Download PLANET EARTH: Deserts

PLANET EARTH: Deserts
Teacher’s Guide
Grade Level: 9-12 Running Time: 42 minutes
Program Description
Voyage to the world’s harshest environments and learn how life manages to keep a
precarious hold in every desert. From the frigid expanses of Mongolia to the blistering
craters of California’s Death Valley, the program examines the incredible physical
and behavioral adaptations that allow creatures to survive in unimaginable conditions
governed by sand storms, droughts, flash floods, and extreme temperatures. Searching
for water, shelter, and other resources dominates the lives of plants and animals in
a desert habitat, but unique features in the ecosystem make life possible for such
creatures as guanacos, wild Bactrian camels, cacti, lizards, and red kangaroos.
Learning Objectives
After viewing the program and participating in discussion, students will be able to:
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Explain the transfer of energy between organisms in an ecosystem;
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View desert biomes from ecological and biological perspectives;
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Relate plant and animal behaviors to underlying biological and chemical processes;
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Understand the erosion process and recognize how erosion impacts deserts;
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Consider the relationship between resources and population size in an ecosystem.
Classroom Connections
How does erosion shape the desert landscape? In addition to wind, what other
environmental forces cause erosion?
What are some common adaptations among desert animals? Have students write
down their answers individually and then share them with a partner.
Explain the unique way guanacos obtain water in the Atacama. Could this behavior be
considered an adaptation? Explain your answer.
How do locusts communicate in swarms? Can you think of other animals that use
pheromones to communicate?
Are reptiles warm-blooded or cold-blooded? Why would a desert make a good habitat
for a reptile?
In addition to competition for resources, what other factors limit population growth in a
desert? How would a flash flood change a desert ecosystem?
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Do you think the red kangaroo’s strategies for keeping cool are learned behavior or
instinctual behavior? Explain your answer.
Describe the relationship between bats and cacti in Arizona’s Sonoran Desert. How does
the relationship help both species?
How do desert animals and plants react to flash floods? Provide at least three examples.
Classroom Activities
Connect ecology, climate change, and conservation to a growing environmental
threat—desertification. Working in groups, have students research desertification on
the Internet and at the school library. Assign each group a different region or country
affected by desertification: the Sahel; Al Merida, Spain; Madagascar; China; and the
Aral Sea. The groups should write a two-page report on their regions and address the
following questions:
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Where is the region located? Are there any deserts near the region?
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What human and environmental factors caused desertification in the area?
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How has desertification affected agriculture and industry in the region?
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Has desertification harmed any indigenous wildlife?
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What steps are being taken to stop desertification?
Demonstrate how the process of transpiration helps plants (like cacti) transport water
throughout their stalks and leaves. Mix water and a few drops of food coloring in a
glass container and place celery stalks (with leaves) in the water. Add the stalks to the
water four days prior to the activity. Next add food coloring and water to another glass
container, this time inserting a test tube (with the opening facing down) into the water.
At the start of the activity, ask students why water is creeping up the test tube. Discuss
the forces of adhesion and cohesion at work in the test tube then ask the class why
the water rose higher in the celery stalks than it did in the test tube. Have students view
a cross-section of the celery under the microscope to view the plant’s xylem cells. For
further exploration, students can collect leaves from around the school and paint the
undersides of the leaves with clear nail polish. Once the polish is dry, peel the polish
off the leaf with transparent tape. Affix the tape to a microscope slide and search for
the imprint of stomata in the polish. Compare the number of stomata on the top and
bottom of the leaf.
Compare food webs among different deserts around the world. Separate the class
into groups. Have each group choose a different desert and research the organisms
that live there (plants, animals, and other eukaryotic and prokaryotic organisms). After
selecting at least ten different organisms, ask the groups to organize their organisms
into a food web. The web should be presented on a poster or large piece of paper.
Once the webs are completed, have groups compare their webs to the webs of other
groups in the class, noting any similarities and differences.
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Target Vocabulary*
adaptation - modification of an organism or its parts that makes it more fit for
existence under the conditions of its environment
desert - arid land with usually sparse vegetation; especially: such land having a very
warm climate and receiving less than 25 centimeters (10 inches) of sporadic rainfall
annually
dromedary - camel
erode - to wear away by the action of water, wind, or glacial ice (flooding eroded the
hillside)
nocturnal - active at night (a nocturnal predator)
desiccate - to dry up
predator - an animal that lives by predation (a mode of life in which food is primarily
obtained by the killing and consuming of animals)
prey - an animal taken by a predator as food
habitat - the place or environment where a plant or animal naturally or normally lives
and grows
ecosystem - the complex of a community of organisms and its environment
functioning as an ecological unit
food chain - an arrangement of the organisms of an ecological community according
to the order of predation in which each uses the next usually lower member as a food
source
food web - the totality of interacting food chains in an ecological community
pollination - the transfer of pollen from an anther to the stigma in angiosperms or
from the microsporangium to the micropyle in gymnosperms
pheromone - a chemical substance that is usually produced by an animal and serves
especially as a stimulus to other individuals of the same species for one or more
behavioral responses
biome - a major ecological community type (as tropical rain forest, grassland, or
desert)
* By permission. From the Merriam-Webster Online Dictionary ©2007 by
Merriam-Webster, Incorporated (www.Merriam-Webster.com).
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Academic Standards
National Science Education Standards (National Research Council, NAS, 1996)
The National Academy of Sciences provides standards for science content and science
teaching in grades K–12.
Standards specific to this PLANET EARTH program:
Grades 9–12: Biological Evolution (p. 185); Interdependence of Organisms
(p. 186); Matter, Energy, and Organization in Living Systems (p. 186); The Behavior
of Organisms (p. 187); Population Growth (p. 198); Natural Resources (p. 198);
Environmental Quality (p. 198)
To view the standards, visit the NSES Web site:
http://books.nap.edu/html/nses/html/overview.html#content.
AAAS Benchmarks for Science Literacy
Developed by the American Association for the Advancement of Science (AAAS),
Benchmarks for Science Literacy states what all students should know and be able to
do in science, mathematics, and technology by the end of grades 2, 5, 8, and 12.
Benchmarks addressed in this PLANET EARTH program:
Chapter 5: Diversity of Life (p. 103); Interdependence of Life (p. 116); Flow of Matter
and Energy (p. 119); Evolution of Life (p. 123)
AAAS Benchmarks for Science Literacy is available on the Web at: http://www.
project2061.org/publications/bsl/online/bolintro.htm.
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Published by Discovery Education, Inc., a division of Discovery Communications, LLC. © 2007. All rights reserved. Based on
PLANET EARTH © BBC. Distributed under exclusive license from Educational Publishers LLP.
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