Ecological Relationships

Ecological Relationships

Middle School

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Learning Objectives

• Define and compare predation, competition, and symbiosis in an ecosystem.

• Describe mutualism, commensalism, and parasitism with examples of each symbiotic relationship.

• Explain how keystone species and limiting factors affect a community's carrying capacity.

• Compare and contrast primary and secondary succession as processes of community change.

Key Vocabulary

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Predation

A feeding relationship where one animal, the predator, hunts and eats another animal, the prey.

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Competition

The struggle between organisms when they require the same limited resources like food or space.

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Symbiosis

A close and long-term relationship where two different species live together, often benefiting each other.

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Keystone Species

A species that has a very large effect on the structure and health of its ecosystem.

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Ecological Succession

The gradual process by which the mix of species in a community changes over a period.

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Predation and Competition

Predation

• ​One organism, the predator, hunts and consumes another organism, the prey.

• ​​This interaction plays a crucial role in keeping ecosystem populations in balance.

• ​Examples include lions hunting gazelles and herbivores, like deer, eating plants.

Competition

• ​This occurs when organisms require the same limited resources, such as food.

• ​​Competition can be between different species or members of the same species.

• ​For instance, lions and hyenas compete for the same food source, like zebras.

Multiple Choice

A flock of seagulls fighting over a single food source is an example of what?

• Intraspecific competition

• Interspecific competition

• Predation

• Mimicry

Types of Symbiosis

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Mutualism (+/+)

• ​Both species benefit from this close and long-term relationship.

• ​​A plover bird gets a meal by eating parasites.

• ​A bee gets nectar while helping the flower with pollination.

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Commensalism (+/0)

• ​One species benefits while the other species is not affected.

• ​​Remora fish attach to sharks to eat leftover food scraps.

• ​Tree frogs use plants for protection without affecting the plant.

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Parasitism (+/-)

• ​One organism benefits at the expense of the other organism.

• ​​Mistletoe harms a tree by drawing out its valuable nutrients.

• ​Ticks and leeches feed on the blood of their hosts.

Multiple Choice

A clownfish lives safely within a sea anemone, which is in turn protected from predators by the clownfish. What type of relationship is this?

• Commensalism

• Mutualism

• Competition

• Parasitism

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Cooperation and Keystone Species

Cooperation

• ​Organisms of the same species work together as a team to achieve a common goal.

• ​​This is different from mutualism, which involves partnerships between completely different species.

• ​For example, dolphins in a pod will hunt together to herd fish into a small area.

Keystone Species

• ​A species that plays a critical role in maintaining the structure of its community.

• ​​Removing a keystone species can cause a ripple effect that harms many other organisms.

• ​Sea otters are key as they eat sea urchins, which would otherwise destroy kelp forests.

Multiple Choice

Why are sea otters considered a keystone species in their environment?

• They control the sea urchin population, which protects the kelp forest habitat.

• They have a symbiotic relationship with kelp.

• They are the top predators in the community.

• They work together with other otters to hunt for fish.

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Community Dynamics

Limiting Factors

• Limiting factors are resources like food and water that can restrict a population's growth and size.

• These factors determine an environment's carrying capacity, the maximum population that can be supported over time.

• Predation and competition for resources between different species are also considered to be limiting factors.

Ecological Succession

• Ecological succession is the gradual change in the species of a community over time, often after a disturbance.

• Primary succession begins on bare surfaces, where pioneer species must first build up the soil.

• Secondary succession happens in an area that already has soil, allowing for a much faster regrowth process.

Multiple Choice

What is the key difference between primary and secondary succession?

• Primary succession only involves plants, while secondary succession involves animals.

• Primary succession begins with soil, while secondary succession begins with bare rock.

• Secondary succession begins with soil, while primary succession begins with bare rock.

• Secondary succession is caused by disturbances, while primary succession is not.

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Common Misconceptions in Ecology

Misconception	Correction
All symbiotic relationships are mutually beneficial.	Only mutualism benefits both partners. Others are commensalism and parasitism.
Competition only happens between different species.	Competition also occurs between members of the same species (intraspecific).
Keystone species are always top predators.	A keystone species' role defines its importance, not its rank.

Multiple Choice

How does intraspecific competition differ from interspecific competition?

• It involves members of the same species competing for resources.

• It always results in one species being eliminated.

• It involves different species competing for resources.

• It only occurs between predators.

Multiple Choice

What is the primary role of pioneer species, like lichens, in primary succession?

• To provide a food source for the first animals that arrive.

• To break down bare rock and create the first layer of soil.

• To compete with any existing plants in the area.

• To establish a climax community quickly.

Multiple Choice

A wildfire sweeps through a forest, clearing most vegetation but leaving the soil intact. Predict the ecological process that will follow.

• The complete collapse of the ecosystem with no chance of recovery.

• Secondary succession, leading to a gradual regrowth of the community.

• The establishment of a permanent grassland with no trees.

• Primary succession, as pioneer species colonize bare rock.

Multiple Choice

Analyze the relationship between limiting factors and carrying capacity. How would the introduction of a new, fast-spreading disease likely impact the carrying capacity for a deer population?

• The carrying capacity would remain unchanged as disease is a natural factor.

• The carrying capacity would decrease because the disease is a new limiting factor.

• The carrying capacity would increase because there would be less competition.

• The carrying capacity would only be affected if the disease also impacted the deer's food source.

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Summary

• Community members interact through predation, competition, symbiosis, and cooperation.

• Symbiosis can be mutualistic, commensalistic, or parasitic.

• Keystone species have a large community impact; carrying capacity limits population size.

• Ecological succession is the process of community change over time.

Poll

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

• 1

• 2

• 3

• 4