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You are reading an older version of this FlexBook® textbook: Human Biology Ecology Teacher's Guide Go to the latest version.

Key Idea

  • All resources (except energy, which tends to diffuse) are cycled in undisturbed ecosystems.

Overview

The last section concentrated on the interdependence of organisms in a food web. This section introduces the idea of the cycling of resources, such as water and oxygen, in the natural environment. Students identify the major components of the water cycle-evaporation, condensation, precipitation, and transpiration. Students should recognize that water is constantly reused. This is a very important concept for them to appreciate as they examine the different parts of the water cycle because the water we have now-dirty or clean-is all the water we will ever have. Students investigate other important cycles in the natural environment, such as the carbon, nitrogen, and phosphorus cycles.

Objectives

Students:

\checkmark identify the major components of the water cycle-evaporation, condensation, precipitation, and transpiration.

\checkmark explain how water cycles on Earth.

\checkmark recognize that water is constantly reused.

\checkmark evaluate the effects of different environmental conditions on the rate of evaporation and/or rate of condensation.

\checkmark identify the carbon, nitrogen, and phosphorus cycles.

Vocabulary

carbonification, cycle, evaporate, fossil fuels, greenhouse gas, groundwater, global warming, open water, precipitation

Student Materials

Activity 4-1: A Day in the Life of a Water Molecule

  • None

Teacher Materials

Activity 4-1: A Day in the Life of a Water Molecule

  • Resource

Advance Preparation

See Activity 4-1 in the Student Edition

Activity 4-1: A Day in the Life of a Water Molecule

  • You may want to make an audiotape of someone reading the story. If you choose not to audiotape the reading, you can read the story to the class.

Enrichment Activities

Enrichment 4-1: What Goes Up Must Come Down-Water Cycle Simulation

Students construct a model of water moving through the water cycle.

Ask the students to collect, or collect yourself, clear plastic containers with lids such as those used for take-out foods.

Enrichment 4-2: Water Underground

Students examine the portion of the water cycle that occurs beneath the surface of the earth by constructing a model of the water cycle that demonstrates groundwater movement and collection.

  • Collect empty, clear plastic 2-liter bottles.
  • Obtain modeling or potter's clay, potting soil, and gravel.
  • An excellent reference for working with plastic bottles is Bottle Biology, by P. H. Williams, published by Kendall-Hunt Publishing Company, 1993.

Background Information

Energy and the Carbon Cycle Energy is contained in the chemical bonds holding the carbon, hydrogen, and oxygen atoms in a sugar molecule together. Light energy from the sun was changed into chemical energy stored in the bonds. When sugar is broken down in a cell, the chemical bonds are broken releasing the stored energy and converting it into a form (ATP) that is used by the cell.

One fun demonstration that you might want to try is dropping a bit of concentrated sulfuric acid onto a sugar cube. It will turn black revealing the carbon in a more recognizable form. Alternatively, you can burn a sugar cube to reveal the black carbon in the ash.

Nitrogen and Phosphorus Cycles Plants need nitrogen to make amino acids, which are the building blocks for proteins. Proteins are essential for life because they are needed for cellular growth, repair, and replacement. Proteins are also enzymes that facilitate all of the chemical reactions that occur in cells. Phosphorus is a micronutrient that is required for the formation of ATP, nucleic acids, phospholipids, and several coenzymes.

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