Lesson Plan

Web of Life (Teacher's Guide/Ecology)

Clarks Nutcracker on pine tree

The Clarks Nutcracker consumes and stores pine nuts and in turn helps grow trees in new locations.

Doug Owen

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Grade Level:
Third Grade
Subject:
Biology: Animals, Biology: Plants, Ecology, Environment
Duration:
1 hour
Group Size:
Up to 36
Setting:
classroom
National/State Standards:
Nature of Science, Biology:
3.2

Overview

Students learn about the complexity of life and interrelationships between living things by constructing a Craters food web.

Objective(s)

  • Students will be able to describe several relationships between living things at Craters.
  • Students will be able to trace the flow of energy through a food web.

Background

John Muir said, "When we try to pick anything out by itself, we find it hitched to everything else in the universe." For example, lichens accelerate the erosion of rock and tree trunks on which they grow, enriching nearby soil and improving growing conditions for syringa. Syringa creates shade and further enriches the soil when it dies and is decomposed by wind-dispersed fungi and bacteria. A host of insects colonize the crevice where the syringa grows. A spider eats the insects. A Clark's nutcracker hides a limber pine nut in the cool syringa crevice but is later caught by a Cooper's hawk. The pine nut germinates and finds the crevice to its liking and begins to grow, owing its future to all that came before it.

The story of life is about interrelationships, something of which we are largely ignorant. Our lack of ecological knowledge towers over what little we know of nature's ways. For example, the first step in understanding life is identifying the species and we don't know how many there are-not even to the nearest order of magnitude. The number could be could 10 or 100 million.

We do know that nothing lives in isolation. However, we often act as though life on Earth were a massive tool box, with many unnecessary minor nuts and bolts. In North America we once used the wonder pesticide DDT, but were ignorant of its effect on the rest of the food chain, where it caused egg shell thinning in predatory birds and tainted mothers' milk. Today, third world countries use DDT widely. How will long-term use of this and other pesticides affect the global environment? We condone the liquidation of ancient forests around the world by doing little to stop it. Is it mere poetry to refer to them as the lungs of the world and a treasure trove of biodiversity, or will their loss have catastrophic effects on Earth? How did the species that become extinct every day around the world fit into their ecosystem? Will their loss have far-reaching ecological effects or will it simply be an aesthetic loss? We don't know the answers to these questions - perhaps we can't know them, until it's too late.

To get a grasp of the complex interactions between living things, we can start by looking at a simple linear food chain: sun, dandelion, rabbit, and hawk. Sunlight is converted into chemical energy by green plants. Part of that energy is captured by herbivorous insects and vertebrates when they eat the plant. Carnivores then eat herbivores. In reality, however, the flow of energy through an ecosystem is more like a web. Species share energy back and forth in subtle ways. If we consider other relationships (i.e., plants that provide cover and nesting habitat to animals; insects, birds, and bats that pollinate flowers; rodents that disperse seeds; animals that require shade created by plants; and so on), our web approaches a symbol of what nature is really like.

See "Additional Resources" for an introduction to the ecology of Craters of the Moon.

Materials

  • Ball of string 300-400 feet long
  • Enclosed Craters species cards

Procedure

Additional Resources

Ecology of Craters of the Moon

Vocabulary

biodiversity
ecosystem
carnivore
herbivore
life web