Following the Energy

Following the Energy

Middle School

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Learning Objectives

• Define the roles of producers, consumers, and decomposers within an ecosystem.

• Describe how energy flows and matter cycles using a food web model.

• Analyze how the 10% rule of energy transfer leads to the trophic pyramid.

• Explain the environmental impact of toxins like DDT through biomagnification.

Key Vocabulary

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Ecosystem

An ecosystem is a community of living organisms interacting with their nonliving environment.

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Cycling of Matter

The continuous movement of essential atoms and molecules between the living and nonliving parts of an ecosystem.

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Flow of Energy

The one-way transfer of energy from one organism to another through the different levels in an ecosystem.

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Biomagnification

The increasing concentration of toxic substances in organisms at successively higher levels in a food chain.

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Trophic Level

This describes an organism's specific position within a food web, showing its feeding relationship to others.

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Biomass

Biomass is the total mass of all living or recently deceased organic matter within a specific area.

Key Vocabulary

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Food Web

A model showing feeding relationships and how energy flows through an ecosystem among different organisms.

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Producer

An organism, like a plant, that produces its own food using light, water, or chemicals.

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Consumer

An organism that obtains energy by feeding on other organisms in a food web.

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Decomposer

An organism that breaks down dead organic material, returning nutrients back to the ecosystem.

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DDT

DDT, or Dichlorodiphenyltrichloroethane, is a long-lasting synthetic pesticide used to control insects.

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Conservation of Matter

The principle that matter is not created or destroyed, only changed and recycled in ecosystems.

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Rachel Carson and Biomagnification

• Biologist Rachel Carson was concerned about chemical pesticides like DDT after World War II.

• These chemicals were used to protect crops and control disease-carrying insects.

• DDT entered the food chain and was absorbed by small organisms.

• This biomagnification process harmed top predators like the bald eagle.

Multiple Choice

What is biomagnification?

• The process where toxins become more concentrated as they move up a food chain.

• The process where pesticides are safely broken down by soil and water.

• The process where animals develop a resistance to chemical pesticides.

• The process where fragile eggs are caused by a lack of calcium.

Multiple Choice

According to Rachel Carson's research, how did a pesticide like DDT first enter the food chain?

• It was directly sprayed on top predators like bald eagles.

• It entered the soil and water, where it was taken in by small organisms.

• It caused eggs to become fragile before entering the food chain.

• It was a chemical that only affected plants, not animals.

Multiple Choice

Which organisms in a food chain are most severely affected by biomagnification, and why?

• The small organisms, because they are the first to absorb the toxins.

• The top predators, because they accumulate toxins from everything they eat.

• All organisms would be affected in the exact same way.

• The soil and water, because that is where the toxins are originally found.

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The People Demand Action

• Rachel Carson's 1962 book, Silent Spring, sparked public debate over pesticide dangers.

• A presidential committee confirmed Carson’s warnings, leading to new pesticide control laws.

• In 1970, the Environmental Protection Agency (EPA) was established to control pollution.

• The 1972 ban on DDT helped the bald eagle population recover.

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Multiple Choice

What was the main reason the Environmental Protection Agency (EPA) was established in 1970?

• To control pollution.

• To publish books about pesticide dangers.

• To help the bald eagle population recover.

• To confirm the warnings in Rachel Carson's book.

Multiple Choice

What was the relationship between Rachel Carson's book Silent Spring and the U.S. government?

• The book's warnings led to government investigation and new laws.

• The government hired Rachel Carson to work for the EPA.

• The book was written to celebrate the creation of the EPA.

• The government immediately banned all pesticides mentioned in the book.

Multiple Choice

What is the most important conclusion that can be drawn from the ban on DDT and its effect on bald eagles?

• Government actions to control harmful substances can lead to the recovery of animal populations.

• The bald eagle is the only animal that was affected by the pesticide DDT.

• The EPA was created for the sole purpose of protecting the bald eagle.

• Rachel Carson's book was mainly about the recovery of the bald eagle.

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Modeling an Ecosystem

Living Components

• Producers, such as plants, make their own food using sunlight.

• Consumers are animals that get energy by eating other living things.

• Decomposers, like fungi and bacteria, break down dead organic material.

Nonliving Components

• Nonliving parts include air, with gases like carbon dioxide (CO₂).

• Water, soil, and minerals provide essential matter for organisms to grow.

• Sunlight provides the primary source of energy that powers the ecosystem.

Multiple Choice

Which type of organism gets its energy by breaking down dead organic material?

• Producer

• Consumer

• Decomposer

• Sunlight

Multiple Choice

What is the combined role of nonliving components like sunlight, water, and soil in an ecosystem?

• They provide the matter and energy that living things need to grow and survive.

• They are the main food source for all the consumers in the ecosystem.

• They convert living components into soil and minerals.

• They are responsible for creating their own food from nothing.

Multiple Choice

Based on the relationships in an ecosystem, what would be the most likely outcome if all producers were removed?

• Consumers would not have a source of food energy.

• Decomposers would stop breaking down dead material.

• The amount of carbon dioxide in the air would decrease.

• The amount of water and soil would increase.

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Trophic Levels and Food Webs

• A food web shows how matter and energy move between organisms.

• Arrows show the direction of energy flow from the eaten to the eater.

• An organism's trophic level is its position in the food web.

• Producers have the most biomass, followed by consumers at higher trophic levels.

Multiple Choice

What is the primary function of a food web diagram?

• To show how matter and energy are transferred between organisms

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

• To describe the reproductive cycles of different species

• To compare the physical sizes of various organisms

Multiple Choice

In a food web, what is the specific meaning of the arrows between organisms?

• The direction of energy flow from the organism that is eaten

• Which organism is the predator in a relationship

• The path of animal migration within an ecosystem

• The amount of biomass an organism contains

Multiple Choice

Based on the principles of trophic levels and biomass, what would be the most likely consequence of a sudden disease that wipes out most of the producers in a food web?

• The total biomass at all other trophic levels would likely decrease.

• The total biomass in the food web would not be affected.

• The amount of energy available to producers would increase.

• Organisms at the top of the food web would not change.

The Flow of Energy

• Energy flows in one direction and is mostly lost as heat.

• Only about 10% of energy transfers to the next consumer.

• Energy loss at each level limits the length of food chains.

Multiple Choice

What is the fundamental pattern of energy flow within a food chain?

• It flows in one direction from one organism to another.

• It cycles back and forth between organisms.

• It is created at each level of a food chain.

• It is completely lost at the first level.

Multiple Choice

What is the relationship between the levels in a food chain and the amount of energy transferred between them?

• The amount of available energy significantly decreases at each level.

• The amount of available energy increases at each level.

• All of the energy is transferred completely to the next level.

• Energy is shared equally among all levels in the food chain.

Multiple Choice

Which statement best explains why food chains are rarely longer than four or five levels?

• There is not enough energy remaining to support populations at higher levels.

• Organisms at higher levels reproduce too slowly to survive.

• There are too many predators at the top of the food chain.

• Producers at the bottom cannot create enough initial energy.

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The Cycling of Matter

• Unlike the one-way flow of energy, matter is cycled in an ecosystem.

• ​This follows the law of conservation of matter, where atoms are rearranged.

• Producers absorb matter like carbon and water from the nonliving environment.

• Decomposers return these atoms to the soil, water, and air.

Multiple Choice

Which statement best describes how matter moves through an ecosystem?

• It is cycled and reused continuously by living and nonliving parts of the ecosystem.

• It flows in one direction and is eventually used up.

• It is created by producers and destroyed by decomposers.

• It moves from nonliving parts to living parts, but not back.

Multiple Choice

What are the primary roles of producers and decomposers in the cycling of matter?

• Producers take in matter from the environment, while decomposers return matter to it.

• Producers destroy matter, while decomposers create new matter.

• Both producers and decomposers take in matter from other living things.

• Decomposers provide matter directly to producers to eat.

Multiple Choice

A tree dies in a forest, but nothing breaks it down. Based on the principle of conservation of matter, what would be the most likely result?

• The atoms that make up the dead tree would not be returned to the soil for producers to use.

• The atoms in the dead tree would be destroyed and disappear from the ecosystem.

• Producers would start making new atoms to replace the ones in the dead tree.

• Energy would stop flowing through the ecosystem entirely.

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The Role of Decomposers

• Decomposers, like bacteria and fungi, consume dead organisms and waste products.

• ​This decay process breaks down complex organic material into simple chemicals.

• This role is essential as it recycles nutrients back into the soil and water.

• Without decomposers, producers would lack nutrients needed for the ecosystem to survive.

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Multiple Choice

What is the main role of decomposers, such as bacteria and fungi?

• To produce energy from sunlight

• To break down dead organisms and waste products

• To consume living plants and animals

• To provide shelter for small animals

Multiple Choice

Why is the decay process essential for an ecosystem?

• It turns simple chemicals into complex materials.

• It recycles nutrients that producers need to grow.

• It provides a direct food source for large animals.

• It cleans the water by removing all chemicals.

Multiple Choice

Based on the role of decomposers, what would most likely happen if they were all removed from an ecosystem?

• Dead organisms would stop accumulating.

• The soil would become overly rich in nutrients.

• Producers would not have enough nutrients to survive.

• Animals would start breaking down their own waste.

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Common Misconceptions

Misconception	Correction
Energy is recycled in an ecosystem.	Energy flows one way and is lost as heat; matter is recycled.
When something dies, its matter disappears.	Decomposers return atoms from dead organisms back to the environment.
Food chains are more accurate than food webs.	Food webs are more realistic, showing complex feeding relationships.
Organisms at the top of the food pyramid are the most numerous.	The number of organisms decreases at higher trophic levels.

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Summary

• In ecosystems, energy flows through food webs, while matter is constantly cycled.

• Only about 10% of energy transfers between trophic levels, limiting food chain length.

• Decomposers are vital for recycling matter from dead organisms back into the environment.

• Human-made toxins like DDT can build up in food webs, harming top predators.

Poll

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

• 1

• 2

• 3

• 4