Biomes: Freshwater, Seawater: Teacher’s Guide
Grade Level: 6-8
Curriculum Focus: Ecology
Lesson Duration: Three class periods
Program Description
Water takes many forms and has many functions on our planet. This dynamic presentation helps
students understand the chemical and physical properties of a substance that is crucial to life on
Earth. This program includes one feature segment and two short segments.
Onscreen Questions
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Why is it useful for people to be able to turn seawater into freshwater?
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What kinds of animals live in freshwater?
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How do freshwater habitats change from season to season?
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How are tsunami waves formed?
Lesson Plan
Student Objectives
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Conduct fieldwork to determine water quality of a freshwater habitat.
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Observe an organism’s behavior and adaptations.
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Answer questions about the differences between habitats with still and flowing water.
Materials
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Field guides of pond life or freshwater life
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Small fish nets, long-handled dip nets, kick seine or other nets
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Collecting buckets, preferably white
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pH paper
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Thermometers, preferably without mercury
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Meter sticks or tape measures
Biomes: Freshwater, Seawater: Teacher’s Guide
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Fish floats, leaves, or any objects that will float
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Stopwatches or watches with a second hand
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Magnifying glasses or bug boxes
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Old shoes or boot s
2
Procedures
1. Explain that scientists consider freshwater habitats to have salinity, or saltwater content, of less
than .005 percent. Freshwater habitats are ponds, lakes, bogs, rivers, streams, creeks, marshes,
swamps, or even puddles and drainage ditches. A reservoir is an artificial freshwater resource.
2. Brainstorm with students a list of freshwater habitats close to school. Ask students to
hypothesize about the health of a nearby habitat and its diversity of life. Would students
consider it healthy or unhealthy? Why? Explain that some organisms can tolerate a polluted
freshwater environment.
3. Introduce the word “macroinvertebrate” to the class. Explain that this is an animal without a
backbone living in one stage of its life cycle, usually the nymph or larval stage. Visible without a
microscope, macroinvertebrates can spend a few years living in a freshwater habitat. Many are
benthic organisms, or bottom-dwellers.
4. Explain that scientists determine a freshwater habitat’s health by the number and type of its
organisms. The water quality of such a habitat is good when it is rich in oxygen and supports a
variety of organisms. Water quality is fair when it has less oxygen and low levels of pollutants,
and poor when it has high levels of pollutants. Some organisms can survive only in freshwater
of good quality, while others can live in any quality.
5. Review the following chart of organisms and the quality of water their presence indicates. The
presence of stonefly larvae indicates good water quality because they are highly sensitive to
chemical and physical changes. But leeches can live in any water, so their presence may indicate
poor quality.
Good Water Quality
Fair Water Quality
Poor Water Quality
Mayfly larvae
Crayfish
Aquatic worms
Stonefly larvae
Scud
Leech
Caddisfly larvae
Dragonfly nymph
Pouch snail
Dobsonfly larvae
(Hellgrammite)
Cranefly larvae
Midge fly larvae
Water penny
Clam
Blackfly larvae
Riffle beetle
Damselfly larvae
Carp
Trout
Sow bug
Catfish
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Biomes: Freshwater, Seawater: Teacher’s Guide
3
6. Divide students into teams of three or four. Explain that students will study shallow and deep
areas of the freshwater habitat. (Shallow water in a stream is no higher than the ankle, and deep
water reaches the knee.)
7. Review safety precautions to follow during fieldwork: Wear old boots that will keep feet dry;
remember wet surfaces, such as rocks with algae, are slippery; check depth before stepping into
water; handle organisms gently and return them to the habitat alive; be aware that some
organisms can bite or pinch; never drink the water.
8. Have each team gather equipment and choose a place to work in the habitat. Have students
observe the water’s edge and surface, then look through the water to the bottom of the habitat.
Have the students record their observations on a data sheet.
9. Have students measure the water temperature with a thermometer and record depth with a
meter stick. They will measure the velocity of flowing water by recording the distance a float
travels in 10 seconds, and measure the water’s pH with pH paper. They should record all data
on their data sheets.
10. In a stream, have students collect macroinvertebrates in riffles, or areas with higher oxygen
content.
11. Students should place a kick seine net, or a large net with a small mesh, downstream. Have
them hold the net so it rests on the bottom of the stream.
12. Have students dislodge organisms by disturbing the stream bottom and rubbing rock surfaces.
After a few minutes, students will raise their nets and gently put organisms into a bucket. In
still water, students must carefully sift through mud or sand in the net. Students should identify
and count the organisms, and record their data before releasing them
Assessment
Use the following three-point rubric to evaluate students’ work during this lesson.
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3 points: Students worked exceptionally well in the field and completed data sheets
accurately with detailed observations; answered the questions completely and shared
observations with the class; demonstrated a clear understanding of the fieldwork.
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2 points: Students worked somewhat carefully in the field and completed data sheets, but
answers lacked detailed observations; completed most of the questions; demonstrated a
general understanding of the fieldwork.
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1 point: Students did not engage in fieldwork and partially completed the data sheets;
answered some of the questions; did not demonstrate an understanding of the fieldwork.
Vocabulary
benthic
Definition: Relating to the bottom of a body of water
Context: Organisms are benthic dwellers if they live on the bottom of freshwater habitats.
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biodiversity
Definition: The number and variety of organisms found within a specific geographic region
Context: A freshwater habitat’s health can be determined by its biodiversity.
habitat
Definition: The place an animal or plant normally lives
Context: Trout live in salty and freshwater habitats.
larva (plural: larvae)
Definition: The newly hatched, wingless, often wormlike form of many insects before
metamorphosis
Context: Fly larvae are macroinvertebrates living in freshwater habitats.
macroinvertebrate
Definition: An animal without a backbone usually in a nymph or larval stage
Context: Scientists determine freshwater habitat health by the quantity and diversity of
macroinvertebrates.
riffle
Definition: A stretch of choppy water
Context: Macroinvertebrates thrive in riffles, which have more oxygen than still water.
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 standard:
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Life Science: Populations and ecosystems
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 http://www.mcrel.org/.
This lesson plan addresses the following national standards:
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Science—Life Sciences: Understands biological evolution and the diversity of life
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Language Arts—Writing: Gathers and uses information for research purposes
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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
DVD Content
This program is available in an interactive DVD format. The following information and activities are
specific to the DVD version.
How To Use the DVD
The DVD starting screen has the following options:
Play Video—This plays the video from start to finish. There are no programmed stops, except by
using a remote control. With a computer, depending on the particular software player, a pause
button is included with the other video controls.
Video Index—Here the video is divided into four parts (see below), indicated by video thumbnail
icons. Watching all parts in sequence is similar to watching the video from start to finish. Brief
descriptions and total running times are noted for each part. To play a particular segment, press
Enter on the remote for TV playback; on a computer, click once to highlight a thumbnail and read
the accompanying text description and click again to start the video.
Curriculum Units—These are specially edited video segments pulled from different sections of the
video (see below). These nonlinear segments align with key ideas in the unit of instruction. They
include onscreen pre- and post-viewing questions, reproduced below in this Teacher’s Guide. Total
running times for these segments are noted. To play a particular segment, press Enter on the TV
remote or click once on the Curriculum Unit title on a computer.
Standards Link—Selecting this option displays a single screen that lists the national academic
standards the video addresses.
Teacher Resources—This screen gives the technical support number and Web site address.
Video Index
I. Fit to Drink (5 min.)
Pure drinking water is essential to human life. Explore how scientists are obtaining new sources of
potable water—some from outer space!
II. Asian Waters (15 min.)
Seventy percent of our planet’s freshwater is frozen, locked up as ice and snow. Travel to northeast
Asia to learn about animal life in its icy rivers, lakes, and oceans.
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Biomes: Freshwater, Seawater: Teacher’s Guide
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III. Freshwater Freeze (21 min.)
Winter brings freezing temperatures to northeast Asia—and the promise of replenished freshwater.
Watch as the animals of northeast Asia cycle through the seasons.
IV. Waves of Destruction (7 min.)
Unlike normal ocean waves, tsunamis can be 700 meters long. See how scientists are protecting
coastal communities from these heavy-hitting waves.
Curriculum Units
1. Substances and Mixtures
Pre-viewing question
Q: What are some substances that don’t mix well?
A: Answers will vary.
Post-viewing question
Q: How is a pure substance different from a mixture?
A: Pure substances are a single kind of matter—either one element or one compound (a
combination of elements that have combined chemically). Mixtures, on the other hand, are two or
more pure substances that haven’t combined chemically—they keep their original properties.
Seawater is a mixture; freshwater, the chemical compound of hydrogen and water, is a pure
substance.
2. Desalination
Pre-viewing question
Q: Where can we get fresh, potable water?
A: Answers will vary.
Post-viewing question
Q: Why is it problematic to rely on desalination for our drinking water?
A: Answers will vary.
3. Adapting to Winter
Pre-viewing question
Q: How do animals adapt to the seasons?
A: Answers will vary.
Post-viewing question
Q: What would our planet be like if all the frozen freshwater melted?
A: Answers will vary.
4. Surviving the Winter
Pre-viewing question
Q: How do fish survive the icy winter?
A: Answers will vary.
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Post-viewing question
Q: If kingfishers did not eat yamame, how would the river ecosystem change?
A: Answers will vary.
5. The Thaw
Pre-viewing question
Q: How do animals depend on one another for survival?
A: Answers will vary.
Post-viewing question
Q: Why is timing crucial for a spawning female frog?
A: When a female frog lays her eggs, the water must be shallow enough so the eggs can be warmed
by the sun, but not so shallow that it dries out before the eggs hatch. If a frog’s timing is wrong, all
her offspring could be destroyed.
6. Swimming Into Spring
Pre-viewing question
Q: Is life more dangerous for freshwater or ocean fish?
A: Answers will vary.
Post-viewing question
Q: What changes do yamame undergo as they mature?
A: When they begin their journey toward the river mouth, the patterns on their bodies—a defining
feature of the yamame—start to fade. Their skin turns silver and the tip of their dorsal fin turns
black. They are now known as sakura masu or cherry salmon.
7. Cranes and Their Young
Pre-viewing question
Q: Why do many animals breed during the spring and summer?
A: Answers will vary.
Post-viewing question
Q: What are the greatest dangers facing young cranes?
A: Along with predators, weather is a great danger. If the weather in the marshlands is
unseasonably wet and cold, crane chicks can die from hypothermia.
8. Freshwater Fish
Pre-viewing question
Q: Do males play a major role in the lives of young animals?
A: Answers will vary.
Post-viewing question
Q: What do cranes eat during the summer?
A: Freshwater plants, fish, insects, and crayfish
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Biomes: Freshwater, Seawater: Teacher’s Guide
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9. Lake Baikal
Pre-viewing question
Q: What is a marsh?
A: A low-lying wetland area with grassy vegetation; marshes are often lakes in the process of being
filled in by a steady accumulation of silt.
Post-viewing question
Q: What plants and animals are found in Lake Baikal?
A: Branching sponges live in the lake’s coastal shallows. These sponges are kept clean by herds of
grazing amphipods, which feed off microscopic algae and waste. Lake Baikal is also home to the
world’s only freshwater polykleep worm and more than 300 species of amphipods.
10. Completing the Cycle
Pre-viewing question
Q: Why do salmon return to freshwater rivers to spawn?
A: Answers will vary.
Post-viewing question
Q: What dangers do cherry salmon face as they swim upriver?
A: They are forced to swim through shallow stretches of the river and face predators that include
the black bear and fish owl.
11. Preparing for Winter
Pre-viewing question
Q: How do you prepare for winter?
A: Answers will vary.
Post-viewing question
Q: What signals the return of winter to the Asian marshlands?
A: The freshwater rivers begin turning to ice, insects start to disappear, cranes start their migration
to warmer climates, and frogs prepare for hibernation.
12. Tsunamis
Pre-viewing question
Q: What do you know about ocean waves and tsunamis?
A: Answers will vary.
Post-viewing question
Q: How do tsunamis differ from normal ocean waves?
A: Tsunamis have wavelengths between 100 and 700 kilometers, while typical ocean waves are
between 40 and 400 meters long. Wind energy on the ocean’s surface produces ocean waves.
Tsunamis are caused by underwater earthquakes, landslides, or volcanic activity.
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