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APES 3.2 - Energy in Ecosystems Part 2
Kaitlin Kogut
Created on October 20, 2024
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Transcript
What happens when a species is removed from a food web?
Food Webs
Food Chains
10% Rule
- Determine how the energy decreases as it flows through ecosystems.
- Describe food chains and food webs, and their constituent members by trophic level.
Energy in Ecosystems (Part 2)
Lesson 3.2
Most of the energy consumed by an organism is used for its own bodily functions like movement, digestion, and heat generation, leaving only a small percentage to be transferred to the next trophic level when it is eaten by another organism. This is an example of the Second Law of Thermodynamics in nature!
Producers (photosynthetic organisms) are responsible for producing the energy for an ecosystem - the Net Primary Productivity. That energy gets transferred to the next trophic level when the producers are eaten by herbivores. But much of that energy (90% of it) gets "lost" in the transfer. The 10% rule means that when energy is passed in an ecosystem from one trophic level to the next, only ten percent of the energy will be passed on. So where did the other 90% go?
Energy decreases with each new trophic level...
- If one species in the chain goes extinct, the chain is "broken," and all other species will be impacted.
- A food chain is a linear sequence that shows how energy and nutrients move through an ecosystem as one organism eats another.
- Food chains are made up of trophic levels, which are the sequential stages in the chain. Each organism in the food chain occupies a specific trophic level.
Simple food chains are susceptible to stress...
- A food web is a system of interconnected food chains.
- Because of this interconnectedness, if one species goes extinct, the other species in the web have other options for where they can get their energy. This makes food webs more resilient to stressors than chains.
Food webs are more resilient than single chains...
Trophic cascades are not all bad. In this example, removing the apex predator (the wolf) allows the deer population to grow, but all those extra deer drastically limit the producers. Keeping the apex predator in the food web ensures the producers can thrive.
A trophic cascade occurs when a species in a food web is suppressed or reintroduced, and the effects ripple through the food web.