APE Scholars Exam Review Session 2025

Introduction

• Review session covers units 1 to 5
• Moderators: Kyra and Reed
• Important resources available in video description and link tree
• Chat will move fast, focus on content review

Last-Minute Study Advice

• Unit 9: 15-20% of exam, focus on environmental solutions
• Unit 5: 10-15% of exam, frequently on FRQs
• Math Review: Important, especially FRQ #3

Unit 1: Ecosystems (6-8% of Exam)

Carbon Cycle

• Direct Exchange: Movement of carbon between atmosphere and ocean
• Ocean as a Carbon Sink and Source: Important for understanding CO2 impact
• Sedimentation: Carbon becomes sedimentary rock, removing it from atmosphere

Nitrogen Fixation

• Biological Fixation: By bacteria in root nodules, converting N2 to ammonia
• Synthetic Fixation: Uses fossil fuels, creates environmental challenges

Trophic Pyramid and 10% Rule

• Energy transfer through trophic levels is limited (10% efficiency)
• Implications for food webs and ecosystem structure

Important Vocabulary

• Carbon sequestration, Trophic level, 10% rule

FRQ Topics

• Carbon cycle, primary productivity, 10% rule

Unit 2: Biodiversity

Levels of Biodiversity

• Ecosystem, Species, Genetic Diversity: All contribute to ecosystem resilience
• Importance: Stability against environmental stressors

Ecosystem Services

• Categories: Provisioning, Regulating, Supporting, Cultural

Keystone Species

• Have a disproportionate impact on their ecosystem (e.g., beavers)

Important Vocabulary

• Ecosystem resilience, Keystone species

FRQ Topics

• Ecosystem services, Keystone species, Biodiversity impacts

Unit 3: Populations

K and R Selection

• K-Selected: Few offspring, high parental care (e.g., elephants)
• R-Selected: Many offspring, low parental care (e.g., insects)

Population Growth and Doubling Time

• Growth Rate Calculation: (CBR - CDR) / 10
• Rule of 70: Doubling time = 70 / growth rate

Total Fertility Rate (TFR)

• Factors Influencing TFR: Education, economic conditions, cultural factors

Demographic Transition

• Stages 1-4: High birth and death rates to low birth and death rates

Important Vocabulary

• Total fertility rate, Replacement level fertility

FRQ Topics

• R and K selection, TFR and economic impacts

Unit 4: Earth Systems and Resources

Weathering vs Erosion

• Weathering: Breakdown of rocks
• Erosion: Movement of sediments

Soil Characteristics

• Permeability vs Water Holding Capacity: Balance needed for healthy soil
• Soil Degradation: Causes and impacts on agriculture

Atmosphere Composition and Layers

• Troposphere and Stratosphere: Key layers related to weather and ozone protection

El Niño and La Niña

• Normal Conditions: Trade winds blow east to west
• El Niño: Weakened trade winds, warmer water east
• La Niña: Stronger trade winds, cooler water east

Important Vocabulary

• Permeability, Erosion, El Niño/La Niña effects

FRQ Topics

• Soil erosion and solutions, Watershed pollutants, El Niño impacts

Conclusion

• Focus for next session: Units 5 through 9
• Emphasis on understanding key terms and their implications