Gradual change of a species over time

Preserved remains or traces of an organism that lived in the past

Millions of fossils that scientists have collected

Theory that evolution occurs slowly but steadily

Time it takes for half the atoms in a radioactive element to decay

Body parts that are structurally similar in related species ant that provide evidence for a common ancestor.

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.

Process by which individuals that are better adapted to their environment are more likely to survive and reproduce than others of the same species

Fossil formed when minerals replace all or part of an organism

Theory that species evolve during short periods of rapid change

Technique used to determine the actual age of a fossil on the basis of the amount of radioactive element it contains

Technique used to determine which of two fossils is older

Well-tested concept that explains a wide range of observations

Group of organisms that are physically similar and can mate with each other and produce offspring that can also mate and reproduce

Any difference between individuals of the same species

Historical remnants of a structure that was thought to have greater importance in its’ ancestors, but has little importance now