Ecology

Ecology

Middle School

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Learning Objectives

• Define ecology and distinguish between biotic and abiotic factors.

• Describe the different levels of the ecological hierarchy, from population to biosphere.

• Explain how energy flows through an ecosystem via producers, consumers, and decomposers.

• Illustrate energy transfer using food chains, food webs, and the 10% rule.

• Differentiate between a species' niche and its habitat.

Key Vocabulary

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Ecology

The scientific study of how living things interact with each other and their surrounding environment.

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Biotic Factor

The living or once-living parts of an environment, such as the plants and animals.

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Abiotic Factor

The non-living physical and chemical components of an environment, like sunlight, soil, and water.

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Ecosystem

All living organisms and the non-living things in a specific area, including their interactions.

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Niche

The specific role a species plays in its ecosystem, including all of its interactions.

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Habitat

The natural environment where a species lives and to which it has adapted over time.

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Biotic vs. Abiotic Factors

Biotic Factors

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

• This includes all organisms, from the smallest bacteria to the largest animals.

• Examples include predators, their prey, plants, fungi, and members of a species.

Abiotic Factors

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

• Key abiotic factors include sunlight, water, soil, climate, and temperature.

• These factors determine which species can survive in a particular ecosystem.

Multiple Choice

A fish in a river is affected by the other fish, the plants it eats, and the bacteria in the water. It is also affected by the water's temperature and the amount of sunlight. Which of the following is a complete list of the abiotic factors mentioned?

• Water temperature and amount of sunlight.

• The fish, the plants, and the water temperature.

• Only the amount of sunlight.

• Other fish, plants, and bacteria.

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Levels of Organization in Ecology

• Ecology is studied in levels, from a single species up to the entire planet.

• A population is all members of one species living in the same area.

• A community contains all the different populations that interact in the same area.

• An ecosystem is the community plus nonliving factors like water, soil, and air.

Multiple Choice

All of the different populations of species, including squirrels, oak trees, bees, and fungi, that live and interact in a single forest make up which level of ecological organization?

• A population

• An ecosystem

• A biome

• A community

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Core Ecological Concepts: Niche, Habitat, and Competition

• A species' niche is its specific role or 'job' in an ecosystem.

• A habitat is the natural environment or 'address' where a species lives.

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

• One species will be outcompeted or must adapt to different resources.

Multiple Choice

What does the Competitive Exclusion Principle suggest will happen if two different species try to occupy the exact same niche in a community?

• The two species will merge to become a single new species.

• Both species will immediately go extinct.

• One species will likely outcompete the other or evolve to fill a different niche.

• The two species will share the resources equally and coexist indefinitely.

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Energy Flow: Producers & Consumers

Producers (Autotrophs)

• ​Producers are organisms that create their own food and form the first trophic level.

• ​​Photoautotrophs, like plants, use sunlight to make food in a process called photosynthesis.

• ​Chemoautotrophs use energy from chemical compounds to make their own food through chemosynthesis.

Consumers (Heterotrophs)

• ​Consumers are organisms that get their energy by eating other living things for food.

• ​​Herbivores eat only producers, while carnivores get their energy by eating other animals.

• ​Omnivores are consumers that eat a diet that consists of both plants and animals.

Multiple Choice

What is the primary difference between a photoautotroph and a chemoautotroph?

• One is a plant and the other is an animal.

• Photoautotrophs are herbivores, while chemoautotrophs are carnivores.

• Photoautotrophs are consumers, while chemoautotrophs are producers.

• The source of energy they use to make food.

The Role of Decomposers

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Scavengers

• ​Scavengers consume the soft tissues of larger dead animals.

• ​​They are an important part of nature's cleanup crew.

• ​Vultures are a classic example of this type of decomposer.

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Detritivores

• ​Detritivores consume organic litter like dead leaves and animal waste.

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

• ​Earthworms are a common and well-known example of detritivores.

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Saprotrophs

• ​Saprotrophs perform the final step of the decomposition process.

• ​​They return vital nutrients back into the soil and water.

• ​Fungi and bacteria are the main types of saprotrophs.

Multiple Choice

Which group of organisms is responsible for performing the final step of decomposition, returning nutrients to the soil and water?

• Producers

• Detritivores

• Scavengers

• Saprotrophs

Modeling Energy Flow

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Food Chain

• Shows a simple, linear path for how energy flows in an ecosystem.

• For example: Grass is eaten by a deer, which is eaten by a wolf.

• Each step in the chain is called a trophic level.

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Food Web

• This is a complex network of many interconnected food chains in an ecosystem.

• It represents the multiple feeding relationships that exist in nature.

• Food webs are a more realistic model of how energy flows.

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The 10% Rule

• Only about 10% of energy moves from one trophic level to the next.

• The other 90% is used by organisms or is lost as heat.

• This rule limits the total number of trophic levels in an ecosystem.

Multiple Choice

If the producers in a food chain contain 10,000 units of energy, approximately how much energy will be available to the secondary consumers according to the 10% Rule?

• 10,000 units

• 1,000 units

• 10 units

• 100 units

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Common Misconceptions in Ecosystems

Misconception	Correction
A habitat and a niche are the same thing.	A habitat is an organism's address; a niche is its job.
Energy is recycled in an ecosystem.	Matter is recycled, but energy flows in one direction.
Food chains are a realistic model of nature.	Food webs are more realistic, showing many interconnected food chains.
Decomposers are not important in an ecosystem.	Decomposers are essential for recycling nutrients back into the ecosystem.

Multiple Choice

How do abiotic factors like sunlight availability and water temperature directly influence the types of biotic factors found in an aquatic ecosystem?

• They have no influence on the biotic factors.

• They only affect the number of predators in the ecosystem.

• They only change the color of the water and the organisms.

• They determine which organisms, like specific plants and animals, are adapted to survive and thrive there.

Multiple Choice

Based on the ecological hierarchy, why is studying an entire community more informative for understanding species interactions than studying a single population?

• A community and a population are the same thing.

• A population includes the abiotic factors, which are more important.

• A community includes the interactions between all different species, not just interactions within one species.

• Studying a community is easier because it involves fewer organisms.

Multiple Choice

If a disease drastically reduces the herbivore (primary consumer) population, what is the most likely immediate effect on the producers and secondary consumers?

• Producer populations will decrease, and secondary consumer populations will increase.

• Both producer and secondary consumer populations will increase.

• There will be no change to either population.

• Producer populations will increase due to less grazing, and secondary consumer populations will decrease due to less food.

Multiple Choice

Two species of birds live in the same forest and primarily eat the same type of small seed. According to the Competitive Exclusion Principle, what is a likely long-term outcome for these two species?

• The two species will learn to share the seeds perfectly and both will thrive equally.

• They will merge into a single new bird species through interbreeding.

• The forest will create more of the small seeds to support both species equally.

• One species may become more successful, or one might adapt to eat larger seeds, thus occupying a different niche.

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Summary

• Ecology studies interactions between living (biotic) and non-living (abiotic) factors.

• The environment is organized into levels, and each species has a habitat and niche.

• Energy flows in one direction through an ecosystem, from producers to consumers.

• Matter is recycled, while only 10% of energy transfers between trophic levels.

Poll

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

• 1

• 2

• 3

• 4