Five Levels of the Biosphere

By Starr Kang
A view of Earth from a satellite.

The biosphere consists of all living organisms on Earth, including human beings and other animals, plants and microorganisms, along with the organic matter they produce. The term "biosphere" was coined by Eduard Suess in 1875 but was further refined in the 1920s by Vladimir Vernadsky to denote its current scientific usage. The biosphere has five levels of organizational structure.



Earth's Biomes

The biosphere is divided into regions called biomes. Biomes are the largest of the five organizational levels. Scientists classify biomes into five main types -- aquatic, desert, forest, grassland and tundra. The main reason for classifying the biosphere into biomes is to highlight the importance of physical geography on communities of living organisms. A biome may contain several ecosystems and is defined by the geography, climate and the species native to the region. Factors to determine climate include average temperature, amount of rainfall and humidity. When classifying species, scientists traditionally focus on the types of vegetation native to a particular region.

Ecosystem Characteristics

Ecosystems are the second organizational classification when examining the five levels of the biosphere. An ecosystem contains biotic factors such as animals and plants, and abiotic factors such as oxygen, nitrogen and carbon. Ecosystems are divided based on the interaction and the transfer of energy. Within each ecosystem, energy is consumed, and matter is cycled in the form of chemicals and nutrients among different groups of organisms and their environment. A basic example is that primary producers, such as plants, obtain energy from the sun through photosynthesis. Consumers, such as animals, eat the plants to obtain energy. When the animals die, decomposers eat the bodies and release chemicals that enrich the soil, allowing plants to grow.

Communities of Species

A community is the third level of organization in the biosphere. Multiple populations of species make up a community. Communities share a particular habitat or environment. The communities in a particular location are limited to species that can survive given the region's abiotic factors such as temperature, pH and nutrients found in the air and soil. The communities of species are also limited by biotic factors such as predators and available food sources.

Population Count

A population, the fourth level of the biosphere, includes all members of a single species living in a particular habitat. A population can include thousands of members or only a few hundred members. The addition or removal of a population can affect an entire ecosystem. Indicator species are important groups that scientists use to determine the health of an ecosystem, while the presence of keystone species can result in profound effects for ecosystem as a whole.

At the Base: Organisms

Organisms, the final level of the biosphere, are defined as living creatures that use DNA to replicate. Single organisms are referred to as individuals, while groups of organisms are considered a species. Organisms are usually classified in one of two ways: by their cellular structure or by the way they obtain energy. Cellular structure divides organisms into prokaryotes, with free-floating DNA inside cells without a nuclei, and eukaryotes, whose DNA is contained in cell’s nucleus. Organisms are considered either autotrophs, such as plants, which obtain energy by feeding themselves, and heterotrophs, such as animals, which must consume other organisms to obtain energy.