The Process of Speciation
1. Define species: group of similar organisms that can breed and produce fertile
offspring.
2. As new species evolve, populations become reproductively isolated from each
other.
3. What stops an eastern meadowlark from breeding with a western meadowlark?
They have different mating songs
4. Give an example (or description) of geographic isolation: ( 2 populations are
separated by geographic barriers such as rivers, mountains, or bodies of H 2O.) The
Abert squirrel; when the Colorado River split 10,000 years ago, it also split the
Abert squirrel into 2 separate populations. 2 separate gene pools were formed.
Genetic changes that appeared in one group were not passed to the other. Natural
selection worked separately on each group and led to the distinct subspecies, the
Kibab squirrel.
5. What are the two squirrel species that exist on opposite sides of the Colorado
river and what is their color?
Squirrel 1 Abert
Squirrel 2 Kibab
color: grey
color: black
6. When two species cannot reproduce at the same time, it is called temporal
isolation.
7. Examine Figure 16-3 and identify what each of the following finches eats:
insects-woodpecker, fruit-vegetarian,
seeds-sharp-beaked,
insects-large
insectivorous
Testing Natural Selection in Nature
8. Once Darwin discovered that the birds were all finches, he hypothesized that
they descended from a common ancestor.
9. Darwin's hypothesis relied on two testable assumptions:
1) There must be
heritable variation in those traits and
2) Differences in shape must produce
differences in fitness, that cause natural selection to occur.
Peter and Rosemary Grant tested the hypothesis. Complete each
statement about their observations.
10. The Grants measured and [ identified / tagged ] as many birds as possible.
11. They recorded which birds [ died / migrated ] and which succeeded in
breeding.
12. The purpose of measuring the birds was to show that they have [fitness /
variation].
13. During a [ season / drought ], differences in beak size can mean the difference
between life and death.
14. A feeding [ generalist / specialist ] is a type of bird that chooses food based on
what its beak handles best.
15. Finches with [ large / small ] beaks were most likely to survive.
16. The next generation of finches had [ larger / smaller ] beaks.
Speciation in Darwin's Finches
17. Where did the first finches on the islands come from? South American
mainland These first finches were called founders.
18. Over time, populations on the island became adapted to their local
environments.
19. How do finches choose their mates? They choose mates with the same size
beak.
20. Most specialized birds have less competition for food.
21. How many different finch species can be found on the Galapagos? 13
Studying Evolution Since Darwin
22. New data from what three scientific fields supports the theory of evolution by
natural selection?
genetics, molecular biology, and evolutionary theory
23. The Grants observed changes in beak size, but they didn't actually see what?
Evolutionary change
24. Define SCIENTIFIC THEORY: A scientific theory summarizes a hypothesis or
group of hypotheses that have been supported with repeated testing. If enough
evidence accumulates to support a hypothesis, it moves to the next step—known as
a theory—in the scientific method and becomes accepted as a valid explanation of
a phenomenon.