living things on Earth today are not the same as those millions of years ago. Species change slowly across many generations. This process is called evolution. It explains why there are so many different animals and plants, and why each species fits its surroundings so well.
Natural selection
In every group of living things, not all are the same. Some are faster, bigger, or better camouflaged than others. An animal that is better adapted to its surroundings is more likely to survive and to have more offspring. Its offspring inherit the useful traits. Over time, what fits best comes out on top. This process is called natural selection.
After 0 generations: 50 % camouflaged
The environment selects, the beetle does not decide: camouflaged beetles are eaten less often.
Two ingredients: variation and heredity
For evolution to work, two ingredients are needed. First, variation: offspring are never exactly alike, there are always small differences. They arise by chance through tiny changes in the genetic material, the building instructions of a living thing. Second, heredity: parents pass their traits on to their children. A good example is camouflage. A beetle whose color matches the ground gets eaten less often and passes its color on more frequently. After many generations, almost all beetles are well camouflaged.
Common ancestors
If you go far enough back in time, many species share the same ancestors. The house cat and the lion both belong to the cat family and had a common ancestor around 10 million years ago, and even you are distantly related to all living things. Such changes need a great deal of time, though, often many thousands or millions of years. Within a single human lifetime you see almost none of it.
Exercises
0 of 6 solvedTime to try it yourself. You can't break anything, every attempt counts.
What does evolution describe?
Which two ingredients does evolution need?
Of 10 beetles, 6 are well camouflaged and survive, and all the rest get eaten. How many beetles get eaten?
Put the steps of natural selection into the correct order, using a camouflaged beetle as the example.
- 1A beetle whose color matches the ground gets eaten less often
- 2After many generations almost all beetles are well camouflaged
- 3The offspring inherit the matching color
- 4This beetle is more likely to survive and has more offspring
- 5In the beetle group there are small differences in color
In a bird species each generation has twice as many well adapted offspring as the generation before. In generation 1 there are 5. How many are there in generation 2?
An animal that is better adapted to its surroundings is more likely to survive and to have more … .
Where this leads