Ecology and Ecosystems

Ecology and Ecosystems

Middle School

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Learning Objectives

• Define ecology, ecosystem, and the roles of biotic and abiotic factors.

• Explain niche, habitat, and the competitive exclusion principle.

• Describe energy flow by identifying producers, consumers, and decomposers.

• Differentiate between food chains, food webs, and explain trophic levels.

Key Vocabulary

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Ecology

Ecology is the scientific study of how living organisms interact with each other and their surrounding environment.

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Ecosystem

An ecosystem includes all the living (biotic) and non-living (abiotic) parts interacting within a specific area.

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Niche

A niche is the specific role an organism plays, including its interactions with the environment and other species.

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Abiotic Factor

An abiotic factor is a non-living part of an ecosystem, like sunlight, water, temperature, or soil composition.

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Biotic Factor

A biotic factor is any living component that affects another organism or shapes the ecosystem, including all organisms.

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Trophic Level

A trophic level describes an organism's position in a food chain, indicating what it eats and what eats it.

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The Components of an Ecosystem

Biotic Factors

• Biotic factors are all the living or once-living parts of an ecosystem.

• This includes all of the plants, animals, fungi, and even tiny bacteria.

• The interactions between these organisms help define the ecosystem's community.

Abiotic Factors

• Abiotic factors are the non-living physical and chemical parts of an environment.

• Key examples include sunlight, temperature, soil type, and the availability of water.

• These factors determine which kinds of life can survive within an ecosystem.

Multiple Choice

What is the primary difference between biotic and abiotic factors in an ecosystem?

• Biotic factors are living or once-living, while abiotic factors are non-living.

• Biotic factors determine which life can survive, while abiotic factors define the community.

• Biotic factors include sunlight and soil, while abiotic factors include bacteria and fungi.

• Biotic factors are only animals, while abiotic factors are only plants.

Multiple Choice

How do abiotic factors like sunlight and temperature affect the biotic parts of an ecosystem?

• They determine which types of organisms are able to live and survive.

• They create the interactions between the different plants and animals.

• They are less important than the interactions between living things.

• They are the living parts that make up an ecosystem's community.

Multiple Choice

A new island forms from a volcanic eruption. At first, it is just bare rock. If the island develops a warm climate with plenty of sunlight and rainfall, what is the most likely long-term outcome?

• Plants and animals that can thrive in those conditions will begin to establish a community.

• The temperature and sunlight will decrease as more rocks are formed.

• The interactions between organisms will cause the amount of sunlight to increase.

• Only non-living factors like water and soil will exist on the island.

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A Species' Role in an Ecosystem

• A niche is the specific role an organism plays in its ecosystem.

• This includes its habitat, what it eats, and how it finds food.

• Two different species cannot occupy the exact same niche in the same habitat.

• They compete for resources, and one species will eventually be pushed out.

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Multiple Choice

What is an organism's niche?

• The physical size of the organism

• The total number of organisms in a habitat

• The age of the organism when it reproduces

• The specific role it plays in its ecosystem

Multiple Choice

According to the principle of competitive exclusion, why can't two different species occupy the exact same niche?

• Different species are active at different times of day

• One species will always be a predator of the other

• They will compete for the same limited resources

• They will not be able to find mates

Multiple Choice

A new species of bird that eats the same berries and builds its nests in the same type of tree as a native bird is introduced to a forest. What is the most likely long-term outcome for the two species?

• The new species will change the type of food it eats

• The two species will learn to share the resources

• The two species will begin to help each other

• One species will eventually be pushed out

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The Producers: Autotrophs

Photoautotrophs

• These producers capture energy from the sun to make their own food.

• This food-making process, using sunlight, is well known as photosynthesis.

• Examples include all green plants, algae, and some types of bacteria.

Chemoautotrophs

• These producers use energy from chemical compounds to make their own food.

• This process is called chemosynthesis and occurs in places without sunlight.

• This group includes certain types of bacteria and other microorganisms called archaea.

Multiple Choice

What is the defining characteristic of an autotroph?

• They produce their own food from an energy source.

• They rely on a host organism for survival.

• They break down dead organic material for nutrients.

• They consume other living organisms for energy.

Multiple Choice

What is the primary difference between how photoautotrophs and chemoautotrophs make food?

• The size of the organism.

• The temperature of their environment.

• The source of energy they use.

• The type of food they create.

Multiple Choice

Scientists discover a new microorganism living near a volcanic vent deep in the ocean where there is no sunlight. How does this organism most likely obtain its energy?

• By absorbing heat directly from the volcanic vent.

• By eating other small organisms that live nearby.

• By capturing the very faint sunlight that reaches the ocean floor.

• By using chemical compounds from the vent to make food.

The Consumers: Heterotrophs

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Herbivores

• Herbivores are consumers that get their energy by only eating producers.

• Producers are organisms like plants, algae, and some types of bacteria.

• Examples of herbivores include deer, rabbits, and many types of insects.

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Carnivores

• Carnivores are consumers that get their energy by eating other animals.

• Some carnivores eat herbivores, while others may eat other carnivores.

• Lions, sharks, and insect-eating frogs are all examples of carnivores.

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Omnivores

• Omnivores are consumers that eat both producers and other consumers.

• Their varied diet can include plants, animals, fungi, and algae.

• Humans, brown bears, and pigs are common examples of omnivores.

Multiple Choice

How do all consumers get their energy?

• By producing their own food using sunlight

• By drinking water from their environment

• By eating other organisms

• By absorbing nutrients from the soil

Multiple Choice

What is the primary difference that separates herbivores, carnivores, and omnivores into distinct groups?

• The habitat where the consumer lives

• The time of day the consumer is active

• The types of food the consumer eats

• The size of the consumer

Multiple Choice

A frog eats an insect, which in turn eats plants. Based on this information, which of the following statements is correct?

• The frog is an omnivore because it eats both insects and plants.

• The frog is a herbivore because its food eats plants.

• The frog is a producer because it is part of a food chain.

• The frog is a carnivore, and its energy originally came from a producer.

The Decomposers

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Scavengers

• ​These organisms consume the tissues of other dead animals.

• ​​They help to remove large carcasses from the environment.

• ​Vultures and raccoons are two common examples of scavengers.

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Detritivores

• ​These decomposers consume organic waste like dead leaves and feces.

• ​​They break down this waste material into much smaller pieces.

• ​Earthworms and dung beetles are key examples of detritivores.

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Saprotrophs

• ​These organisms perform the final step of the decomposition process.

• ​​They consume any organic material left by other decomposers.

• ​Fungi and protozoa are the most common examples of saprotrophs.

Multiple Choice

Which type of organism is best described as a consumer of the tissues of other dead animals?

• Scavenger

• Detritivore

• Saprotroph

• Producer

Multiple Choice

What is the primary difference between the role of a detritivore, like an earthworm, and a scavenger, like a vulture?

• Detritivores break down organic waste into smaller pieces, while scavengers consume large dead animals.

• Detritivores perform the final step of decomposition, while scavengers start the process.

• Detritivores consume dead animals, while scavengers consume dead plants.

• Detritivores are fungi, while scavengers are animals.

Multiple Choice

A tree falls in the forest and begins to decay. Which of the following correctly predicts the order of decomposers that will break it down?

• Saprotrophs (protozoa) will arrive first to break the wood into small pieces.

• Saprotrophs (fungi) will consume the last remaining material after other decomposers.

• Scavengers (vultures) will consume the dead wood and leaves first.

• Detritivores (earthworms) will consume the large branches and trunk of the tree.

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Energy Flow in Ecosystems

Food Chain

• A food chain shows a single, linear pathway for how energy flows.

• Each step is a trophic level, starting with producers and moving to consumers.

• This model is a simple way to track energy from one organism to another.

Food Web

• A food web shows many interconnected food chains within an ecosystem.

• It provides a more realistic picture of complex feeding relationships in nature.

• Only about 10% of energy moves to the next level in the web.

Multiple Choice

What is the primary purpose of both food chains and food webs in ecology?

• To show how organisms reproduce within a habitat.

• To track the flow of energy from one organism to another.

• To describe how producers create their own food.

• To list all the different species living in an ecosystem.

Multiple Choice

Why is a food web considered a more realistic model of an ecosystem than a food chain?

• Because it proves that all energy is transferred to the next level.

• Because it shows a single, linear path for energy flow.

• Because it includes only producers and primary consumers.

• Because it represents the many interconnected feeding relationships.

Multiple Choice

Given that only about 10% of energy moves to the next trophic level, what is the most likely consequence for the structure of an ecosystem?

• Energy is recycled, so all trophic levels have an equal number of organisms.

• Producers have less energy available to them than consumers do.

• The number of organisms at the highest levels is limited by the lack of available energy.

• There are more organisms at higher trophic levels than at lower ones.

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Common Misconceptions

Misconception	Correction
An ecosystem has to be a large area like a forest.	Ecosystems can be any size, even as small as a puddle.
All energy is passed from one trophic level to the next.	Only about 10% of energy is transferred to the next level.
Food chains are an accurate model of how all animals eat.	Food webs are more realistic as they show multiple feeding relationships.
Decomposers are the unimportant “end” of the food web.	Decomposers are crucial for recycling nutrients back into the soil.

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Summary

• Ecology studies interactions in ecosystems, shaped by biotic and abiotic factors.

• Each species has a unique niche, which helps avoid competition for resources.

• Energy flows from producers to consumers, and decomposers recycle matter.

• Only about 10% of energy is transferred between trophic levels in a food web.

Poll

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

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