PART 5: Summary Activities 17. Construct an explanation based on the evidence. Write an explanation for how the process of evolution
primarily results from competition for limited resources (such as water, shelter, and mates) and differences
in the abilities of individuals in a population to survive and reproduce in that environment. Write
your
explanation in a notebook or on a piece of paper using the evidence in Figures 1-4 and information from the
HHMI film
Figure 1. Phylogentic Tree Showing
Relationships among Galápagos
Finches.
Small ground
Medium ground.
Large ground
Mainland het
2-3
Cactus
Large cactus
Sharp-beaked ground.
Small tree
Large tree
Medium tree
Mangrove
Woodpecker
Vegetarian
Warbler
50
50
1976 Parents
1976 Parents
40
Number of Birds
Number of Birds
20
20
10
10
0
0
73 78 8.3 8.8 93 98 103 108 11.3
Beak Depth (mm)
73 7.8 8.3 8.8 9.3 9.8 10.3 10.8 11.3
Beak Depth (mm)
Figure 3. Beak Sizes of Medium Ground Finches Living on
Daphne Major In 1976 (gray bars) and Finches That
Survived the Drought of 1977 (black bars).
Figure 2. Beak Sizes of a Sample of 200 Medium
Ground Finches Living on Daphne Major in 1976.
40
1978 Offspring
Number of Birds
ulli
10
0
7.3 7.8 8.3 8.8 9.3 9.8 10.3 10.8 113
Beak Depth (mm)
Figure 4. Beak Sizes of Offspring of Medium Ground Finches
That Survived the Drought of 1977.