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Peter and Rosemary Grant's

pioneering work on the Galápagos Island finches has given us a unique insight into how   species evolve over generations. The film The Origin of Species: The Beak of the Finch illustrates that some traits may   enable an animal to find food or attract mates better than other individuals can. If beneficial traits like these have a genetic basis and can be passed on to future generations, we refer to them as adaptations, which are selected for by the environment through a process called natural selection. Beneficial traits increase an individual's fitness by allowing it to survive and ultimately produce more offspring than individuals without the traits. This can lead to evolution if, over time, these traits (and their associated genetic variants, or alleles) become more common in the population while unfavorable traits slowly disappear.


One crucial insight into how adaptation occurs came from the medium ground finch (Geospiza fortis). With its short, blunt beak, the medium ground finch is perfectly adapted to picking up seeds from the ground, although beak size varies slightly within medium ground finch populations. When food was plentiful and included different seed sizes, all ground finches were able to find food. However, when drought struck the small island of Daphne Major in 1977, the vegetation and the available seeds changed considerably, so that the finches now had to compete for food. When the smaller seeds disappeared, the finches had to turn to the much larger, spiny seeds that were hard to crack open. The smaller medium ground finches with slightly smaller beaks ran out of food. But finches that had slightly larger beaks could still forage on the much bigger, spiny seeds, which gave them a survival advantage.

This activity will demonstrate why a slight difference in beak size can significantly impact a bird's ability to survive. You will act as the finches and fight for survival by "eating" as many seeds as possible within the allotted time. You will use two different types of tools to represent different beak types to see which is best adapted to collect and "eat" food under different conditions. The activity exaggerates the differences in beak size to illustrate that a beak is like any other tool: You need the right tool for the right job.



Each group will use the following:

·          1 box

·          Two types of tools: regular tweezers and pliers (your two different "beaks")

·          Substrate  (astroturf)

·          Two types of seeds (rice, beans)

·          4 beakers for seed collection (2 for each tool)

·          Timer

·          Beakers and conical tubes for measuring



Form groups of three to four students. At any one time, two group members will act as finches, each equipped with a different tool, while the others will be observers.

Finches will try to collect as many seeds as possible with their tool under three different food conditions. There will be small and large seeds, but to feed on a large seed with a tough shell, large seeds have to be cracked open to get to the nutritious insides. So whenever a large seed is collected, crush it or it won't count!

Observers add the food to the environment, oversee and time the foraging trials, and count the "eaten" seeds.

Observers also have to make sure that large seeds, if present, are crushed and counted correctly.

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