TOPICS: Plant reproduction, seed dispersal
LEVEL: Middle and high school
TIME: One period
ADVANCE PREPARATION: Have students collect samples of winter weeds or you may choose to collect the samples yourself. Fifteen or more different species are recommended. Flasks make good "vases" to display the sample. Choose 10 samples that are given in the key and that have seeds which are fairly easy to identify as wind or animal dispersed (such as milkweed, aster, goldenrod, burdock, beggar-ticks). Label the samples by letters A-J. You may wish to display the "extras" to give students additional experience in using the key, or as a winter bouquet
.
STEP A.
Some students may need help using the key. You may want to do an example with the class. Insist that students use the key for each sample. The pictures should only be used to verify their identifications.
QUESTIONS
:
1.
Answers will vary. Aster, goldenrod, milkweed, cattails are probably most familiar
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2.
Seeds of different species differ in size, shape, color, and quantity
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3.
Burdock and beggar-ticks stick to clothing
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4.
Milkweed, cattail, aster, goldenrod seeds may be seen floating in the air
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5.
The two most common agents of winter seed dispersal are wind and animal fur. (At other times of the year, seeds may be dispersed by water, animals eating fruit with indigestible seeds, and so on. See the Seed Dispersal Teacher Background
.)
6.
Seeds that are very tiny, or that have plumes or wings are probably dispersed by wind; those with hooks or burs are dispersed by animals
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7.
Any of these with relatively large seeds or large numbers of seeds (dock, ragweed, milkweed) may provide winter food for birds or small mammals
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8.
Those with plumes (milkweed, cattail, aster, goldenrod) may provide nesting material.