Unit C: Earth's Surface

How does building a dam affect plants and animals?

1. Get Set to Explore


  • environment: All the living and nonliving things that surround an organism.
  • habitat: A place where an organism lives.
  • oxygen: A gas in air and in water that most living things need to survive.

Building Background

  • Review what dams are, showing students pictures, if available. Guide students to realize that a dam is a human-made structure, not a natural landform. Point out that dams are built across the bed of a river. This floods the land behind the dam.
  • Define the vocabulary words for the class. You can give students context for the use of these words in this simulation with these sentences: Building a dam changes the environment in the area near the dam. Some habitats in or near the river may be destroyed; new habitats may be created. Dams slow the flow of rivers, which can lower the amount of oxygen in the water. Go over the meaning of each sentence with the class.
  • Ask students the Discover! question. Students can tell how they think a dam will affect plants and animals that live in and near the river. Write their answers on the board to refer to later.

2. Guide the Exploration

  • Direct students to launch the Discover! Simulation. Students can work in pairs on this simulation. They should listen closely to the introductory information.
  • Point out that the simulation has two parts. In the first part, students compare pictures of a river before and after a dam was built across it. Students should spend time moving their cursor over different parts of the pictures and clicking them to learn about the plants and animals and to find out what happened to them once the dam was built.
  • After students have compared the two pictures, they should proceed to the second part of the simulation. In this part, they note how the dam changed the natural environment by matching causes of the changes and their effects. Explain that students should drag the causes, one at a time, to the Cause column. They should drag the effect statement to the Effect column, right across from the cause it goes with. Tell students that when they have correctly matched all of the statements, they will be done with the second part of the simulation.

3. Review/Assess

  • Discuss Step 3's Wrap-up text with the class. Let students refer to the list they made before they did the simulation and add to it or revise it based on what they learned.
  • Pose the Extension questions: Which plants and animals were harmed by the dam? Which ones benefited from it? Students should return to the simulation to answer the questions. Have them take notes in a two-column chart. Then let the class compare ideas. Make a class chart that incorporates this information:
    • Organisms that were harmed by the dam include the cottonwood trees, deer, veeries, salmon, and pebblesnails.
    • Those that benefit include ducks, crops that need water from the lake behind the dam, and people who farm and use electricity generated from the dam.

If time permits, present students with the following questions:

  • Critical Thinking Evaluate Based on what you've learned from doing this simulation, do you think building a dam across a river is a good idea or not? Explain. Answer: Some students may say yes, because building dams aids farmers, prevents fossil fuel pollution with the generation of electricity from a renewable resource, and aids water birds, such as ducks. Other students may say no, because building dams destroys habitats and reduces populations of many animals and plants that used to live in or near the river.
  • Inquiry Skill Predict Pebblesnails are not the only river-dwelling animals that need water with high levels of oxygen. Certain kinds of fish, including trout, also need high levels of oxygen in the water to survive. What might happen to trout populations in a river that is upstream from a dam? Answer: The trout population would be likely to decrease.

4. Reaching All Learners


Encourage interested students to build models of different types of rivers: narrow, fast-flowing rivers; wide, slow-moving rivers; rivers with more than one dam. They should show how dams affect each of these different rivers. A protected sandbox, large dishpans of sand or gravel, or a water table might be good places for students to make their models. Let students show and explain their models to the class.