Ecology: Interactions between Organisms and the Environment

Vocabulary terms and definitions covering the levels of organization, historical definitions, and energy flow within the field of ecology.

Ecology (Etymology)

Derived from the Greek words ‘oikos’ meaning home and ‘logos’ meaning to study (Ernst Haeckel 1869).

Population

A group of individuals of the same species living in a particular geographic area.

Community

All of the organisms that inhabit a particular area, representing an assemblage of populations of different species.

Ecosystem

The communities of plants and animals together with the abiotic factors with which they interact.

Autotrophs

Organisms such as plants and algae capable of synthesizing all their required organic molecules from simple inorganic substances and an energy source.

Heterotrophs

Organisms such as animals that cannot synthesize complex organic compounds and must feed on organic material formed by other organisms for energy and growth.

Haeckel (1869) Definition

Defined ecology as the ‘total relations of the animals to both its organic and its inorganic environments’.

Elton (1927) Definition

Defined ecology as ‘scientific natural history’.

Andrewartha (1961) Definition

Defined ecology as ‘the scientific study of the distribution and abundance of organisms’.

Odum (1963) Definition

Defined ecology as ‘the study of the structure and function of nature’.

Krebs (1994) Definition

Defined ecology as ‘the scientific study of the interactions that determine the distribution and abundance of organisms’.

Knox et al. (2009) Definition

Defined ecology as ‘the study of interactions between organisms and their environment’.

Organismal ecology

Concerned with the evolutionary adaptations that enable individual plants or animals to meet challenges imposed by their environment.

Population ecology

Focuses on the factors that affect population size and distribution.

Community ecology

Studies the ways in which interactions affect the structure and function of the community.

Ecosystem ecology (Focus)

Focuses on energy flow and the cycling of materials between parts of the ecosystem.

Biosphere

The global ecosystem; the sum of all Earth's ecosystems, or all of life and where it lives.

Biotic Component

The living component of the environment, such as reptiles, frogs, insects, trees, ferns, fungi, and orchids.

Abiotic Component

The non-living component of the environment, such as rocks, air, water, soil, buildings, sunlight, temperature, and disturbance processes.

Energy Flow

Moves in a unidirectional way and does not cycle; it requires a continuous input into an ecosystem.

Solar Radiation

The energy driving the biosphere and all ecosystems, captured via photosynthesis by autotrophs.

Producers

The level in a trophic diagram representing plants that provide an energy value of $10,000\,kcal$.

Primary consumers

Organisms like rabbits that consume producers and represent an energy value of $1,000\,kcal$.

Secondary consumers

Organisms like snakes that consume primary consumers and represent an energy value of $100\,kcal$.

Tertiary consumers

Organisms like eagles at the top of the trophic levels representing an energy value of $10\,kcal$.