AP Environmental Science Unit 1 — The Living World: Ecosystems

Ecosystem

All the living and nonliving things in an area and how they interact.

Biotic Factors

The living parts of an ecosystem, such as plants, animals, bacteria, and fungi.

Abiotic Factors

The nonliving parts of an ecosystem, including sunlight, water, temperature, soil, air, and rocks.

Biogeochemical Cycle

The movement of nutrients and elements through living and nonliving parts of Earth.

Sink

A place that stores a substance, such as oceans storing carbon.

Source

Something that releases a substance, like burning fossil fuels releasing carbon dioxide.

Photosynthesis

Process by which plants take in CO₂ from the atmosphere and use sunlight to make food.

Cellular Respiration

Process where plants and animals break down food and release CO₂.

Decomposition

The breakdown of dead organisms and waste, returning carbon to the soil and atmosphere.

Combustion

Burning fossil fuels that releases stored carbon as CO₂.

Nitrogen Fixation

The process that converts atmospheric N₂ into usable forms like NH₃/NH₄⁺.

Nitrification

The process where bacteria convert NH₃/NH₄⁺ into nitrite (NO₂⁻) and then nitrate (NO₃⁻).

Assimilation

The process by which plants take up nitrate (NO₃⁻) or nitrogen compounds to make proteins.

Ammonification

The conversion of dead organisms and waste back into NH₃/NH₄⁺ by decomposers.

Denitrification

The process where bacteria convert NO₃⁻ back into atmospheric N₂.

Major Reservoir of Nitrogen

The atmosphere, which holds the majority of Earth’s nitrogen.

Phosphorus Cycle

The movement of phosphorus through rocks, soil, plants, animals, and back to rocks.

Eutrophication

A process that occurs when excessive nutrients, especially nitrogen and phosphorus, enter a body of water.

Mutualism (+/+)

An interaction where both species benefit, such as bees and flowers.

Parasitism (+/−)

An interaction where one species benefits and the other is harmed, like ticks and dogs.

Trophic Cascade

When a change at one trophic level causes changes at other trophic levels.

10% Rule

The principle that only about 10% of energy is transferred from one trophic level to the next.

Specialist

A species with a narrow niche that depends on specific resources.

Generalist

A species with a broad niche that can use many different resources.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Every energy transfer results in some energy being lost as heat.

Major Carbon Sink

The oceans, which store large amounts of carbon.

Major Carbon Source

Burning fossil fuels, which releases carbon dioxide.

Primary Productivity

The rate at which producers create biomass or chemical energy.

GPP (Gross Primary Productivity)

The total amount of energy captured by producers through photosynthesis.

NPP (Net Primary Productivity)

The energy left for plant growth after some energy is used for respiration.