Unit A: Energy and Matter Exchange in the Biosphere Chapter 2 Section 2.2 Scientific Models

Ecological Pyramids An ecological pyramid is a representation of the energy flow in a food chain or a food web. There are three types of ecological pyramids: Pyramids of Numbers Pyramids of Biomass Pyramids of Energy

Pyramids of Numbers A pyramid of numbers can be drawn by counting the number of organisms at each trophic level in an ecosystem. When these numbers are represented in a visual graph they often take the shape of pyramids because the number of organisms decreases with each trophic level.

Pyramids of Numbers

Pyramids of Biomass Biomass is the total dry mass of all the living material in an ecosystem. Since organisms store energy as organic molecules, biomass is a measure of stored energy content. A pyramid of biomass represents the total biomass at each trophic level per 1m2.

Pyramid of Biomass

Primary Consumers = 1 x 109 kJ Secondary Consumers = 1 x 108 kJ Pyramids of Energy Pyramids of energy are a representation of the amount of energy available at each trophic level. The energy available decreases with each level because only 10% of the energy at each step is passed on. Producers = 1 x 1010 kJ Primary Consumers = 1 x 109 kJ Secondary Consumers = 1 x 108 kJ

Pyramids of Energy

Sample Question #1 Pg. 30 in textbook

Practice Question #1 Trophic Level Number of Organisms Area of Box (cm²) ≈ Length of 1 Side (cm) 1 100 10 3.2 2 9800   3 500 4 5

Sample Question #2 Pg. 32 in textbook

Practice Question #2 Organism Energy (kJ) Area of Box (cm²) ≈ Length of 1 Side (cm) Phytoplankton 20 000 000 200 14.1 Zooplankton   Herring Salmon

Practice Question #3 Pg. 32 in textbook