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

• Genetic diversity: Variation in alleles within a population. Higher genetic diversity → better response to environmental stress. Population bottlenecks reduce genetic diversity.
• Species diversity: Number of different species (species richness) in an ecosystem. More species → faster recovery from disruptions.
• Habitat diversity: Variety of different ecosystems and microhabitats. Loss of habitat eliminates specialists first, then generalists; species with large territorial needs suffer most.

• Islands colonized by species arriving from elsewhere.
• Isolation and open niches on islands can drive specialization through adaptive radiation, but island species may evolve as specialists or as generalists (ecological release) depending on competition and resource variability.
• Specialist risk: Invasive generalist species outcompete and eliminate specialists.
• Island isolation drives unique evolutionary pathways and adaptation.

When interpreting data or scenarios:

• Identify whether question asks for description (what), explanation (why/how), or application (in context).
• Distinguish genetic vs. species vs. habitat diversity—each has different consequences.
• Recognize specialist vs. generalist trade-offs, especially with invasive species or habitat loss.
• Link succession type to starting conditions and recovery timeline.
• Use tolerance ranges to predict organism presence/absence given environmental data.
• Connect ecosystem services to human activities and economic/ecological outcomes.