1. Chapter 5
“CHANGES OVER TIME”

2. A group of similar organisms that can mate with each other and produce offspring?
SPECIES

3. The preserved remains or traces of an organism that lived in the past?
FOSSIL

4. A trait that helps an organism survive and reproduce?
ADAPTATION

5. The gradual change in a species over time?
EVOLUTION

6. A well-tested concept that explains a wide range of observations?
SCIENTIFIC THEORY

7. The process by which individuals that are better adapted to their environment are more likely to survive and reproduce?
NATURAL SELECTION

8. Any difference between individuals of the same species?
VARIATON

9. Body parts that are structurally similar in related species?
HOMOLOGOUS STRUCTURES

10. A diagram that shows how scientists think different groups of organisms are related?
BRANCHING TREE

11. *A fossil formed when minerals replace all or part of an organism?
PETRIFIED FOSSIL

12. *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?
MOLD

13. *A type of fossil that forms when a mold becomes filled in with minerals that then harden?
CAST

14. *A technique used to determine which of two fossils is older?
RELATIVE DATING

15. *A technique used to determine the actual age of a fossil on the basis of the amount of radioactive element it contains?
RADIOACTIVE
DATING

16. *An unstable element that breaks down into a different element?
RADIOACTIVE ELEMENT

17. The time it takes for half of the atoms in a radioactive element to break down?
HALF-LIFE

18. The millions of fossils that scientists have collected?
FOSSIL RECORD

19. Term used to indicate a species that no longer exists?
EXTINCT

20. The theory the evolution occurs slowly but steadily?
GRADUALISM