Community Ecology Lecture Notes

Definition of a Community

• A community is a group of species that occupy a given area.
• Interactions within a community can be direct or indirect.

Biological Structure of a Community

• Defined by species composition (species present and their relative abundances).

Concepts of Community

• Organismal Concept: Views the community as a unit, an association of species forming an integrated whole.
• Individualistic Concept: Views species co-occurrence due to similarities in requirements and tolerances.

Species Composition and Diversity

• Species Richness: Number of species in the community.
• Species Diversity: Includes species richness and species evenness (distribution of individuals among species).

Dominance

• Dominant species: Predominate in a community, often the most abundant, but not solely determined by abundance.

Keystone Species

• Disproportionate impact on the community relative to their abundance.
• Their removal can lead to significant changes and potential loss of diversity.

Feeding Relationships

• Food Chain: Series of arrows indicating food sources within a community.
• Food Web: Complex interconnections of food chains.
  • Basal Species: Fed on, but do not feed on others.
  • Top Predators: Feed on others but are not prey.
  • Intermediate Species: Both predators and prey.

Guilds and Functional Groups

• Guilds: Groups of species exploiting a common resource similarly.
• Functional Groups: Defined based on common responses to the environment, life history, or role.

Community Structure

• Physical Structure: In terrestrial communities, defined by vegetation.
  • Vertical Structure: Reflects life forms of plants.
• Aquatic Communities: Defined by physical features like light, temperature, oxygen.

Layers of a Community

• Autotrophic Layer: Conducts photosynthesis.
• Heterotrophic Layer: Consumes carbon from autotrophs.

Zonation

• Zonation: Changes in physical structure and biological communities across a landscape.
• Most pronounced in environments with sharp physical changes.

Community Classification

• Depends on the scale used to define boundaries.

Restoration Ecology

• Goal: Restore a community or ecosystem to its pre-disturbance condition.
• Requires understanding of ecological processes affecting community dynamics.