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Not Just A Bag Of Beans

By Myrtle Brijbasi


  • Class Activity
  • Laboratory

Type of Activity:

  • Hands-on
  • Simulation
  • Authentic assessment
  • Group/cooperative learning
  • Reinforcement

Target Audience:

  • Life Science/Biology
  • Advanced/AP Biology
  • Environmental Studies
  • Genetics, Biotechnology
  • Special Needs (gifted)
  • Special Education
  • Other Special Needs (Big print & audiotaped instructions, larger beans eg. lima beans, or large, bright colored, or rough edged, paper cut-outs for visually impaired; peer-tutoring/teacher assistant for other handicaps; low tables for wheelchair students.)


At the end of this activity students will be able to answer the following conceptual questions in addition to more specific questions based on their data.
  • Does variation exist in a given population? If so, what causes it?
  • Does natural selection occur in a population and what is the most common type?
  • What is the connection between natural selection and adaptation?
  • How does this laboratory activity explain evolution and population genetics?

Background Information:

Notes to the teacher:
  • Students are required to be familiar with the following Biological concepts/topics - DNA structure, mutation, population genetics (gene pool, allele frequency), natural selection, evolution, adaptation, genetic variation.
  • Students are expected to have the following mathematical skills - use a metric rule, construct and interpret graphs, analyze data.
  • Students should be able to follow instructions, collect and analyze data.

Preparation: 10 - 15 minutes to assemble and lay out the materials for the class.

Class Time: 2 - 45 minute periods, or 1 - double period


DNA, the genetic blueprint of living organisms, plays an essential role in the continuity of life. Therefore, the structure and function of DNA must be explained to students as simply as possible, using the most appealing methodologies.

DNA is often described by scientists as "the chemical language of life" (Monsanto, 1990). If the language were "edited" or changed, then the message it delivers to the cell might also be changed. The result of such changes is variation in the population - an integral part of the evolutionary process. Evolution is the genetic change in a population of organisms over time, produced by the integrating agencies of natural selection and variation (Beck, Liems, Simpson, 1991).

In this laboratory activity, students will (1) determine the types of natural selection, and (2) demonstrate that variation exists in a population, using beans.


  • 4 pounds of kidney beans
  • 1 - wide mouth container, or 1 - 1000 mL beaker
  • 15 or 30 cm metric ruler
  • 5 - 50 mL beakers or bathroom dixie cups
  • Lab notebook, pen, pencil, colored pencils, graph paper data charts


  • Pour all of the beans into the 1000 mL beaker or wide mouth container.

  • One student from each group will take a 50 mL beaker or a bathroom dixie cup and fill it with beans from the wide mouth container or 1000 mL beaker (whichever used), and take back to the group.

  • Count out any 50 - 100 beans and measure the length of each one in millimeters (mm), and record the measurements of Data Table 1.


  • Complete the Summary Data Table.

Data Table 1: Bean Size

Summary Data Table:

Bean size:
Bean #'s:

Analysis of Data:

  • Graph and analyze the data. Determine the mean, median, mode, and range.
  • Determine/identify the type(s) of natural selection that is occurring in the population - stabilizing, directional, or disruptive.
  • Compare your graph with another group, and put that information on your graph also.

Answer the Following Questions:

  1. From your population of beans explain the terms selection and fitness. Which traits were found? Is this biotechnology in nature?

  2. Translate this information in terms of a farmer who plants kidney beans in large quantities for commercial purposes.


  1. Explain how this activity demonstrates variation in a population.

  2. Suggest any or all environmental factors that can influence variation in this population of beans.

  3. Explain your results in terms of gene/allele frequency for length of bean in this population. Relate to Hardy-Weinberg Principle.

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