Biology – Virtuallab Chapter 2: Model EcosystemsNameHr

Problem:

What happens to the number of organisms (and to the total amount of available energy) as you move up the food chain in a community?

Hypothesis:

The number of organisms will (increase/decrease/stay the same) as you move up the food chain

Procedure:

Study and analyze the five simplified ecosystems in virtuallab 2. Use the field notes included with the program to learn more about the organisms in the ecosystems.

  • Correctly place each organism in its proper trophic level on the ecological pyramid. Use the CHECK button to make sure that they are placed correctly.
  • Click the PYRAMID OF NUMBERS button. The program will total the total number of organisms at each trophic level. Record the totals in your data table.
  • Click the PYRAMID OF ENERGY button. The program will total up the stored energy within all the organisms at each trophic level. Record the totals in your data table.
  • Make sure that you collect data from all 5 ecosystems.

Data:

Pyramid of Numbers
Producers / 1st order heterotrophs / 2nd order heterotrophs / 3rd order heterotrophs
Deciduous Forest
Hot Desert
Grassland
Antarctic OceanShore
Freshwater Lake

Does the population size increase or decrease at higher trophic levels? Why?

Pyramid of Energy
Producers / 1st order heterotrophs / 2nd order heterotrophs / 3rd order heterotrophs
Deciduous Forest
Hot Desert
Grassland
Antarctic OceanShore
Freshwater Lake

Pyramid of Energy – Energy Transfer between Trophic Levels (use to answer #2&3)

Calculate the Ratio:
(round to one decimal place) / 1st order Producers / 2nd order
1st order / 3rd order
2nd order
Deciduous Forest
Hot Desert
Grassland
Antarctic OceanShore
Freshwater Lake

Analysis and Conclusion Questions:

1.What fraction of the energy from one trophic level carries up to the next trophic level? (from your calculations)

2.What fraction of the energy from one trophic level is lost from one trophic level to the next? What happens to that energy?

3.Compare and contrast 2 of the ecosystems you studied. How is the energy conversion similar or different?

4.What might happen to an ecological pyramid of numbers in a forest ecosystem if most of the deer were killed due to hunting or disease?

5.What would happen to an ecosystem if the decomposers disappeared?

6.Could there be a food chain without herbivores and carnivores? Explain.