Natural selection

2. - in biology, a change in an organism, over time, that better enables it to survive and multiply
4. - a sudden, apparently abnormal change or alteration in a genetically determined structure, as opposed to gradual evolutionary change
7. a variety
8. - the child or young of a particular human, animal, or plant
11. - everything that surrounds a particular type of living thing and affects its growth and health
14. - the degree to which something varies; amount of change or difference
15. - money or things that are available for a particular use
16. - a condition that causes harm to the health of a person, animal, or plant; illness; sickness

1. - something that pollutes, esp. a waste substance that makes air, water, or land impure or unhealthy; contaminant.
3. organisms with traits best suited to their environment are more likely to survive and reproduce.
5. - an animal being hunted, caught, and eaten by another animal
6. - a way of hiding something by covering or coloring it so that it looks like its surrounding
9. of the Fittest - in biology, the evolutionary principle that only the forms of plants or animals best suited to or most easily able to adapt to existing conditions will survive, while other less suited forms will become extinct
10. to have young or offspring
12. - to fill with more inhabitants than available resources can sustain
13. animal that hunts other animals for food