Unit 8: Ecology – Interactions and Changes in Communities and Ecosystems

Unit 8: Ecology

Introduction to Ecology

Ecology is the scientific study of interactions among organisms and their environment. These interactions can lead to significant changes in both communities and ecosystems, affecting biodiversity, resource availability, and ecosystem stability.

• Ecology: The branch of biology that examines how organisms interact with each other and with their physical surroundings.

• Community: All the populations of different species that live and interact in a particular area.

• Ecosystem: A community of organisms and their abiotic (non-living) environment functioning together as a system.

• Biodiversity: The variety of life in the world or in a particular habitat or ecosystem.

Example: The introduction of a new predator can alter prey populations, which in turn affects plant communities and nutrient cycling within an ecosystem.

Interactions in Communities

Interactions between complex living organisms, such as competition, predation, mutualism, and parasitism, shape the structure and dynamics of communities.

• Competition: Occurs when two or more species rely on the same limited resource.

• Predation: One organism (predator) feeds on another (prey), influencing population sizes and community structure.

• Mutualism: Both species benefit from the interaction (e.g., bees and flowering plants).

• Parasitism: One organism benefits at the expense of another (e.g., tapeworms in mammals).

Example: Removal of a keystone species, such as sea otters, can lead to dramatic changes in community composition and ecosystem function.

Changes in Ecosystems

Ecological interactions can lead to changes in ecosystem structure and function, including succession, nutrient cycling, and energy flow.

• Succession: The process by which the structure of a biological community evolves over time. Primary succession occurs in lifeless areas, while secondary succession follows disturbances in existing communities.

• Nutrient Cycling: The movement and exchange of organic and inorganic matter back into the production of living matter (e.g., carbon, nitrogen cycles).

• Energy Flow: The passage of energy through the components of an ecosystem, typically entering as sunlight and leaving as heat.

Example: After a forest fire (a disturbance), secondary succession allows for the gradual return of plant and animal life, restoring the ecosystem over time.