APES Key Concepts: Nitrogen, Water, and Ecosystem Cycles

Ammonification

Decomposers convert organic nitrogen from dead organisms/waste into ammonium (NH₄⁺). Key step in the nitrogen cycle. Significance in APES: Recycles nitrogen for plant use, supporting ecosystem productivity and nutrient cycling.

Assimilation

Plants absorb inorganic nutrients (nitrates/ammonium) and incorporate them into organic molecules. Occurs in nitrogen and carbon cycles. Significance in APES: Transfers nutrients from abiotic to biotic components, linking soil fertility to plant growth and food webs.

Background Extinction

Natural, low-rate species extinction over time. Occurs without major environmental catastrophes. Significance in APES: Provides a baseline to evaluate human-driven extinction; informs biodiversity conservation.

Benthos

Organisms living on or near the bottom of aquatic ecosystems. Examples: clams, crabs, worms. Significance in APES: Play roles in decomposition, nutrient cycling, and water quality monitoring.

Biogeochemical Cycle

Movement of elements/compounds between living and non-living components. Includes carbon, nitrogen, phosphorus, sulfur, and water cycles. Significance in APES: Explains nutrient flows, ecosystem function, and human impact on natural cycles.

Deciduous Plants

Plants that shed leaves seasonally (cold/dry periods). Common in temperate forests. Significance in APES: Affect nutrient cycling, carbon storage, and soil fertility.

Carbon Cycle

Movement of carbon among atmosphere, biosphere, hydrosphere, and geosphere. Includes photosynthesis, respiration, decomposition, fossil fuel use. Significance in APES: Central to climate change understanding; affected by human activities.

Carbon Sink

Reservoir that absorbs more carbon than it releases. Examples: forests, oceans, soil. Significance in APES: Mitigates climate change; conservation and restoration maintain ecosystem balance.

Climax Community

Stable, final stage of ecological succession. Species composition remains relatively constant. Significance in APES: Shows ecosystem stability and recovery; guides conservation and management.

Coastal Wetland

Wetlands along coasts (marshes, estuaries). High productivity, nutrient-rich, buffer against storms. Significance in APES: Provide habitat, filter pollutants, protect shorelines, sensitive to human impact.

Competitive Exclusion

Two species competing for identical resources cannot coexist indefinitely. One outcompetes the other or adapts to a different niche. Significance in APES: Explains species distribution and biodiversity; important for invasive species management.

Coniferous Trees

Trees with cones and needle-like leaves (usually evergreen). Adapted to cold or dry climates. Significance in APES: Carbon storage, timber production, habitat, and climate regulation via CO₂ sequestration.

Denitrification

Microbes convert nitrates (NO₃⁻) into nitrogen gas (N₂). Returns nitrogen to the atmosphere. Significance in APES: Maintains soil nitrogen balance, reduces water pollution, crucial for agriculture.

Detritivore

Organisms that feed on dead organic matter. Examples: earthworms, crabs, insects. Significance in APES: Facilitate nutrient recycling and energy flow; maintain ecosystem health.

Detritus

Dead organic material from plants and animals. Food for decomposers and detritivores. Significance in APES: Drives decomposition and nutrient cycling; supports ecosystem productivity.

Detritus Feeder

Organism consuming detritus; synonym for detritivore. Examples: worms, crabs, insects. Significance in APES: Connects decomposition to energy flow; recycles nutrients.

Diffusion

Movement of molecules from high to low concentration. Passive process (no energy required). Significance in APES: Explains gas, nutrient, and pollutant movement; essential for ecosystem function.

Ecological Niche

Species' role and position in an ecosystem. Includes habitat, resources, and interactions. Significance in APES: Explains species coexistence, resource competition, and informs conservation efforts.

Energy Productivity

Rate at which energy is captured and stored by producers in an ecosystem. Measured as biomass produced per unit area/time. Significance in APES: Indicates ecosystem efficiency; relates to food webs, energy flow, and sustainability.

Estuary

Coastal area where freshwater and saltwater mix. Highly productive and nutrient-rich. Significance in APES: Supports fisheries, biodiversity, and buffers against pollution and flooding.

Fundamental Niche

Full range of environmental conditions and resources a species could theoretically use. Significance in APES: Helps predict species potential distribution; informs habitat conservation.

Generalist Species

Species that can thrive in a wide range of conditions and use varied resources. Significance in APES: Adaptable to environmental changes; often resilient to human impact.

Geographic Isolation

Separation of populations by physical barriers (mountains, rivers, etc.). Limits gene flow. Significance in APES: Drives speciation and biodiversity; critical for understanding evolution and conservation.

Gross Primary Productivity (GPP)

Total energy captured by producers through photosynthesis per unit area/time. Significance in APES: Measures ecosystem energy input; important for assessing productivity and resource management.

Habitat

Physical environment where a species lives. Provides food, water, shelter, and space. Significance in APES: Essential for species survival; habitat loss is a major driver of biodiversity decline.

Hydrologic Cycle

Movement of water through atmosphere, lithosphere, biosphere, and hydrosphere. Includes evaporation, condensation, precipitation, infiltration, runoff. Significance in APES: Maintains freshwater supply, regulates climate, supports ecosystems, and is affected by human activity.

Indicator Species

Species sensitive to environmental changes; signal ecosystem health. Examples: amphibians for water quality, lichens for air quality. Significance in APES: Early warning for pollution or habitat degradation; guides conservation efforts.

Infiltration

Movement of water from surface into soil. Significance in APES: Recharges groundwater, reduces runoff, affects soil moisture and plant growth.

Interspecific Competition

Competition between different species for the same resource. Significance in APES: Influences species distribution, ecosystem structure, and biodiversity.

Intraspecific Competition

Competition among individuals of the same species. Significance in APES: Regulates population size and natural selection within species.

Kilocalorie (kcal)

Unit of energy; amount of energy to raise 1 kg of water by 1°C. Significance in APES: Used to quantify energy in ecosystems, food webs, and human diets.

Leaching

Loss of nutrients or chemicals from soil due to water movement.

Limiting Factor

Resource or condition that restricts population growth.

Mass Extinction

Rapid loss of a large number of species globally.

Net Energy

Energy remaining after subtracting the energy used to obtain, process, or extract a resource.

Net Primary Productivity (NPP)

GPP minus energy used by producers for respiration.

Niche

Role and function of a species within an ecosystem.

Nitrogen Cycle

Movement of nitrogen through atmosphere, soil, water, and living organisms.

Nitrogen Fixation

Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or related compounds by bacteria or lightning.

Nitrification

Conversion of ammonium (NH₄⁺) to nitrites (NO₂⁻) and then nitrates (NO₃⁻) by bacteria.

Phosphorus Cycle

Movement of phosphorus through rocks, soil, water, and living organisms.

Phytoplankton

Microscopic photosynthetic organisms in aquatic ecosystems.

Plankton

Organisms that float/drift in water.

Pioneer Species

First organisms to colonize barren or disturbed areas.

Primary Productivity

Rate at which producers convert sunlight into chemical energy.

Primary Succession

Establishment of a community in a previously uninhabited area.

Producer

Organism that produces energy-rich organic compounds from sunlight or chemicals.

Pyramid of Energy Flow

Diagram showing energy transfer between trophic levels.

Range (Statistical)

Difference between highest and lowest values in a data set. Significance in APES: Used in ecological data analysis, population studies, and environmental monitoring.

Reproductive Isolation

Mechanisms preventing species from interbreeding. Can be behavioral, temporal, or geographic. Significance in APES: Drives speciation and maintains biodiversity.

Resource Partitioning

Species divide resources to reduce competition. Allows coexistence of similar species. Significance in APES: Explains biodiversity and ecosystem structure.

Riparian Zones

Areas along rivers and streams. Vegetation stabilizes banks and filters pollutants. Significance in APES: Supports habitat, water quality, and flood control.

Runoff

Water flow from precipitation over land into water bodies. Significance in APES: Can carry nutrients/pollutants; affects soil erosion and freshwater availability.

Scavenger

Organism that consumes dead animals. Examples: vultures, hyenas. Significance in APES: Removes carcasses, recycles nutrients, reduces disease spread.

Second Law of Thermodynamics

Energy transfer is inefficient; some energy is lost as heat. Significance in APES: Explains decreasing energy at higher trophic levels; limits ecosystem efficiency.

Secondary Succession

Recovery of an ecosystem after disturbance where soil remains intact. Significance in APES: Shows ecosystem resilience; relevant for land management.

Specialist Species

Species with narrow habitat/resource requirements. Examples: koalas, pandas. Significance in APES: Vulnerable to environmental change; indicators of ecosystem stability.

Species Evenness

Relative abundance of species in a community. Significance in APES: Indicator of biodiversity and ecosystem health.

Species Richness

Number of species in a community. Significance in APES: Measures biodiversity; important for conservation planning.

Sulfur Cycle

Movement of sulfur through rocks, water, and living organisms. Includes volcanic emissions, decomposition, and atmospheric deposition. Significance in APES: Affects soil fertility, acid rain, and ecosystem health.

Surface Runoff

Precipitation that flows over land into streams and rivers. Significance in APES: Influences water availability, erosion, and pollution transport.

Surface Water

Water on the Earth's surface (lakes, rivers, reservoirs). Significance in APES: Supplies drinking water, irrigation, hydroelectric power; affected by pollution.

Terrestrial

Land-based ecosystems. Significance in APES: Supports human and wildlife populations; studied for land management and biodiversity.

Transpiration

Release of water vapor from plants into the atmosphere. Significance in APES: Drives water cycle, regulates climate, and supports ecosystem function.

Water Cycle

Continuous movement of water through atmosphere, land, and oceans. Includes evaporation, condensation, precipitation, infiltration, runoff. Significance in APES: Maintains freshwater supply, climate regulation, and ecosystem processes.

Water Table

Upper level of groundwater saturated with water. Significance in APES: Determines availability of groundwater for ecosystems and human use.

Zones of Aeration and Saturation

Aeration zone: Soil and rock not fully saturated; contains air and water. Saturation zone: Soil/rock fully saturated with water. Significance in APES: Key for groundwater recharge, water supply, and hydrology studies.