Student Exploration: Rainfall and Bird Beaks
Vocabulary: adaptation, beak depth, directional selection, drought, evolution, natural selection,
range, stabilizing selection
Prior Knowledge Questions (Do these BEFORE us
...
Student Exploration: Rainfall and Bird Beaks
Vocabulary: adaptation, beak depth, directional selection, drought, evolution, natural selection,
range, stabilizing selection
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
During the voyage of the HMS Beagle (1831–1836), the young Charles Darwin collected several
species of finches from the Galápagos Islands. Two of Darwin’s finches are shown below.
1. Which species do you think is best adapted to a diet of small,
delicate seeds? Explain why you think so.
____The Geospiza fortis because of its smaller
beak.___________________________________________________
_______________________________________________________
2. Which species do you think is best adapted to a diet of large,
tough-to-crack seeds? Explain.
_The Geospiza magnirostris because of its larger
beak.___________________________________________________
___
_______________________________________________________
Gizmo Warm-up
Darwin’s finches are one of many types of animals on the
Galápagos Islands that have unique adaptations, or traits that
help an organism survive in its environment. The Rainfall and
Bird Beaks Gizmo™ allows you to explore how rainfall influences
the range of beak shapes found in a single finch species.
1. The beak depth of a finch is the distance from the top of the beak to the bottom, as
shown.
A. What is the current average beak depth in the Gizmo?
___9.77_____________________
B. Select the BAR CHART tab. Do all the finches have the same beak depth? ____
no___2. Click Play ( ) and let the simulation play for five years with average rainfall (5
inches/yr). Select the GRAPH tab and view the Finches vs time and Beak depth vs time
graphs.
A. How does the finch population change? ___It lessens by
600._______________________________
B. Does the beak depth change significantly? ___It decreases by .7
mm.__________________________
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