ENGLISH

2. normally live and thrive in a particular ecosystem.
4. a variety in the genetic makeup of individuals in a population.
7. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental condi- tions.
9. the process by which the earth’s life forms change genetically over time.
10. occurs when an entire species ceases to exist.
13. the remains or traces of past organisms
14. which are changes in the coded genetic in- structions in the DNA in a gene.
16. Each species plays a role within the ecosystem it inhabits
17. Species found in only one area
19. transfer of segments of DNA with the desired trait from one species to another
20. life on earth sharply reduces by several periods during which there is a significant rise in extinction rates.

1. play several critical roles in helping to sustain ecosystems.
3. Species that provide early warnings of changes in environmental conditions in an ecosystem
5. change the genetic characteristics of populations with similar genes
6. able to live in only one type of habitat, eat only one or a few types of food, or tolerate a narrow range of environmental conditions.
8. which is the variety of genes found in a population or in a species
11. occurs when different groups of the same population of a species become physically isolated from one another for a long time.
12. individuals possess heritable traits that give them advantage over other individuals in the population.
15. species that migrate into or that are deliberately or accidentally introduced into an ecosystem
18. diagrams that depict the hypothetical evolution of various species from common ancestors.