Dynamic Ecosystems

Dynamic Ecosystems

Middle School

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Learning Objectives

• Describe the flow of energy and cycling of matter among living and non-living things.

• Analyze how resources affect the growth and population sizes of organisms.

• Differentiate between symbiotic, competitive, and predator-prey relationships.

• Explain how natural and human-caused disruptions can impact an ecosystem’s stability.

Key Vocabulary

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Ecosystem

All the living and nonliving things that interact in a specific area together.

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Producer

An organism that can make its own source of food, usually through photosynthesis.

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Consumer

An organism that gets its energy by feeding on and consuming other living organisms.

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Decomposer

An organism that breaks down dead organic matter, which helps in recycling important nutrients.

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Food Web

A model representation showing how energy and matter move through an entire ecosystem.

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Energy Flow

The movement of energy from the Sun through an ecosystem, captured by producers, then passed along to successive trophic levels.

Key Vocabulary

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Matter Cycling

The continuous movement of matter between the living and nonliving parts of an ecosystem.

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Limiting Factor

A resource, like limited food or water, that restricts the size of a population.

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Carrying Capacity

The maximum population size that an environment can successfully sustain over a long period.

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Symbiosis

A close and long-term interaction between two different biological species living together in an ecosystem.

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Ecological Succession

The gradual process of change in the species structure of an ecological community over time.

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Eutrophication

The over-enrichment of a body of water with minerals and nutrients, causing excessive algae growth.

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Levels of Ecological Organization

• An individual is a single organism, like an elephant.

• A population is a group of the same species in an area.

• A community is all the different populations living together.

• An ecosystem includes all living and non-living things in an area.

• The biosphere is the part of Earth and its atmosphere where life exists.

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Multiple Choice

Which of the following best defines a population?

• A single organism, such as an elephant.

• A group of the same species living in the same area.

• All the living and non-living things in a specific place.

• All the different populations that live together in an area.

Multiple Choice

What is the primary difference between a community and an ecosystem?

• A community is larger than an ecosystem.

• An ecosystem includes the non-living things in an area, while a community includes only living things.

• A community has only one species, while an ecosystem has many.

• An ecosystem describes a single organism, while a community describes a group.

Multiple Choice

A scientist is studying a herd of zebras, the lions that hunt them, the grasses they eat, and the local water sources in a savanna. Which is the highest level of ecological organization the scientist is studying?

• Population

• Community

• Ecosystem

• Biosphere

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How Energy Moves in Ecosystems

• Energy in an ecosystem flows in one direction, starting with the sun.

• Producers, like plants, use sunlight to make their own food through photosynthesis.

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

• Herbivores eat producers, while carnivores get energy by eating other consumers.

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Multiple Choice

What is the initial source of energy for the one-way flow of energy in an ecosystem?

• The sun

• The moon

• The soil

• The water

Multiple Choice

What is the fundamental difference in how producers and consumers obtain energy?

• Producers make their own food, while consumers get energy by eating other organisms.

• Producers eat consumers, while consumers eat producers.

• Producers get energy from other animals, while consumers get energy from sunlight.

• Producers and consumers both make their own food using sunlight.

Multiple Choice

If a disease wiped out all the producers in an ecosystem, what would be the most likely long-term effect on the carnivores?

• The carnivore population would decline because its food source would eventually disappear.

• The carnivore population would increase because there would be more space.

• The carnivore population would not be affected because they do not eat producers.

• The carnivore population would learn to get energy through photosynthesis.

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Matter Cycling in Ecosystems

• Unlike the one-way flow of energy, matter is recycled within an ecosystem.

• Decomposers, like bacteria and fungi, break down waste and dead organisms.

• This process returns essential nutrients and atoms to the soil and water.

• Producers use these recycled materials, allowing the cycle to continue for others.

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Multiple Choice

Summarise the core concept of energy transfer within an ecosystem.

• It is continuously recycled within the ecosystem.

• It flows in only one direction and is then lost.

• It is created by producers and destroyed by decomposers.

• It is converted directly from sunlight by plants.

Multiple Choice

What is the primary function of decomposers in the cycling of matter?

• To create new energy for producers to use.

• To consume producers for their stored energy.

• To break down waste and dead organisms, returning nutrients to the soil.

• To convert sunlight into chemical energy for the ecosystem.

Multiple Choice

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

• The soil would become poor in nutrients, limiting the growth of producers.

• Producers would find new ways to create their own essential materials.

• The one-way flow of energy would stop, causing the ecosystem to collapse.

• Waste and dead organisms would be converted directly into energy.

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Food Webs: Modeling Energy and Matter

• A food web models how energy and matter move through an ecosystem.

• It shows many interconnected feeding relationships between different organisms.

• Energy flows from producers to consumers, while decomposers cycle all matter.

• A change in one population can affect the entire ecosystem’s stability.

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Multiple Choice

What is the main purpose of a food web?

• To model how energy and matter move through an ecosystem

• To list every organism living in a particular habitat

• To show how organisms in an ecosystem look

• To track the migration patterns of animals

Multiple Choice

How do energy and matter move between producers, consumers, and decomposers?

• Energy flows from consumers to producers, while decomposers create energy.

• Producers consume both consumers and decomposers for energy.

• Energy flows from producers to consumers, while decomposers cycle matter.

• Decomposers transfer energy directly to consumers.

Multiple Choice

Based on the relationships in a food web, what would happen if a major producer population were to suddenly decrease?

• The consumer populations would likely increase.

• The stability of the entire ecosystem would be threatened.

• There would be no significant effect on the ecosystem.

• The decomposers would stop cycling matter.

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Resource Availability and Carrying Capacity

• Environmental factors like limited food, water, or space can restrict a population's size.

• Carrying capacity is the maximum population size an environment can sustainably support over time.

• Limited resources lead to increased competition for survival among organisms within a habitat.

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Multiple Choice

What is an environment's carrying capacity?

• The starting number of organisms in a habitat.

• The maximum population size an environment can sustainably support.

• The total amount of water available in an ecosystem.

• The number of different species living in an area.

Multiple Choice

What happens when the amount of available resources, like food and water, decreases in a habitat?

• The carrying capacity of the habitat will increase.

• Organisms will stop needing food and water.

• Competition for resources will increase.

• The population will begin to grow more rapidly.

Multiple Choice

A population of rabbits on an island has plenty of space, but a plant disease suddenly kills most of their primary food source. What is the most likely long-term effect on the island's environment?

• The rabbit population will grow indefinitely.

• The carrying capacity of the island will decrease.

• The rabbits will adapt to eat something other than plants.

• The amount of available space for the rabbits will increase.

Population Status: Extinct, Endangered, and Threatened

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Extinct Species

• A species is considered extinct when no individuals of it are left.

• Extinction can be caused by events like natural disasters or overhunting.

• The giant moa is an example of a bird that went extinct.

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Endangered Species

• An endangered species has a very high risk of becoming extinct soon.

• Their population size is often very small and continues to decrease.

• The mountain gorilla is an example of an endangered animal.

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Threatened Species

• A threatened species is likely to become endangered in the near future.

• California sea otters were threatened due to overhunting in the past.

• Protection laws have helped their population recover from being threatened.

Multiple Choice

What does it mean for a species to be considered extinct?

• When no individuals of the species are left anywhere.

• When the species has a very small population size.

• When the species is likely to become endangered soon.

• When the species is being impacted by overhunting.

Multiple Choice

What is the key difference between a threatened species and an endangered species?

• An endangered species is closer to extinction than a threatened species.

• A threatened species always has a smaller population than an endangered one.

• Only threatened species are affected by natural disasters.

• Only endangered species can be helped by protection laws.

Multiple Choice

If a species with a very small, decreasing population is protected by new laws that prevent overhunting, what is a possible future outcome?

• The species could recover, moving from an endangered to a threatened status.

• The species would be considered extinct immediately.

• The species' population size would not be able to increase.

• The species would no longer be affected by natural disasters.

Types of Symbiotic Relationships

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Mutualism

• In this relationship, both of the species will benefit from it.

• Clownfish are protected by the stinging tentacles of the sea anemones.

• Anemones get nutrients from the waste produced by the clownfish.

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Commensalism

• In this relationship, one species benefits while the other is unaffected.

• Epiphytes are plants that grow on trees to get more sunlight.

• The tree is not affected by the epiphytes growing on it.

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Parasitism

• One organism, the parasite, benefits by harming the other organism.

• For example, a wasp lays its eggs inside of a spider.

• The spider is harmed as the wasp larvae grow and eat it.

Multiple Choice

What is the definition of mutualism?

• A relationship where both species benefit from the interaction.

• A relationship where one species benefits and the other is harmed.

• A relationship where one species benefits and the other is unaffected.

• A relationship where both species are harmed by the interaction.

Multiple Choice

How does commensalism differ from parasitism?

• In commensalism one species benefits while the other is unaffected, whereas in parasitism one species benefits by harming the other.

• In commensalism both species benefit, whereas in parasitism both species are harmed.

• In commensalism one species is harmed while the other is unaffected, whereas in parasitism both species benefit.

• Commensalism and parasitism are the same type of relationship.

Multiple Choice

A wasp lays its eggs inside a spider. The wasp larvae then grow by eating the spider. Which statement best explains this relationship?

• Mutualism, because the wasp is protected and the spider is provided with food.

• Commensalism, because the wasp benefits from laying its eggs and the spider is unaffected.

• Parasitism, because the wasp's larvae benefit by eating the spider, which is harmed.

• Parasitism, because the spider benefits by being a host for the wasp's eggs.

Interactions: Predator-Prey, Competition, and Cooperation

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Predator-Prey

• A predator is an organism that hunts and eats another organism, the prey.

• This interaction helps to control the overall size of the prey population.

• For example, an osprey is a predator that catches fish for food.

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Competition

• Competition is when organisms need the same limited resource to survive.

• This struggle for survival limits organism growth and their ability to reproduce.

• Resource availability is a major factor that constrains the population size.

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Cooperation

• Cooperation is when organisms of the same species work together to survive.

• Leaf-cutter ants work together as a group to grow fungus for food.

• Elephants cooperate to raise their young and watch together for any predators.

Multiple Choice

What is the primary distinction between a predator and its prey?

• A predator is hunted by other organisms, while prey hunts other organisms.

• A predator helps other organisms, while prey harms other organisms.

• A predator works together with other organisms, while prey lives alone.

• A predator hunts other organisms, while prey is hunted by other organisms.

Multiple Choice

How are the outcomes of predator-prey interactions and competition similar?

• They both involve organisms working together.

• They both only happen between different species.

• They both can limit the size of a population.

• They both result in all organisms getting enough resources.

Multiple Choice

Leaf-cutter ants cooperate to grow fungus for food. If a new organism that also eats the same fungus is introduced to the area, what is the most likely outcome for the ants?

• The ants would start cooperating with the new organism.

• The ants would have more fungus to eat than before.

• The ants would face increased competition for their food source.

• The ants would become predators of the new organism.

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How Ecosystems Change: Ecological Succession

Primary Succession

• This process begins in new areas of land that have little or no soil.

• It starts on surfaces like bare rock after a volcanic eruption or on new sand dunes.

• Pioneer species like lichens are the first to grow, creating soil for other plants to follow.

Secondary Succession

• This process occurs in an area where an existing ecosystem has been disturbed or destroyed.

• It happens in places like a forest regrowing after a fire or on abandoned farmland.

• A key difference is that the soil already exists, allowing for faster regrowth of plants.

Multiple Choice

What is the starting condition for primary succession?

• An area with little or no soil

• An existing ecosystem after a flood

• A forest that was recently cleared for farming

• A grassland affected by drought

Multiple Choice

What is the main role of a pioneer species like lichen during primary succession?

• To create new soil by breaking down rock

• To provide shade for larger trees to grow

• To serve as a food source for the first animals

• To absorb water from the existing soil

Multiple Choice

After a forest fire, the soil remains. Why would this ecosystem likely recover faster than an area of bare rock left by a volcanic eruption?

• Because the presence of soil allows for secondary succession, which is faster.

• Because volcanic rock is too hot for plants to grow for centuries.

• Because pioneer species like lichens only grow after fires.

• Because fires add all the necessary nutrients to the air for plants.

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Changes in Aquatic Ecosystems

Aquatic Succession

• ​Freshwater ecosystems change over time in a natural, predictable process called succession.

• ​​Over time, sediments and decaying matter build up on the bottom of a pond.

• ​The pond can eventually fill with soil and transform into a land ecosystem.

Eutrophication

• ​Eutrophication is when a body of water becomes overly rich in nutrients.

• ​​Human activities can cause large algae blooms by adding excess nutrients to the water.

• ​These blooms use up the oxygen in the water, which can harm or kill fish.

Multiple Choice

What is the natural, predictable process of change that occurs in freshwater ecosystems over time?

• Succession

• Eutrophication

• Sedimentation

• Oxygenation

Multiple Choice

How do the large algae blooms associated with eutrophication affect fish in the ecosystem?

• They use up the oxygen that fish need to survive.

• They become a new source of food for all fish.

• They cause the water to become deeper and colder.

• They prevent sediments from building up in the pond.

Multiple Choice

If excess nutrients from human activities cause eutrophication in a pond, what is the most likely long-term outcome?

• The pond will have more oxygen, leading to more fish.

• The process of succession will slow down or stop completely.

• The buildup of dead plants and animals will speed up the pond filling with soil.

• The excess nutrients will be converted into healthy soil for land plants.

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Ecosystem Disruptions: Natural and Human-Caused

Natural Disruptions

• These are changes to ecosystems caused by natural events like forest fires, floods, volcanic eruptions, and disease.

• While these events can be destructive, some can be beneficial for the ecosystem's long-term health.

• For example, a small forest fire can clear away dead plants, allowing new ones to grow.

Human-Caused

• Human activities can severely impact ecosystems, causing long-term damage that is difficult to reverse.

• Resource extraction, such as cutting down forests or drilling for oil, destroys habitats and removes resources.

• Introducing non-native species can harm native organisms and disrupt the natural food web of the ecosystem.

Multiple Choice

What is the primary distinction between the two main types of ecosystem disruptions?

• Whether the change is caused by natural events or human activities

• Whether the change affects plants or animals

• Whether the change occurs in a forest or a volcano

• Whether the change is permanent or temporary

Multiple Choice

How do the typical consequences of natural and human-caused disruptions differ?

• Natural disruptions are always destructive, while human-caused disruptions are always beneficial.

• Natural disruptions only affect plants, while human-caused disruptions only affect animals.

• Natural disruptions can sometimes be beneficial, while human-caused disruptions often cause severe, long-term damage.

• Natural disruptions are easily reversed, while human-caused disruptions are always permanent.

Multiple Choice

A specific forest ecosystem experiences a rapid decline in its native bird population. This decline began shortly after a new, more aggressive bird species, not originally from the area, was introduced. What is the most likely explanation for this disruption?

• A natural forest fire that cleared away dead plants.

• The introduction of a non-native species by humans.

• Resource extraction that removed trees from the habitat.

• A flood that temporarily washed away food sources.

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Common Misconceptions

Misconception	Correction
Energy is created in an ecosystem.	Energy flows through an ecosystem, starting from the sun.
A parasite always kills its host.	A successful parasite relies on its host for long-term survival.
Populations can grow indefinitely without any limits.	Every ecosystem has a carrying capacity that limits population growth.
Forest fires are always bad for an ecosystem.	Low-intensity fires can be beneficial for an ecosystem.

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Summary

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

• Matter is cycled in an ecosystem, with decomposers playing a vital role.

• Food webs model the complex transfer of energy and matter.

• Limiting factors determine an ecosystem's carrying capacity and drive competition.

• Ecological succession describes the gradual change in an ecosystem over time.

• Ecosystems can be disrupted by both natural events and human activities.

Poll

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

• 1

• 2

• 3

• 4