Biodiversity & Conservation: every key term you need (+ practice quiz)

More AP Environmental Science guides

• Earth Systems
• Populations & Communities
• Energy Flow & Nutrient Cycles
• Land Use & Sustainability

Population Growth

Increase in number of organisms; exponential growth when resources unlimited; logistic when resources limited.

Exponential Growth

Population grows at constant rate; doubling time remains fixed; J-shaped curve.

Logistic Growth

Population growth slows as resources limit; carrying capacity reached; S-shaped curve.

Carrying Capacity

Maximum population size environment can sustain indefinitely; limited by resources.

Density-Dependent Factors

Population growth affected by density (disease, competition); greater impact at high density.

Density-Independent Factors

Population affected regardless of density (weather, disaster); affects all individuals equally.

Birth Rate

Number of births per 1,000 individuals per year; varies by age structure and access to reproduction.

Death Rate

Number of deaths per 1,000 individuals per year; increases with age and disease prevalence.

Migration

Movement of individuals into (immigration) or out of (emigration) population; affects population size.

Age Structure

Distribution of population by age groups; pyramids reveal population momentum.

Demographic Transition

Shift from high birth/death rates to low birth/death rates as societies develop.

Total Fertility Rate

Average number of children per woman; replacement level is 2.1 in developed countries.

Survivorship Curve

Graph showing proportion of cohort surviving to each age; reveals mortality patterns.

Predation

Interaction where one organism (predator) kills and eats another (prey).

Competition

Interaction where organisms compete for same resource (food, space, light).

Symbiosis

Close relationship between different species; includes mutualism, commensalism, parasitism.

Mutualism

Both species benefit from relationship; example: bees and flowers.

Parasitism

One organism benefits; other is harmed; parasite feeds on host.

Commensalism

One species benefits; other unaffected; example: remora fish on shark.

Succession

Predictable change in community composition over time; primary follows disturbance; secondary after removal.

Genetic diversity

Variety of alleles within a population; buffers against disease and environmental change and is lost in bottlenecked or inbred populations.

Species richness vs. evenness

Richness is the number of species present; evenness is how equally abundant they are. Both feed into diversity indices.

Ecosystem services (four types)

Provisioning (food, timber), regulating (flood control, pollination), cultural (recreation), supporting (nutrient cycling, soil formation).

Island biogeography

Species richness on islands (or habitat patches) rises with area and nearness to a source; large, close islands hold the most species.

Ecological tolerance

Range of conditions (temperature, salinity, pH) an organism can endure; performance drops in zones of stress and death beyond limits.

Generalist vs. specialist

Generalists tolerate wide conditions and varied diets (raccoons); specialists need narrow niches (koalas) and are more extinction-prone.

Keystone species

Species with disproportionately large effect relative to its abundance; removal (sea otters, wolves) restructures the community.

Indicator species

Organism whose presence or condition signals ecosystem health, such as trout or mayfly nymphs indicating well-oxygenated water.

Bottleneck effect

Sharp population decline that leaves reduced genetic diversity even after numbers recover (cheetahs, northern elephant seals).

Habitat fragmentation

Breaking habitat into isolated patches, increasing edge effects, blocking gene flow, and reducing area for interior species.

Edge effect

Altered light, wind, temperature, and predation along a habitat boundary; small or narrow fragments are nearly all edge.

Wildlife corridor

Strip of habitat connecting fragments so animals can migrate and breed, counteracting isolation.

HIPPCO

Major drivers of biodiversity loss: Habitat destruction, Invasive species, Population growth, Pollution, Climate change, Overexploitation.

Ecological succession pioneer species

First colonizers of bare rock or disturbed land (lichens, mosses, fireweed) that build soil and set the stage for later species.

Climax community

Relatively stable, mature community at the end of succession, though disturbance keeps most systems in a shifting mosaic.

Ecosystem resilience

Ability of an ecosystem to recover after disturbance; higher species diversity generally increases resilience.