MH

APES Unit 2 PPT

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.