Unit 1: The Living World: Ecosystems (AP Environmental Science)

A comprehensive set of practice flashcards covering key concepts from Unit 1: The Living World: Ecosystems, including ecosystem definitions, biomes, energy flow, cycles (carbon, nitrogen, phosphorus, hydrologic), trophic levels, interactions, productivity, aquatic systems, and related topics.

What is an ecosystem?

An integration of abiotic (non-living) and biotic (living) factors interacting with one another.

What is a population?

A group of individuals of the same species living in the same area.

What is a community?

Multiple species living in the same space and time.

What is a biome?

A group of ecosystems in the same region that share climate and typical communities of organisms.

What is the biosphere?

The regions on Earth’s surface and atmosphere occupied by living organisms.

What is a species?

A group of individuals who can reproduce and have offspring that can reproduce.

What is a trophic level?

A position in a food chain or web occupied by organisms with a similar feeding mode.

List the major trophic levels in order from producers onward.

Producers; Primary consumers; Secondary consumers; Tertiary consumers; Quaternary consumers; Decomposers (often treated separately from strict trophic levels).

What is the difference between biotic and abiotic factors?

Biotic factors are living organisms; abiotic factors are non-living environmental factors.

Give examples of biotic factors.

Bacteria, archaea, fungi, animals, and plants.

Give examples of abiotic factors.

Air, salinity, soil, temperature, light, water, minerals, pH, humidity.

How is matter treated in ecosystems vs energy?

Matter is recycled through biogeochemical cycles; energy flows in from the sun and is lost as heat (10% rule) as it moves through trophic levels.

What is the 10% rule?

Approximately 10% of the energy at one trophic level is transferred to the next level.

What are the four major types of species interactions?

Competition, Predation, Mutualism, and Commensalism (with additional roles like parasitism).

What is resource partitioning?

Different species use different resources or the same resource in different ways/usages to reduce competition.

What is temporal resource partitioning?

Different species feed at different times (e.g., day vs night) to reduce competition.

What is spatial resource partitioning?

Different species use different spaces or habitats to access the same resource.

What is a producer?

An organism that makes its own energy via photosynthesis (autotrophs).

What is a primary consumer?

An organism that eats producers (herbivore).

What is a secondary consumer?

An organism that eats primary consumers (carnivore/omnivore).

What is a tertiary consumer?

An organism that eats secondary consumers (top predator in many chains).

What is a quaternary consumer?

An organism that eats tertiary consumers (top predator in some systems).

What is a decomposer?

An organism that breaks down dead organic matter and recycles nutrients back into the ecosystem.

What is GPP (Gross Primary Productivity)?

The total rate of photosynthesis in a given area.

What is NPP (Net Primary Productivity)?

The rate of energy storage by photosynthesizers after subtracting respiration.

What units measure productivity?

Energy per unit area per unit time (e.g., kcal/m²/yr).

What factors affect terrestrial productivity?

Temperature and precipitation.

What factors affect aquatic productivity?

Light (depth) and nutrient availability.

What is a trophic cascade?

Predators limit the density or behavior of prey, enhancing the survival of the next lower trophic level (e.g., wolves in Yellowstone).

What is the difference between energy transfer and biomass loss in food chains?

With each transfer, roughly 10% of energy is passed on; the rest is lost as heat or used for metabolism.

What is a food web?

A model of an interlocking pattern of food chains showing energy and nutrient flow in an ecosystem.

What is a food chain?

A linear sequence showing who eats whom in a particular pathway.

What is eutrophication?

Nutrient enrichment causing dense plant growth and oxygen depletion (dead zones).

What is the largest carbon sink?

The ocean.

What are major carbon reservoirs?

Ocean, biosphere, sediments (including limestone), coral reefs, soil.

What is burial in the carbon cycle?

A slow geological process that stores carbon in underground sinks (sediments/limestone).

What is extraction in the carbon cycle?

Digging up or mining fossil fuels.

What is combustion in the carbon cycle?

Burning fossil fuels releases CO2 into the atmosphere.

What is ocean acidification?

CO2 dissolves in seawater forming carbonic acid, reducing carbonate availability for calcifying organisms.

Where is the major nitrogen reservoir?

The atmosphere (N2) is the major reservoir.

What is nitrogen fixation?

Atmospheric N2 is converted to ammonia, usable by plants.

What is nitrification?

Conversion of ammonia to nitrite and nitrate by bacteria.

What is denitrification?

Conversion of nitrate to atmospheric N2, returning nitrogen to air.

What is ammonification/assimilation?

Ammonification: decomposition converts organic N to ammonium; Assimilation: plants take up nitrate/ammonium.

Why is phosphorus a limiting factor?

Phosphorus is scarce in many ecosystems and essential for ATP, DNA, and cell membranes.

What is the phosphorus cycle missing atmospheric component?

There is no atmospheric reservoir in the phosphorus cycle; it moves between rocks, soils, water, and organisms.

What is the major phosphorus reservoir?

Sedimentary rocks.

What are the main phosphorus sources?

Fertilizers (NPK), phosphates in rocks, living organisms.

What is the hydrologic cycle?

The movement of water through the atmosphere, surface, and subsurface reservoirs driven by solar energy.

What is cohesion and adhesion in water?

Cohesion is attraction between water molecules; adhesion is attraction between water and other surfaces; together enable capillary action.

What are freshwater biomes?

Rivers and streams, lakes and ponds, wetlands, estuaries; important water resources.

What are marine biomes?

Oceans, coral reefs, marshland, estuaries; marine ecosystems that support oxygen production and biodiversity.

What is the difference between lotic and lentic systems?

Lotic systems are flowing waters (rivers); lentic systems are still waters (lakes).

What is the flood pulse concept?

Periodic inundation and drought control the lateral exchange of water, nutrients, and organisms between the main river channel and its floodplain.