Energy Movement in Ecosystems: Trophic & Energy Pyramid

• Organisms can be classified into trophic (feeding) levels depending on how they get their energy.
• Organisms that get their energy from nonliving sources (sun, organic matter) are called autotrophs (producers) and make up the 1st trophic level.
• Organisms that get their energy from other living things are called heterotrophs (consumers).
• Heterotrophs that eat autotrophs make up the 2nd trophic level and are called primary consumers.
• The third trophic level consists of secondary consumers and eat primary consumers.
• Ecosystems are normally limited to about 5 trophic levels.
• All energy in an ecosystem is derived from the sun*.
• This energy is converted to sugar (chemical energy) by plants through the process of photosynthesis.
• A food chain shows the transfer of energy from one trophic level to another.
• Whenever energy is transferred, some get lost.

Energy Pyramids

• Since energy is lost each time it is transferred, each trophic level receives less energy than the level before it.
• Also, energy gets used at each level, so only 10% of the energy from one trophic level gets passed onto the next trophic level.
• This can be shown using an energy pyramid.
• The size of the boxes represents the amount of energy in each trophic level.

Ecological Niches

• The function a species serves in its ecosystem, including what it eats, what eats it, and how it behaves.
• No two species occupy identical niches.

Types of Consumers

• A sequence of organisms, each feeding on the next, showing how energy is transferred from one organism to another.
• pine cone -> red squirrel -> weasel -> goshawk
• Energy is continuously lost from all levels of the food chain.
• Food chains do not exist in nature.
• Create a sample food chain using the following organisms: grass, snakes, snails, birds.
• What happens when one link is broken in a food chain?

Trophic Level

• The level of an organism in an ecosystem depends on its feeding position along a food chain.
• First trophic level – producers
• Second trophic level – primary consumers
• Third trophic level – secondary consumers
• Fourth trophic level – tertiary consumers

Ecological Pyramids

• A representation of energy, numbers, or biomass (the mass of living organisms in a given area) relationships in ecosystems.
• Energy pyramid – Energy loss and transfer between trophic levels; the size of each layer represents the amount of energy available at that trophic level.
• Only about 10% of the energy taken in by the individuals at one trophic level is passed on to individuals at the next level.
• 10% of it is used to build new biomass (the rest going to metabolic processes). In a pyramid of productivity, each step will be 10% the size of the previous step (100, 10, 1, 0.1, 0.01)

Energy Pyramid

• Pyramid of Energy Flow
• 10% passed on to next level (a lot energy is lost as HEAT or to fuel prey’s bodily functions)
• At each trophic level, the bulk of the energy received from the previous level is used in metabolism
• This energy is released as heat energy and lost to the ecosystem
• Eventually, all energy is released as heat

Numbers and Biomass Pyramids

• In a forest ecosystem, the tiny plant-feeding insects in the second trophic level outnumber the trees in the first trophic level.
• However, the biomass of all the trees is much greater than the biomass of herbivores.
• Example Biomass Pyramid

William Anderson (Schoolworkhelper Editorial Team)

William completed his Bachelor of Science and Master of Arts in 2013. He current serves as a lecturer, tutor and freelance writer. In his spare time, he enjoys reading, walking his dog and parasailing. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2024 | Creative Commons 4.0

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