The Private Life of Plants: Plant Politics:
Teacher’s Guide
Grade Level: 6-8
Curriculum Focus: Life Science
Lesson Duration: Two or three class periods
Program Description
Plants may be the ultimate opportunists, eagerly capitalizing on the misfortune of others. Visit the
hurricane-torn woodlands of Great Britain and the fire-scorched Australian bush to see how some
plants thrive on disaster and can even engineer catastrophes to meet their own needs.
Onscreen Questions
Part I—Before watching the video
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Many plants have special characteristics that allow them to live in different habitats. How do
you think they survive natural disasters?
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How can some plants survive domination by other plants?
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As you watch, note the survival mechanisms of different plants.
Part I—After watching the video
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Explain how plants respond to sunlight. Compare plants that grow in shade or thick forests to
plants that grow in harsh sunlight.
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How have plants where you live adapted to either one of these conditions?
Part II—Before watching the video
•
Forests contain a variety of plants that grow at different levels. What characteristics do you
think plants need to live in the forest canopy?
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How can plants survive growing on the forest floor?
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While you watch the program, pay attention to the special characteristics of plants that allow
them to live at different levels.
Part II—After watching the video
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Forest fires can be very destructive, but they can also provide benefits to plant life. Discuss the
advantages and disadvantages of forest fires.
•
How do you think the U.S. Forest Service should manage forest fires? Be sure to support your
answer.
The Private Life of Plants: Living Together and It’s a Jungle Out There: Teacher’s Guide
2
Lesson Plan
Student Objectives
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Complete a scientific experiment testing a single variable.
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Understand how plants respond to different environmental conditions.
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Identify how geotropism affects plants.
Materials
For the class
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Dissecting microscope
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Computers with Internet access (optional but very helpful)
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Reference materials: books and encyclopedias
For groups of three students
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One petri dish
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Four soaked corn seeds
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One piece of filter paper
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One graduated cylinder
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Water (If there is no sink in the classroom, bring water to class in a bucket.)
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Cotton
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Cellophane tape
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Grease pencil
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Scissors
Note: Prepare for the experiment by soaking four corn seeds per group of three students at least 24 hours
before you do this activity.
Procedures
1. Discuss with the class this interesting characteristic: Plants can change their growth in response
to their environment. These changes are called tropisms. Plants can exhibit the following kinds
of tropism:
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Phototropism—the way a plant grows or bends in response to light
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Geotropism—the way a plant grows or bends in response to gravity
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Hydrotropism—the way a plant grows or bends in response to water
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Thigmotropism—the way a plant grows or bends in response to touch
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The Private Life of Plants: Living Together and It’s a Jungle Out There: Teacher’s Guide
3
2. Explain that tropic responses can be positive or negative. In a positive response a plant moves
in the direction of the stimulus; in a negative response a plant moves away from the stimulus.
For example, roots respond positively to gravity by growing down in soil. A tree trunk and
branches respond negatively to gravity by growing toward the sky. You may also want to point
out that the trunk and branches respond positively to light.
3. Divide students into groups of three. Tell them that they are going to perform an experiment to
test geotropism, a root's response to gravity. Have students follow the steps below:
(1.) Take four well-soaked corn seeds. Place them flat in a petri dish with the seeds'
pointed ends facing inward. Think of them as numbers on a clock: 12, 3, 6, and 9.
(2.) Cut a piece of filter paper so that it fits snugly inside the petri dish. Place the filter
paper over the seeds. (Take care not to disturb the positions of the seeds.)
(3.) Without moving the petri dish, pour 15 milliliters of tap water on the filter paper.
Then place enough cotton over the filter paper so that with the petri dish cover in
place, the paper and seeds will not move. The cotton should absorb excess water.
(4.) Tape shut the petri dish cover. Turn the petri dish over. You should be able to see the
seeds through the bottom; they should have remained in their original positions.
(5.) With a grease pencil, write the name of your group on the side of the petri dish.
(6.) Tape the petri dish containing seeds to the wall of a cupboard, with the bottom of the
dish (showing the seeds) facing out. Close the cupboard door so no light can reach
the seeds for the next few days. (The dishes are kept in a dark cupboard so that the
only variable tested is a response to gravity—not a response to light. Students should
find that the roots grow downward, illustrating the effects of geotropism.)
4. After students have finished setting up and storing their petri dishes, have each student predict
the results of the experiment by drawing how they think the roots will grow from each of the
four seeds. Have students write their predictions on a sheet of paper labeled “Geotropism
Data.”
5. Students should make an observation and record the data on their sheets for three days. Have
them write the date and draw how the roots from each seed are growing. As students are
collecting data, have them look in reference books and on the Internet to learn more about
tropisms. Have them fill out a data table like the one below.
Observations
Day
How the Roots Grew
Sketch of Petri Dish
Day 1
Date:
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The Private Life of Plants: Living Together and It’s a Jungle Out There: Teacher’s Guide
Day
How the Roots Grew
4
Sketch of Petri Dish
Day 2
Date:
Day 3
Date:
6. Have students write a short paragraph summarizing the results of the experiment on their data
sheets. Did the root growth match the predicted sketch? What do these results show about how
roots grow?
Assessment
Use the following three-point rubric to evaluate students’ work during this lesson.
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3 points: Students were able to work successfully in their groups to set up the experiment
and develop a hypothesis about the way the roots will grow; students could keep complete
records of their observations, including sketches, and could write a clear, concise summary
of the experiment.
•
2 points: Students worked somewhat successfully in their groups to set up the experiment
and develop a hypothesis about the way the roots will grow; students were able to record
most of their observations, including some sketches, and wrote a short paragraph
summarizing the experiment.
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1 point: Students worked in their groups to set up the experiment and develop a hypothesis
about how the roots will grow; students were able to make some observations, but they did
not include sketches with each observation; students wrote some ideas summarizing the
experiment.
Vocabulary
geotropism (gee AH truh pizm)
Definition: Growing or bending in response to gravity
Context: The effect of geotropism on plants is tremendous, causing both the roots and the stems
and leaves to grow in a particular way.
gravity
Definition: Force drawing objects to the center of Earth
Context: Gravity causes the plant roots to grow down so that the plant is anchored in the ground
and has enough water to grow and thrive.
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The Private Life of Plants: Living Together and It’s a Jungle Out There: Teacher’s Guide
5
hydrotropism (hi DRAW truh pizm)
Definition: Growing or bending in response to water
Context: One of the reasons that roots grow down is in search of water, exhibiting most plants'
tendency toward positive hydrotropism.
photoperiodism (fo toe PEER ee uh dizm)
Definition: The response of an organism to naturally occurring changes in light during a 24hour period
Context: Sunflowers are known for their photoperiodism, or their ability to open and close in
response to the changing position of the sun throughout the day.
phototropism (fo TAH truh pizm)
Definition: Growing or bending toward light
Context: The stems and leaves of a geranium plant growing on the windowsill always turn
toward the light, an example of phototropism.
Academic Standards
National Academy of Sciences
The National Science Education Standards provide guidelines for teaching science as well as a
coherent vision of what it means to be scientifically literate for students in grades K-12. To view the
standards, visit http://books.nap.edu.
This lesson plan addresses the following science standards:
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Life Science: Regulation and behavior
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Science as Inquiry: Abilities necessary to do scientific inquiry
Mid-continent Research for Education and Learning (McREL)
McREL's Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education
addresses 14 content areas. To view the standards and benchmarks, visit link:
http://www.mcrel.org/compendium/browse.asp
This lesson plan addresses the following national standards:
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Science—Life Sciences: Understands relationships among organisms and their physical
environment; Nature of Science: Understands the nature of scientific inquiry
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Language Arts—Writing: Uses the general skills and strategies of the writing process,
Gathers and uses information for research purposes
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The Private Life of Plants: Living Together and It’s a Jungle Out There: Teacher’s Guide
6
Support Materials
Develop custom worksheets, educational puzzles, online quizzes, and more with the free teaching tools
offered on the Discoveryschool.com Web site. Create and print support materials, or save them to a
Custom Classroom account for future use. To learn more, visit
•
http://school.discovery.com/teachingtools/teachingtools.html
Published by Discovery Education. © 2005. All rights reserved.