The Earth's biosphere consists of five levels of organization.
The biosphere consists of all living factors on Earth, including human beings and other animals, plants and microorganisms. 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's five levels of organizational structure are a specific reference to the biosphere as it pertains to ecological and biological study.
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--according to the University of California. 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 categorizing species for classification purposes, scientists traditionally focus on the types of vegetation native to a particular region.
Ecosystems
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 between 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 obtaining the energy. When the animals die, decomposers eat the bodies and release chemicals that enrich the soil, allowing plants to grow.
Communities
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.
Populations
A population is the forth level of the biosphere, and includes all members of a 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 indicates the presence of certain other populations in the same ecosystem.
Organisms
Organisms are the final level of the biosphere, and 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, that obtain energy by feeding themselves, and heterotrophs, such as animals, who must consume other organisms to obtain energy.
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