2.1 Introduction to Biodiversity

2.1.1 Ecosystem Diversity

• Ecosystems have structures and diversity that evolve over time.

• Key components of ecosystem diversity include:

  • Species Diversity: The variety of species within an ecosystem.

  • Genetic Diversity: Genetic variation among individuals of a species.

  • Habitat Diversity: Variety of habitats present within a region.

2.1.2 Importance of Biodiversity

• Response to Environmental Stressors

  • Higher genetic diversity enables better population resilience against stressors.

  • Genetic bottlenecks can decrease diversity, making species more vulnerable.

• Ecosystem Recovery

  • Ecosystems with a larger number of species are better able to recover from disruptions.

• Loss of Habitat

  • Habitat loss leads to the extinction of specialist species, followed by generalists.

2.1.3 Levels of Biodiversity

1. Genetic Diversity

   • Refers to the variety of genes within a species.

   • Populations with higher genetic variation are more robust against environmental changes.

2. Species Diversity

   • Defined as the number of different species and their relative abundances in an area.

   • Important for ecosystem health and stability.

3. Habitat Diversity

   • Represents the variety of ecosystems in a specific region, affecting overall biodiversity.

2.1.4 Definitions and Estimates

• Species: A group of organisms that can interbreed and produce viable offspring.

• Estimates of total species on Earth range from 5 to 100 million, with a common estimate around 10 million.

• Most Common Organism: The bacterium Pelagibacter ubique, dominant in marine environments, crucial for the carbon cycle.

2.1.5 Special Considerations in Biodiversity

• Generalist vs. Specialist Species

  • Generalist species can thrive under a wide range of conditions (e.g., coyotes, house flies).

  • Specialist species require specific conditions and are more vulnerable to habitat loss (e.g., pandas).

2.1.6 Genetic Diversity and Survival

• Populations with low genetic diversity face risks such as disease susceptibility and reduced adaptability to environmental shifts.

• Bottleneck Effect: A dramatic decrease in population size leading to reduced genetic variation can have long-term consequences.

2.1.7 Ecosystem Resilience

• More Species Equals More Resilience: Biodiverse ecosystems can better withstand disruptions and maintain functionality.

• The Portfolio Effect: By having diverse genetic backgrounds, populations enhance their chances of survival and adaptation.

2.1.8 Measuring Biodiversity

• Species Richness: Total number of different species found in an area.

• Species Evenness: Relative abundance of individuals of each species in a community.

• Shannon-Wiener Index: A method for assessing species diversity in ecosystems, considering both richness and evenness.

2.1.9 Human Impact on Biodiversity

• Human actions often decrease species diversity, leading to ecosystem changes.

• Conservation Strategies: Encouraging biodiversity in urban planning (e.g., planting diverse tree species) safeguards against the spread of diseases affecting specific species.