Chapter 7: Change Over Time

3. A scientist who studies fossils.
5. A behavior or physical characteristic that allows an organism to survive or reproduce in its environment.
7. The preserved remains or traces of an organism that lived in the past.
9. The disappearance of all members of a species from Earth.
11. The process of grouping things based on their similarities.
12. Body parts that are structurally similar in related species.
14. A classification grouping that consists of a number of similar, closely related species.
16. An organism whose cell contain nuclei.
18. A type of fossil formed when a shell or other hard part of an organism dissolves, leaving an empty space in the shape of the part.
19. A type of fossil that provides evidence of the activities of ancient organisms.
20. A type of fossil that forms when a mold becomes filled in with minerals that then harden.
21. The system for naming organisms in which each organism is given a unique, two-part scientific name.
23. A difference between individuals of the same species.

1. A process by which individuals that are better adapted to their environment are more likely to survive and reproduce than others of the same species.
2. An organism whose cells lack a nucleus and some other cell structure.
3. A fossil formed when minerals replace all or part of an organism.
4. The theory that evolution occurs slowly but steadily.
6. The scientific study of how living things are classified.
8. The theory that species evolve during short periods of rapid change.
10. The specific environment that provides the things an organism needs to live, grow, and reproduce.
13. A well tested concept that explains a wide range of observation.
15. A group of organisms that are physically similar and can make mate with each other and reproduce.
17. The comparison of the structures of different organisms.
22. The gradual change in a species over time.