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Animals Can Run Away, but Plants Must Stay

Responses to Herbivory

By Nicole D. Tunbridge, Carol Pollock, Joan Sharp

Animals Can Run Away, but Plants Must Stay


 

Abstract

In this PowerPoint-driven case study, students consider the many challenges faced by plants and discuss which of these might induce a morphological response. Examples of phenotypic variation within a plant species are presented and students discuss in small groups how to determine whether the observed variations have a genetic basis. The concept of a "common garden" experiment, in which plants are grown in a common environment and variation is measured, is elucidated and discussed. A specific example of phenotypic variation is introduced: Plectritis congesta from islands without herbivores (deer) are taller than the same species from islands with deer. An experiment with simulated herbivory is described and students are asked to predict results, assessing whether modification of pattern of growth is an induced response or a constitutive defense. A field experiment involving deer predation is introduced. The morphological response of Plectritis to predation is presented as an evolutionary tradeoff. The case is appropriate for introductory general biology (majors and non-majors), ecology, and plant biology courses and, with some modification, introductory evolution courses.

   

Date Posted

05/02/2018

Overview

Objectives

  • Explain how biotic and abiotic factors can act as agents of selection.
  • Distinguish between constitutive defenses and induced responses and explain the conditions under which each may be adaptive.
  • Explain how a common garden experiment can distinguish between genetic and environmental causes of phenotypic variation in plants.
  • Plan common garden and field experiments, and identify dependent and independent variables from these experiments.
  • Interpret data from common garden and field experiments.

Keywords

Natural selection; adaptation; evolution; evolutionary fitness; phenotypic variation; common garden experiment; experimental design; plant defenses; constitutive defenses; induced responses; herbivory; plasticity

  

Subject Headings

Biology (General)
Botany / Plant Science
Ecology
Evolutionary Biology
Genetics / Heredity
Science Education

EDUCATIONAL LEVEL

Undergraduate lower division

  

FORMAT

PDF, PowerPoint

   

TOPICAL AREAS

Scientific method

   

LANGUAGE

English

   

TYPE/METHODS

Clicker, Discussion, Interrupted

 

 

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