2.3 - island biogeography

AP Environmental Science: Unit 2 – The Living World: Biodiversity

Topic: 2.3 Island Biogeography

Page 1: Overview of Island Biogeography Theory

• Definition of Island Biogeography Theory (IBT)

  • Describes the process of how islands are colonized by organisms after their formation.

  • Immigration and extinction rates are crucial in determining ecosystem establishment.

  • As extinction rates increase, immigration rates decrease.

  • Larger islands or those closer to the mainland have higher immigration rates.

• Equilibrium Point

  • A balance between immigration and extinction rates is reached, which is ideal for the island's ecosystem.

Page 2: Factors Influencing Species Richness

• Size and Distance

  • Larger islands generally support more species than smaller islands.

  • Proximity to mainland affects accessibility for organisms.

• Endemic Species

  • Defined as species that are native to a specific geographical area.

  • These species have specialized niches and are sensitive to environmental changes.

• Impact of Invasive Species

  • Invasive species are often generalists with few natural predators.

  • They can outcompete endemic species, leading to their decline or extinction.

• Evolutionary Effects

  • Example: Darwin's Finches on the Galapagos Islands.

    • A small population adapted to the islands after being isolated from the mainland.

    • Unique evolutionary pressures on each island led to the development of fifteen distinct species.

Page 3: Relationship Between Island Size and Species Richness

• Key Terms

  • Darwin's Finches: A group of bird species that illustrate adaptive evolution.

  • Ecological Niche: The role of an organism in its environment, including resource use and interactions.

  • Endemic Species: Species found only in a specific region.

  • Invasive Species: Non-native species that disrupt local ecosystems.

  • Island Biogeography Theory: Explains how island size and distance affect species diversity.

• Species Richness Insights

  • Larger islands tend to have more species due to habitat diversity and lower extinction rates.

  • Smaller islands may have higher competition and speciation rates, but overall species richness is inversely proportional to island size.

Page 4: Understanding Species Richness

• Definition of Species Richness

  • Refers to the number of different species in a specific area.

  • Indicates biodiversity and the health of an ecosystem.

Conclusion

• The Island Biogeography Theory provides a framework for understanding how island characteristics influence biodiversity, species interactions,