Key Vocabulary
What are variations?
Slight differences in inherited traits among individuals in a population.
What is the name of the island where the finches were studied?
The Galápagos Islands.
Why did no new seeds form on the island?
Because it did not rain.
How did the drought act as a selective pressure?
It limited food to hard seeds, so only birds with large beaks could survive.
What are mutations?
Changes in DNA that can lead to changes in traits.
What did the finches mainly feed on in 1976?
Small, soft seeds.
Why did many finches die during the drought?
Because they could not eat the large, hard seeds.
Why was beak size important for survival?
Because it determined which birds could eat the available food.
What are examples of variations?
Differences in traits such as feather color or nest-building skills.
What environmental change happened the following year?
A drought (no rain).
Why did some finches survive?
Because they had larger beaks that could crack hard seeds.
Explain how survival affected the next generation of finches.
Birds with large beaks survived and their offspring also had larger beaks.
What is a population?
A group of the same species living in one area.
What trait changed in the finch population?
Beak size.
What happened to the average beak size by 1978?
It increased.
Why did the population’s average beak size increase instead of decrease?
Because more large-beaked birds survived and reproduced.
What is average beak size?
The trait that increased in the finch population over two years.
After the drought, what did that trait change into?
Larger (bigger) beaks.
Why did the finch population change in two years?
Birds with larger beaks survived and became more common.
What would most likely happen if another long drought occurred?
Large beaks would continue to be common in the population.