Biology – Virtuallab Chapter 2: Model Ecosystems
Name
Hr
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 Ocean Shore
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 Ocean Shore
Freshwater Lake
Pyramid of Energy – Energy Transfer between Trophic Levels (use to answer #2&3)
Calculate the Ratio:
(round to one decimal place)
Deciduous Forest
Hot Desert
Grassland
Antarctic Ocean Shore
Freshwater Lake
1st order
Producers
2nd order
1st order
3rd order
2nd order
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.