AP Environmental Science

10% rule

An ecological principle stating that approximately 10% of the energy available at one trophic level is transferred to the next trophic level, with the remaining 90% lost.

Energy transfer

The movement of energy from one trophic level to another through feeding relationships in an ecosystem.

Laws of thermodynamics

Physical principles that explain energy transformations, including that energy cannot be created or destroyed and that energy tends to become less organized and available for work.

Trophic level

The position an organism occupies in a food chain or food web, determined by the number of energy transfer steps from the primary producer.

Commensalism

A type of symbiosis in which one species benefits while the other species is neither helped nor harmed.

Competition

The struggle between organisms in an ecosystem for limited resources such as food, territory, mates, and habitat.

Mutualism

A type of symbiosis in which both species benefit from the interaction.

Parasitism

A type of symbiosis in which one species (the parasite) benefits while the other species (the host) is harmed.

Predator

An organism that hunts and eats another organism (prey) for food.

Predator-prey relationship

An interaction between two species in which a predator organism hunts and consumes another organism (the prey) for food.

Prey

An organism that is hunted and eaten by a predator.

Resource partitioning

The use of resources in different ways, places, or at different times by different species to reduce the negative impact of competition.

Symbiosis

A close and long-term interaction between two species living in an ecosystem.

Energy flow

The movement of energy from one trophic level to the next through an ecosystem, beginning with solar energy captured by producers.

Feedback loops

Mechanisms in ecosystems where changes in one component affect other components, which can either amplify (positive feedback) or dampen (negative feedback) the initial change.

Food chain

A linear sequence showing the transfer of energy and nutrients from one organism to the next, starting with a producer and moving through consumers.

Food web

A model depicting interlocking patterns of multiple food chains that shows the complex flow of energy and nutrients among organisms in an ecosystem.

Nutrient flow

The movement of chemical nutrients and elements through an ecosystem via food chains and food webs.

Altitude

The elevation above sea level, which affects temperature and precipitation and influences biome characteristics.

Biome

A large geographic area characterized by distinctive climate, vegetation, and animal communities adapted to those environmental conditions.

Climate

Long-term patterns of atmospheric conditions, including average temperature and precipitation, over decades or centuries at a specific location.

Desert

A terrestrial biome characterized by very low precipitation, extreme temperatures, and sparse vegetation adapted to arid conditions.

Global climate change

Long-term shifts in global temperatures and weather patterns caused by increased concentrations of greenhouse gases in the atmosphere.

Latitude

The angular distance north or south of the equator, which affects the intensity of solar radiation received at a location.

Nutrient availability

The presence and accessibility of essential nutrients in soil that support plant growth and affect biome productivity.

Savanna

A terrestrial biome with scattered trees and shrubs, grasses, seasonal rainfall, and warm temperatures year-round.

Shrubland

A terrestrial biome dominated by low-growing woody plants and shrubs, typically with moderate precipitation and seasonal variation.

Soil

The layer of weathered rock and organic material on Earth's surface that supports plant growth and varies among biomes.

Taiga

A terrestrial biome characterized by coniferous forests, long cold winters, and short growing seasons, located at high latitudes.

Temperate grassland

A terrestrial biome characterized by grasses and herbaceous plants, moderate precipitation, and temperature variations between seasons.

Temperate rainforest

A terrestrial biome with high precipitation, moderate temperatures, and dense vegetation found in temperate regions.

Temperate seasonal forest

A terrestrial biome with moderate precipitation, distinct seasons, and deciduous or mixed forests in temperate regions.

Tropical rainforest

A terrestrial biome near the equator characterized by high precipitation, warm temperatures year-round, and high biodiversity.

Tundra

A terrestrial biome at high latitudes or high altitudes with permanently frozen soil, low precipitation, and vegetation adapted to extreme cold.

Algae

The major photosynthetic organisms in aquatic biomes that form the base of aquatic food webs.

Aquatic biomes

Ecosystems characterized by water environments, including both freshwater and marine systems.

Coral reefs

Marine ecosystems built by coral organisms that provide habitat for diverse species and are sensitive to temperature changes, sediment, and fishing practices.

Depth

The vertical distance of water in aquatic biomes, affecting light penetration and organism distribution.

Estuaries

Transitional marine ecosystems where rivers meet oceans, with varying salinity levels.

Freshwater biomes

Aquatic ecosystems with low salinity water, including streams, rivers, ponds, lakes, and freshwater wetlands.

Freshwater wetlands

Freshwater ecosystems with saturated soil and shallow water, supporting specialized vegetation.

Lakes

Large freshwater ecosystems with still water, typically deeper than ponds.

Marine biomes

Aquatic ecosystems characterized by saltwater, including oceans, coral reefs, marshlands, and estuaries.

Marshland

Marine or brackish wetland ecosystems with salt-tolerant vegetation.

Oceans

The primary reservoir of water at Earth's surface in the hydrologic cycle.

Ponds

Small, shallow freshwater ecosystems with still water.

Rivers

Large flowing freshwater ecosystems that transport water across landscapes.

Salinity

The concentration of dissolved salts in water, affecting the distribution of aquatic organisms.

Streams

Flowing freshwater ecosystems, typically smaller than rivers.

Temperature

A measure of thermal energy that affects organism survival and is a key factor in ecological tolerance.

Turbidity

The cloudiness or clarity of water, affecting light penetration in aquatic ecosystems.

Carbon cycle

The biogeochemical process by which carbon moves between the atmosphere, living organisms, soil, and water systems.

Carbon dioxide

A greenhouse gas produced by combustion of fossil fuels and respiration; a principal contributor to global climate change.

Cellular respiration

The metabolic process in living organisms that breaks down organic compounds and releases carbon dioxide back into the atmosphere.

Decomposition

The process by which dead organic matter is broken down by microorganisms, releasing CO2 and other nutrients back into the environment.

Fossil fuels

Non-renewable energy sources formed from ancient organic matter, including coal, oil, and natural gas, that release carbon dioxide when burned.

Photosynthesis

The process by which plants convert carbon dioxide and light energy into organic compounds, removing carbon from the atmosphere.

Reservoir

A storage location or system that holds compounds (such as nitrogen, phosphorus, carbon, or water) for varying periods of time in biogeochemical cycles.

Sinks

Locations or systems that absorb and store substances (water, carbon, etc.) from the environment in biogeochemical cycles.

Sources

Origins or locations from which substances (water, carbon, etc.) are released into the environment in biogeochemical cycles.

Ammonia

A nitrogen compound (NH₃) produced during nitrogen fixation that is available for uptake by plants.

Atmospheric nitrogen

Nitrogen gas (N₂) present in the atmosphere, which is the major reservoir of nitrogen on Earth.

Nitrogen cycle

The movement of nitrogen atoms and molecules between sources and sinks in the environment, including the atmosphere, living organisms, and soil.

Nitrogen fixation

The process by which atmospheric nitrogen is converted into ammonia or other nitrogen compounds that plants can use and incorporate into plant tissue.

ATP

Adenosine triphosphate, a biological molecule containing phosphorus that stores and transfers energy in cells.

DNA

A biological molecule containing phosphorus that stores genetic information in organisms.

Phosphates

Compounds containing phosphorus that are absorbed by plant roots and incorporated into biological molecules.

Phosphorus availability

The amount of phosphorus accessible to plants and algae in soils and aquatic systems, which limits their productivity.

Phosphorus cycle

The movement of phosphorus atoms and molecules between sources and sinks in the environment, including rock, sediments, soil, organisms, and aquatic systems.

Phosphorus-bearing minerals

Rock and sediment minerals that contain phosphorus as a major component and serve as the primary phosphorus reservoirs.

RNA

A biological molecule containing phosphorus involved in protein synthesis and gene regulation.

Groundwater

Water stored beneath Earth's surface in soil and rock layers, serving as a smaller reservoir in the hydrologic cycle.

Hydrologic cycle

The continuous movement of water in its various solid, liquid, and gaseous phases between Earth's surface and the atmosphere, powered by solar energy.

Ice caps

Smaller reservoirs of water stored as ice at Earth's poles and high elevations in the hydrologic cycle.

Blue light

Wavelengths of light that penetrate deeper than 100 meters in clear water, affecting photosynthesis at greater depths.

Gross primary productivity

The total rate of photosynthesis in a given area, representing all energy captured by photosynthesizers.

Net primary productivity

The rate of energy storage by photosynthesizers in a given area after accounting for energy lost to respiration.

Organic compounds

Carbon-containing molecules produced by living organisms, such as glucose and other carbohydrates.

Photosynthesizers

Organisms, primarily plants and algae, that perform photosynthesis to convert solar energy into organic compounds.

Primary productivity

The rate at which solar energy is converted into organic compounds via photosynthesis over a unit of time.

Red light

Wavelengths of light that are primarily absorbed in the upper 1 meter of water, affecting aquatic photosynthesis.

Respiration

The metabolic process by which organisms break down organic molecules to release energy, producing CO2 as a byproduct.

Solar energy

Energy from the sun in the form of light and heat that is captured by living organisms.

Biogeochemical cycles

Cycles that move matter (such as carbon, nitrogen, and phosphorus) through the biotic and abiotic components of ecosystems.

Conservation of matter

The principle that matter is neither created nor destroyed but is recycled and transformed through biogeochemical cycles.

High-quality energy

Energy in a concentrated, usable form (such as solar radiation) that ecosystems require for functioning.

Producers

Organisms, primarily plants and photosynthetic organisms, that convert solar energy into chemical energy at the lowest trophic level.

Biodiversity

The variety of all living organisms and species within an ecosystem, region, or the entire planet.

Generalist species

Species that can survive and reproduce in a wide variety of environmental conditions and food sources, and tend to be advantaged in changing habitats.

Genetic diversity

The variation in genes within a population, which enables the population to respond to environmental stressors.

Habitat diversity

The variety of different habitats or environments within an ecosystem.

Population bottleneck

A drastic reduction in population size that leads to a loss of genetic diversity.

Specialist species

Species that are adapted to specific environmental conditions and have narrow habitat requirements.

Species diversity

The variety of different species present in an ecosystem.

Species richness

The number of different species present in an ecosystem.

Cultural services

Ecosystem services that provide non-material benefits to humans, including recreation, spiritual value, and aesthetic enjoyment.

Ecological consequences

The effects on natural systems and organisms resulting from disruptions to ecosystem services, such as biodiversity loss or habitat degradation.

Ecosystem services

The benefits that humans receive from natural ecosystems, including resources, regulation of environmental processes, and cultural values.

Human disruptions

Changes or disturbances to ecosystems caused by human activities that alter natural processes and functions.

Provisioning services

Ecosystem services that provide direct material benefits to humans, such as food, water, timber, and other natural resources.