Principal Ecological Question Addressed

What is the interplay between competition, predator-prey interactions, and sequential evolution of prey defenses and predator responses?

What Happens

In this game, students play the roles of different insect predators (represented by foraging appendages constructed from plastic utensils (see Figure 1, drawing of appendages) as they capture suitable prey (i.e., candy). After each round, remaining prey reproduce and predators suffer differential mortality. In some rounds, a particular prey species is designated as poisonous. Student predators learn to recognize dangerous prey by getting ill after feeding. In future rounds, predators may evolve to circumvent certain prey defenses. For each generation, students follow population dynamics of the predators and prey. Students answer questions based on the outcomes and they discuss concepts, including predator-prey interactions, evolution of specialist predators, and extinction. This lab is a fun way to demonstrate natural selection and ecological tradeoffs.

Lab Objectives

Through participating in the exercise, students will learn that:

• Insect predators use three general forms of appendages for attacking prey,
• Prey respond to predation pressure in a variety of ways, including evolving physiological defenses,
• As prey become poisonous, their numbers increase, leading to an advantage for predators to that overcome the defenses,
• Through time, a stable community supporting a diversity of predators and prey can develop.

Specifically, at the end of the lesson, students will be able to:

1. Discuss insect predation methods and tradeoffs associated with prey defenses,
2. Predict how a community will change when driven by predator-prey relationships,
3. Recognize the importance of generalist predators in responding to potential prey populations.

Equipment/Logistics Required

For a class of 24 students working independently:

• Paper cups for stomachs
• Feeding appendages consisting of pairs of plastic forks, knives, or spoons held together as forceps using rubber bands and a paper spacer (see Figure 1). Fifteen of each is typically more than enough.
• Prey items — three types of beans, candy (Skittles, M&Ms, and candy corn), plastic insects, buttons, etc., can be used. Also, Goldfish Crackers of three varieties can be substituted.
• Three balances and containers for weighing prey items
• A computer with Microsoft Excel
• 24 copies of handouts, including worksheet, blank graphs, figure of different insect predators
• Optional habitat structures that can easily be made from carpet samples taped together. If conducted outside, a grassy area can be used.
• Optional — pinned specimens of different insect predators that are simulated in this exercise (i.e., raptorial forelegs predators such as praying mantises, mandibles such as used by ground beetles, all legs such as used by dragonflies and damselflies)

Summary of What is Due

At a minimum, students complete worksheets and answer questions at the end of the exercise. Students also can be instructed to write a report about their findings.

Keyword Descriptors

Ecological Topic Keywords:

community ecology, predator-prey relations, predation, adaptation

Science Methodological Skills Developed:

theoretical thinking (reflection on practice), identify biotic interactions, use of graphing programs, use of spreadsheets

Pedagogical Methods Keywords:

active learning, guided inquiry, game to teach ecology, role-playing