Unit 2: Biodiversity

Biodiversity Basics

• Levels of Biodiversity

  • Genetic Diversity: Variability in genes within a population, important for adaptability.

  • Species Diversity: Includes both the number of different species and the balance of their populations.

  • Habitat Diversity: Variety of habitats in an ecosystem, supporting various species.

  • Importance: Ecosystems with higher biodiversity are more resilient to environmental stress and disturbances.

Factors Affecting Biodiversity

• Population Bottlenecks: Sudden decreases in population can lead to reduced genetic diversity, making species more vulnerable.

• Species Richness:

  • Refers to the total number of different species in an ecosystem.

  • Higher species richness indicates better ecosystem health.

Species Richness & Evenness

• Richness (r): Total number of different species in an ecosystem.

• Evenness: Measures the balance of individual organisms among different species.

  • High richness and evenness correlate with healthy ecosystems, providing better resources.

Genetic Diversity

• Arises from random mutations and recombination during sexual reproduction.

• Benefits: Populations with greater genetic diversity have better resilience to environmental stressors like disease and drought.

Population Bottleneck Events

• Result from environmental disturbances that drastically reduce population size.

• Lead to loss of genetic diversity, making populations more susceptible to future changes.

Inbreeding Depression

• Occurs in smaller populations where individuals are more likely to breed with relatives, increasing harmful genetic mutations.

• Example: Florida panther faced genetic issues due to severe population decline in the 1900s; was later saved through breeding with Texas cougars.

Ecosystem Resilience

• Defined as the ability of an ecosystem to return to original conditions after a disturbance.

• Higher species diversity contributes to greater resilience by ensuring availability of plants and other resources for recovery.

Ecosystem Services

• Categories:

  • Provisioning: Products directly obtained from ecosystems like food, wood, and medicine.

  • Regulating: Ecosystem processes that moderate environmental conditions (climate, water quality, etc.).

  • Cultural: Benefits derived from ecosystems through recreation and enjoyment.

  • Supporting: Processes that maintain the conditions for life, such as nutrient cycling and soil formation.

Human Disruptions to Ecosystem Services

• Human activities, such as agriculture and urbanization, often diminish ecosystem functions and services.

  • Examples include deforestation and overfishing, which have immediate ecological and economic consequences.

Island Biogeography

• Study of species distribution on islands and the ecological relationships that arise:

  • Colonization: Islands are often colonized by species arriving from mainland.

  • Specialists vs. Generalists: Island species often evolve to specialize due to limited resources; introductions of invasive generalists can threaten specialist species.

Theory of Island Biogeography

• Larger islands support greater species diversity and richness due to more resources and niches.

• Proximity to the mainland influences species richness; closer islands see more colonization and genetic diversity.

Evolution on Islands

• Adaptive radiation occurs when a single species evolves into multiple to utilize different resources, e.g., Galapagos finches adapting to different food sources.

Ecological Tolerance

• Refers to the range of environmental conditions (temperature, salinity, etc.) that a species can endure.

• Range of Tolerance Zones:

  • Optimal: Conditions in which organisms thrive.

  • Physiological Stress: Conditions under which organisms can survive but face stress.

  • Intolerance: Conditions leading to death.

Adaptations & Natural Selection

• Organisms adapt over time to their environment via natural selection, where advantageous traits become more common in a population.

• Changes in environment can shift which traits are advantageous, influencing evolution.

Ecological Succession

• Process of change in species composition in an ecosystem over time. Two types:

  • Primary Succession: Begins in lifeless areas (bare rock) leading to soil formation; characterized by pioneer species like lichens.

  • Secondary Succession: Occurs in areas where a disturbance has cleared much of the life but left soil intact; includes species like grasses and shrubs.

Key Concepts in Ecological Succession

• Pioneer Species: First to colonize barren environments, enhancing soil quality for subsequent species.

• Climax Community: Stable community reached at the end of succession, often characterized by larger, slower-growing species.