All Subjects



AP Enviro



Unit 3

3.0 Unit 3 Overview: Populations

2 min readapril 29, 2020

Karla Jauregui Sandoval


Image Courtesy of Pixabay

Unit 3 in APES covers the relationship between ecosystems and the change in their environment. The main questions to focus on throughout this unit is 

  • What are the major characteristics of populations? 

  • How do populations react to environmental conditions changing? 

  • What are the differences in species’ reproductive patterns? 

  • How can a population change be calculated using a formula? 

⚡ Key Terms 

This list of key terms will help you better understand the content and prepare you for the multiple choice section of the exam and FRQ. 

3.1 Generalist and Specialist Species 

  • Generalist Species 

  • Specialist species 

3.2 K Selected and r selected species 

  • K selected species 

  • R selected species 

  • Biotic potential 

3.3  Survivorship curves 

  • Survivorship curve

3.4 Carrying Capacity

  • Carrying Capacity 

  • Population Overshoot  

  • Environmental resistance 

3.5 Population Growth and Resource Availability 

  • Population Growth 

  • Logistic growth 

  • Exponential growth 

3.6 Age Structure Diagrams 

  • Age structure diagram 

  • Top heavy age structure 

  • Stationary age structure diagram 

  • Inverted pyramid age structure diagram 

  • Constrictive age structure diagram 

  • Expansive pyramid age structure diagram 

3.7 Total fertility rate 

  • Total fertility rate 

  • Crude Birth rate 

  • Crude death rate 

  • Family planning 

  • Infant mortality rate 

  • Life expectancy 

  • Replacement level fertility 

3.8 Human Population Dynamics 

  • Population density 

  • Immigration and Emigration 

  • Density dependent factor 

  • Density independent factor 

  • Rule of 70 

3.9 Demographic Transition 

  • Demographic Transition 

  • Pre industrial demographic transition 

  • Transitional demographic transition 

  • Industrial demographic transition

  • Post Industrial demographic transition

⚡ Quick Study - Key Terms 

  • Age structure diagrams: An age structure diagram shows the distribution of population for a country. If a population is stable then there will be an equal distribution amongst the age groups. If a population is predicted to decline then there will be a large group of elders. 

  • Biotic potential ➪ Refers to the maximum reproductive rate of a population in ideal conditions 

    • how many times an organism can reproduce 

    • r is much higher than K 

    • exponential growth without limited

  • Carrying capacity ➪  The maximum population size of the species that the environment can sustain, given the food, habitat, water and other necessities available in the environment  

  • Density-dependent Factors ➪  The size of the population will affect survival ➪ access to clean water and air, food availability ,disease, territory size  

  • Density-independent Factors ➪ Affect population regardless of population density (size) ➪ weather, climate, storms fires, heatwaves, droughts 

  • Survivorship curve ➪  A line that displays the relative survival rates of a cohort - a group of individuals of the same age- in a population, from birth to the maximum age reached by any one cohort member. Type 1,2,3 curves 

  • The Rule of 70 ➪ The rule of 70 states that dividing the number of 70 by the percentage population growth rate approximates the populations doubling it

🎥 Watch: AP Environmental Science Streams


Was this guide helpful?

Join us on Discord

Thousands of students are studying with us for the AP Environmental Science exam.

join now

Browse Study Guides By Unit

Free Response Questions (FRQs)

Multiple Choice Questions (MCQs)

Unit 1: The Living World: Ecosystems

Unit 2: The Living World: Biodiversity

Unit 4: Earth Systems and Resources

Unit 5: Land and Water Use

Unit 6: Energy Resources and Consumption

Unit 7: Atmospheric Pollution

Unit 8: Aquatic and Terrestrial Pollution

Unit 9: Global Change