• The biosphere is made up of the parts of Earth where life exists. The biosphere extends from the deepest root systems of trees, to the dark environment of ocean trenches, to lush rain forests and high mountaintops.

    Scientists describe the Earth in terms of spheres. The solid surface layer of the Earth is the lithosphere. The atmosphere is the layer of air that stretches above the lithosphere. The Earth’s water—on the surface, in the ground, and in the air—makes up the hydrosphere.

    Since life exists on the ground, in the air, and in the water, the biosphere overlaps all these spheres. Although the biosphere measures about 20 kilometers (12 miles) from top to bottom, almost all life exists between about 500 meters (1,640 feet) below the ocean’s surface to about 6 kilometers (3.75 miles) above sea level.

    Origin of the Biosphere

    The biosphere has existed for about 3.5 billion years. The biosphere’s earliest life-forms, called prokaryotes, survived without oxygen. Ancient prokaryotes included single-celled organisms such as bacteria and archaea.

    Some prokaryotes developed a unique chemical process. They were able to use sunlight to make simple sugars and oxygen out of water and carbon dioxide, a process called photosynthesis. These photosynthetic organisms were so plentiful that they changed the biosphere. Over a long period of time, the atmosphere developed a mix of oxygen and other gases that could sustain new forms of life.

    The addition of oxygen to the biosphere allowed more complex life-forms to evolve. Millions of different plants and other photosynthetic species developed. Animals, which consume plants (and other animals) evolved. Bacteria and other organisms evolved to decompose, or break down, dead animals and plants.

    The biosphere benefits from this food web. The remains of dead plants and animals release nutrients into the soil and ocean. These nutrients are re-absorbed by growing plants. This exchange of food and energy makes the biosphere a self-supporting and self-regulating system.

    The biosphere is sometimes thought of as one large ecosystem—a complex community of living and nonliving things functioning as a single unit. More often, however, the biosphere is described as having many ecosystems.

    Biosphere Reserves

    People play an important part in maintaining the flow of energy in the biosphere. Sometimes, however, people disrupt the flow. For example, in the atmosphere, oxygen levels decrease and carbon dioxide levels increase when people clear forests or burn fossil fuels such as coal and oil. Oil spills and industrial wastes threaten life in the hydrosphere. The future of the biosphere will depend on how people interact with other living things within the zone of life.

    In the early 1970s, the United Nations established a project called Man and the Biosphere Programme (MAB), which promotes sustainable development. A network of biosphere reserves exists to establish a working, balanced relationship between people and the natural world.

    Currently, there are 563 biosphere reserves all over the world. The first biosphere reserve was established in Yangambi, Democratic Republic of Congo. Yangambi, in the fertile Congo River Basin, has 32,000 species of trees and such endemic species as forest elephants and red river hogs. The biosphere reserve at Yangambi supports activities such as sustainable agriculture, hunting, and mining.

    One of the newest biosphere reserves is in Yayu, Ethiopia. The area is developed for agriculture. Crops such as honey, timber, and fruit are regularly cultivated. However, Yayu’s most profitable and valuable resource is an indigenous species of plant, Coffea arabica. This shrub is the source of coffee. Yayu has the largest source of wild Coffea arabica in the world.

    The biosphere is simply the home of all known life that has ever existed in the entire universe.

    Biosphere 2
    In 1991, a team of eight scientists moved into a huge, self-contained research facility called Biosphere 2 in Oracle, Arizona. Inside an enormous, greenhouse-like structure, Biosphere 2 created five distinct biomes and a working agricultural facility. Scientists planned to live in Biosphere 2 with little contact with the outside world. The experiments carried out in Biosphere 2 were designed to study the relationship between living things and their environmentand to see whether humans might be able to live in space one day.

    The mission was supposed to last 100 years, with two teams of scientists spending 50 years each in the facility. Instead, two teams made it just four years, and the scientists moved out in 1994. Though the live-in phase is over, research is still taking place in Biosphere 2, with a main focus on global warming.

  • Term Part of Speech Definition Encyclopedic Entry
    absorb Verb

    to soak up.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    ancient Adjective

    very old.

    animal Noun

    organisms that have a well-defined shape and limited growth, can move voluntarily, acquire food and digest it internally, and can respond rapidly to stimuli.

    archaea Plural Noun

    (singular: archaeon) a group of tiny organisms often living in extreme environments, such as ocean vents and salt lakes.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    bacteria Plural Noun

    (singular: bacterium) single-celled organisms found in every ecosystem on Earth.

    basin Noun

    a dip or depression in the surface of the land or ocean floor.

    Encyclopedic Entry: basin
    biosphere Noun

    part of the Earth where life exists.

    Encyclopedic Entry: biosphere
    biosphere reserve Noun

    location recognized by the United Nations as important to the relationship between people and the natural environment.

    carbon dioxide Noun

    greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.

    coal Noun

    dark, solid fossil fuel mined from the earth.

    coffee Noun

    plant native to Africa whose dried berries and seeds are used for a drink of the same name.

    coffee arabica Noun

    species of shrub native to east Africa and the Arabian Peninsula, whose berries are harvested for coffee.

    consume Verb

    to use up.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    cultivate Verb

    to prepare and nurture the land for crops.

    decompose Verb

    to decay or break down.

    decrease Verb

    to lower.

    disrupt Verb

    to interrupt.

    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    Encyclopedic Entry: Earth
    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    endemic species Noun

    species that naturally occurs in only one area or region.

    establish Verb

    to form or officially organize.

    evolve Verb

    to develop new characteristics based on adaptation and natural selection.

    fertile Adjective

    able to produce crops or sustain agriculture.

    food web Noun

    all related food chains in an ecosystem. Also called a food cycle.

    Encyclopedic Entry: food web
    forest Noun

    ecosystem filled with trees and underbrush.

    forest elephant Noun

    species of elephant native to the Congo River rain forest in Africa.

    fossil fuel Noun

    coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.

    function Verb

    to work or work correctly.

    honey Noun

    sweet substance produced by bees from pollen or nectar.

    hunt Verb

    to pursue and kill an animal, usually for food.

    hydrosphere Noun

    all the Earth's water in the ground, on the surface, and in the air.

    Encyclopedic Entry: hydrosphere
    indigenous Adjective

    characteristic to or of a specific place.

    Encyclopedic Entry: indigenous
    industrial Adjective

    having to do with factories or mechanical production.

    lithosphere Noun

    outer, solid portion of the Earth. Also called the geosphere.

    Encyclopedic Entry: lithosphere
    lush Adjective

    abundant and rich.

    Man and the Biosphere Programme (MAB) Noun

    United Nations program established to support a working, balanced relationship between people and the natural world.

    mining Noun

    process of extracting ore from the Earth.

    mountain Noun

    landmass that forms as tectonic plates interact with each other.

    nutrient Noun

    substance an organism needs for energy, growth, and life.

    Encyclopedic Entry: nutrient
    ocean trench Noun

    a long, deep depression in the ocean floor.

    Encyclopedic Entry: ocean trench
    oil Noun

    fossil fuel formed from the remains of marine plants and animals. Also known as petroleum or crude oil.

    oil spill Noun

    accidental release of petroleum products into a body of water, either by an oil tanker or an offshore oil rig.

    oxygen Noun

    chemical element with the symbol O, whose gas form is 21% of the Earth's atmosphere.

    photosynthesis Noun

    process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.

    plant Noun

    organism that produces its own food through photosynthesis and whose cells have walls.

    profitable Adjective

    able to make money.

    prokaryote Noun

    organism whose cells have no nucleus.

    rain forest Noun

    area of tall, mostly evergreen trees and a high amount of rainfall.

    Encyclopedic Entry: Rain forest
    red river hog Noun

    mammal (pig) native to African rain forests.

    resource Noun

    available supply of materials, goods, or services. Resources can be natural or human.

    root system Noun

    all of a plant's roots.

    shrub Noun

    type of plant, smaller than a tree but having woody branches.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    sphere Noun

    round object.

    sugar Noun

    type of chemical compound that is sweet-tasting and in some form essential to life.

    sustainable agriculture Noun

    processes for growing crops and raising livestock that makes the most efficient use of resources. Sustainable agriculture aims to cultivate the land so it may be used by future generations.

    sustainable development Noun

    human construction, growth, and consumption that can be maintained with minimal damage to the natural environment.

    timber Noun

    wood in an unfinished form, either trees or logs.

    unique Adjective

    one of a kind.

    United Nations Noun

    international organization that works for peace, security and cooperation.