Ecology and Biogeochemical Cycles: Key Concepts and Definitions

Abiotic

Non-living physical and chemical components of the environment (e.g., sunlight, water, temperature).

Adaptation

A trait or behavior that increases an organism's chances of survival and reproduction.

Aerobic

Processes or organisms that require oxygen.

Ammonification

Conversion of organic nitrogen into ammonia by decomposers.

Anaerobic

Processes or organisms that occur or live without oxygen.

Assimilation

The process by which plants absorb nutrients from the environment and incorporate them into organic molecules.

Autotroph

Organisms that produce their own food from inorganic substances (e.g., plants, algae).

Average

A measure of central tendency, often the mean of a set of numbers.

Background extinction

The normal, gradual rate of extinction for species in Earth's history.

Bacteria

Single-celled microorganisms that can be beneficial or pathogenic.

Benthos

Organisms that live on, in, or near the bottom of aquatic environments.

Biodiversity

The variety of life in all its forms, levels, and combinations.

Biogeochemical cycle

The movement of elements and compounds through living organisms and the environment.

Biological diversity

Another term for biodiversity; the variety of life forms.

Biome

A large ecological area with distinct climate, plants, and animals.

Biosphere

The global sum of all ecosystems; the zone of life on Earth.

Biotic

Living components of the environment (e.g., plants, animals, microbes).

Deciduous plants

Plants that lose their leaves seasonally.

Carbon cycle

The movement of carbon through the atmosphere, biosphere, oceans, and geosphere.

Carbon sink

A reservoir that absorbs more carbon than it releases (e.g., forests, oceans).

Carnivore

An organism that eats primarily other animals.

Climax community

A stable, mature ecological community with little change in species composition.

Coastal wetland

Wetlands located along coastlines, often flooded by tides.

Commensalism

A symbiotic relationship where one species benefits and the other is unaffected.

Community

All the populations of different species living and interacting in an area.

Competitive exclusion

The principle that two species competing for the same resources cannot coexist.

Coniferous trees

Trees that produce cones and needle-like leaves (e.g., pines, spruces).

Coral reef

A diverse underwater ecosystem built from coral skeletons.

Decomposer

Organisms that break down dead matter into simpler substances.

Denitrification

Conversion of nitrates into nitrogen gas by bacteria.

Detritivore

Organisms that feed on dead organic matter (detritus).

Detritus

Dead organic material, such as fallen leaves or dead organisms.

Detritus feeder

Another term for detritivore; organisms that consume detritus.

Diffusion

The passive movement of particles from high to low concentration.

Ecological diversity

The variety of ecosystems within a region.

Ecological niche

The role and position a species has in its environment.

Ecology

The study of interactions between organisms and their environment.

Ecosystem

A community of organisms and their physical environment interacting as a system.

Endangered species

A species at risk of extinction.

Endemic species

Species found only in a specific geographic area.

Energy productivity

The rate at which energy is produced in an ecosystem.

Estuary

A coastal area where freshwater mixes with seawater.

Evolution

The change in species over time through natural selection and other mechanisms.

Extinction

The permanent loss of a species.

Fundamental niche

The full range of environmental conditions a species can potentially occupy.

First law of thermodynamics

Energy cannot be created or destroyed, only transformed.

Food chain

A linear sequence of organisms through which energy and nutrients pass.

Food web

A network of interconnected food chains.

Generalist species

Species that can thrive in a wide range of environmental conditions.

Genetic diversity

The variety of genes within a species.

Geographic isolation

Physical separation of populations, which can lead to speciation.

Gross primary productivity (GPP)

The total energy captured by producers in an ecosystem.

Groundwater

Water stored beneath the Earth's surface in soil or rock.

Habitat

The natural environment where an organism lives.

Herbivore

An organism that eats plants.

Heterotroph

An organism that obtains energy by consuming other organisms.

Host

An organism that provides a source of energy or shelter for a parasite.

Hydrologic cycle

The movement of water through the environment (evaporation, precipitation, etc.).

Indicator species

Species sensitive to environmental changes, used to assess ecosystem health.

Infiltration

The process of water soaking into soil.

Interspecific competition

Competition between different species for the same resources.

Intraspecific competition

Competition within the same species for resources.

Keystone species

A species that has a disproportionately large effect on its ecosystem.

Kilocalorie (kcal)

A unit of energy; the amount needed to raise 1 kg of water by 1°C.

Law of conservation of energy

Energy in a system remains constant; it can change forms but is neither created nor destroyed.

Law of conservation of matter

Matter cannot be created or destroyed, only transformed.

Leaching

The removal of soluble materials from soil by water.

Limiting factor

A factor that restricts the growth of a population.

Mass extinction

A widespread and rapid decrease in the number of species on Earth.

Median (statistical)

The middle value in a data set when arranged in order.

Mutualism

A symbiotic relationship where both species benefit.

Natural selection

The process by which favorable traits become more common in a population.

Net energy

The energy remaining after energy losses during transfer in an ecosystem.

Net primary productivity (NPP)

The energy that remains after producers use some for respiration, available to consumers.

Niche

The functional role of a species in its ecosystem.

Nitrogen cycle

The movement of nitrogen through the atmosphere, organisms, and soil.

Nitrogen fixation

Conversion of atmospheric nitrogen into forms usable by plants.

Nitrification

Conversion of ammonia into nitrites and nitrates by bacteria.

Omnivore

An organism that eats both plants and animals.

Parasitism

A relationship where one species benefits and the other is harmed.

Phosphorus cycle

The movement of phosphorus through the lithosphere, hydrosphere, and biosphere.

Photosynthesis

The process by which plants use sunlight to produce glucose and oxygen.

Phytoplankton

Microscopic, photosynthetic organisms in aquatic ecosystems.

Plankton

Small organisms that float in water and are carried by currents.

Pioneer species

The first species to colonize a barren area during succession.

Population

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

Precipitation

Water released from clouds as rain, snow, sleet, or hail.

Predation

An interaction where one organism hunts and eats another.

Primary consumer

Organisms that eat producers (herbivores).

Primary productivity

The rate at which producers convert energy into biomass.

Primary succession

The colonization of an area with no previous life.

Producer

An organism that makes its own food (autotroph).

Pyramid of energy flow

A diagram showing energy loss at each trophic level.

Range (statistical)

The difference between the highest and lowest values in a data set.

Reproductive isolation

When populations cannot interbreed due to behavioral, geographic, or genetic barriers.

Respiration

The process of breaking down glucose to release energy.

Resource partitioning

When species divide resources to reduce competition.

Riparian zones

Areas along rivers and streams that support unique plant and animal communities.

Runoff

Water that flows over land into streams or rivers.

Scavenger

An organism that feeds on dead animals.