AP Biology Unit 8 Topic 4: Community ecology

What to Know

Species interactions include competition, predation, parasitism, mutualism, and commensalism.
Niches describe how species use resources and interact with their environment.
Community composition can change through succession, disturbance, and species introductions.
Always connect this topic back to the larger unit: Ecology.

Detailed Notes

Community ecology belongs to Unit 8: Ecology. Community ecology studies interactions among species and how those interactions shape diversity, abundance, and stability. Treat the topic as a relationship between structure, process, evidence, and biological function instead of memorizing an isolated definition.

Key relationships: Species interactions include competition, predation, parasitism, mutualism, and commensalism. Niches describe how species use resources and interact with their environment. Community composition can change through succession, disturbance, and species introductions.

Model to use: Use a food web or interaction table to predict how a change in one species can affect others. A clear model should label the parts, show the direction of movement or information flow when relevant, and connect the diagram back to the biological outcome.

AP-style move: For community scenarios, identify the interaction type and explain the effect on each species involved. Strong answers name the concept, apply it to the scenario, and explain the reasoning in complete sentences.

Key Vocabulary

Niche

A species' role, resource use, and environmental requirements.

Competition

An interaction in which organisms use the same limited resource.

Predation

An interaction in which one organism kills and eats another.

Mutualism

An interaction that benefits both species involved.

Keystone species

A species with a large effect on community structure relative to its abundance.

Ecological succession

Change in community composition over time after new habitat or disturbance.

Quick Practice

How would you explain Community ecology in one or two AP-style sentences?

Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.

Official Alignment

Reference and Attribution

Biology concept reference: Biology for AP Courses by OpenStax, Rice University. Access for free at OpenStax. Licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. EduCompanion used this source as a conceptual reference and rewrote the study notes in original wording.