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Studying a Piece of an Ecosystem

Dorothea W. Sinclair



Modified from BSCS Green Version, 3rd ed., 1973, Investigation 1.4


Type of Activity:

  • Inquiry lab

Target Audience:

  • Biology
  • Environmental studies

This lab helps students identify the components of an ecosystem, and how the biotic and abiotic factors interact with each other.


Background Information

Notes for teacher:

This lab is an excellent culmination of a unit on ecology. After teaching about food chains, energy flow, abiotic and biotic factors, and ecological relationships (mutualism, commensalism, predation, parasitism, competition), the students can apply this information in their study. Selection of the study site is important. It does not have to be large (10 x 10 m ) but it should show some diversity of plants and have some animal life in the area. An unmowed corner of the campus, a section of trees behind the gym, or even a vacant lot down the street can be used. I try to use a different 10 x 10 m area for each class so that it is not so trampled by the end of the day. I also go over in advance and check the area for anything that could harm the students or make walking difficult. It helps to write the instructions for each student. If this is not practical, then put the data on the board or an overhead transparency and have the students copy it on their own paper.

Requirement of students:

  • A clipboard to take into the field would be useful.
  • Additional guides to plants, insects, birds, mammals and binoculars are also helpful.

Preparation time:

  • One hour to go to study site, checking for problems like uneven terrain, poison ivy, brambles, as well as identifying the major plants present and looking for examples of ecological relationships, birds, mammals and insects. Look to see where good study sites could be located. A site needs to have an area where a 10 x 10 m square can be marked off and there be vegetation present, but not so much vegetation that it is impenetrable.
  • Two hours gathering field guides, making direction cards and data sheets, assigning students to groups based on their talents (if you wish to assign rather than ask for volunteers) and gathering other equipment.
  • Total time: 3 hours.

Class time: 4 to 5 days:

  • 1 day to give assignments and explain job
  • 2 or 3 days in field gathering data
  • 1 day back in classroom sharing data


Abstract:

Students carry out an outdoor land study of a 10x10 m area in which they identify organisms living in the soil, plants, insects, and any other animals living within the site. Groups also examine abiotic factors in the same study site. Students work in teams, share data, then respond to a series of questions concerning their data in a paper.

Materials needed:

  • 8 stakes
  • hammer
  • measuring rope (10m)
    marked in meters
  • string 60 m long
  • rain gauge
  • soil pH test kit
  • thermometer
  • sling psychrometer
  • relative humidity table
  • rulers
  • wire ring
  • trowel
  • binoculars
  • insect nets
  • large ziploc bags
  • marking pens
  • data sheets
  • pencils
  • instruction cards
  • large enamel pans
  • forceps
  • dissecting scope or
    magnifying glasses
  • field guides to:
    • insects
    • trees
    • flowering plants
    • ferns
    • mosses
    • lichens
    • mushrooms
    • birds
    • mammals
    • reptiles
    • amphibians


Procedure:

  1. Select a study site close by.

  2. Assign students to the following groups or let them volunteer. All tasks need to be accomplished. The following list gives the name of the group and the procedure for that group

    • Staking (3 students minimum). Using the measuring rope, students will mark a 10 m x 10 m square. Inside the square they need to mark off a 2 m x 10 m rectangle, and a .5 m x 2 m rectangle. Mark the corners of the square and rectangles with stakes, then connect the stakes with string. At the end of the period rewind the string and take up the stakes.
    • Trees (a plant with a stem more than 1 cm. in diameter): Count and identify each type of tree in the 10 m x 10 m square
    • Shrubs (a plant with a stem greater that .5 cm. in diameter but less than 1 cm. in diameter): Count and identify each type of shrub in the 2 m x 10 m rectangle
    • Herbs (a plant with a stem less than .5 cm in diameter): Count and identify each herb in the .5 m x 2 m area
    • Primitive plants (ferns, mosses, liverworts, etc.): Count and identify each one in the .5 m x 2 m area
    • Soil and litter organisms: Throw a tennis ball or stone into the 10 m x 10 m area over your shoulder. Where the ball lands place the wire ring. Remove the leaf litter in the ring and place it in the plastic bag. Label the bag "litter." Using the trowel, dig down to a depth of 10 cm. Place the soil in another bag. Label the bag. Repeat this for a total of 3 sites. When you return to the classroom, pour the soil or litter into a large pan. Using forceps, carefully go through the material and identify any organisms using field guides. Use magnifying glasses or dissecting scopes if needed.
    • Insects: Using the insect nets, make 3 sweeps of the 10 x 10 m square from corner to corner. Identify insects collected, then release them.
    • Birds: Identify any birds in the vicinity of the study site.
    • Mammals, reptiles and amphibians: Look for tracks, burrows, or other signs of these animals in or near the 10 m x 10 m area. Identify animal or its sign. DO NOT PICK UP ANY SNAKES.
    • Temperature: Take the air temperature at head, shoulder, waist, knee, and ground level in the open, under a tree, and under a shrub.
    • Soil pH: Take soil samples at the same location as the soil and litter group. Follow directions of the soil pH kit.
    • Rain: On the first day, set out the rain gauge in the study site at a location that is not sheltered by vegetation. Check each day for any rain. Read and record.
    • Relative humidity: Using a sling psychrometer, determine the relative humidity at head, shoulder, waist and knee level under a tree, under a shrub and in the open of the 10 m x 10m area. Record wet and dry bulb temperatures. Then use a relative humidity chart to determine the humidity at each location.
    • Description: Describe what the study site looks like. Try to paint a picture with words.

  3. Go out for 2 or 3 days and gather the data for assigned group. In addition, each student is responsible for finding 10 ecological relationships and identifying it within the study area.

  4. Return to classroom and share data. Soil and litter people will need to go through soil of organisms. Some groups may need help with identifying their samples.


Method of evaluation:

A written paper. The paper should include the following:
  • Title
  • Purpose
  • Procedure of the student's own group
  • Data of all groups in the class. This can be done as tables, bar graphs or pie graphs, as appropriate.
  • Discussion questions:
    • Show the abundance and type of producers, consumers, herbivores, carnivores, and decomposers in the food web. This may be diagrammed.
    • Using the information you have, construct an energy-flow diagram for the area.
    • Discuss how the abiotic factors (organisms) have on the abiotic factors? Again, refer to your data with a minimum of 3 examples.
    • What ecological relationships did you observe? Give specific examples of each.
    • Describe the community structure, including any layers.
    • Describe the niche of one organism to the best of your ability.
    • Can you see any relationship between the abundance of an organism, its size and its place in the food chain? Explain.

Extension/Reinforcement:

Use the organisms found as reference points when discussing plants and animals later in the year.


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