Chapter 17: Variation and Evolution – worksheet extended
Case 1
Human skin color varies widely and is influenced by both genes and environment (e.g., exposure to
sunlight).
Questions
1. State whether skin color shows continuous or discontinuous variation.
2. Explain why skin color shows a wide range of values.
3. Describe the role of polygenic inheritance in skin color.
4. Suggest how environmental factors can influence skin color.
Case 2
Cacti grow in deserts with very little water. They show several special features that help them survive.
Questions
5. Describe three adaptations of cacti to survive in deserts.
6. Explain how each adaptation helps the cactus survive.
7. Suggest why these adaptations would not be useful in a rainforest environment.
Case 3
Darwin observed finches on the Galápagos Islands. Each species had a different beak shape suited to its
food source.
Questions
8. Explain how beak shape is an example of adaptation.
9. Describe how natural selection could lead to the evolution of different beak shapes in finches.
10. Suggest what might happen if food sources change dramatically on the islands.
Case 4
Farmers breed wheat plants that produce high yields. Over time, these plants show reduced resistance to
certain diseases.
Questions
11. Explain how artificial selection is used in crops.
12. Suggest one advantage and one disadvantage of artificial selection in agriculture.
13. Compare artificial selection with natural selection.
Case 5
Part A: A mutation in the gene for hemoglobin causes sickle cell anemia.
Part B: Some bacteria become resistant to antibiotics after repeated exposure.
Part C: Fossils of horses show gradual changes in size and leg structure over millions of years.
Questions
14. Explain how a mutation can change the structure of hemoglobin.
15. Describe how antibiotic resistance develops in bacteria through natural selection.
16. Explain how fossils provide evidence for evolution.