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Journal Entry:

Finch beak depth was measured before and after a severe drought in 1977. The averaged results are shown in Figure 1. After the drought, there were fewer seeds available for the finches to eat and the seeds that did remain were larger and harder to crack open. Researchers claim that when large, hard seeds are the predominate food source, the average beak depth of these finches tends to increase in subsequent generations.

Using the evidence provided, which of the following best justifies the researchers' claim?

A) Finch beak depth increased after the drought because the overall numbers of finches decreased, reducing competition for resources.

B) Finch beak depth increased as a consequence of selective pressure after the drought because the remaining seeds were larger and harder.

C) Finch beak depth increased after the drought due to intraspecific competition since finches with deeper beaks attract more mates.

D) Finch beak depth increased after the drought due to increased predation since finches with deeper beaks can fight off predators more effectively.

Learning Intentions

• You can describe how genetic drift occurs in small populations.

• You can analyze how the reduction of genetic variation within a given population can increase the differences between populations of the same species.

• You can describe how different factors within a population can influence evolution of a population through a population genetics computer simulation.

• You can describe the founder effect and bottleneck effect and their influence on population genetics.

Content Standards being covered:

Topics:
EVO-1.K  Describe the conditions under which allele and genotype frequencies will change in populations.
EVO-1.L Explain the impacts on the population if any of the conditions of Hardy-Weinberg are not met.
SYI-3.D Explain how the genetic diversity of a species or population affects its ability to withstand environmental pressures.

Science Practices:
3.B State the null or alternative hypotheses, or predict the results of an experiment.
5.A.a  Perform mathematical calculations, including mathematical equations in the curriculum.
6.C Provide reasoning to justify a claim by connecting evidence to biological theories.

Habits of Mind/Life skills being covered:

Applying past knowledge to current situations