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Energy through an Ecosystem - Food Webs

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Energy through an Ecosystem - Food Webs Answer Key

1. 
Which graphic best represents the flow of energy in a biome?
  1. food chain
  2. food web
  3. energy pyramid
  4. food circle
2. 
The diagram shows a typical food web in a forest ecosystem.
Food Web
A. 
In the food web, which organism would be considered a tertiary consumer?
Food Web
  1. mushroom
  2. mouse
  3. snake
  4. hawk
B. 
Considering the food web, what would be the most likely impact on the ecosystem if a pesticide is applied to the grass, which causes the grass to die?
Food Web
  1. The mouse population would increase from eating more mushrooms.
  2. The snakes would change their feeding mechanisms from consumers to producers.
  3. The hawk population would ultimately crash because there was nothing for them to eat.
  4. The number of mushrooms would increase dramatically due to increased decomposition.
C. 
Which position in the food web is occupied by mushrooms?
Food Web
  1. primary consumers
  2. decomposers
  3. producers
  4. tertiary consumers
D. 
A mountain lion with an affinity for eating snakes has moved into this ecosystem. What is a possible outcome of this disturbance?
  • While it is possible the ecosystem can support both the hawk and mountain lion as top predators, most likely there will be competition between the two species for food. Both species have adaptations that allow them to survive, so it is really unknown which one will prosper.
3. 
Choose whether 'biomagnification' or 'bioaccumulation' best completes the sentence. Write the correct term in the blank.

Bioaccumulation describes the process by which toxins are taken up and held in an organism from either exposure to or by eating food containing the toxin. Biomagnification occurs when concentrations of toxins in an organism increase due to transfer through the food chain, and specifically from energy loss across trophic levels.
4. 
Why are decomposers such an essential part of any food web and ecosystem?
  1. Decomposers recycle nutrients that keep the flow of energy going.
  2. Decomposers provide the base of all energy production in the food web.
  3. Decomposers are responsible for keeping the numbers of herbivores in check.
  4. Decomposers prevent new species from coming into the system.
5. 
In a food web, the arrows that connect the organisms always point toward the organism that does the eating.
  1. True
  2. False
6. 
The loss of energy from one trophic level to the next is called the 10 percent rule.
7. 
Why is it very uncommon for a food chain in a food web to have more than five steps?
  • A food web (or food chain) shows the transfer of energy between trophic levels in an ecosystem. Since most of the energy from each level is used by the organism itself for its own metabolism, there is very little energy to get passed to the next level. This means that by the time a top consumer eats, there is so little energy left that it has to consume an enormous amount of food to meet its needs. After five steps, the amount of energy left is so small that many organisms could not survive.

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