AP Biology: Global Ecology – Climate Patterns, Biomes, Biodiversity, Conservation Biology

Global Ecology – Climate Patterns, Biomes, Biodiversity, Conservation Biology

Concept Summary

• Climate: Long-term average of temperature, precipitation, and wind patterns; determines biome distribution and species adaptations.
• Biome: Large-scale terrestrial or aquatic ecosystem defined by dominant vegetation and climate; classified by temperature and precipitation gradients.
• Biodiversity: Variety of life at genetic, species, and ecosystem levels; critical for ecosystem resilience and human well-being.
• Conservation Biology: Applied science focused on preserving biodiversity, mitigating human impacts, and restoring ecosystems.
• Anthropogenic Climate Change: Human-driven alterations to global climate (e.g., CO? emissions); accelerates habitat loss and species extinction.

Core Questions

WHAT (definitional)

Q: What is the rain shadow effect? A: A dry region on the leeward side of a mountain range caused by orographic lifting and adiabatic cooling of moist air. Trap/Clarification: Students confuse leeward (dry) with windward (wet) sides—remember, rain shadows form after air crosses the peak.

Q: What is species richness vs. species evenness? A: Richness = number of species; evenness = relative abundance of each species in a community. Trap/Clarification: High richness-high evenness (e.g., 100 species with 99% dominance by one species is not diverse).

Q: What is an edge effect in conservation? A: Altered abiotic/biotic conditions at habitat boundaries (e.g., increased light, predation) that reduce core habitat quality. Trap/Clarification: Edge effects decrease biodiversity in fragmented habitats, not increase it.

WHY (causal/explanatory)

Q: Why does latitude affect biome distribution? A: Solar energy input decreases from equator to poles, creating temperature/precipitation gradients that define biomes (e.g., tropical rainforests at 0°, tundra at 60°+). Trap/Clarification: Altitude mimics latitude (e.g., alpine tundra at high elevations near the equator), but not due to solar angle—it’s temperature/pressure changes.

Q: Why is biodiversity hotspot conservation prioritized? A: Hotspots (e.g., Madagascar, Coral Triangle) contain ?1,500 endemic plant species and ?70% habitat loss, offering high return on investment for preserving irreplaceable species. Trap/Clarification: Hotspots-areas with most species (e.g., Amazon has high richness but lower endemism than Madagascar).

Q: Why is genetic diversity critical for conservation? A: Low genetic diversity (e.g., inbreeding) reduces population adaptability to environmental changes (e.g., disease, climate shifts). Trap/Clarification: Small populations lose diversity faster due to genetic drift, not gain it.

HOW (process/application)

Q: How do you calculate Simpson’s Diversity Index (D)? A: D = 1 – ?(pi)², where pi = proportion of individuals in species i; higher D = greater diversity. Trap/Clarification: Students forget to subtract from 1—D ranges from 0 (low diversity) to 1 (high diversity).

Q: How does island biogeography theory predict species richness? A: Richness = balance between immigration (distance from mainland) and extinction (island size); larger/closer islands support more species. Trap/Clarification: "Island" applies to any isolated habitat (e.g., mountaintops, lakes)—not just oceanic islands.

Q: How do corridors mitigate habitat fragmentation? A: Connect isolated patches to increase gene flow, reduce edge effects, and allow species migration (e.g., wildlife overpasses). Trap/Clarification: Corridors can spread disease/invasive species if not carefully designed.

CAN (conditions/possibilities)

Q: Can climate change shift biome boundaries? A: Yes—rising temperatures and altered precipitation can convert biomes (e.g., boreal forest-temperate forest, tundra-shrubland). Trap/Clarification: Shifts are not uniform; some species may lag due to dispersal limits (e.g., slow-growing trees).

Q: Under what conditions does secondary succession occur? A: After a disturbance (e.g., fire, logging) without total soil loss; pioneer species (e.g., grasses) colonize first, followed by climax community. Trap/Clarification: Primary succession (e.g., volcanic rock) requires soil formation—secondary does not.

Quick Facts & Traps

• Fact: Tundra has permafrost (permanently frozen soil) that limits root growth and stores massive carbon reserves.
• Trap: "Deserts are always hot."-Reality: Cold deserts (e.g., Gobi) exist; defined by low precipitation (<25 cm/year), not temperature.
• Fact: Coral reefs cover <0.1% of ocean floor but support ~25% of marine species (highest biodiversity per unit area).
• Trap: "All rainforests are tropical."-Reality: Temperate rainforests (e.g., Pacific Northwest) have high rainfall but cooler temperatures.
• Fact: Keystone species (e.g., sea otters, wolves) disproportionately affect ecosystem structure; their removal causes trophic cascades.
• Trap: "Endangered species = low population."-Reality: Threatened species (e.g., polar bears) have declining populations but may still be numerous.

Rapid-Fire True/False

• Statement: "The greenhouse effect is entirely harmful." Answer: FALSE Why the common mistake happens: Confuses natural greenhouse effect (essential for life) with enhanced effect from human emissions.

• Statement: "Biodiversity is highest in the tropics due to stable climates." Answer: TRUE Why the common mistake happens: Students overlook the role of energy input (high solar radiation-more niches) and evolutionary time (older ecosystems).

• Statement: "Invasive species always reduce biodiversity." Answer: FALSE Why the common mistake happens: Some invasives increase local richness (e.g., by filling empty niches), but they often disrupt ecosystem function.