Analysis of Energy in the Environment

Introduction to Biomass

• Elton's advancement from pyramid of numbers to pyramid of biomass.
• Pyramid of biomass provides a clearer picture of energy transfer compared to previous representations.

Definition of Biomass

• Biomass is the mass of living material in each trophic level.
  • Example: Biomass of plants in a rainforest, earthworms in soil.
• Represents both mass and sample size at each trophic level.
  • Sample size: Biomass = mass of organism x total number of organisms in that trophic level.

Importance of Biomass

• Allows comparison of food value between small/large organisms at different trophic levels.
• Pyramid of numbers does not account for biomass variation among organisms.
• Biomass at a trophic level is usually less than that of the level below.

Energy Transfer Efficiency

• Most food consumed is not converted into new tissue; only a fraction is usable energy.
  • Example: For every 100 kilojoules of energy consumed by a cow, only 4 kilojoules convert into new tissue.
• 43 kilojoules lost through undigested food.
• To improve energy conversion, provide easily digestible food to reduce digestive energy loss.

Structure of the Pyramid of Biomass

• Forest Ecosystem:
  • Upright pyramid due to larger net biomass of producers compared to consumers.
• Aquatic Ecosystem:
  • Inverted pyramid because:
    • Phytoplankton at the base have the least biomass despite being primary producers.
    • Biomass increases towards predatory fish (e.g., sharks, whales).
    • Turnover of phytoplankton: Rapid life cycle and high grazing by herbivorous zooplankton limit biomass size.

Ecosystem Dynamics

• Why do larger species survive despite low phytoplankton biomass?
  • High reproduction rate of phytoplankton ensures continuous food supply, sustaining larger fish populations.
• Environmental changes can drastically affect plankton populations, impacting fish and insect populations.

Limitations of Biomass and Numbers Pyramids

• Both pyramids can misrepresent or misinterpret energy flow in an ecosystem.