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Scattering SeedsScattering-Seeds

  • Subject:
  • |
  • Grade(s): 6-8
  • |
  • Duration: One to two class periods

Lesson Plan Sections

Objectives


Students will do the following:
1. Investigate how seeds are dispersed.
2. Understand the variety of seed dispersal that exists in the plant kingdom.
3. Understand how factors in the natural environment can affect how far a seed is dispersed.

Materials


Students will need the following:
• Variety of seeds
• Magnifying glass or microscope
• Meter stick
• Fan
• Small dry seed, one for each student (bean or watermelon)
• Paper (to be cut for wind-dispersed seed demonstration)

Procedures


1. Have students collect a variety of different seeds from the school grounds, their yard at home, an unmowed field, or the grocery store. Common seeds to collect include coconut, maple, ash, elm, dandelion, milkweed, grasses, burdock, jewelweed, wisteria, cedar, watermelon, pumpkin, tomato, acorn, and apple.
2. Explain that most seeds have some type of dispersal mechanism or characteristic that enables the seed to scatter or travel a distance from its parent plant. Seeds may disperse by wind, water, animals, burrs, or mechanical means, depending on the habitat. A seed's dispersal mechanism often reflects the conditions within the habitat. Have students consider why it is important for plants to have their seeds dispersed away from the parent plant.
3. Set up a number of stations in the lab for each type of seed collected. Each station should include a magnifying glass or a microscope so students can observe small seeds.
4. At each station, students should
  • describe the seed's characteristics,
  • sketch a diagram of the seed,
  • label the diagram with significant seed parts,
  • hypothesize how the seed is dispersed, and
  • list conditions in the habitat that affected seed dispersal.
5. Following is a list of common seeds that may have been collected, listed by their dispersal mechanism. (Note that seeds may utilize more than one dispersal mechanism.) Share the list with your students. Did they correctly identify the dispersal mechanisms and conditions within the habitat that affected seed dispersal?
Dispersal Mechanism Seed Type
water coconut
wind maple, ash, elm, dandelion, milkweed, grasses
burr burdock
mechanical jewelweed, wisteria
animals cedar, watermelon, pumpkin, tomato, acorn, apple
6. Give each student a small dry seed, such as a bean or watermelon seed. Have students design a wind-dispersed seed mechanism for their seed. The wind-dispersed seed should be designed to travel the farthest distance. All students should use the same supplies for their seed design: feathers or paper, tape or glue.
7. Have the students drop their seed designs, all from the same height, in front of a room fan. Next, have them measure the distance their seed traveled. Repeat trials should be made, with calculations of the average distance traveled.
8. Have students discuss what design worked best. How would they improve their design? The students could research to find a naturally occurring seed that is similar to their designed seed.

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Adaptations


Adaptation for older students:
Have students collect seeds they find at different times in the year. Compare dispersal mechanisms to the season. Have students estimate the population potential for certain plants (depending on the number of seeds it produces) and explain reasons why that potential is never reached.

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Discussion Questions


1. How long and under what conditions can seeds remain dormant? Should scientists pursue animating ancient seeds in an effort to bring back extinct species? Why or why not?
2. Discuss how seeds get to new island habitats and establish life there. Consider studies occurring in Surtsey, Iceland, or the new island in the Solomon Islands, Kavachi.
3. Debate which method of seed dispersal is most beneficial to plants in your community. How do the dispersal mechanisms vary with seasons?
4. Discuss ways that plant species should be protected. How should the community protect endangered plant species in your area?
5. Explain how alien plant species have traveled to this country. Is this a benefit or hindrance to this country? Provide examples to support each view.
6. Debate the idea of genetically altering crops to support human consumption. Should seeds be stored or protected? Why or why not?

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Evaluation


Discuss results with the class and evaluate students on their oral contributions. Display the students' seed sketches and grade them on the amount of scientific information shown. The seed dispersal lab can be evaluated as a traditional lab report.

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Extensions


Seedy Boots
Have students wear shoes or boots with ruts in their soles. Take the students for a walk in an area with moist soil. Return from your walk and remove the caked-on soil, placing it in a small container with a bit of water to make it moist. After letting the muddy mixture sit overnight, add it to some potting soil and place it in a plant pot. Over the next few weeks, observe what grows. Can students identify the plants? As a comparison, the soil on a shoe bottom could be dried. Carefully have students remove any seeds they find. Could they identify the plants from the seeds? Compare this identification to the identification of the plants that grew.

Variables for Seed Growth
Have students set up a one-variable experiment to test seed germination. They should hypothesize the best environment for seed growth and test their hypothesis. Variables could be temperature, light, moisture, or soil nutrients. Results could be expressed as a percentage of successful germination. If students used different seed types, they would keep the specific environmental variable constant. Determine what seed type grew best in the specific environment that was designed.

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Suggested Readings


The Private Life of Plants: A Natural History of Plant Behavior
David Attenborough. Princeton University Press, 1995.
We usually think of plants as just being there... not doing much other than living. By closely examining vegetation in rainforests, deserts, and gardens, the author shows us that plants are constantly struggling to find food, reproduce, fight predators and each other, and increase their territory. Amazing close-up and stop-action photographs show the details of plants' struggles as you've never seen before.

Incredible Plants
Barbara Taylor. DK, 1997.
Photographs of detailed three-dimensional models provide a revealing way of learning about the basics of plant structures and functionality. From an inside look at a plant cell and photosynthesis to descriptions of carnivorous and parasitic plants, this book shows the amazing vitality and variety of plants.

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Links


FLOWERING PLANT REPRODUCTION: Fertilization and Fruits
Text and great graphics fruits and seeds; does include propagation
 

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Vocabulary


Click on any of the vocabulary words below to hear them pronounced and used in a sentence.
speaker    adapt
Definition: To make suitable to a specific use or situation.
Context: Seeds have adapted different methods of dispersal to suit their environment. Some travel by wind, some by animals, and others by water.
speaker    cotyledon
Definition: A leaf of the embryo of a seed plant.
Context: Inside of every seed are one or two cotyledons, which are special leaves that provide food for a germinating plant as it begins to grow.
speaker    disperse
Definition: To scatter or distribute widely.
Context: Seeds disperse from their parent plant so that they have room to grow and develop and not be in competition for light, nutrients, or moisture.
speaker    germinate
Definition: To begin to sprout or grow.
Context: If the conditions are favorable, seeds will germinate and the plant will begin to grow.
speaker    seed
Definition: A ripened plant ovule containing an embryo.
Context: Most plants that live on Earth reproduce by forming seeds. A seed contains one or two cotyledons and an embryo plant, which are covered by a seed coat.
speaker    spore
Definition: A small, single-celled reproductive body that can grow into a new organism.
Context: Some primitive plants, such as moss and fern, reproduce by forming spores, not seeds.
speaker    viable
Definition: The ability to live, develop, or germinate under favorable conditions.
Context: After a period of seed dormancy, viable seeds will germinate to produce a new adult plant.

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Standards


This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
 
Grade level: 6-8
Subject area: Science
Standard:
Knows about the diversity and unity that characterize life.
Benchmarks:
Knows that animals and plants have a great variety of body plans and internal structures that serve specific functions for survival (e.g., digestive structures in vertebrates, invertebrates, unicellular organisms, and plants).

Grade level: 6-8
Subject area: Science
Standard:
Knows about the diversity and unity that characterize life.
Benchmarks:
Knows evidence supporting the idea that there is unity among organisms despite the fact that some species look very different (e.g., similarity of internal structures in different organisms, similarity of chemical processes in different organisms, evidence of common ancestry).

Grade level: 6-8
Subject area: Science
Standard:
Knows the general structure and functions of cells in organisms.
Benchmarks:
Knows the levels of organization in living systems, including cells, tissues, organs, organ systems, whole organisms, and ecosystems, and the complementary nature of structure and function at each level.

Grade level: 9-12
Subject area: Science
Standard:
Knows the general structure and functions of cells in organisms.
Benchmarks:
Understands cell differentiation (e.g., the progeny from a single cell form an embryo in which the cells multiply and differentiate to form the many specialized cells, tissues, and organs that make up the final organism; each cell retains the basic information needed to reproduce itself).

Grade level: 6-8
Subject area: Science
Standard:
Understands how species depend on one another and on the environment for survival.
Benchmarks:
Knows that organisms can react to internal and environmental stimuli through behavioral responses (e.g., plants have tissues and organs that react to light, water, and other stimuli; animals have nervous systems that process and store information from the environment), which may be determined by heredity or from past experience.

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Credit


Mary C. Cahill, middle school science coordinator, Potomac School, McLean, Virginia.

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