Understanding Pyramids of Energy: How Energy Flows in Ecosystems (Extended)

 

What Is a Pyramid of Energy?

A pyramid of energy shows the flow of energy through each trophic level of a food chain over a specific period. 

• Pyramids of energy, like pyramids of biomass form pyramid shapes. This is because energy decreases as you move up the trophic levels.

 

Why Do Energy Pyramids Always Form a Pyramid Shape?

• Why does enegy decrease between trophic levels?
  • Enegy Loss: 
    • A large amount of energy is wasted and not transferred into making cells that can be consumed by the consumer
    • The 'wasted' energy is transfered into include:
      • Movement
      • heat
      • excretion, i.e urine and feces 
    • In addition to the wasted energy some of the organism is wasted  when eaten.
    • For example if a crow was to eat a from there would be waste in the form of bones and uneaten body parts. 
    • This adds to enery not making it to the consumer
  • Energy Efficiency:
    • Only $10\%$ of energy passes from one level to the next. This is called the $10\%$ Rule.

 

Structure of a Pyramid of Energy

Trophic Level	Energy Flow Example	Percentage of Original Energy
Producers	Grass $( 100,000 J )$	$100\%$
Primary Consumers	Grasshoppers $( 10,000 J )$	$10\%<span class="mord">$
Secondary Consumers	Frogs $( 1,000 J )$	$1\%<span class="mord">$
Tertiary Consumers	Snakes $( 100 J  )$	$0.1\%<span class="mord">$

 

 

Advantages of Pyramids of Energy

Feature	Why It’s Useful
Measures energy flow over time	Gives an accurate understanding of energy transfer between levels.
Always pyramid-shaped	Avoids anomalies seen in pyramids of numbers (e.g., one tree supporting insects).
Highlights inefficiencies in energy transfer	Helps explain why food chains have limited trophic levels.

 

Why Are Food Chains Short?

• Energy transfer is inefficient, with most energy lost at each level.
• Typically, there are fewer than five trophic levels, as energy becomes too scarce to support higher levels.

 

Human Food Chain & Energy Transfer

• These energy chains and flows apply to humans also however as humans are omnivores we have more options on what we eat
• Based on the knowledge of pyramids of energy it is way more efficient for humans to corn than to eat chicken: $$\text{corn} \to \text{chicken} \to \text{human} \\ \text{corn} \to \text{human}$$
• This is as by eating chicken we have less enery available to use as the chicken has wasted energy and not all of it is consumable 
• So in terms of energy efficiency it is better for humans to be herbivores compared to carnivores due to lost energy
• However, in actual fact animals often eat or are feed things we can't process properly or wouldn't eat.
• So by eating meat we are able to indirectly consume things we wouldn't normally be able to eat, i.e  $$\text{plankton} \to \text{sardines} \to \text{human}$$