Changing Ecosystems

Changing Ecosystems

Middle School

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Learning Objectives

• Define primary and secondary succession and how ecosystems change over time.

• Analyze how resource availability affects organism growth and population size.

• Describe how energy flows and matter cycles in an ecosystem.

• Explain how disruptions affect the balance of an ecosystem.

Key Vocabulary

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Ecological Succession

The gradual process by which the species structure of a biological community changes over time.

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Primary Succession

This is a type of ecological succession that begins in a place without any soil.

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Secondary Succession

This type of succession occurs in an area that previously had life and still contains soil.

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Eutrophication

The process where a body of water becomes overly enriched with minerals and various nutrients.

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Dynamic Equilibrium

A state of balance where ecosystem components remain stable despite ongoing changes and processes.

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Resource Availability

The supply of necessary items like food, water, and living space available to organisms.

Key Vocabulary

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Competition

The struggle between organisms for limited resources like food, water, and space in an ecosystem.

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Producer

An organism, like a plant, that makes its own food, usually through the process of photosynthesis.

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Consumer

An organism that gets its energy by eating other organisms in order to survive and grow.

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Decomposer

An organism that breaks down dead plants and animals, returning important nutrients back to the soil.

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Food Web

A model that shows how energy and matter flow through an ecosystem, connecting many food chains.

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Ecological Succession on Land

Primary Succession

• ​Starts in new areas with little to no soil, like on bare rock.

• ​​Pioneer species, such as lichens, are the first organisms to arrive.

• ​They help create soil by breaking down rock over a long time.

Secondary Succession

• ​Happens in areas where soil is already present after a disturbance.

• ​​The process usually begins with grasses and wildflowers growing in the soil.

• ​This succession is much faster because soil is already available for plants.

Multiple Choice

What is the key difference between primary and secondary succession?

• Primary succession begins on bare rock, while secondary succession begins in an area with soil.

• Primary succession happens quickly, while secondary succession happens over a long time.

• Primary succession starts with grasses, while secondary succession starts with lichens.

• Primary succession occurs after a disturbance, while secondary succession occurs in new areas.

Multiple Choice

What is the specific role of pioneer species, such as lichens, during primary succession?

• They break down rock to begin the process of soil formation.

• They are the last organisms to appear in an ecosystem.

• They grow quickly in areas where soil is already present.

• They provide a food source for large animals.

Multiple Choice

A wildfire burns a forest, clearing away the trees and plants, but the soil remains. Which process is most likely to happen next and why?

• Secondary succession, because the soil is already present.

• Primary succession, because all the plants were removed.

• Primary succession, because pioneer species like lichens will arrive first.

• Secondary succession, because it always starts with bare rock.

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Resource Availability and Competition

Plentiful Resources

• Organisms have easy access to essentials for life like food, water, and sunlight.

• With plenty of resources, populations can grow larger and individuals can thrive and be healthy.

• There is little to no need for organisms to compete with each other for survival.

Limited Resources

• Organisms struggle to find enough food, water, or other necessities to survive in their habitat.

• Competition increases as organisms with similar needs must fight for the few available resources.

• This scarcity can lead to smaller populations and can limit the growth of individual organisms.

Multiple Choice

Under which condition are organisms most likely to compete with each other?

• When they live in different habitats with different types of food

• When they have similar needs for resources that are not abundant

• When there is easy access to essentials like food and water

• When populations are small and healthy

Multiple Choice

What is the relationship between plentiful resources and the health of a population?

• Organisms must fight with each other to find enough food

• Populations can grow larger and individuals can thrive

• The growth of individual organisms is limited

• Competition between organisms for water increases

Multiple Choice

Imagine a forest ecosystem experiences a severe drought, significantly reducing the amount of available water. Based on the principles of resource availability, what is the most likely outcome?

• The animals will learn to share the limited water, and the population will grow.

• Competition for water will increase, and the overall population size will likely decrease.

• The animals will have easy access to essentials, and individuals will be healthier.

• There will be no need for competition, and the population size will stay the same.

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Energy Flow and Matter Cycling

Flow of Energy

• Energy powers ecosystems and flows in one direction, usually starting from the sun.

• Producers, like plants, capture the sun's energy to make their own food.

• Energy is transferred through the food web as consumers eat other living organisms.

Cycling of Matter

• Matter, in the form of atoms and nutrients, is cycled within an ecosystem.

• Decomposers break down dead organisms, returning matter to the soil, air, and water.

• This recycled matter is then available for producers to use all over again.

Multiple Choice

What is the main difference between how energy and matter move through an ecosystem?

• Energy flows in one direction, while matter is cycled.

• Energy is cycled, while matter flows in one direction.

• Both energy and matter are created by producers.

• Both energy and matter flow in one direction.

Multiple Choice

What is the primary function of decomposers in an ecosystem?

• To capture energy from the sun to make food.

• To transfer energy by eating other living things.

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

• To convert matter into a one-way flow of energy.

Multiple Choice

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

• The flow of energy would stop because the sun's energy could not be captured.

• The cycling of matter would stop, and producers would run out of nutrients.

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

• Consumers would have more food to eat.

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How Aquatic Ecosystems Change

Aquatic Succession

• ​Aquatic succession is the gradual process of change in freshwater ecosystems over a long period.

• ​​Sediments and decaying organisms build up on the bottom of a pond or lake over time.

• ​The water body gradually fills with soil, eventually transforming into a land ecosystem.

Eutrophication

• ​Eutrophication occurs when water becomes too rich in nutrients, often accelerated by human activity.

• ​​Runoff from farms can add excess fertilizers to the water, causing large algae blooms.

• ​These algae consume most of the oxygen, which harms or kills fish and other aquatic life.

Multiple Choice

What is the term for the gradual process of change in a freshwater ecosystem over a long period?

• Aquatic succession

• Eutrophication

• Nutrient runoff

• Oxygen depletion

Multiple Choice

What is the relationship between fertilizer runoff and the health of a lake?

• Fertilizer runoff causes algae to grow, which reduces oxygen for fish.

• Fertilizer runoff adds soil, which helps fish build nests.

• Fertilizer runoff makes the water clearer, which helps plants grow.

• Fertilizer runoff has no effect on the overall health of a lake.

Multiple Choice

If a shallow pond slowly fills with sediments and decaying organisms over hundreds of years, what is the most likely long-term outcome?

• The pond will eventually become a land ecosystem.

• The pond will become deeper and support more fish.

• The water in the pond will become extremely rich in nutrients.

• The pond will experience a massive bloom of algae.

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Ecosystem Disruptions

Natural Disruptions

• Natural events such as forest fires, floods, and diseases can disrupt ecosystems without any human influence.

• These disruptions change the physical environment and affect the availability of essential resources for survival.

• Changes in resources can directly impact the growth and survival of different populations within the ecosystem.

Human Disruptions

• Human activities like deforestation, pollution, and introducing nonnative species significantly impact the ecosystem’s balance.

• Deforestation removes vital food and shelter resources, which can harm the species that depend on them.

• Pollution can contaminate water sources, making them unusable and increasing competition among different animal populations.

Multiple Choice

What is the primary effect of a major disruption in an ecosystem?

• It changes the physical environment and affects resource availability.

• It only causes harm to the plants in an ecosystem.

• It helps all animal populations grow larger.

• It exclusively involves human activities like pollution.

Multiple Choice

How does the human activity of deforestation harm species within an ecosystem?

• By removing the food and shelter that species depend on.

• By making water sources unusable for all animals.

• By introducing new types of diseases to the ecosystem.

• By causing natural events like floods and fires.

Multiple Choice

If a large flood forces a population of animals to migrate to a new, smaller forest, what is the most likely consequence for that ecosystem?

• Competition for resources will likely increase among the animal populations.

• The new species will immediately adapt and find new food sources.

• The existing animal populations will not be affected by the change.

• The overall number of resources in the ecosystem will increase.

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Common Misconceptions

Misconception	Correction
Energy and matter are the same in an ecosystem.	Energy flows through an ecosystem, while matter is cycled within it.
All forest fires are bad for ecosystems.	Low-intensity fires can be beneficial, clearing underbrush and returning nutrients to soil.
Adding nutrients to a lake helps all organisms.	Too many nutrients can cause algae to overpopulate, harming other aquatic life.

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Summary

• Energy flows through an ecosystem, while matter is constantly cycled.

• Competition for resources determines the growth and size of populations.

• Ecosystems change over time and can be upset by natural or human disruptions.

• Eutrophication from excess nutrients can harm aquatic life by reducing oxygen.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1 (Not confident)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)