Evolution

3. In ___________ populations, an allele can become more or less common simply by chance.
6. Natural selection on single-gene traits can lead to changes in ______________ frequencies.
10. for According to Charles Darwin, members of a species must ___________________ limited resources.
14. Shuffling Most inheritable differences are due to ______________________ that occurs during the production of gametes.
15. According to Darwin, the word _______________ would indicate organisms' ability to survive and reproduce in their particular environments.
17. effect The type of genetic drift that follows the colonization of a new habitat by a small group of individuals is called....
20. Because all members of a population can ________________, biologists often study their genes as a single group.
21. A well-tested explanation that unifies a broad range of observations.
22. changes in species over time
23. The term fitness refers to an organism's ability to survive and _________ in a specific environment
25. breeders In artificial selection, ____________ , rather than the environment, select the variations of traits to be passed to offspring.
26. America The first step of the speciation of the Galápagos finches likely was the arrival of founders from

1. Preserved remains or evidence of an ancient organism.
2. In a population of snakes with a range of body lengths, if the longest individuals have the highest fitness, ____________________ selection is likely to occur.
4. In a gene pool, as the relative frequency of one allele for a trait increases, the relative frequencies of other alleles for that trait
5. with modification The fact that species today look different from their ancestors can be described as
7. selection When individuals at one end of a bell-shaped curve of phenotype frequencies have higher fitness than individuals in the middle the result is.
8. Inherited characteristic that increases chances of survival
9. of evolution Darwin viewed the fossil record as....
11. drift may occur when a small group of individuals colonize a new habitat.
12. Mutations do not always affect an organism's ______________—its physical, behavioral, and biochemical characteristics.
13. breeding Artficial selection as practiced by farmers
16. selection When individuals near the center of the curve have higher fitness than individuals at either end of the curve, the result is....
18. Darwin Credited with the theory of evolution
19. descent Principle that living things were derived from common ancestors.
24. Ancestor The number and location of bones of many fossil vertebrates are similar to those in living vertebrates. Most biologists would probably explain this fact on the basis of