MS-LS2-3: Energy Flow in an Ecosystem

MS-LS2-3
Energy Flow in an Ecosystem

Middle School

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Learning Objectives

• Develop a model for how matter cycles and energy flows in an ecosystem.

• Analyze how the one-way flow of energy limits organisms between trophic levels.

• Explain the roles of producers, consumers, and decomposers in an ecosystem.

• Explain how the conservation of matter ensures atoms are cycled through an ecosystem.

Key Vocabulary

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Ecosystem

An ecosystem is a community of living organisms interacting with their non-living physical environment.

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Trophic Level

This describes an organism's position in a food web based on its source of energy.

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Food Web

A food web is a model showing the complex network of feeding relationships in an ecosystem.

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Producer

A producer is an organism, like a green plant, that produces its own food using sunlight.

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Consumer

A consumer is an organism that obtains its energy by feeding on other living organisms.

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Decomposer

A decomposer breaks down dead organic material, recycling nutrients back into the ecosystem for producers to use.

Key Vocabulary

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Energy Flow

Energy flow is the one-way transfer of energy through an ecosystem, from producers to consumers.

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Cycling of Atoms

The cycling of atoms is the continuous process of atoms moving between living and nonliving things.

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Conservation of Matter

The conservation of matter is the principle that matter is not created or destroyed, only changed.

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Biomass

Biomass refers to the total mass of all living or recently living organisms in a specific area.

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Biomagnification

Biomagnification is the process where toxins become more concentrated in organisms at higher trophic levels.

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Abiotic Factor

An abiotic factor is a non-living chemical or physical part of an ecosystem, like water or sunlight.

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Defining an Ecosystem

• An ecosystem has all living and nonliving parts of an environment.

• Living parts are producers, consumers, and decomposers.

• The Mono Lake ecosystem has salty water and a specialized food web.

• Algae, brine shrimp and flies, and migratory birds form the food web.

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Multiple Choice

What is an ecosystem?

• All the living and nonliving parts of an environment

• Only the living parts of an environment

• Only the animals and plants in a food web

• The salty water and birds of a specific lake

Multiple Choice

Which statement correctly classifies the parts of the Mono Lake ecosystem?

• The salty water is a nonliving part, while the algae, shrimp, and birds are living parts.

• The algae and brine shrimp are nonliving parts that the birds consume.

• All parts of the Mono Lake ecosystem, including the water, are living.

• The producers and consumers are nonliving parts of the environment.

Multiple Choice

If a change in the environment caused the algae in Mono Lake to die off, what would be the most likely impact on the food web?

• The brine shrimp and fly populations would decrease due to a lack of food.

• The migratory bird population would increase.

• The saltiness of the water would decrease.

• The nonliving parts of the ecosystem would not be affected.

Trophic Levels and Energy Flow

• Organisms are grouped into feeding levels called trophic levels.

• Energy flows from producers to consumers in an ecosystem.

• Only 10% of energy is transferred to the next level.

Multiple Choice

What are trophic levels in an ecosystem?

• The different feeding levels that organisms are grouped into.

• The process of energy creation by producers.

• The total number of organisms in an ecosystem.

• The path that water travels through an environment.

Multiple Choice

What is the relationship between producers, consumers, and the flow of energy?

• Energy moves from the consumers to the producers.

• Energy is shared equally among all organisms.

• Energy moves from the producers to the consumers.

• Energy is created at each trophic level.

Multiple Choice

If the producers in a food chain have 1,000 units of energy, how much energy is passed on to the consumers at the very next level?

• 1,000 units

• 900 units

• 100 units

• 10 units

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Food Webs: Energy Flow and Matter Cycling

Energy Flows

• A food web is a model showing how energy is transferred through an ecosystem.

• It illustrates the complex, overlapping feeding relationships between many different organisms.

• Energy travels in one direction and is eventually lost from the ecosystem as heat.

Matter Cycles

• Decomposers, like bacteria and fungi, are crucial for recycling matter in an ecosystem.

• They break down dead plants and animals, returning nutrients back to the environment.

• This ensures the chemical building blocks of life are available for producers to use.

Multiple Choice

What is the primary purpose of a food web model?

• To show how energy is transferred between organisms in an ecosystem.

• To list all the animals that live in a particular habitat.

• To explain how decomposers create new energy for producers.

• To show how matter is lost from an ecosystem as heat.

Multiple Choice

What is the main function of decomposers, such as bacteria and fungi, in an ecosystem?

• They create energy from sunlight for the entire ecosystem.

• They consume producers to control their population.

• They break down dead organisms and return nutrients to the environment.

• They help energy flow in one direction by hunting consumers.

Multiple Choice

What would most likely happen in an ecosystem if all decomposers were removed?

• The amount of energy in the ecosystem would increase over time.

• Producers would have to find a new source of energy.

• The cycling of matter would stop, and producers would lack necessary nutrients.

• Consumers would have more dead plants and animals to eat.

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Conservation of Matter: The Cycling of Atoms

• The principle of conservation of matter means that matter is not created or destroyed.

• The same atoms are continuously cycled between living and nonliving parts of the ecosystem.

• Matter is transferred at every level of the food web when organisms are eaten.

• Decomposers return atoms from dead organisms back to the soil and the air.

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Multiple Choice

What does the principle of conservation of matter state?

• Matter is not created or destroyed, only cycled.

• New matter is constantly created by producers.

• Matter is permanently lost when an organism dies.

• Only living parts of an ecosystem contain matter.

Multiple Choice

How does a food web contribute to the cycling of matter in an ecosystem?

• By creating new atoms for growing animals.

• By transferring atoms from one organism to another when they are eaten.

• By destroying the atoms of organisms that have died.

• By moving atoms only from nonliving to living parts of the ecosystem.

Multiple Choice

What would be the most likely consequence for an ecosystem if all decomposers were removed?

• Atoms from dead organisms would not be returned to the soil and air.

• The total amount of matter in the ecosystem would slowly decrease.

• Matter would stop being transferred between living organisms in the food web.

• The cycling of atoms between living and nonliving things would speed up.

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What is Biomagnification?

• Harmful substances like the pesticide DDT build up in an organism's body.

• The toxin’s concentration magnifies as it moves up each trophic level.

• High DDT levels in bald eagles caused their eggshells to become too thin.

• Rachel Carson’s book Silent Spring led to a ban on DDT in the U.S.

Multiple Choice

What is the definition of biomagnification?

• The increasing concentration of toxins at higher trophic levels.

• The process of toxins breaking down in an organism's tissues.

• The removal of harmful substances from an ecosystem.

• The creation of harmful substances by top predators.

Multiple Choice

According to the information presented, what was the primary effect of high DDT levels on bald eagles?

• It caused the shells of their eggs to become thin and break easily.

• It reduced the availability of fish for them to eat.

• It prevented the eagles from building strong nests.

• It made the eagles' feathers weaker and unable to fly.

Multiple Choice

In an aquatic food chain, algae absorb a toxin. The algae are eaten by zooplankton, which are eaten by small fish. An osprey then eats the small fish. In which organism would the toxin concentration be highest?

• The osprey, because it is the top predator.

• The algae, because it is the original source of the toxin.

• The zooplankton, because they are small and vulnerable.

• The small fish, because they eat many zooplankton.

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Common Misconceptions

Misconception	Correction
Energy is recycled within an ecosystem.	Energy flows one-way through an ecosystem; it is matter that is recycled.
When an organism dies, its matter is destroyed.	Matter is conserved and returned to the ecosystem by decomposers.
The top of the food web has the most energy.	The least amount of energy is available at the top of the food web.
Organisms only have one role in a food web.	Many animals, called omnivores, can feed at multiple different levels.

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Summary

• Energy flows in one direction, while matter is recycled in an ecosystem.

• Only about 10% of energy is transferred between each trophic level.

• Producers capture energy, consumers transfer it, and decomposers recycle matter.

• Harmful substances can become more concentrated at higher trophic levels.

Poll

On a scale of 1-4, how confident are you about explaining how energy flows and matter cycles through an ecosystem?

• 1

• 2

• 3

• 4