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Population Sampling Lab

You can’t count every plant in a meadow or every fish in a pond. In this lab, students estimate a meadow’s plants by counting a few squares, then estimate a pond’s fish with mark and recapture. Then they test what goes wrong when the method’s assumptions are broken. It runs in the browser on any device, with no login and no equipment needed, and it works in English and Spanish.

What Students Do

1. Count the Plants. Count the plants in a few squares of a 100-square meadow, estimate the whole meadow, and check how close you got. Compare squares you choose yourself with squares the computer picks at random, using 3, 10 and 20 squares.
2. Count the Fish. Use mark and recapture: catch fish, tag them, release them, and catch a second batch. Estimate = M × C ÷ R. Compare 5 trials with small catches (20 fish) and 5 trials with large catches (40 fish).
3. When Counting Goes Wrong. Predict first, then test what happens to the estimate when tags fall off or when tagged fish dodge the net.

Worksheet and Answer Key

Nothing in the lab is saved, so students record their numbers and answers on the worksheet. It has a data table for each part, a screenshot beside each step, and questions 1A to 3D. The answer key has the exact numbers for the seed link below, plus model answers.

• Population Sampling Lab Worksheet (PDF)
• Population Sampling Lab Answer Key (PDF)

Use the Seed Link With the Worksheet

Give students this link: https://activities.zornscience.org/population-sampling-lab/?seed=517

The ?seed=517 part makes every student see the same meadow and the same pond. The Random button and every fish trial then give the same results, so the numbers in the answer key match what students see. Without the seed, the lab still works, but each student gets different numbers. The ideas in the model answers still apply.

Related Lesson

This lab goes with the Biology lesson Population Sampling in Unit 2: Populations.

Looking for more simulations? See all of the Biology Virtual Labs.