Unit 1: The Living World – Ecosystems

Abiotic Factors

Non-living physical and chemical elements in an environment, like water, sunlight, soil, and temperature.

Biotic Factors

Living organisms within an ecosystem, including plants, animals, fungi, and bacteria.

Biome

Large regions of Earth with similar climates, plants, and animals (e.g., tundra, rainforest, desert).

Ecosystem

A community of organisms and their interactions with abiotic factors in their environment.

Community

All populations of different species that live and interact in a specific area.

Population

Individuals of the same species living in the same area and interbreeding.

Species

A group of organisms capable of reproducing to produce viable, fertile offspring.

Respiration (Cellular Respiration)

A process where organisms convert glucose and oxygen into energy (ATP), releasing carbon dioxide and water.

Decomposition

The breakdown of organic matter into simpler compounds by decomposers like fungi and bacteria.

Photosynthesis

The process in plants and other producers that converts sunlight, CO₂, and water into glucose and oxygen.

Source/Sink

Sources release substances (e.g., fossil fuel emissions), while sinks absorb them (e.g., forests absorb CO₂).

Nitrogen Fixation

Conversion of atmospheric nitrogen (N₂) into forms usable by plants (e.g., ammonium), often by bacteria.

Denitrification

Conversion of nitrates back into nitrogen gas (N₂), returning it to the atmosphere by denitrifying bacteria.

Hydrologic Cycle

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

Transpiration

Loss of water vapor from plant leaves into the atmosphere.

Infiltration

Water seeping into the soil from the surface

Percolation

Downward movement of water through soil layers into groundwater

Evaporation

Conversion of liquid water into water vapor due to heat.

Runoff

Water that flows over land into bodies of water, often carrying pollutants.

Energy Flow

Movement of energy through an ecosystem, starting with producers and flowing to consumers and decomposers.

Chemical Cycles

Natural cycles that move elements like carbon, nitrogen, and phosphorus through ecosystems.

Food Web/Chain

Food chains are linear sequences of energy flow; food webs are complex, interconnected networks of feeding relationships.

10% Rule

Only 10% of energy transfers from one trophic level to the next, while 90% is lost as heat or used for metabolism.

Trophic Levels

Steps in the food chain, such as producers, primary consumers, and secondary consumers.

Primary Productivity

The rate at which producers convert sunlight into chemical energy

Gross Primary Productivity (GPP)

Total energy produced by photosynthesis.

Net Primary Productivity (NPP)

Energy left for consumers after producers use some for respiration (NPP = GPP - Respiration).