- 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.
- 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.
- 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?
- 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
- 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)
- 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
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