Community Ecology and Biodiversity

Community and Ecosystem Basics

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

Niches

• 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

• 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.

Competition

• 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 and Co-evolution

• 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

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

Biodiversity

• 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).

Diversity Indices

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

Invasive Species

• 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

• 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 and Succession

• 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.

Types of Human Disturbances

• 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.

Factors Affecting Biodiversity

• 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.

Conclusion

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