AP Biology Unit 8: Ecology Overview

Introduction

• Focus: Ecology for the AP Bio exam or Unit 8 test
• Coverage: Concepts, models, vocabulary
• Topics:
  • Responses to the environment
  • Energy utilization and flow
  • Matter flow in ecosystems
  • Biogeochemical cycles
  • Population growth
  • Community ecology
  • Biodiversity
  • Ecosystem disruption

8.1 Responses to the Environment

• General Guidance: Objectives are broad; exclusion statements mean specific knowledge isn't required
• Case Studies:
  • Predator Warnings:
    • Alarm signals in animals (e.g., Belding's ground squirrels)
    • Calls are altruistic (e.g., inclusive fitness, kin selection)
    • Females are more likely to call due to proximity to kin
• Eusociality:
  • Social structure where only some reproduce (e.g., bees, ants)
  • Haplodiploidy in bees explains worker altruism

8.2 Metabolism and Energy Use

• Definitions:
  • Metabolism: Sum of chemical processes
  • Metabolic rate: Energy expended over time
• Endotherms vs. Ectotherms:
  • Endotherms: Generate heat internally (e.g., mammals, birds)
  • Ectotherms: Body temperature conforms to environment
• Energy Flow in Ecosystems:
  • Trophic levels: Producers, consumers (primary, secondary, tertiary)
  • 10% Rule: Only 10% energy passes to next level
  • Pyramids of energy, biomass, and numbers

8.3 to 8.4 Population Growth

• Factors Changing Population Size: Births, deaths, immigration, emigration
• Exponential Growth: Occurs under ideal conditions, limited by carrying capacity
• Logistic Growth Model: Incorporates carrying capacity and limiting factors
  • Density-dependent factors: Competition, parasitism
  • Density-independent factors: Natural disasters
• Population Cycles: Predator-prey dynamics

8.5 Community Ecology

• Symbiosis Types:
  • Competition, mutualism, predation, herbivory, commensalism, parasitism
• Competitive Exclusion Principle: Two species can't coexist in same niche
• Resource Partitioning: Leads to character displacement
• Keystone Species:
  • Influence community structure (e.g., sea stars, wolves)
  • Trophic cascades: Effects that trickle through ecosystem
• Ecological Succession:
  • Primary vs. secondary succession
  • Stages from pioneer species to climax community

8.6 Biodiversity

• Components: Ecosystem diversity, species diversity, genetic diversity
• Benefits:
  • Increases resilience, provides ecosystem services
  • Enhances intrinsic and potential benefits
• Simpson Diversity Index: Measures diversity using species richness and evenness

8.7 Ecosystem Disruption

• Causes:
  • Habitat destruction and fragmentation
  • Overexploitation
  • Invasive species
  • Deforestation
• Impact: Leads to sixth mass extinction, biodiversity loss

Conclusion

• Resources: Learn-biology.com for interactive learning and AP Bio exam preparation.
• Success Tips: Study consistently, use available resources, understand key concepts and models.