Science 7–10 · Year 10

Beaks as tools: selective advantage in a changing environment

Science understanding: Biological sciences

Practical, model not builtLow risk

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The idea

Small differences in a structure change how much food an individual can gather, and when food changes the trait that gathers more becomes more common in later generations.

What you need

A box with a substrate that hides small seeds better than large ones (play sand or artificial turf, as the HHMI Beaks as Tools educator materials suggest)
Small seeds (rice) and large seeds (kidney beans): 36 g of rice with 120 g of beans for the mixed condition, 60 g of beans alone and 18 g of rice alone, the quantities in the HHMI student handout
Tweezers (small beak) and pliers (large beak), one of each per group
Paper cups as stomachs, a stopwatch, a results table

How to do it

One learner takes the tweezers and one the pliers. With both seed types in the box, each collects seeds into their cup for 30 seconds; a small seed counts when picked up, a large seed counts only when it is picked up and crushed, as the HHMI activity rules.
Count rice and beans collected by each beak; run at least four trials and take means.
Model the 1977 drought: only large seeds (beans) in the box. Repeat the 30 second trials.
Model the conditions after 1983: only small seeds (rice) in the box. Repeat.
For each condition, decide which beak gathered more food and by how much.
Feed the survival advantage into the population model below and run ten generations.

What you should see

With both seed types the pliers take mostly beans and the tweezers mostly rice. When only beans remain the pliers are expected to gather more, because the tweezers struggle to crush large seeds; when only rice remains the tweezers are expected to gather more, because they reach between the substrate. The HHMI educator notes explain that in the 1977 drought small seeds became scarce and finches with large beaks were more likely to survive, which increased the average beak size. The learner knows it worked when the repeats agree on which beak wins in each condition and the winner changes between the beans-only and rice-only conditions.

What changes

What you change: Seed types available (both, beans only, rice only)
What you measure: Seeds eaten per 30 seconds by each beak type
What you keep the same: Time (30 s)
Box and substrate
Seed quantities per condition
Rule for counting a seed as eaten
Same collectors

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Individuals adapt their beaks during their lifetime.
Selection works toward a goal or a perfect beak.
The less fit type disappears in one generation.

Safety card

Low riskLearners carry it out

Hazards

Pliers pinching fingers
Dust from the substrate
Crushed bean fragments

Controls

Seeds only in the pliers; no throwing; crushed beans binned, not reused; dust settled with a damp cloth

Note

No hazardous chemicals; record a RiskAssess risk assessment for the activity as school procedure requires.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC5-GEV-01 SC5-WS-04 SC5-WS-05 SC5-WS-06
Australian Curriculum v9AC9S10U02AC9S10I02AC9S10I04AC9S10I05

Sources

The pages the author read to write this activity.

All Concept Studio activities