Mechanisms of Evolution Worksheet
Patterns of Natural Selection Worksheet
PART 1: Vocabulary Review: Define the following terms:
1. Stabilizing Selection:
2. Directional Selection:
3. Disruptive Selection:
PART 2: Write the pattern of Natural Selection that matches the description below:
4. Human babies born smaller than average are likely to be less healthy and less likely to survive. Larger babies are likely to have difficulty being born. The larger or smaller weight babies have a disadvantage. Over time the average-sized babies become more common in the population.
5. Birds with bigger, thicker beaks can feed more easily on larger, harder seeds. A food shortage causes the supply of small and medium seeds to run low, leaving only larger seeds. Birds with bigger beaks are more successful than birds with medium or small beaks. Over time more birds with bigger beaks survive and reproduce.
6. The orange and black pattern of a Monarch butterfly serves as a warning to sharp-eyed birds that the Monarch is poisonous to eat and tastes bad. Individuals with the brightest color pattern are more likely to warn off birds and survive to reproduce than those with a dull or medium color pattern. Over time and many generations, the Monarch population became more brightly-colored.
7. In birds, feather color among males is more likely to attract a mate, but also more likely to attract a predator. Over time and many generations, the most successful males are those with medium colors, while males with very dull colors and males with very bright colors became increasingly rare.
8. A population of birds lives in an area where plants with medium sized seeds are wiped out by a fungal infection. Birds with unusually large or small beaks are more successful than those with medium sized beaks. Over time the population splits into two subgroups; one that eats small seeds and one that eats large seeds.
9. A population of Madagascar hissing cockroaches lives in a woodpile. The cockroaches are preyed on by small-headed lizards. Because of their small heads, the lizards are unable to eat the very largest adult cockroaches, and instead prey upon small and medium sized adults. What type of selection do the lizards impose on the roaches?
10. Starlings produce an average of five eggs in each clutch. If there are more than five, the parents cannot adequately feed the young. If there are fewer than five, predators may destroy the entire clutch.
PART 3: Natural Selection Diagram
11. How is the population of mice different in figure 3 than in figure 1?
12. Which mice in this population have the advantage? Explain Why.
13. What type of selection is occurring? Use a graph to illustrate your answer.
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