Discuss these questions with your partner. Then scan the text quickly to find the answers.
1. What is variation?
2. What is mutation?
3. Are mutations harmful or beneficial?
4. How do X-rays influence the mutation rate?
Exercise A. Match the words with their definitions:
| 1. | ultimate | A | being the only one of its kind |
| 2. | unique | B | a process by which two or more things have an effect on each other and work together |
| 3. | distinguish | C | the final and the most important one |
| 4. | source | D | the air, water and land in which people, animals and plants live |
| 5. | feature | E | someone`s child or children; animal`s baby or babies |
| 6. | spontaneous | F | how tall someone is |
| 7. | twin | G | a thing, place, activity that you get something from |
| 8. | offspring | H | a part of something that you notice because it seems important, interesting, or typical |
| 9. | identical | I | to be able to recognize and understand the difference between two similar things or people |
| 10. | environment | J | happening or done without being planned or organized |
| 11. | interaction | K | one of two children born at the same to the same mother |
| 12. | height | L | exactly the same |
■ Read and translate the given text and make your essential assignments:
The Earth is inhabited by billions of organisms, every one of which is unique. Individuals belonging to different species are usually easy to distinguish; members of the same species may differ only in small ways; but even clones (such as identical twins) show some subtle differences. The differences between individuals of the same species are called variation.These differences may be the result of genetic differences, the influence of the environment, or a combination of genetic and environmental influences.
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