AP Environmental Science Units 1–4 — KNOWT-READY RE-TEACH SET

What is environmental science?

Study of natural systems and how humans interact with and impact those systems.

What is sustainability?

Using resources at a rate that allows them to replenish naturally for future generations.

What is the tragedy of the commons?

Overuse of shared resources due to individual self-interest.

What is a system?

A set of interacting components with inputs, processes, and outputs.

Negative feedback loop

A process that counteracts change and stabilizes a system.

Positive feedback loop

A process that amplifies change and destabilizes a system.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Second Law of Thermodynamics

Energy conversions increase entropy and reduce usable energy.

What are trophic levels?

Feeding levels in an ecosystem (producer to top consumer).

10% Rule

Only about 10% of energy transfers to the next trophic level.

Why is the energy pyramid always upright?

Energy is lost as heat at each trophic transfer.

GPP

Total energy captured by producers through photosynthesis.

NPP

GPP minus energy used for respiration; energy available to consumers.

Carbon cycle

Movement of carbon through atmosphere, biosphere, hydrosphere, and geosphere.

Major human impact on carbon cycle

Burning fossil fuels increases atmospheric CO₂.

Nitrogen cycle order

Nitrogen fixation → nitrification → assimilation → ammonification → denitrification.

Why is nitrogen often a limiting nutrient?

Plants cannot use atmospheric nitrogen directly.

Phosphorus cycle key trait

Has no atmospheric phase.

Why is phosphorus hard to manage?

It accumulates in sediments and is slow to cycle.

Water cycle processes

Evaporation, condensation, precipitation, runoff, infiltration.

Primary productivity

Rate at which producers convert solar energy into biomass.

Where is NPP highest?

Tropical rainforests and estuaries.

Food chain

Linear transfer of energy.

Food web

Interconnected food chains showing multiple energy pathways.

What is biodiversity?

Variety of life at genetic, species, and ecosystem levels.

Why is biodiversity important?

Increases ecosystem resilience and stability.

Ecosystem services

Benefits humans receive from ecosystems.

Provisioning services

Food, water, timber.

Regulating services

Climate regulation, pollination, flood control.

Cultural services

Recreation and spiritual value.

Supporting services

Nutrient cycling and soil formation.

Island biogeography theory

Species richness depends on island size and distance from mainland.

Which islands have the most species?

Large and close islands.

Ecological tolerance

Range of environmental conditions a species can survive in.

Natural disruptions

Fires, floods, hurricanes, volcanic eruptions.

Why can natural disruptions be beneficial?

They can reset succession and increase biodiversity.

Adaptation

Inherited trait that increases survival or reproduction.

Succession

Gradual change in species composition over time.

Primary succession

Occurs where no soil exists.

Secondary succession

Occurs where soil remains after disturbance.

Generalist species

Species with broad niches and high adaptability.

Specialist species

Species with narrow niches and low adaptability.

r-selected species

Many offspring, early reproduction, little parental care.

K-selected species

Few offspring, late reproduction, high parental care.

Survivorship curve Type I

High survival until old age.

Survivorship curve Type II

Constant death rate.

Survivorship curve Type III

High early mortality.

Carrying capacity

Maximum population an environment can sustainably support.

Exponential growth

Population grows rapidly with unlimited resources.

Logistic growth

Population growth slows as it approaches carrying capacity.

Limiting factor

Environmental condition that restricts population growth.

Density-dependent limiting factor

Disease, competition.

Density-independent limiting factor

Natural disasters, weather.

Age structure diagram

Graph showing population age distribution.

Wide base age structure

Rapid population growth.

Narrow base age structure

Population decline.

Total fertility rate (TFR)

Average number of children per woman.

Replacement-level fertility

About 2.1 children per woman.

Demographic transition model

Model showing population change as countries develop.

Convergent plate boundary

Plates collide.

Divergent plate boundary

Plates move apart.

Transform plate boundary

Plates slide past each other.

Soil formation

Weathering of rock plus organic matter.

Soil erosion

Removal of topsoil by wind or water.

Loam soil

Balanced mixture of sand, silt, and clay.

Troposphere

Lowest atmosphere layer; weather occurs here.

Stratosphere

Contains ozone layer.

Global wind patterns

Caused by uneven heating of Earth.

Hadley cells

Circulation cells near the equator.

Why deserts form at 30° latitude

Descending dry air from Hadley cells.

Watershed

Land area that drains into a common water body.

Why watersheds matter

Pollution travels downstream.

Solar radiation and seasons

Caused by Earth’s axial tilt.

El Niño

Warm Pacific currents alter global weather.

La Niña

Cooler Pacific currents with opposite effects.