Community Ecology, Biodiversity, and Disruptions

Community and Ecosystem Interactions

Community: A group of populations of different species living closely together and capable of interacting.

Habitat: A place or part of an ecosystem occupied by an organism.
Ecological Niche: The role and position a species has in its environment.
- Fundamental Niche: Potential niche if there were no limiting factors (predators, competitors, etc.).
- Realized Niche: The portion of the fundamental niche that the species actually occupies.

Interspecific Interactions: Interactions between individuals from different species.
- Competition: -/- relationship where different species compete for limited resources.
- Predation: +/- relationship where one species (predator) kills and eats another (prey).
- Herbivory: +/- relationship where one organism eats parts of a plant or alga.
- Symbiosis: Direct contact relationships between species.
- Parasitism: (+/-) one organism benefits at the expense of another.
- Mutualism: (+/+) both organisms benefit.
- Commensalism: (+/0) one organism benefits; the other is neither helped nor harmed.
- Facilitation: (+/+ or 0/+) one species benefits another without direct contact.

Competitive Exclusion Principle: Two species competing for the same resource cannot coexist permanently; the stronger competitor will eliminate the weaker.
Niche Partitioning: Natural selection drives competing species into different patterns of resource use or niches.

Adaptations in Predation:
- Cryptic Coloration: Camouflage to evade capture.
- Batesian Mimicry: Harmless species mimics a harmful one.
- Mullerian Mimicry: Bad-tasting species resemble one another.

Species Diversity: Variety of different organisms within a community.
- Species Richness: Total number of different species.
- Relative Abundance: Proportion of each species compared to the total number of individuals in the community.

Simpson’s Diversity Index: A measure that considers both species richness and relative abundance to assess biodiversity.
- High Diversity Index: Indicates high biodiversity.
- Low Diversity Index: Indicates low biodiversity.

Keystone Species: Not always abundant but play a crucial role in maintaining the structure of a community.
- Examples:
- Coral: Forms reefs that provide habitat and protection for many species.
- Honey Bees: Serve as pollinators important for ecosystem function.

Disturbance: An event that alters a community, typically by removing organisms or changing resource availability (e.g., fires, droughts).
Ecological Succession: Gradual process in which species composition changes after a disturbance.
- Primary Succession: Occurs in a new habitat that has not been colonized previously.
- Secondary Succession: Follows disturbances that leave soil intact but remove organisms.

Human Activity: The strongest force disrupting ecosystems.
- Major Threats:
- Habitat Loss: Most significant risk to biodiversity (e.g., urbanization, agriculture).
- Invasive Species: Non-native species that can outcompete natives.
- Overharvesting: Unsustainable harvesting reducing populations (e.g., overfishing).
- Global Change: Climate alterations that impact ecosystems (e.g., pollution, CO2 emissions).

Biogeographical Factors: Large-scale factors influencing biodiversity.
- Latitude: Greater diversity in tropical regions than polar regions.
- Area: Larger areas tend to support more species due to habitat variety.

Pathogens: Organisms causing disease have pronounced effects in less diverse ecosystems.

Species Richness and Abundance: Analyze differences between two communities with the same species richness but varying relative abundance.
Photosynthesis Disruption: Identify processes affected in a dominant plant species infected by a virus hindering its ability to photosynthesize.