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I'm Looking Over a White-Striped Clover

A Natural Selection Case

Co Authors:

Susan Evarts
Minnesota Zoological Gardens

Alison Krufka
Department of Biological Sciences
Rowan University

Chester Wilson
Department of Biology
University of St. Thomas


This case is an exploration of the process of natural selection using white clover (Trifolium repens) as an example. In general, two forms of white clover can be found around the world in various habitats. One type is able to produce cyanide in its leaves, while the other is not. This variation within the clover species, along with the fact that cyanide production is paired with the production of a white stripe on the leaf, is used to teach the process of evolution through natural selection. Students use the scientific method to explore these concepts. As an introduction to evolutionary concepts in biology, the case would be appropriate for both high school and college biology courses.

  • Understand the process of natural selection and the importance of environment-specific adaptations.
  • Acquire an understanding of the concepts of variation, natural selection, fitness, selection pressure, evolution, and adaptation.
  • Using these concepts, describe the frequency of the two types of white clover.
  • Be able to predict the distribution of cyanogenic clover in given microhabitats.
  • Gain experience with the scientific method and be able to propose hypotheses and justifications to explain the frequency of the two types of white clover.
  • Design experiments to test hypotheses and describe data that would support these hypotheses.
  • Understand and synthesize information from figures and tables.
Keywords: Natural selection; variation; adaptation; evolution; white clover; trifolium repens; cyanide; cyanogenesis; experimental design
Topical Area: Scientific method
Educational Level: High school, Undergraduate lower division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Biology (General)   Evolutionary Biology   Botany / Plant Science  
Date Posted: 11/28/06
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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Wonderful case study. I incorporate an intro to the nitrogen cycle and a review of cellular respiration/metabolic poisons and genetics. The white clover project lab activity from Washington University goes well with the activity as well:

Beth Adler
Oak Ridge High Shcool
Oak Ridge, TN
Fantastic case study! I teach A.P. Environmental Science and I cover this during my evolution section. It is also gives me an opportunity to review genetics and a little preview of toxicology that I cover later in the course. Wonderful!

Renee Diamond
Brick Township High School
Brick, NJ

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