Ecosystem (page 2)

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Author: Janice VanCleave

Design Your Own Experiment

  1. Measure the angle of the slope (steepness of an inclined surface) of each subplot. Do this by constructing and using an Abney level. Make the level by using masking tape to attach a protractor to the center of a yardstick (meterstick). Tie a 12- inch (30-cm) piece of string to the center of the protractor and attach a washer to the free end of the string (see Figure 22.2). Hold the measuring stick parallel to the ground of each subplot while a helper reads the angle on the protractor made by the hanging string. When the slope is zero, the string hangs straight down across the 90° mark. To determine the angle of slopes, subtract the angle reading from 90°. For example, if the protractor reads 50°, the angle of the slope is 90° – 50°, or 40°.
  2. Interactions

    1. Observe the types of plants in each subplot. Collect leaf samples from the plants and, using plant field guides, identify the types of each plant present. Land plants are commonly classed as trees, shrubs, herbs, or vines according to the size and type of stem. Land plants are either a woody plant (a plant containing stems with a large amount of wood) with relatively hard stems or a nonwoody plant (a plant containing stems with a small amount of wood) with relatively soft stems. Wood is the part of a plant made of xylem tubes (tubes that transport water and other nutrients from the root throughout a plant and provide support). A description of the four types of land plants follows:
      • Trees—Plants with a single tall, woody stem called a trunk that grows from the ground and is able to stand erect without support. Other woody stems branch from the trunk.
      • Shrubs—Short, woody plants usually with several stems branched near the ground that are able to stand erect without support. Also called bushes.
      • Herbs or herbaceous plants—Names for nonwoody plants. The stems of these plants remain relatively soft and include grasses and flowers, such as daisies and dandelions.
      • Vines—Flexible, weak-stemmed plants whose long, slender, fast-growing shoots rely on other plants or objects for support. Vines may wind around supporting structures, and/or use thorns, tendrils (slender spiraling stems), or hooks to climb and anchor to a structure. Vines can be woody or nonwoody (herbaceous).
      • Science Fair Hint: You could display labeled photographs of the plants from each subplot along with preserved samples of the leaves or leaf rubbings.

    2. Observe and record the presence of different fungi and lichens in each subplot. Fungi is a group of plantlike organisms that have no leaves, flowers, or chlorophyll, and include mildew, mold, mushrooms, and toadstools. Lichen is a plantlike organism made of fungus and algae (a plantlike organism with no leaves, stems, or roots, but that has chlorophyll necessary for photosynthesis). See a biology text for more information about fungi and lichen.
    1. Record the actual presence or indications of the presence of animals. Note the presence of tracks, holes, sounds, claw marks, hair, nests, and so on. Cautiously turn over rocks and logs to discover insects, reptiles, and amphibians. Remember that you are an observer and do not want to change this ecosystem, so return rocks and logs to their original positions.
    2. Make molds of tracks by pouring plaster of paris into the tracks. Mix this liquid by following the directions on the box. You could use the molds as part of a project display.

Get the Facts

  1. When an organism feeds upon another living thing, there is a transfer of materials and energy. This transfer from organism to organism is called a food chain. Find out more about the food chain. What is a food web? What is a pyramid of energy and a pyramid of numbers? Use the information collected in your plot to construct a pyramid of numbers. For information, see Janice VanCleave's Ecology for Every Kid (New York: Wiley, 1996), pp. 37–46.
  2. Energy is constantly lost in an ecosystem and has to be replaced by sunlight. There is a fixed amount of matter within the system. Find out how matter is recycled in an ecosystem. For information, see a biology text.
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