Section 1: Ecological Interactions

Unit 8: Diversity of Life

Objectives

• Describe biotic interactions in an ecosystem.
• Describe how ecosystems change in response to natural and human disturbances.
• Describe the effects of limiting factors on population dynamics and potential species extinction.

Warm-up:

• Based on the food web, which organisms are primary consumers?
• Which organisms are tertiary consumers?
• What is the relationship between a fox and a mouse?

Ecology

• Ecology: the study of the relationships between organisms and their interactions with the environment.

Ecology

• Population: A group of individuals of the same species living in a specific geographical area and reproducing.
• Community: Different populations of organisms interacting in a shared environment.

Ecology

• Ecosystem: a system composed of organisms and nonliving components of an environment.
• Biotic: describes a living, or once-living, factor in an ecosystem
• Abiotic: describes a nonliving factor in an ecosystem

Check for Understanding

Which description is the best example of a population?

A. all of the red foxes in a forest

B. all of the red foxes in every forest

C. all of the organisms in a forest

D. all of the organisms in every forest

Niche

• Organisms will interact with and be affected by biotic and abiotic factors in their environment.
• Niche: the way an organism utilizes the resources of its environment, including the space it requires, the food it consumes, timing of reproduction, and temperature and moisture requirements.

Niche Videos

https://youtu.be/6-aGxYTUPu0

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https://youtu.be/z3eDLQym9qo

Niche

• When organisms share parts of their niche, they end up competing with each other for resources.
• Competition: When individuals or groups of organisms compete for similar resources such as territory, mates, water, and food in the same environment.

Sneaky Squirrels

https://youtu.be/YcdSmFXdbMo

Population Dynamics

• Organisms must also use resources within their environment in order to survive. The amount of individuals that can live in one area is dependent on the amount of resources available.

Population Dynamics

• Population Dynamics: The study of short- and long-term changes in the number of individuals for a given population, as affected by birth, death, immigration, and emigration.

Population Dynamics

• Carrying Capacity: the number of individuals in a population that can be supported in an ecosystem given the resources available and other environmental pressures.

Population Dynamics

• Carrying capacity is affected by interactions and the amount of resources present.
• Limiting Factor: chemical, physical, or biological factor that limits the existence, growth, abundance, or distribution of an individual organism or a population.

Check for Understanding

A farmer observed that an increase in a field’s soil nitrogen content was followed by an increase in producer productivity. What does this observation most likely indicate about the relationship between nitrogen and the producers in the field?

A. Nitrogen was a biotic factor.

B. Nitrogen was a limiting factor.

C. Nitrogen became a surplus resource.

D. Nitrogen became a selection pressure.

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Coevolution and Symbiosis

• Organisms within an ecosystem can interact with each other in different ways, and many are influenced by the changes in other species.
• Coevolution: occurs when the changes in at least two species’ genetic compositions affect each other's evolution.

Coevolution and Symbiosis

• Predation: an interaction between two species where one species consumes the other.
• Both predators and prey have evolved traits that help them stay alive.

Coevolution and Symbiosis

• Symbiotic Relationship: interaction between two different organisms
• Symbiosis can be separated into three categories based on how harmful or beneficial the interactions are.

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Nature’s Cutest Symbiosis: The Bobtail Squid | I Contain Multitudes

Coevolution and Symbiosis

• Mutualism: both organisms benefit from the relationship.
• +/+

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Coevolution and Symbiosis

• Commensalism: one organism benefits and the other is neither helped nor harmed.
• +/o

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Coevolution and Symbiosis

• Parasitism: one organism benefits while the other is harmed
• +/-

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Check for Understanding

A species of snapping turtles has a tongue that resembles a worm. The tongue is used to attract small fish. Which best describes the interaction between the fish and the snapping turtle?

A. predation

B. symbiosis

C. parasitism

D. competition

Check for Understanding

Which example describes a mutualistic relationship between organisms?

A. Young wasps prey on caterpillars.

B. Crabs eat the remains of dead fish.

C. Ants protect a tree on which they feed.

D. Tapeworms feed on food in the intestines of cats.

Nonnative Species

• Interactions within an ecosystem may change when a new, exotic species is introduced.
• Endemic Species: a species that is found in its originating location and is generally restricted to that geographic area.
• Nonnative Species: a species typically living outside a distribution range that has been introduced through either deliberate or accidental human activity
• also known as introduced, alien, nonindigenous, or exotic species

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Nonnative Species

• Examples: zebra mussels, stink bugs, kudzu

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https://youtu.be/8krJFrM4ZwA

Nonnative Species in Pa

• Examples: Spotted Lanternfly, Emerald Ash Borer, Northern Snakehead fish, kudzu

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Spotted Lanternfly

Emerald Ash Borer

Emerald Ash Borer

Northern Snakehead

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Fish And Boat Commission Warns Anglers To Kill Northern Snakeheads If Caught In Pa. Rivers

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Guardians Of The Glades - Discovery Channel (3 min. clip)

Guardians Of The Glades - Discovery Channel (8 min. clip)

Discussion

Why are nonnative species often considered a disturbance in an ecosystem?

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