Levels of Organization in Ecology

  • Stretching from 8 kilometers above the Earth’s surface and diving deep as far as 11 kilometers below the surface of the ocean contains our biosphere, the region of the planet where life exists.
  • Within the biosphere there are large geographic regions of similar climates and a characteristic set of organisms adapted to that climate, which are known as biomes.
  • It is thought that the ocean biome may have been the first to exist on our planet as life may have originated here.
  • The various biomes of Earth share similar characteristics related to the humidity, amount of rainfall, seasonal variability, latitude, and elevation, which are examples of abiotic factors. Abiotic factors are chemical or physical components of the environment.
  • Ecosystems are smaller geographically than biomes.  An ecosystem represents both the organisms that live in a particular area and their physical environment composed of abiotic factors. Groups of similar ecosystems make up individual biomes.
  • Some examples of ecosystems in the Pacific Ocean are kelp forests, the intertidal zone, coral reefs and hydrothermal vents.
  • The different species that live together in an ecosystem are called a community.
  • Organisms can interact in a number of different ways in ecosystems, called interspecific interactions. These include predation (consumption of one species by another), competition (for resources such as food and living space), commensalism (an interaction in which one species benefits and the other is not harmed), mutualism (an interaction in which both species benefit), and parasitism (on species benefits at the expense of another). Symbiotic relationships are those which occur between species living in close association with one another, and include commensalism, mutualism, and parasitism.

Some examples of these relationships include:

  • Predation: consumption of a seal by a shark.
  • Competition: seaweeds competing for light in a kelp forest.
  • Commensalism: barnacles growing on the skin of a whale. Barnacles benefit by constantly being provided a new food source by the swimming whale. The whale is unaffected by the barnacles.
  • Mutualism: cleaner fish are small fish that remove dead skin and parasites from the surface of other fish. Both fish benefit from this interaction.
  • Parasitism: salmon lice are small organisms that attach to the skin of salmon and consume their skin, mucous, and blood. High levels of salmon lice infestation can lead to the death of a salmon.
  • Within a community, a group of organisms of the same species is called a population. These individuals of the same species will also impact each other during intraspecific interactions as they compete for similar resources.
  • A species is a group of similar organisms that can breed and produce fertile offspring. Below are some examples for the different levels of organization within the study of ecology.


  • Within an ecosystem, all organisms (including everything from tiny microorganisms to the largest of animals) function together achieving a delicate balance. An ecosystem won’t survive without adequate access to resources such as food and living space. Within in an ecosystem, each organism has a unique niche, or role to play.
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