AP Environmental Science Unit 1

Ecosystem

A community of organisms interacting with each other and their physical environment.

Biotic Factors

Living components of an ecosystem (plants, animals, microbes).

Abiotic Factors

Nonliving components of an ecosystem (temperature, water, sunlight, soil, nutrients).

Species

A group of organisms that can interbreed and produce fertile offspring.

Population

A group of individuals of the same species in a given area.

Community

All the populations of different species living in one area.

Biome

A large geographic region with distinct climate, vegetation, and wildlife (e.g., desert, tundra, rainforest).

Biodiversity

Variety of life in an ecosystem, measured at genetic, species, and ecosystem levels.

Species Richness

Number of different species in an ecosystem.

Species Evenness

How evenly individuals are distributed among species in an ecosystem.

Producer (Autotroph)

Organism that makes its own food through photosynthesis or chemosynthesis.

Consumer (Heterotroph)

Organism that obtains energy by feeding on other organisms.

Primary Consumer

Herbivores that eat producers.

Secondary Consumer

Carnivores that eat herbivores.

Tertiary Consumer

Carnivores that eat other carnivores (top predators).

Omnivore

Organism that eats both plants and animals.

Decomposer

Organisms (fungi, bacteria) that recycle nutrients from dead matter.

Detritivore

Organisms that feed on dead organic matter (earthworms, vultures).

Trophic Levels

Feeding levels in a food chain (producers → consumers → decomposers).

Food Chain

A single linear sequence showing energy flow between organisms.

Food Web

A complex network of interconnected food chains.

Energy Pyramid

Diagram showing how energy decreases as it moves up trophic levels.

10% Rule

Only about 10% of energy is passed to the next trophic level.

Gross Primary Productivity (GPP)

Total energy captured by producers through photosynthesis.

Net Primary Productivity (NPP)

Energy available to consumers after respiration (NPP = GPP - R).

Primary Productivity

The rate at which producers convert solar energy into chemical energy.

Law of Conservation of Matter

Matter cannot be created or destroyed, only recycled.

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed.

Symbiosis

Close interaction between two species that benefits at least one.

Mutualism

Relationship where both species benefit (+/+).

Commensalism

Relationship where one benefits and the other is unaffected (+/0).

Parasitism

Relationship where one benefits and the other is harmed (+/-).

Predation

One organism (predator) kills and eats another (prey).

Interspecific Competition

Competition between different species for resources.

Intraspecific Competition

Competition within the same species for resources.

Resource Partitioning

Species reduce competition by using resources differently.

Spatial Partitioning

Species use different areas/habitats.

Temporal Partitioning

Species use resources at different times.

Morphological Partitioning

Species evolve different traits to use resources differently.

Niche

An organism's role in its ecosystem (habitat, food source, interactions).

Keystone Species

A species with a disproportionately large impact on its ecosystem.

Indicator Species

Species that reflect environmental health (e.g., amphibians).

Invasive Species

Non-native species that disrupt ecosystems by outcompeting natives.

Ecological Succession

Natural change in ecosystems over time.

Primary Succession

Succession starting on bare rock with no soil.

Secondary Succession

Succession where soil remains (e.g., after a fire).

Biogeochemical Cycles

Movement of nutrients (carbon, nitrogen, phosphorus, water) through ecosystems.

Carbon Cycle

Movement of carbon through the atmosphere, organisms, oceans, and Earth's crust.

Carbon Sink

Natural systems that store carbon (oceans, forests, sediments).

Photosynthesis Equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Cellular Respiration Equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.

Deforestation

Removal of forests; decreases carbon storage, increases CO₂.

Fossil Fuels

Carbon-rich energy sources that release CO₂ when burned.

Sedimentation

Process where particles settle and form layers, storing carbon.

Nitrogen Cycle

Movement of nitrogen through the atmosphere, soil, and organisms.

Nitrogen - Largest Reservoir

Atmosphere (N₂ gas).

Nitrogen Fixation

Bacteria or lightning convert N₂ → NH₃/NH₄⁺.

Assimilation

Plants absorb nitrates (NO₃⁻) and ammonium (NH₄⁺).

Ammonification

Decomposers convert organic nitrogen → NH₄⁺.

Nitrification

Bacteria convert NH₄⁺ → NO₂⁻ → NO₃⁻.

Denitrification

Bacteria convert nitrates back to N₂ gas.

Phosphorus Cycle

Movement of phosphorus through rocks, soil, water, organisms (no atmospheric phase).

Weathering

Breaking down of rocks, releasing phosphorus into soil/water.

Excretion

Waste products returning nutrients to the environment.

Lithification

Conversion of sediments into rock.

Water Cycle (Hydrologic Cycle)

Movement of water through evaporation, condensation, precipitation, infiltration, runoff, and transpiration.

Evaporation

Water changes from liquid to gas.

Transpiration

Plants release water vapor through leaves.

Evapotranspiration

Combined evaporation and transpiration.

Precipitation

Water falling from the atmosphere (rain, snow, sleet).

Infiltration

Water soaks into the ground.

Runoff

Water flows across the surface into rivers, lakes, and oceans.

Solar Heating

Sun drives evaporation and climate patterns.

Largest Water Reservoirs

Oceans, glaciers/ice caps, atmosphere, groundwater.

Ocean

Largest reservoir of water on Earth.

Glaciers/Ice Caps

Store most of Earth's freshwater.

Atmosphere

Short-term reservoir for water vapor.

Groundwater

Stored water beneath Earth's surface.

Rivers

Flowing freshwater ecosystems.

Lakes

Standing freshwater ecosystems.

Lake Littoral Zone

Shallow area near shore with sunlight.

Lake Limnetic Zone

Open surface water, well-lit.

Lake Profundal Zone

Deep, dark water with little oxygen.

Lake Benthic Zone

Bottom of lake; includes sediments.

Wetlands

Ecosystems with water-saturated soils (swamps, marshes, bogs).

Estuaries

Areas where freshwater rivers meet saltwater oceans.

Salt Marshes

Coastal wetlands flooded by saltwater.

Coral Reefs

Biodiverse marine ecosystems formed by corals in shallow warm seas.

Intertidal Zones

Coastal areas between high and low tide.

Open Ocean

Deep water away from shore.

Photic Zone

Sunlit upper ocean layer (photosynthesis possible).

Aphotic Zone

Deep ocean without sunlight (no photosynthesis).

Turbidity

Measure of water clarity (high = murky).

Salinity

Concentration of dissolved salts in water.

Depth

Determines light, temperature, and pressure in aquatic systems.

Eutrophication

Nutrient enrichment → algal blooms → oxygen depletion.

Latitude

Distance north/south of equator; affects sunlight and climate.

Tropical Rainforest

Warm, wet biome with highest biodiversity.

Biome Shift

Change in biome due to shifts in temperature/precipitation.

Limiting Factor

Environmental condition that restricts population growth (nutrients, space, water).