Community Ecology and Biodiversity

Community: A group of populations of different species living closely together, capable of interacting.
Includes both biotic (living organisms) and abiotic (environmental) components.

Niche: The role/position a species has in its environment; akin to its job.
Habitat: Physical area where an organism lives; refers to the home of the species.
Types of niches:
Fundamental Niche: The potential niche if no limiting factors (like predators) were present.
Realized Niche: The actual niche occupied by the species, accounting for limiting factors.

Interspecific Interactions: Interactions between individuals of different species; can include:
Competition (−−): Species compete for limited resources.
Predation (+−): One organism kills and eats another.
Herbivory (+−): Organism consumes parts of plants/algae.
Symbiosis: Different forms, including:
- Parasitism (+−): One organism feeds on another without killing it.
- Mutualism (++): Both organisms benefit from the interaction.
- Commensalism (+0): One organism benefits while the other is unaffected.
Facilitation: A positive or neutral effect on another species without direct contact.

Competitive Exclusion Principle: No two species can occupy the same niche permanently; one will outcompete the other.
Leads to Niche Partitioning, where competing species evolve to use different resources/niches.

Predation: Involves adaptations on both sides (predator and prey) leading to co-evolution.
Types of mimicry:
- Cryptic Coloration: Camouflage to avoid being seen by predators.
- Batesian Mimicry: Harmless species mimics harmful species to avoid predation.
- Müllerian Mimicry: Two harmful species resemble each other, reinforcing predator avoidance.

Herbivory: Consumption of parts of plants/algae, creating a plus-minus relationship for the plant.

Biodiversity: Variety of different organisms within a community, including:
Species Richness: Number of different species in a community.
Relative Abundance: Proportion of each species represented compared to all individuals in the community.
Importance of Biodiversity:
Increases ecosystem productivity and resilience to disturbances (e.g., disease).

Simpson's Diversity Index: Mathematical formula to calculate biodiversity based on species richness and abundance.
Higher index indicates greater biodiversity and resilience.

Invasive Species: Non-native species that establish outside their native range, often due to human activity.
Cause harm to native species via competition (relevant to the competitive exclusion principle).

Keystone Species: Species that play a critical role in maintaining the structure of an ecological community, not necessarily abundant but vital.
Examples include coral (marine) and honeybees (pollinators). Removal can lead to ecosystem collapse.

Disturbances: Events that change communities by removing organisms or altering resource availability.
Types:
- Primary Succession: Occurs in previously lifeless habitats.
- Secondary Succession: Follows a disturbance that leaves the soil intact.
Human activities are significant disturbants to ecosystems.

Habitat Loss: Major reason for biodiversity loss due to urbanization and agricultural development.
Overharvesting: Can lead to declines in species populations (e.g., overfishing).
Global Change: Changes in climate and atmospheric conditions due to pollution.

Latitude and Area: More biodiversity in tropics than in polar areas; larger areas support greater diversity.
Pathogens: Affect species diversity, especially in populations with low biodiversity.

Human impact and various ecological dynamics shape ecosystem health and biodiversity. Understanding these interactions is critical for conservation efforts and ecosystem management.