AP Environmental Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Net primary productivity

Energy stored in producer biomass after respiration; calculated as gross primary productivity minus the respiration of producers, and it sets the energy base for the food web.

Ten percent rule

Roughly 10 percent of energy at one trophic level transfers to the next; most is lost as heat, so food chains rarely exceed four or five levels.

Keystone species

A species whose influence on community structure far exceeds its abundance, so its removal causes large cascading changes to other populations.

Nitrogen fixation

Conversion of atmospheric N2 into ammonia by bacteria such as Rhizobium or by lightning; it makes nitrogen biologically available for building proteins and nucleic acids.

Eutrophication

Nutrient enrichment of water that triggers algal blooms; decomposition of the algae depletes dissolved oxygen, causing hypoxia and fish kills.

Species richness versus evenness

Richness is the number of species present; evenness is how similar their abundances are. High evenness raises diversity when richness is equal.

Island biogeography

Principle that larger islands and those closer to the mainland hold more species, because colonization is easier and extinction rates are lower.

Ecosystem services

Benefits people obtain from ecosystems, grouped as provisioning (food, timber), regulating (climate, water), cultural, and supporting (nutrient cycling).

Bottleneck effect

Sharp population reduction randomly eliminates alleles, leaving survivors with reduced genetic diversity and lower capacity to adapt to change.

Logistic growth

Population growth that slows as size approaches carrying capacity K; the rate is fastest at K/2 and reaches zero at K.

Rule of 70

Doubling time in years equals 70 divided by the annual percentage growth rate, giving a quick estimate of population doubling.

Carrying capacity

Maximum population size an environment can sustain indefinitely given available food, water, space, and other limiting resources.

Density-independent factors

Limiting factors such as fire, drought, and storms that reduce populations regardless of how crowded they are.

Age structure diagram

Graph of population by age and sex; a broad base predicts rapid future growth, while a narrow base predicts decline.

Soil horizons

Vertical layers from O (litter) and A (topsoil) through E, B, and C to R bedrock; the A horizon holds most organic matter and root activity.

Porosity versus permeability

Porosity is total void space; permeability is how readily fluid flows through. Clay is porous but nearly impermeable, so it traps water.

El Niño

Weakened trade winds allow warm water to spread across the eastern Pacific, shifting rainfall patterns and disrupting fisheries worldwide.

Convergent plate boundary

Where plates collide; oceanic crust subducts beneath continental or oceanic crust, producing trenches, volcanoes, and earthquakes.

Salinization

Accumulation of salts in topsoil from repeated irrigation and high evaporation, which reduces crop yields and can render land unusable.

Integrated pest management

Strategy combining biological controls, crop rotation, and limited pesticide use to suppress pests while slowing the evolution of resistance.

Tragedy of the commons

Depletion of a shared open-access resource when individuals each gain from overuse while the cost is spread across the whole group.

Impervious surface

Paved or built cover that blocks infiltration, increasing stormwater runoff volume, flooding, and pollutant delivery to streams.

Net energy

Energy returned minus energy invested in obtaining a fuel; a high ratio means a large usable surplus after extraction and processing costs.

Photovoltaic cell

Device that converts sunlight directly into electricity using semiconductor material, with no combustion and no direct emissions during operation.

Cogeneration

Combined heat and power system that captures waste heat from electricity generation for heating, raising overall fuel efficiency.

Photochemical smog

Brown haze formed when nitrogen oxides and volatile organic compounds react in sunlight, worst on warm, sunny, low-wind days.

Thermal inversion

Layer of warm air above cooler surface air that prevents vertical mixing, trapping pollutants near the ground and worsening air quality.

Acid deposition

Sulfur dioxide and nitrogen oxides convert to sulfuric and nitric acids and fall as rain or snow, acidifying lakes and mobilizing soil aluminum.

Biomagnification

Increase in concentration of persistent, fat-soluble toxins at each higher trophic level, reaching highest levels in top predators including humans.

Nonpoint-source pollution

Diffuse pollution entering water from broad areas such as farm fields and streets, which is harder to regulate than a single pipe discharge.

LD50

Dose of a substance that kills 50 percent of a test population; a lower value indicates greater acute toxicity.

Ocean acidification

Dissolved carbon dioxide forms carbonic acid and lowers ocean pH, impairing calcification in corals, shellfish, and plankton.