Cornell Notes Unit 2 APES

2.1 Introduction to Biodiversity

Learning Objective:Explain levels of biodiversity and their importance to ecosystems.

Essential Knowledge Summary

• Biodiversity Types:

  • Habitat Diversity: Variety of different habitats within a geographic area.

  • Genetic Diversity: Differences in DNA among organisms.

  • Species Richness: Number and variety of species in a specific region.

• Causes of Reduced Species: Distinction between specialist and generalist species.

Questions/Main Ideas

• How to compare species biodiversity?

  • Example Comparison:

    • Site A:

      • 11 total species, 8 of each species, 88 total members.

    • Site B:

      • 11 total species; random numbers of each species, 88 total members.

  • Species Richness:

    • Both sites have the same species richness (11 species).

  • Species Evenness:

    • Site B has more rare and dominant species compared to Site A.

Impact of Habitat Diversity on Species

• Increased Diversity:

  • High habitat diversity leads to high species diversity and genetic diversity.

  • More productivity in an ecosystem means more resources and niches available for species.

• Ecological Fitness and Natural Selection:

  • More offspring and higher survival rates correlate with natural selection processes.

  • Selective Pressure:

    • Environmental factors impact survival and reproduction.

Genetic Diversity & Population Dynamics

• Gene Pool:

  • A large gene pool ensures more options within a species; crucial for adaptation.

• Population Bottleneck:

  • This occurs when a significant reduction in population size decreases genetic diversity.

  • Effects:

    • Inbreeding, increased susceptibility to diseases, birth defects, and inability to adapt.

Selective Factors

• Biotic Factors:

  • Changes like color adaptation for camouflage against predators.

• Abiotic Factors:

  • Environmental conditions such as pH, temperature, and salinity impacting selective processes.

Recovery and Adaptation

• Genetic Variation Benefits:

  • Populations with high genetic diversity respond better to environmental changes.

• Biodiversity Loss Consequences:

  • Habitat loss results in the disappearance of specialist species, followed by generalist species.

  • Reduces numbers of species with extensive territorial needs.

Definitions & Concepts

• Species Richness:

  • Refers to the count of different species in an ecosystem.

• Species Types:

  • Generalist Species:

    • More adaptable to changing environments.

  • Specialist Species:

    • Difficulty in adapting to swift or drastic environmental changes.

• Genetic Biodiversity Impacts:

  • High Genetic Diversity:

    • Resilient to minor disturbances (e.g., surface fires, floods).

  • Low Genetic Diversity:

    • Vulnerable to extreme disturbances (e.g., hurricanes, clear-cutting) and continuous environmental stress.

  • Geographic isolation and invasive species can exacerbate biodiversity loss.

Summary

• Biodiversity encompasses genetic, species, and habitat diversity.

• Higher genetic diversity fosters better responses to environmental stressors.

• Population bottlenecks can diminish genetic diversity and overall ecological health.

• Ecosystems with more species can recover more effectively from disruptions, while habitat loss leads to a cascading loss of biodiversity beginning with specialist species.