AP® Environmental Science

Pick a unit

• Unit 1

  6–8% of exam

  The Living World: Ecosystems

  11 topics · 59 videos

  • Species interact through predation, competition and symbiosis
  • Climate decides which biome is found where
  • Matter cycles between reservoirs, but energy flows one way
  • Only about 10% of energy passes to the next trophic level
  • Nitrogen and phosphorus often limit how much plants can grow
  Open unit 1: The Living World: Ecosystems

• Unit 2

  6–8% of exam

  The Living World: Biodiversity

  7 topics · 38 videos

  • More diverse ecosystems recover from disruptions more easily
  • Nature provides services people rely on and that have economic value
  • Island size and distance shape how many species live there
  • Natural selection lets populations adapt over generations
  • Ecosystems rebuild in stages after a disturbance
  Open unit 2: The Living World: Biodiversity

• Unit 3

  10–15% of exam

  Populations

  9 topics · 48 videos

  • Generalists cope with change better than specialists
  • r-selected species have many offspring; K-selected species invest in a few
  • Every environment has a carrying capacity
  • A population's age structure predicts its future growth
  • As countries develop, birth and death rates tend to fall
  Open unit 3: Populations

• Unit 4

  10–15% of exam

  Earth Systems and Resources

  9 topics · 48 videos

  • Plate boundaries explain where earthquakes, volcanoes and mountains form
  • Soil forms slowly but can erode quickly
  • Uneven heating by the sun drives winds and climate
  • Earth's tilt, not its distance from the sun, causes the seasons
  • El Niño and La Niña shift weather patterns worldwide
  Open unit 4: Earth Systems and Resources

• Unit 5

  10–15% of exam

  Land and Water Use

  17 topics · 90 videos

  • Shared resources get overused when no one manages them
  • Modern farming feeds billions but can harm soil and water
  • Meat takes far more land, water and energy than plant foods
  • Paved cities change how water moves across the land
  • Sustainability means meeting today's needs without using up resources for the future
  Open unit 5: Land and Water Use

• Unit 6

  10–15% of exam

  Energy Resources and Consumption

  13 topics · 68 videos

  • Nonrenewable fuels run out; renewable sources refill on a human timescale
  • Most power plants heat water into steam to spin a turbine and generator
  • Every energy source has trade-offs, even renewable ones
  • Where energy resources are found shapes what each region uses
  • Using less energy is often the cheapest and cleanest choice
  Open unit 6: Energy Resources and Consumption

• Unit 7

  7–10% of exam

  Atmospheric Pollution

  8 topics · 44 videos

  • Primary pollutants are released directly; secondary pollutants form in the air
  • Burning fossil fuels is the biggest human source of outdoor air pollution
  • Sunlight drives the chemistry that makes smog
  • Weather can trap pollution close to the ground
  • Laws and control technologies have cut many air pollutants
  Open unit 7: Atmospheric Pollution

• Unit 8

  7–10% of exam

  Aquatic and Terrestrial Pollution

  15 topics · 78 videos

  • Point sources are easy to pinpoint; nonpoint sources are spread out and harder to control
  • Extra nutrients can choke a lake by using up its oxygen
  • Some chemicals don't break down and get more concentrated up the food chain
  • Making less waste beats finding better places to put it
  • The dose makes the poison, and dose-response data measure toxicity
  Open unit 8: Aquatic and Terrestrial Pollution

• Unit 9

  15–20% of exam

  Global Change

  10 topics · 55 videos

  • The ozone layer blocks harmful UV, and a global treaty is helping it recover
  • Greenhouse gases trap heat, and adding more warms the planet
  • Oceans soak up heat and CO₂, which makes them warmer and more acidic
  • Habitat loss is the biggest threat to biodiversity
  • Protecting a species usually means protecting its habitat
  Open unit 9: Global Change