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Ecology: Understanding the Flow of Matter and Energy in Ecosystems

Ecology: Understanding the Flow of Matter and Energy in Ecosystems

Author: Leah Gissler

NGSS Matter and Energy in Organisms and Ecosystems:   HS-LS2-4.     Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.

NGSS Interdependent Relationships in Ecosystems:   HS-LS2-6.     Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.

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BioNinja's Help with Understanding Food Chains and Food Webs

Click on the following link to the BioNinja's webpage on trophic levels, food chains, and food webs.

BioNinja: Trophic Levels

On a separate sheet of paper:

i. Draw a food chain making sure to label the trophic level of each organism in the chain.

ii. Draw a food web making sure to label the (approximate) trophic levels of each organism in the food web.

iii. List 3 differences between a food chain and a food web.

iv. Which is more realistic, a food chain or a food web, and why?

Trophic Levels and Energy Conversion Efficiency

1. Click on the following link: 

Glenco Online Learning: Modeling Ecosystems

2. Click on "Modeling Ecosystems" under Virtual Labs. You should be taken to a separate tab with a trophic pyramid and a list of organisms on the right hand side. You may be asked to activate Adobe Flash Player, to which you should click agree.

3. Read the introduction information under the essential question, "How does energy flow through an ecosystem?"

4. On a separate sheet of paper, define the following terms: producer/autotroph, heterotroph/consumer, decomposer, trophic level, herbivore, carnivore, first order heterotroph, second order heterotroph, energy conversion efficiency

5. Follow the directions for placing organisms within their respective trophic levels for 3 of the 5 ecosystems of your choice. To change between the ecosystems, click the drop down menu located above the third order heterotrophs. For each of these ecosystems:

i. Draw the trophic pyramid with the organisms labeled inside of each level.

ii. Include the number of organisms at each trophic level and the amount of energy.

iii. Calculate the energy conversion efficiency and write your answers at the transition line between the trophic levels on the left hand side.

6. After completing your drawings and calculations, answer the following questions.

a. Where do autotrophs/producers get their energy?

b. In which direction does energy flow in an ecosystem?

d. How do we calculate the energy conversion efficiency?

c. What are some of the reasons for why the energy conversion efficiency is typically 10% or less between each trophic level?

d. If we consider the amount of energy in the producers/autotrophs as 100%, what percent eventually makes it up to the third order heterotrophs/consumers?

e. Why is a food chain an inaccurate representation of the flow of energy within an ecosystem? (Hint: Does a higher trophic level always only feed on the trophic level right below it? What is an omnivore?)

f. Based on your answer to d, why is a food web a better representation of the flow of energy within an ecosystem and the relationships between organisms than a food chain?

Bozeman Science: Energy Flow in Ecosystems

As you watch the following video from Bozeman Science, answer the following questions on a separate sheet of paper.

a. What are the 2 ways that we can measure the flow of matter and energy within an ecosystem?

b. What is the difference between GPP and NPP?

c. What causes maximum NPP to alternate between the northern and southern hemispheres of the Earth during the year?

d. At which trophic level is there typically more biomass and why?

Amoeba Sisters Talk about Food Webs and Energy Pyramids

Watch the following video by the Amoeba Sisters to help reinforce the definitions of trophic levels, food chain, and food web.

After watching the video, answer the following question on a separate sheet of paper:

- What is biodiversity and why is more biodiversity better for an ecosystem than less biodiversity?

The Ecological Domino Effect

Read the following article from Science Daily and answer the following questions on a separate sheet of paper.

- What is an ecological domino effect?

- How did the death of the sunflower star fish cause an ecological domino effect?

- If the kelp forests are a home to many organisms, how will an explosion in the green sea urchin population affect the other organisms in the community?


Trophic Cascades: Another example of what happens when we alter the food chain

Watch the following TED-talk that discusses what happened to the Megafauna on Earth, the hope for rewilding our world, and the explanation of trophic cascades. Use the information in the video to answer the following questions.

- What is a trophic cascade?

- How did the introduction of the wolf back into Yellowstone National Park increase biodiversity within the park?

Take Home Message

Click on the link to access the Google form. Respond to the question on the Google form in an essay format using proper grammar and spelling.