Unit 1.9: Trophic Levels & The 10% Rule

Trophic Pyramid - A representation of the distribution of biomass, numbers, or energy among trophic levels

Primary Producers —→ Primary Consumers —→ Secondary Consumers —-→ Tertiary Consumers

• All levels are broken down by scavengers, decomposers, and detritivores

Nutrients are returned back to primary consumers

• Only 1% of all incoming sunlight is captured and converted into GPP (Gross Primary Productivity) via photosynthesis

Only about 40% is converted into biomass/plant growth (NPP)

Second Law of Thermodynamics - Each time energy is transferred, some of it is lost as heat

• Energy loss = respiration (heat), kinetic energy (movement), body growth

Conservation of Matter and Energy (First Law of Thermodynamics) - Energy is never created nor destroyed

• Examples: Biogeochemical Cycles and Food Webs