APES & IBESS Ecosystems and Population Dynamics Vocabulary

Vocabulary flashcards generated from AP Environmental Science and IB Environmental Systems and Societies lecture notes covering ecosystems, biogeochemical cycles, biodiversity, ecological succession, and population demographics.

Terrestrial Biomes

Zones on land where terrestrial ecosystems are grouped by shared climatic and ecological conditions, categorized by climate, hydrology, geology, soils, topography, and vegetation.

Aquatic Zones

Water-based ecosystems structured primarily by salinity (the primary categorizing factor separating freshwater and marine) and depth (the secondary factor based on light availability).

Law of Tolerance

The ecological principle defining the degree to which an organism can survive changes in its environment.

Law of the Minimum

The ecological principle stating that organisms will continue to live until their supply materials are exhausted.

Biodiversity

The structural variety of life forms and their biological interactions across habitats, encompassing the number and variety of organisms within an ecosystem and variability within and between species.

Predation

An organism relationship where one organism preys on another organism, known as the prey.

Symbiotic Relationship

An interaction where two organisms rely closely on each other to survive.

Competition

An organism relationship characterized by individuals actively competing for shared resources.

Commensalism

An organism relationship in which one organism benefits while the other remains unaffected.

Transpiration

The process described as plant sweat, involving water movement through plants and its release into the atmosphere as vapor.

Watershed

A land area that channels rainfall and snowmelt into creeks, streams, and rivers.

Percolation

The process of water filtering and seeping slowly downward through soil, sediment, and porous rock.

Sublimation

The phase transition in the water cycle where ice and snow convert directly into vapor, bypassing the liquid state.

River Erosion

The active process where flowing rivers wear away sediment and rock to shape the landscape.

Estuaries

High-productivity ecosystems formed where rivers meet the ocean, characterized by shallow, calm waters, high nutrient levels, and forms such as marshes, mangrove forests, inlets, bays, and river mouths.

Wetlands

Areas where water covers the soil or is present at or near the surface all year or for varying periods, including marshes, swamps, bogs, and floodplains.

Photosynthesis

The biological process expressed by the chemical equation $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$, through which plants capture gaseous carbon to build sugars.

Long-Term Carbon Storage

Deep geological reservoirs holding $99+\%$ of global carbon secure for millions of years, primarily in rocks and fossil fuels (coal, oil, gas).

Short-Term Carbon Storage

Carbon actively and rapidly cycled near Earth's surface across the atmosphere, biosphere, and oceans (the largest short-term sink), taking months to centuries to cycle through.

Nitrogen Fixation

The key biological process in the nitrogen cycle that converts atmospheric nitrogen ($\text{N}_2$) into forms available and usable for plants.

Phosphorus Cycle

A major biogeochemical cycle circulating through the biosphere, lithosphere, and hydrosphere that does not enter the atmosphere due to the lack of a stable gaseous phase.

Gross Primary Productivity (GPP)

The rate of energy storage by photosynthesis minus respiration in an ecosystem, measured in energy per area per time ($\text{kcal/m}^2/\text{yr}$).

Marine Light Absorption

The differential absorption of solar light in aquatic environments, where red light is absorbed within $1\text{ m}$ while blue light penetrates up to $100\text{ m}$.

10% Rule

The thermodynamic principle stating that approximately $10\%$ of input energy is transferred between successive trophic levels, limiting food chain length as the rest is lost as heat.

Entropy

A measure of disorder, chaos, or uncertainty within a system, which constantly increases in physical and biological processes according to the 2nd Law of Thermodynamics.

Species Richness

The total number of unique species represented in an ecological community or area.

Species Evenness

The relative abundance of individuals within each species in an ecological community.

Gene Pool

The total availability of different genes and traits within a population, providing the genetic raw material for natural selection.

Bottleneck Effect

A massive and rapid decrease in population size that severely reduces the overall gene pool, causing inbreeding, birth defects, and limiting long-term adaptive capacity.

Anthropogenic

Environmental impacts, pressures, or pollution originating directly from human activity.

Stewardship

The active role of humans in protecting, managing, and looking after nature.

Direct Value

Measurable and immediate economic metrics applied directly to natural assets and resources, such as financial costs and market price.

Indirect Value

Less tangible, non-monetary benefits tied to natural existence, ethical values, aesthetics, and moral worth.

Provisioning Services

Ecosystem services comprising physical products extracted directly from nature, such as food, drinking water, timber, fuels, and medicinal plants.

Regulating Services

Ecosystem services providing benefits obtained from the moderation of natural processes, including air and soil quality regulation, flood control, pollination, and carbon storage.

Cultural Services

Non-material benefits obtained from ecosystems that contribute to human intellectual, creative, and social advancement, including art, architecture, and recreation.

Supporting Services

Fundamental underlying natural processes necessary for the production of all other ecosystem services, such as photosynthesis, nutrient cycling, soil formation, and the water cycle.

Island Biogeography

The study of ecological relationships and community structures on islands, where species richness is governed primarily by island size and isolation distance from the mainland.

Ecological Tolerance

The range of abiotic conditions (e.g., temperature, salinity, flow rate, sunlight) an organism or species can endure before experiencing stress, injury, or death.

Dissolved Oxygen (DO)

Microscopic bubbles of gaseous oxygen mixed and dissolved directly into water resources that aquatic organisms absorb through gills to survive.

Periodic Disruptions

Natural ecosystem disruptions that occur at regular, predictable intervals over time, such as annual spring flooding.

Episodic Disruptions

Natural ecosystem disruptions that occur irregularly or sporadically without a strict schedule, such as earthquakes.

Random Disruptions

Natural disruptions that have no predictable pattern or frequency of occurrence, such as tornadoes.

Primary Succession

The gradual process of ecological community development starting in a lifeless, soilless environment (such as bare rock left by volcanoes or glaciers).

Pioneer Species

The initial colonizing organisms (such as lichens) with broad tolerance that physically and chemically break down rock to create basic soil in bare habitats.

Secondary Succession

The recolonization and rebuilding of an ecological community following a localized disturbance in an area where fertile soil remains intact.

Keystone Species

Species whose activities play a uniquely significant role in determining overall community structure and supporting other organisms.

Ecosystem Engineers

Organisms that create, significantly change, or destroy physical habitats, such as beavers constructing wetlands.

Indicator Species

Organisms with narrow ecological tolerance whose presence, absence, or abundance demonstrates the specific health or environmental quality of an ecosystem.

Generalist Species

Species that succeed by maintaining a broad niche, adapting quickly, consuming a varied diet, and enduring wide abiotic tolerance limits in changing environments.

Specialist Species

Species that excel by tuning to a narrow niche with specific food and habitat requirements, making them highly vulnerable to environmental disruptions.

K-Selected Species

Species characterized by large body sizes, few offspring per reproduction event, high energy and parental investment, long lifespans, and stable habitats with high resource competition.

r-Selected Species

Species characterized by small body sizes, producing many offspring with minimal energy investment, early maturity, short lifespans, and the ability to thrive in disturbed habitats.

Type I Survivorship

A survivorship pattern characterized by high survival rates throughout most of life, followed by rapid mortality in old age (e.g., humans).

Type II Survivorship

A survivorship pattern characterized by a constant mortality rate experienced relatively equally across all age groups (e.g., birds).

Type III Survivorship

A survivorship pattern characterized by high early mortality rates, with very few individuals surviving to reach old age (e.g., trees).

Carrying Capacity ($K$)

The maximum number of organisms of a population that an environment can support indefinitely without resource degradation.

Biotic Potential

The maximum reproductive rate of a population under ideal environmental conditions.

Density-Dependent Factors

Biotic resistance factors that exert strong influence when population density reaches a certain level, such as resource competition, predation, and disease.

Density-Independent Factors

Abiotic resistance factors that affect all populations regardless of size or density, such as natural disasters, severe weather events, and drought.

Total Fertility Rate (TFR)

The average number of children a woman will have during her childbearing years (ages $15\text{--}49$).

Rule of 70

A formula used to estimate population doubling time assuming constant exponential growth: $\text{Doubling Time} = \frac{70}{r}$, where $r$ is the growth rate expressed as a percentage.

Demographic Transition

A historical model showing how birth rate, death rate, and total population correlate as societies industrialize across four stages: Pre-Industrial, Transitional, Industrial, and Post-Industrial.