Ecological Pyramids Lab






  1. Ecosystem


  1. Trophic level


  1. Biomass



Energy Flow Diagram:


Energy Flow in an Ecosystem





























Energy Pyramid:





Each table group will be receiving a bag which represents a particular ecosystem. The colored beans in the bag represent the organisms that live in the ecosystem. Each color of bean stands for an organism from a particular trophic level. One color of bean stands for the producers in the ecosystem. Another color stands for the primary consumers (herbivores), the secondary consumers (carnivores or omnivores), and the tertiary consumers (top carnivores). Your task as a group is to examine the numbers of organisms in each trophic level and record it in your data tables. Then you will be constructing biomass and numbers pyramids based on your data.







  1. Each table group selects an ecosystem (bag).
  2. Count the number of organisms in each trophic level (number of colored beans in the bag). Put the colored beans in 4 separate piles. Record the numbers in the data table below.
  3. Weigh the empty paper cup on the scale provided.
  4. Put each pile of colored beans in the cup one at a time and weigh the beans.
  5. Record the mass (to the nearest 0.1 of a gram) of each group of colored beans in the table provided (remember to subtract the weight of the cup from the weight of the beans + cup in order to ONLY find the weight of the beans)

Data Table:




(Trophic Level 1)

Primary Consumers

(Trophic Level 2)

Secondary Consumers

(Trophic Level 3)



(Trophic Level 4)






Mass (g)






  1. Graph the numbers and masses of the different colored beans below. Remember that the mass and numbers are recorded on the x-axis (horizontal axis) and the trophic level is recorded on the y-axis (vertical axis).
  2. Next, fill in the pyramids for numbers and mass based on your data.





Numbers Graph Mass Graph


Numbers Pyramid Biomass Pyramid






Prediction Questions:


1. In the ecosystem you just studied, there is a long, devastating drought, and 1/2 of all the producers die. Over time the numbers of organisms at all the trophic levels will change. Describe how the trophic levels of primary, secondary, and tertiary consumers will change. What will the new numbers pyramid come to look like?


  1. A disease kills off 50 of the secondary consumers. Over time, what will the new numbers pyramid come to look like?



  1. 100 new producers are introduced into the ecosystem. What will happen to the numbers of the other trophic levels? What will be the new numbers of primary, secondary, and tertiary consumers?




  1. In an ecosystem, there are 4,000 producers, and 400 primary consumers. Based on the data you have collected. How many secondary and tertiary consumers would you predict are in this ecosystem?




  1. In an ecosystem there are 50 tertiary consumers and 500 secondary consumers. Predict how many primary consumers and producers are in this ecosystem.