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Investigation 3 – PreLab









Natural resources technicians perform a variety of duties relating to the maintenance and restoration of woodland, wetland, prairie, and aquatic natural areas.


This Investigation is designed to help you to answer the following Focus Questions:

  • What is the relationship between the energy and biomass of producers and the levels that an ecosystem can support? 

  • What affects the amount of energy in an ecosystem? 

Note: These questions are located in your SDR at the beginning and end of the Investigation.



As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • Ecologists cannot determine exact amounts of biomass for large ecosystems, but he or she can estimate these amounts by taking equal-sized samples from different areas of the ecosystem. The ecologist can then use the average amount of biomass to calculate an estimated total biomass for the ecosystem being studied. 
  • Biomass increases as plants grow.
  • Plants grow because they undergo photosynthesis.
  • Plants use photosynthesis to capture light energy from the Sun.
  • The captured light energy is stored in the plant’s biomass.



These terms should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • ecosystem
  • producers
  • consumers
  • detritivore
  • detritus
  • trophic level
  • biomass
  • Law of Conservation of Energy
  • Law of Conservation of Matter

Note: Definitions of these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.


As a class, review what was discovered in Investigations One and Two.

    • Note: You discovered that the amount of energy in each level of an ecosystem is smaller than the amount of energy in the level below it and this indicates that energy transfer is inefficient.

      Note: You also discovered that higher levels of an ecosystem have smaller amounts of biomass than the levels below them.

      Note: The models in Investigation Two demonstrated that energy transfer between levels of an ecosystem is inefficient because all of the energy consumed by an organism is not transferred to its consumer. You discovered that one of the primary reasons for this inefficiency was energy usage during cellular respiration.

      • Answer the following questions from the Recall section in your SDR. 
        • Do all ecosystems have the same number of levels of consumers?
        • How does the amount of photosynthesis determine the number of levels an ecosystem can support?
      • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful.
      • After the video, divide into lab groups to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

      Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

      Note: Homework is posted below the video.


    You should review the Investigation and video in preparation for the Lab.