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How do matter and energy flow through ecosystems?
An ecosystem includes both living organisms and the non-living parts of their habitat. Ecosystems can be small or large, and exist both on land and in water.
Imagine a forest ecosystem here in Michigan. All the energy in this ecosystem originates from the sun. Put the following organisms in order in the food chain below to show how energy flows through the forest, beginning with the sun.
Sun → ___________ → ___________ → ___________ → ___________
Mouse Fungi Hawk Oak tree (acorns)
In this ecosystem, plants transform energy from the sun so that it can be used as food for plants and other organisms. The process they use to do this called photosynthesis. During photosynthesis, plants use the sun’s energy to make food (sugars) out of carbon dioxide from the air and water that they absorb through their roots. How does photosynthesis contribute to the rest of the food chain?
Organisms in an ecosystem are often categorized as producers, consumers, or decomposers. Producers create their own food, consumers use other organisms as a source of food, and decomposers break down dead plants and animals. Use the chart below to categorize the organisms from your food chain as producers, consumers, or decomposers.
Producers Consumers Decomposers
Consumers can be herbivores, carnivores, or omnivores. Herbivores eat plants, carnivores eat meat, and omnivores eat both. Look at your list of consumers. What do you think each one is?
What might happen if a producer is removed from an ecosystem? Suppose that a fungus kills most of the oak trees in the ecosystem above. How might the other organisms in the food chain be affected? How would the flow of matter and energy through the ecosystem change?
Now, instead of removing a producer, let’s think about what might happen if a consumer were removed from the ecosystem. Imagine that a disease wipes out the hawk population. How might that affect the other components of the ecosystem?
Teacher Guide
Consumers can be herbivores, carnivores, or omnivores. Herbivores eat plants, carnivores eat meat, and omnivores eat both. Look at your list of consumers. What do you think each one is?
The hawk is a carnivore, because it only eats other animals. Its diet includes small mammals, birds, and reptiles. In this food chain, the mouse is an herbivore that feeds on acorns. However, some mice will eat insects when they are available--so mice can be omnivores too!
What might happen if a producer is removed from an ecosystem? Suppose that a fungus kills most the oak trees in the ecosystem above. How might the other organisms in the food chain be affected? How would the flow of matter and energy through the ecosystem change?
Encourage your students to think through many possibilities related to what might happen if the oak trees were removed from this ecosystem. Remind them that an ecosystem is much more complicated than a single food chain. Are there other food sources that herbivores might turn to if acorns were no longer available? What would that mean for those plant species? With decreased competition from oak trees, other tree species might expand. However, they would likely also experience increased predation from herbivores that previously ate primarily acorns. With less food available, the mouse population might decline. What would that mean for omnivores and carnivores that prey on mice? What about for other species that occupy a similar niche (e.g., voles and rabbits)?
Now, instead of removing a producer, let’s think about what might happen if a consumer were removed from the ecosystem. Imagine that a disease wipes out the hawk population. How might that affect the other components of the ecosystem?
Again, encourage students to think through possibilities beyond the single food chain depicted here. With fewer top predators in the ecosystem, prey populations (like mice and other small mammals) would likely increase. If there are more mice in the ecosystem, they’ll need to eat more acorns. How might this affect the population of oak trees and other plants that mice use for food? If the population of mice increases, but their food sources stay the same, what might happen over time?
