AP Environmental Science Unit 3 - Populations

2 min readoctober 14, 2021

AP Environmental Science ♻️

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AP Environmental Science Populations Review

Here's an organized outline for AP Environmental Science Unit 3 reviews. This outline has been adapted from the 2019 Course Description published by College Board. You can use this to build an AP Enviro Unit 3 study guide.

Species Adaptation

A variety of factors result in the change of populations within ecosystems. 
  • When a population surpasses its carrying capacity organisms will die due to lack of available resources. 
Species tend to fall into one of two categories, specialist or generalist and this allows them to succeed in vastly different ecosystems. 
  • Specialist species are highly adapted to their specific environment and are often unable to survive habitat change. 
  • Generalist species are able to quickly adapt and take advantage of changing habitats, these species are often able to excel in human altered environments. 
Read: AP Environmental Science - Specialist and Generalist Species
Reproductive patterns are grouped into K- or r- selected species and these differences impact the growth patterns in populations. 
  • K-selected species tend to be large, have few offspring per reproduction event, live in stable environments, expend significant energy for each offspring, mature after many years of extended youth and parental care, have long life spans/life expectancy, and reproduce more than once in their lifetime. Competition for resources in K-selected species’ habitats is usually relatively high. 
  • r-selected species tend to be small, have many offspring, expend or invest minimal energy for each offspring, mature early, have short life spans, and may reproduce only once in their lifetime. Competition for resources in r-selected species’ habitats is typically relatively low. 

Population Changes

Read: AP Environmental Science - K-selected & r-selected species
Environmental factors limit the growth of populations. 
Watch: AP Environmental Science - 🎥 Population Dynamics: Carrying Capacity
 Human populations change in reaction to a variety of factors, including social and cultural factors.
  • Age structure diagrams interprete the population growth rates of human groups and can be used to analyze population trends. 
  • Increased birth rate, immigration and access to adequate health care tend to cause populations to increase. 
  • Access to family planning, education and postponement of marriage tend to cause populations to stabilize or decrease.
Read: AP Environmental Science - Human Population Dynamics

Unit 3 Vocab

  • Age structure diagrams
  • Biotic potential
  • Carrying capacity
  • Demographic transition
  • Density-dependent Factors
  • Density-independent Factors
  • Generalist species
  • Global human population
  • Invasive species
  • K-selected species
  • Population growth
  • Population overshoot
  • R-selected species
  • Resource availability
  • Specialist species
  • Survivorship curve
  • The rule of 70
  • Total fertility rate (TFR)
Browse Study Guides By Unit
🏜Unit 1 – The Living World: Ecosystems
🐠Unit 2 – The Living World: Biodiversity
👪Unit 3 – Populations
🌏Unit 4 – Earth Systems & Resources
🏖Unit 5 – Land & Water Use
⚡️Unit 6 – Energy Resources & Consumption
💨Unit 7 – Atmospheric Pollution
♻️Unit 8 – Aquatic & Terrestrial Pollution
🔥Unit 9 – Global Change
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