What is Ecology?| Definition, levels, and branches of Ecology

What is ecology?

Ecology is a branch of biology, associated with the study of relationships between organisms and the environment. The interrelation of organisms and the environment may be,

  • between organism & its place of living
  • Between organism & its neighbour
  • Between organism & its own community
  • Between organism & other communities.

The term ‘Oecology’ was first used by Ernst Haeckel in 1869. The ‘Oecology’ nomenclature created by Haeckel is composed of two Greek words, Oikos (living place or household) and logos (study of), thus ecology basically means the study of living space/environment. Oecology later came to be known as Ecology.

Different definition of ecology

By Ernst Haeckel, “Ecology is the science of relations between organisms and their environment”.

According to Taylor, “Ecology is the the science of all the relations of all organisms to all their environments”.

According to the United States Council on Environmental Quality, “It is the science of the intricate web of relationships between living organisms and their nonliving surroundings”.


Ecologists study environmental relationships ranging from individual organisms to factors influencing global-scale processes. Ecologists also study many kinds of environments like microbes living in the soil, animals and plants residing in a rainforest, or the ocean. Most ecologists study forests, wildlife, wetlands, fisheries, and other natural systems. Ecology is sometimes referred to as the natural environment or human ecology.

The study of ecology deals with

  • Study of structure and function of nature,
  • the behaviour of organisms under natural environment,
  • the interrelations between organisms, populations, and communities.
  • Temporal changes in the abundance, occurrence, and activities of organisms.
  • Productivity of organisms and energy for mankind

Now under ecology, not only the interrelationships between plants and animals and their environment are studied, but also the interactions of human, society and its physical environment are also studied.

Difference between ecology and environment

Environment is the total set of circumstances surrounding life. When we see all biotic and abiotic components absolutely, it is called the environment. whereas, ecology is the study of those environment’s components and their relationship.

One more key difference is that the environment could exist without life, but ecology needs both biotic and abiotic components in order to study relationships between them.

levels of ecological organization

As we know, ecology is the study of relationships ranging from individual organisms to factors affecting global processes. This wide range of subjects can be organized in different levels, called the hierarchy of ecological organization.

Ecological hierarchy

The level of organization is: Individuals, populations, community, ecosystems, landscape, biome, Biosphere.

Individuals: An individual is one organism.  For example human, cow, palm tree, and Cat. types of organisms known as species.

Population: Population is a group of organisms belonging to the same species. For example, the human population in a village.

Community: Community is a sum of all populations from different species, defined in a particular area.

Ecosystems: Ecosystem is an area consisting of different populations, physical environment, biotic, and abiotic factors. For example, a lake could be an ecosystem where different species are found and they interact with each other and  with abiotic factors.

Biome: It is a set of ecosystems, comprising similar characteristics with their abiotic factors.

Biosphere: Biosphere is a huge community of humans, plants, animals, and their habitat, and comprises all biomes. Biospheres define all life on earth and their interaction.

Branches of ecology

Ecology is a broad discipline comprising many sub-branches. The two major subdivisions of ecology are plant ecology and animal Ecology. The ecology can be divided into many sub-branches.

The major and minor sub-disciplines of ecology are below.

  • Population Ecology (Autecology)
  • Community ecology (synecology)
  • Landscape ecology
  • Behavioral ecology
  • Ecosystems ecology
  • Habitat ecology
  • Insect ecology
  • Forest ecology
  • Desert ecology
  • Global ecology
  • Chemical ecology
  • Industrial ecology
  • Conservation ecology
  • Taxonomic Ecology
  • Applied ecology

Ecological niche

The concept of “Ecological niche” was first introduced by Joseph Grinnell. The functional characteristics of a species in habitat are called “niche”.

Niche refers to the sum of all the activities and relationships of a species by which this species uses its habitat resources for its survival and reproduction. The niche of species can be determined by its abiotic requirements, seasonal specialization, food preferences, microhabitat characteristics, or predation avoidance.

Ecological footprint

The ecological footprint is a tool for measuring human demand on nature and compares such demand with the ecological capacity of the Earth to regenerate resources.

The ecological footprint measures the amount of biologically productive area (land and sea) needed to the human population, such as vegetables, fruits, wood, fiber, and space for roads, homes, and buildings. Methods of measuring ecological footprint vary from country to country.