Biosphere
Biosphere
The biosphere is the space on and near Earth’s surface that contains and supports living organisms and ecosystems. The biosphere is, in the broadest sense, the global ecosystem. The biosphere interacts with the lithosphere, atmosphere, and hydrosphere. The lithosphere is the outer surface of Earth composed of solid soil and rock, the atmosphere is the surrounding gaseous envelope, and the hydrosphere refers to Earth’s liquid water including lakes, rivers, and oceans. In order to study the processes associated with the biosphere, a multi-disciplinary effort has been employed by scientists from such fields as chemistry, biology, geology, and ecology.
History
The Austrian geologist Eduard Suess (1831–1914) first used the term biosphere in 1875 to describe the space on Earth that contains life. The concept introduced by Suess had little impact on the scientific community until it was resurrected by the Russian scientist Vladimir Vernadsky (1863–1945) in 1926 in his book, La biosphere. In that work Vernadsky extensively developed the modern concepts that recognize the interplay between geology, chemistry, and biology.
KEY TERMS
Decomposition— The breakdown of the complex molecules composing dead organisms into simple nutrients that can be reutilized by living organisms.
Energy— The ability to do work. Energy occurs in various forms. The most important ones in biospheric processes are solar (electromagnetic), kinetic, heat (or thermal), and chemical-bond energies.
Global warming— Atmospheric warming caused by an increase in the concentration of greenhouse gases, which absorb infrared energy emitted by Earth’s surface, thereby slowing its rate of cooling. Carbon dioxide and water vapor are particularly important in this respect.
Nutrient cycle— The cycling of biologically important elements from one molecular form to another, and eventually back to the original form.
Nutrients— The molecules organisms obtain from their environment and are used for growth, energy, and other metabolic processes.
Photosynthesis— Enzymatic, sunlight-induced reaction between carbon dioxide and water, which produces oxygen and organic molecules. Plants, algae, and certain bacteria are photosynthetic organisms.
Respiration— Enzymatic chemical reactions between organic molecules and oxygen, which result in the production of carbon dioxide, water, and energy.
Requirements for life
In order for organisms to survive, appropriate temperature ranges, moisture conditions, energy supply, and nutrient supply must be present in the environment.
Energy is needed for metabolic functions, including growth, movement, waste removal, and reproduction. In most ecosystems, this energy is supplied from a source outside the biosphere, in the form of electromagnetic energy received from the Sun. This electromagnetic radiation is captured and stored by plants through the process of photosynthesis. Photosynthesis involves a light-induced, enzymatic reaction between carbon dioxide and water, which produces oxygen and glucose, an organic compound. The glucose is used, through an immense diversity of biochemical reactions, to manufacture the huge range of other organic compounds found in organisms. Potential energy is stored in the chemical bonds of organic molecules and can be released through the process of respiration; this involves enzymatic reactions between organic molecules and oxygen to form carbon dioxide, water, and energy. The growth of organisms is achieved by the accumulation of organic matter, also known as biomass. Plants and some microorganisms are the only organisms that can form organic molecules by photosynthesis. Nearly all heterotrophic organisms, including animals, ultimately rely on photosynthetic organisms to supply their energy needs.
The major elements that comprise the chemical building blocks of organisms are carbon, oxygen, nitrogen, phosphorus, sulfur, calcium, and magnesium. Organisms can only acquire these elements if they occur in chemical forms that can be assimilated from the environment; these are termed available nutrients. Nutrients contained in dead organisms and biological wastes are transformed by decomposition into compounds that organisms can reutilize. In addition, organisms can utilize some mineral sources of nutrients. All of the uptake, excretion, and transformation reactions are aspects of nutrient cycling.
The various chemical forms in which carbon occurs can be used to illustrate nutrient cycling. Carbon occurs as the gaseous molecule carbon dioxide, and in the immense diversity of organic compounds that make up living organisms and dead biomass. Gaseous carbon dioxide is transformed to solid organic compounds (simple sugars) by the process of photosynthesis. The process of respiration returns carbon dioxide to the atmosphere at about the same rate that it is consumed.
Evolution of the biosphere
During the long history of life on Earth (about 3.8 billion years), organisms have drastically altered the chemical composition of the biosphere. At the same time, the biosphere’s chemical composition has influenced which life forms could survive. For example, when life first evolved, the atmospheric concentration of carbon dioxide was much greater than today, and there was almost no free oxygen. After the evolution of photosynthesis there was a large decrease in atmospheric carbon dioxide and an increase in oxygen. Much of carbon once present in the atmosphere as carbon dioxide now occurs in fossil fuel deposits and limestone rock.
The increase in atmospheric oxygen concentration had an enormous influence on the evolution of life. It was not until oxygen reached similar concentrations to what occurs today (about 21%, by volume) that heterotrophic multicellular organisms were able to evolve. Such organisms require high oxygen concentrations to accommodate their high rate of respiration.
Current research
Much research investigating the biosphere is aimed at determining the effects of human activities. Pollution, fertilizer application, changes in land use, fuel consumption, and other human activities affect interactions with the hydrosphere, atmosphere and lithosphere and damage functional components of the biosphere. Depletion of the ozone layer that protects organisms from intense exposure to solar ultraviolet radiation and the greenhouse effect that moderates the surface temperature of the planet are two examples of human-induced perterbations to the atmosphere that impact the biosphere. An example of interatctions between the lithosphere, hydrosphere and biosphere are evidenced in the agricultural use of fertilizer, which increases the amounts of nitrogen, phosphorus, and other nutrients in the soil and increases crop yeild. However, excess nutrients in the soil run off into lakes resulting in algal blooms and in some cases massive fish kills.
Recent interest in long-term, manned space operations has spawned research into the development of artificial biospheres. Extended missions in space require that nutrients are cycled in a volume no larger than a building. The Biosphere 2 project, which received a great deal of popular attention in the early 1990s, has provided insight into the difficulty of managing such small, artificial biospheres. Human civilization is also finding that it is difficult to sustainably manage the much larger biosphere of planet Earth.
See also Lithosphere.
Resources
BOOKS
Allen, John. Biosphere 2: The Human Experiment. New York: Viking, 1991.
Bradbury, I. K. The Biosphere. London/New York: Bellhaven Press, 1991.
Hamblin, W.K., and E. H. Christiansen, Earth’s Dynamic Systems. 9th ed. Upper Saddle River: Prentice Hall, 2001.
Poynter, Jane. Two Years and Twenty Minutes Inside Biosphere 2. New York: Thunder’s Mouth Press, 2006.
Thomashow, Mitchell. Bringing the Biosphere Home: Learning to Perceive Global Environmental Change. Boston: The MIT Press, 2003.
PERIODICALS
Huggett, R. J. “Ecosphere, Biosphere, Or Gaia? What To Call The Global Ecosystem.” Global Ecology And Biogeography 8, no. 6 (1999): 425-432.
OTHER
Biosphere 2. 2006. <http://www.bio2.com/> (accessed October 10, 2006).
Steven MacKenzie
Biosphere
Biosphere
The biosphere is the largest possible earthly organismic community. It is a terrestrial envelope of life, or the total global biomass of living matter. The biosphere incorporates every individual organism and species on the face of the earth—those that walk on the ground or live in the crevices of rock and down into the soil , those that swim in rivers, lakes, and oceans, and those that move in and out of the atmosphere .
Bios is the Greek word for life; "sphere" is from the Latin sphaera, which means essentially the "circuit or range of action, knowledge or influence," the "place or scene of action or existence," the "natural, normal or proper place." Combined into biosphere, the two ideas define the normal global place of existence for all earthly life-forms and, increasingly, a global area of influence and action for humans. Thinking of the mass of life forms on the earth as the biosphere also provides an impression of circular, cyclic systems and suggests a holistic concept of integration and unity.
A Scientific American book on the biosphere described it as "this thin film of air and water and soil and life no deeper than ten miles, or one four-hundredth of the earth's radius [that] is now the setting of the uncertain history of man." G. E. Hutchinson in that same book asked, "What is it that is so special about the biosphere?" He suggested that the answer seems to have three parts: "First, it is a region in which liquid water can exist in substantial quantities. Second, it receives an ample supply of energy from an external source, ultimately from the sun. And third, within it there are interfaces between the liquid, the solid and the gaseous states of matter." Both of these might better describe what LaMont Cole labeled the "ecosphere," the global eco system—the biosphere plus its abiotic environment . But the significance of Hutchinson's three-part statement is that those three characteristics of the earth's surface make it possible for life to exist. They provide the conditions necessary for the abundant and diverse organisms of the biosphere to live.
Life began in a very different environment than found today: the atmosphere, for example, was mostly methane , ammonia, and carbon dioxide . As life evolved, it changed the atmosphere (and other abiotic components of the surface of the earth), transforming it into the present oxygen-rich mixture of gases vital to life as it now exists. And those life-forms maintain that critical mixture in a complex, fluctuating system of global cycles.
The diversity and complexity of the biosphere is staggering. The accumulated human knowledge of its workings is prodigious, but even more impressive is the immense ignorance of that complexity. Humans have identified about 1.5 million living members of the biosphere and thus have some knowledge of at least that many. However, conservative estimates of the actual number of species begin at 3 or 3.5–5 million species. Recent and less conservative estimates range up to a possible 100 million. That means humans are totally ignorant of anywhere from 50% to as much as 98.5% of the other members of the earth's biological community . Their existence is suspected, but they cannot be identified or their existence documented by even a name.
One of the concerns about large-scale human ignorance of the biosphere is that many species might be extinguished before they are even known. Human activities, especially destruction of habitat , are increasing the normal rate of species extinction . The diversity of the biosphere may be diminishing rapidly.
Taxonomically, the biosphere is organized into five kingdoms: monera, protista, fungi , animalia, and plantae, and a multitude of subsets of these, including the multiple millions of species mentioned above. G. Piel estimates that of the 1,200–1,800 billion tons dry weight of the biosphere, most of it—some 99%—is plant material. All the life-forms in the other four taxons, including animals and obviously the five billion-plus humans alive today, are part of that less than one%.
The biosphere can also be subdivided into biomes: a biome incorporates a set of biotic communities within a particular region exposed to similar climatic conditions and which have dominant species with similar life cycles, adaptations, and structures. Deserts, grasslands , temperate deciduous forests, coniferous forests, tundra , tropical rain forests, tropical seasonal forests, freshwater biomes, estuaries, wetlands , and marine biomes, are examples of specific terrestrial or aquatic biomes.
Another indication of the complexity of the biosphere is a measure of the processes that take place within it, especially the essential processes of photosynthesis and respiration . The sheer size of the biosphere is indicated by the amount of biomass present. Vitousek and his colleagues estimate the net primary production of the earth's biosphere as 224.5 petagrams, one petagram being equivalent to 1015 grams.
The biosphere interacts in constant, intricate ways with other global systems: the atmosphere, lithosphere, hydrosphere, and pedosphere. Maintenance of life in the biosphere depends on this complex network of biological-biological, physical-physical, and biological-physical interactions. All the interactions are mediated by an equally complex system of positive and negative feedbacks—and the total makes up the dynamics of the whole system. Since each and all interpenetrate and react on each other constantly, outlining a global ecology is a major challenge.
Normally biospheric dynamics are in a rough balance. The carbon cycle , for example, is usually balanced between production and decomposition , the familiar equation of photosynthesis and respiration. As Piel notes: "The two planetary cycles of photosynthesis and aerobic metabolism in the biomass not only secure renewal of the biomass but also secure the steady-state mixture of gases in the atmosphere. Thereby, these life processes mediate the inflow and outflow of solar energy through the system; they screen out lethal radiation, and they keep the temperature of the planet in the narrow range compatible with life." But human activities, especially the combustion of fossil fuels , contribute to increases in carbon dioxide, distorting the balance and in the process changing other global relationships such as the nature of incoming and out-going radiation and differentials in temperature between poles and tropics.
If humans are to better understand the biosphere, many more studies must be undertaken on many levels. A number of levels of biological integration must be recognized and analyzed, each with different properties and each offering scholars special problems and special insights. The totality of the biosphere can be broken down in many different ways, but life extends from the single cell to the totality of the globe. Though biologists usually define their disciplines within the bounds of one level and though they may study only one level, scholars should recognize context, the full range of levels and the interactions between them.
Humans are, of course, one of the species that make up the living biosphere. Homo sapiens fits into the Linnean hierarchy on the primate branch. Using that hierarchy as a connective device, humans may take a first step toward understanding how they relate to the rest of the inhabitants of the biosphere, down to the most remote known species.
Humans are without doubt the dominant species in the biosphere. The transformation of radiant energy into useable biological energy is increasingly being diverted by humans to their own use. A common estimate is that humans are now diverting huge amounts of the net primary production of the globe to their own use: perhaps 40% of terrestrial production and close to 25% of all production is either utilized or wasted through human activity. Net primary production is defined as the amount of energy left after subtracting the respiration of primary producers, or plants, from the total amount of energy. It is the total amount of "food" available from the process of photosynthesis—the amount of biomass available to feed organisms, such as humans, that do not acquire food through photosynthesis.
Humans are displacing their neighbors in the biosphere through a multitude of activities: conversion of natural systems to agriculture, direct consumption of plants, consumption of plants by livestock, harvesting and conversion of forests, desertification , and many, many others. The biosphere is the source of all good: humans are an integral part of the biosphere and depend on its functioning for their well-being, for their very lives.
[Gerald L. Young ]
RESOURCES
BOOKS
Bradbury, I. K. The Biosphere. London/New York: Belhaven Press, 1991.
Clark, W. C., and R. E. Munn, eds. Sustainable Development of the Biosphere. Cambridge: Cambridge University Press, 1986.
Piel, G. "The Biosphere." In Only One World: Our Own to Make and to Keep. New York: W. H. Freeman, 1992.
PERIODICALS
Salthe, S. N. "The Evolution of the Biosphere: Towards a New Mythology." World Futures 30 (1990): 53–67.
Vitousek, P. M., et al. "Human Appropriation of the Products of Photosynthesis." BioScience 36 (1986): 368–373.
Biosphere
Biosphere
The biosphere is the space on or near Earth's surface that contains and supports living organisms. It is subdivided into the lithosphere, atmosphere, and hydrosphere. The lithosphere is Earth's surrounding layer, composed of solids such as soil and rock; it is about 80 to 100 kilometers (50 to 60 miles) thick. The atmosphere is the surrounding thin layer of gas. The hydrosphere refers to liquid environments such as lakes and oceans that lie between the lithosphere and atmosphere. The biosphere's creation and continuous existence results from chemical, biological, and physical processes.
Requirements for life
For organisms to live, certain environmental conditions (such as proper temperature and moisture) must exist, and the organisms must be supplied with energy and nutrients (food). All the animal and mineral nutrients necessary for life are contained within Earth's biosphere. Nutrients contained in dead organisms or waste products of living cells are transformed back into compounds that other organisms can reuse as food. This recycling of nutrients is necessary because there is no source of food outside the biosphere.
Words to Know
Decomposition: The breakdown of complex molecules—molecules of which dead organisms are composed—into simple nutrients that can be reutilized by living organisms.
Energy: Power that can be used to perform work, such as solar energy.
Global warming: Warming of the atmosphere that results from an increase in the concentration of gases that store heat, such as carbon dioxide.
Nutrient: Molecules that organisms obtain from their environment; they are used for growth, energy, and various other cellular processes.
Nutrient cycle: The cycling of biologically important elements from one molecular form to another and back to the original form.
Photosynthesis: Process in which plants capture light energy from the Sun and use it to convert carbon dioxide and water into oxygen and organic molecules.
Respiration: Chemical reaction between organic molecules and oxygen that produces carbon dioxide, water, and energy.
Energy is needed for the functions that organisms perform, such as growth, movement, waste removal, and reproduction. It is the only requirement for life that is supplied from a source outside the biosphere. This energy is received from the Sun. Plants capture sunlight and use it to convert carbon dioxide and water into organic molecules, or food, in a process called photosynthesis. Plants and some microorganisms are the only organisms that can produce their own food. Other organisms, including humans, rely on plants for their energy needs.
The major elements or chemical building blocks that make up all living organisms are carbon, oxygen, nitrogen, phosphorus, and sulfur. Organisms are able to acquire these elements only if they occur in usable
chemical forms as nutrients. In a process called the nutrient cycle, the elements are transformed from one chemical form to another and then back to the original form. For example, carbon dioxide is removed from the air by plants and incorporated into organic compounds (such as carbohydrates) by photosynthesis. Carbon dioxide is returned to the atmosphere when plants and animals break down organic molecules (a process known as respiration) and when microorganisms break down wastes and tissue from dead organisms (a process known as decomposition).
Evolution of the biosphere
During Earth's long history, life-forms have drastically altered the chemical composition of the biosphere. At the same time, the biosphere's chemical composition has influenced which life-forms inhabit Earth. In the past, the rate at which nutrients were transformed from one chemical form to another did not always equal their transformation back to their original form. This has resulted in a change in the relative concentrations of chemicals such as carbon dioxide and oxygen in the biosphere. The decrease in carbon dioxide and increase in atmospheric oxygen that occurred over time was due to photosynthesis occurring at a faster rate than respiration. The carbon that was present in the atmosphere as carbon dioxide now lies in fossil fuel deposits and limestone rock.
Scientists believe that the increase in atmospheric oxygen concentration influenced the evolution of life. It was not until oxygen reached high concentrations such as exist on Earth today that multicellular organisms like ourselves could have evolved. We require high oxygen concentrations to accommodate our high respiration rates and would not be able to survive had the biosphere not been altered by the organisms that came before us.
Current developments
Most research on the biosphere is to determine the effect that human activities have on the environment—especially on nutrient cycles. Application of fertilizers increases the amount of nitrogen, phosphorus, and other nutrients that organisms can use for growth. These excess nutrients damage lakes, causing overgrowth of algae and killing fish. Fuel consumption and land clearing increase carbon dioxide levels in the atmosphere and may cause global warming (a gradual increase in Earth's temperature) as a result of carbon dioxide's excellent ability to trap heat.
Biosphere 2. Interest in long-term, manned space exploration has also generated research into the development of artificial biospheres. Extended missions into space require that nutrients be cycled in a volume no larger than a building. The Biosphere 2 Project, which received a great deal of popular attention in the early 1990s, provided insight into the difficulty of managing such small, artificial biospheres. The idea behind the project was to establish a planet in miniature where the inhabitants not only survived but learned to live cooperatively and happily together. This is quite revealing, given that human civilization has found it difficult to manage sustainably the much larger biosphere of planet Earth.
Gaia Hypothesis
The Gaia hypothesis (pronounced GAY-a), named for the Greek Earth goddess Gaea, is a recent and controversial theory that views Earth as an integrated, living organism rather than as a mere physical object in space. The Gaia hypothesis suggests that all organisms and their environments (making up the biosphere) work together to maintain physical and chemical conditions on Earth that promote and sustain life. According to the hypothesis, organisms interact with the environment as a homeostatic (balancing) mechanism for regulating such conditions as the concentrations of atmospheric oxygen and carbon dioxide. This system helps to maintain conditions within a range that is satisfactory for life. Although scientists agree that organisms and the environment have an influence on each other, there is little support within the scientific community for the notion that Earth is an integrated system capable of regulating conditions to sustain itself. The Gaia hypothesis is a useful concept, however, because it emphasizes the relationship between organisms and the environment and the effect that human activities have on them.
One of the most spectacular structures ever built, Biosphere 2 is located in the Sonoran Desert at the foot of the Santa Catalina Mountains not far from Tucson, Arizona. It is the world's largest greenhouse, made of tubular steel and glass, covering an area of three football fields—137,416 square feet (12,766 square meters)—and rising to a height of 85 feet (26 meters) above the desert floor. Within the structure, there is a human habitat and a farm for the Biospherians or inhabitants to work to provide their own food. There are five other wild habitats or biomes representing a savannah, a rain forest, a marsh, a desert, and an ocean. Biosphere 2 is completely sealed so no air or moisture can flow in or out. Nearby are two balloon-like structures that operate like a pair of lungs for Biosphere 2 by maintaining air pressure inside. Only sunlight and electricity are provided from outside.
On September 26, 1991, four women and four men from three different countries entered the Biosphere 2 and the doors were sealed for the two-year-long initial program of survival and experimentation. During this time, the Biospherians attempted to run the farm and grow their own food in the company of some pigs, goats, and many chickens. They shared the other biomes with over 3,800 species of animals and plants that were native to those habitats. The resident scientists observed the interactions of plants and animals, their reactions to change, and their unique methods of living. The Biospherians also had the assignment of experimenting with new methods of cleaning air and water.
On September 26, 1993, the Biospherians emerged from Biosphere 2. It had been the longest period on record that humans had lived in an "isolated confined environment." Unfortunately, the experiment did not live up to expectations. The Biospherians experienced many difficulties, including an unusually cloudy year in the Arizona desert that stunted food crops, rapid growth and expansion of some ant species, and unusual behavior of bees fooled by the glass walls of the structure. In 1996, Columbia University took over operation of the facility, opening a visitors' center later that year. Biosphere 2 has been maintained for study but without human inhabitants. Its future remains uncertain.
[See also Atmosphere, composition and structure; Gaia hypothesis; Photosynthesis; Respiration ]
Biosphere
Biosphere
The biosphere is the space on and near the earth's surface that contains and supports living organisms and ecosystems. It is typically subdivided into the lithosphere , atmosphere, and hydrosphere . The lithosphere is the earth's surrounding layer composed of solid soil and rock, the atmosphere is the surrounding gaseous envelope, and the hydrosphere refers to liquid environments such as lakes and oceans, occurring between the lithosphere and atmosphere. The biosphere's creation and continuous evolution result from physical, chemical, and biological processes. To study these processes a multi-disciplinary effort has been employed by scientists from such fields as chemistry , biology , geology , and ecology .
History
The Austrian geologist Eduard Suess (1831–1914) first used the term biosphere in 1875 to describe the space on Earth that contains life. The concept introduced by Suess had little impact on the scientific community until it was resurrected by the Russian scientist Vladimir Vernadsky (1863–1945) in 1926 in his book, La biosphere. In that work Vernadsky extensively developed the modern concepts that recognize the interplay between geology, chemistry, and biology in biospheric processes.
Requirements for life
For organisms to live, appropriate environmental conditions must exist in terms of temperature , moisture, energy supply, and nutrient availability.
Energy is needed to drive the functions that organisms perform, such as growth, movement, waste removal, and reproduction. Ultimately, this energy is supplied from a source outside the biosphere, in the form of visible radiation received from the Sun . This electro-magnetic radiation is captured and stored by plants through the process of photosynthesis . Photosynthesis involves a light-induced, enzymatic reaction between carbon dioxide and water , which produces oxygen and glucose, an organic compound. The glucose is used, through an immense diversity of biochemical reactions, to manufacture the huge range of other organic compounds found in organisms. Potential energy is stored in the chemical bonds of organic molecules and can be released through the process of respiration ; this involves enzymatic reactions between organic molecules and oxygen to form carbon dioxide, water, and energy. The growth of organisms is achieved by the accumulation of organic matter , also known as biomass . Plants and some microorganisms are the only organisms that can form organic molecules by photosynthesis. Heterotrophic organisms, including humans, ultimately rely on photosynthetic organisms to supply their energy needs.
The major elements that comprise the chemical building blocks of organisms are carbon, oxygen, nitrogen , phosphorus , sulfur , calcium , and magnesium . Organisms can only acquire these elements if they occur in chemical forms that can be assimilated from the environment; these are termed available nutrients . Nutrients contained in dead organisms and biological wastes are transformed by decomposition into compounds that organisms can reutilize. In addition, organisms can utilize some mineral sources of nutrients. All of the uptake, excretion, and transformation reactions are aspects of nutrient cycling.
The various chemical forms in which carbon occurs can be used to illustrate nutrient cycling. Carbon occurs as the gaseous molecule carbon dioxide, and in the immense diversity of organic compounds that make up living organisms and dead biomass. Gaseous carbon dioxide is transformed to solid organic compounds (simple sugars) by the process of photosynthesis, as mentioned previously. As organisms grow they deplete the atmosphere of carbon dioxide. If this were to continue without carbon dioxide being replenished at the same rate as the consumption, the atmosphere would eventually be depleted of this crucial nutrient. However, carbon dioxide is returned to the atmosphere at about the same rate that it is consumed, as organisms respire their organic molecules, and microorganisms decompose dead biomass, or when wildfire occurs.
Evolution of the biosphere
During the long history of life on Earth (about 3.8 billion years), organisms have drastically altered the chemical composition of the biosphere. At the same time, the biosphere's chemical composition has influenced which life forms could inhabit its environments. Rates of nutrient transformation have not always been in balance, resulting in changes in the chemical composition of the biosphere. For example, when life first evolved, the atmospheric concentration of carbon dioxide was much greater than today, and there was almost no free oxygen. After the evolution of photosynthesis there was a large decrease in atmospheric carbon dioxide and an increase in oxygen. Much of carbon once present in the atmosphere as carbon dioxide now occurs in fossil fuel deposits and limestone rock.
The increase in atmospheric oxygen concentration had an enormous influence on the evolution of life. It was not until oxygen reached similar concentrations to what occurs today (about 21%, by volume ) that multicellular organisms were able to evolve. Such organisms require high oxygen concentrations to accommodate their high rate of respiration.
Current research
Most research investigating the biosphere is aimed at determining the effects that human activities are having on its environments and ecosystems. Pollution , fertilizer application, changes in land use , fuel consumption, and other human activities affect nutrient cycles and damage functional components of the biosphere, such as the ozone layer that protects organisms from intense exposure to solar ultraviolet radiation, and the greenhouse effect that moderates the surface temperature of the planet .
For example, fertilizer application increases the amounts of nitrogen, phosphorus, and other nutrients that organisms can use for growth. An excess nutrient availability can damage lakes through algal blooms and fish kills. Fuel consumption and land clearing increases the concentration of carbon dioxide in the atmosphere, and may cause global warming by intensifying the planet's greenhouse effect.
Recent interest in long-term, manned space operations has spawned research into the development of artificial biospheres. Extended missions in space require that nutrients are cycled in a volume no larger than a building. The Biosphere 2 project, which received a great deal of popular attention in the early 1990s, has provided insight into the difficulty of managing such small, artificial biospheres. Human civilization is also finding that it is difficult to sustainably manage the much larger biosphere of planet Earth.
See also Lithosphere.
Resources
books
Allen, John. Biosphere 2: The Human Experiment. New York: Viking, 1991.
Bradbury, I. K. The Biosphere. London/New York: Bellhaven Press, 1991.
Hamblin, W.K., and E.H. Christiansen. Earth's Dynamic Systems. 9th ed. Upper Saddle River: Prentice Hall, 2001.
Levin, Simon A., ed. Encyclopedia of Biodiversity. San Diego, CA: Academic Press, 2000.
Odum, Eugene. Ecology and Our Endangered Life-Support Systems. 2nd ed. Sunderland, MA: Sinauer Associates, 1993.
Smil, V. Cycles of Life: Civilization and the Biosphere. W.H. Freeman and Co., 1997.
Tudge, Colin. Global Ecology. New York: Oxford University Press, 1991.
periodicals
Clark, B. C. "Planetary Interchange of Bioactive Material: Probability Factors and Implications." Origins of Life and Evolution of the Biosphere no. 31 (2001): 185–197.
Huggett, R. J. "Ecosphere, Biosphere, Or Gaia? What To Call The Global Ecosystem." Global Ecology And Biogeography 8, no. 6 (1999): 425-432.
Salthe, S.N. "The Evolution of the Biosphere: Towards a New Mythology." World Futures. 30 (1990): 53-67.
Steven MacKenzie
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Decomposition
—The breakdown of the complex molecules composing dead organisms into simple nutrients that can be reutilized by living organisms.
- Energy
—The ability to do work. Energy occurs in various forms. The most important ones in biospheric processes are solar (electromagnetic), kinetic, heat (or thermal), and chemical-bond energies.
- Global warming
—Atmospheric warming caused by an increase in the concentration of greenhouse gases, which absorb infrared energy emitted by Earth's surface, thereby slowing its rate of cooling. Carbon dioxide and water vapor are particularly important in this respect.
- Nutrient cycle
—The cycling of biologically important elements from one molecular form to another, and eventually back to the original form.
- Nutrients
—The molecules organisms obtain from their environment and are used for growth, energy, and other metabolic processes.
- Photosynthesis
—Enzymatic, sunlight-induced reaction between carbon dioxide and water, which produces oxygen and organic molecules. Plants, algae, and certain bacteria are photosynthetic organisms.
- Respiration
—Enzymatic chemical reactions between organic molecules and oxygen, which result in the production of carbon dioxide, water, and energy.
Biosphere
Biosphere
The biosphere is the space on and near Earth's surface that contains and supports living organisms and ecosystems. It is typically subdivided into the lithosphere , atmosphere, and hydrosphere. The lithosphere is the earth's surrounding layer composed of solid soil and rock , the atmosphere is the surrounding gaseous envelope, and the hydrosphere refers to liquid environments such as lakes and oceans , occurring between the lithosphere and atmosphere. The biosphere's creation and continuous evolution result from physical, chemical, and biological processes. To study these processes a multi-disciplinary effort has been employed by scientists from such fields as chemistry , biology, geology , and ecology.
The Austrian geologist Eduard Suess (1831–1914) first used the term biosphere in 1875 to describe the space on Earth that contains life. The concept introduced by Suess had little impact on the scientific community until it was resurrected by the Russian scientist Vladimir Vernadsky (1863–1945) in 1926 in his book, La biosphere. In that work, Vernadsky extensively developed the modern concepts that recognize the interplay between geology, chemistry, and biology in biospheric processes.
For organisms to live, appropriate environmental conditions must exist in terms of temperature , moisture, energy supply, and nutrient availability.
Energy is needed to drive the functions that organisms perform, such as growth, movement, waste removal, and reproduction. Ultimately, this energy is supplied from a source outside the biosphere, in the form of visible radiation received from the Sun . This electromagnetic radiation is captured and stored by plants through the process of photosynthesis. Photosynthesis involves a light-induced, enzymatic reaction between carbon dioxide and water , which produces oxygen and glucose, an organic compound. The glucose is used, through an immense diversity of biochemical reactions, to manufacture the huge range of other organic compounds found in organisms. Potential energy is stored in the chemical bonds of organic molecules and can be released through the process of respiration; this involves enzymatic reactions between organic molecules and oxygen to form carbon dioxide, water, and energy. The growth of organisms is achieved by the accumulation of organic matter, also known as biomass. Plants and some microorganisms are the only organisms that can form organic molecules by photosynthesis. Heterotrophic organisms, including humans, ultimately rely on photosynthetic organisms to supply their energy needs.
The major elements that comprise the chemical building blocks of organisms are carbon, oxygen, nitrogen, phosphorus, sulfur, calcium, and magnesium. Organisms can only acquire these elements if they occur in chemical forms that can be assimilated from the environment; these are termed available nutrients. Nutrients contained in dead organisms and biological wastes are transformed by decomposition into compounds that organisms can reutilize. In addition, organisms can utilize some mineral sources of nutrients. All of the uptake, excretion, and transformation reactions are aspects of nutrient cycling.
The various chemical forms in which carbon occurs can be used to illustrate nutrient cycling. Carbon occurs as the gaseous molecule carbon dioxide, and in the immense diversity of organic compounds that make up living organisms and dead biomass. Gaseous carbon dioxide is transformed to solid organic compounds (simple sugars) by the process of photosynthesis, as mentioned previously. As organisms grow they deplete the atmosphere of carbon dioxide. If this were to continue without carbon dioxide being replenished at the same rate as the consumption, the atmosphere would eventually be depleted of this crucial nutrient. However, carbon dioxide is returned to the atmosphere at about the same rate that it is consumed, as organisms respire their organic molecules, and microorganisms decompose dead biomass, or when wildfire occurs.
During the long history of life on Earth (about 3.8 billion years), organisms have drastically altered the chemical composition of the biosphere. At the same time, the biosphere's chemical composition has influenced which life forms could inhabit its environments. Rates of nutrient transformation have not always been in balance, resulting in changes in the chemical composition of the biosphere. For example, when life first evolved, the atmospheric concentration of carbon dioxide was much greater than today, and there was almost no free oxygen. After the evolution of photosynthesis there was a large decrease in atmospheric carbon dioxide and an increase in oxygen. Much of carbon once present in the atmosphere as carbon dioxide now occurs in fossil fuel deposits and limestone rock.
The increase in atmospheric oxygen concentration had an enormous influence on the evolution of life. It was not until oxygen reached similar concentrations to what occurs today (about 21% by volume) that multicellular organisms were able to evolve. Such organisms require high oxygen concentrations to accommodate their high rate of respiration.
Most research investigating the biosphere is aimed at determining the effects that human activities are having on its environments and ecosystems. Pollution, fertilizer application, changes in land use, fuel consumption, and other human activities affect nutrient cycles and damage functional components of the biosphere, such as the ozone layer that protects organisms from intense exposure to solar ultraviolet radiation, and the greenhouse effect that moderates the surface temperature of the planet.
For example, fertilizer application increases the amounts of nitrogen, phosphorus, and other nutrients that organisms can use for growth. An excess nutrient availability can damage lakes through algal blooms and fish kills. Fuel consumption and land clearing increases the concentration of carbon dioxide in the atmosphere, and may cause global warming by intensifying the planet's greenhouse effect.
Recent interest in long-term, manned space operations has spawned research into the development of artificial biospheres. Extended missions in space require that nutrients be cycled in a volume no larger than a building. The Biosphere-2 project, which received a great deal of popular attention in the early 1990s, has provided insight into the difficulty of managing such small, artificial biospheres. Human civilization is also finding that it is challenging to sustainably manage the much larger biosphere of planet Earth.
See also Atmospheric pollution; Earth (planet); Environmental pollution; Evolution, evidence of; Evolution, mechanisms of; Foliation and exfoliation; Forests and deforestation; Fossil record; Fossils and fossilization; Freshwater; Gaia hypothesis; Solar energy
Biosphere
Biosphere
Introduction
The biosphere is that part of Earth comprising the living ecosystem, which includes all living matter of the world and the inorganic components that they rely upon. The biosphere is a part of the world on par with the lithosphere (Earth's rocky crust), the atmosphere (Earth's gaseous envelope), and the hydrosphere (Earth's water realm). As scientists have come to know more about the deeper reaches of Earth's crust and the sea floor, the depth of the biosphere has grown greater. The term biosphere was first used by Austrian geologist Eduard Suess (1831–1914), who said it was “the place on the Earth's surface where life dwells.”
Historical Background and Scientific Foundations
The biosphere may be divided into biomes, or subparts with respect to latitude (climate) and elevation (depth in the ocean, depth in the crust, and altitude on mountains). Polar biomes are found at high latitude. Mid-latitude biomes and equatorial biomes are at lower latitudes respectively. In the ocean, biomes are found at shallow depths (for example, near shore or on continental shelves), at abyssal depths (for example on the sea floor), and in oceanic trenches, where water may be over 5 mi (8 km) in depth. In the crust, biomes exist at shallow depths (for
example, soils and surface rocks) or up to 5.6 mi (9 km) or more in crustal rocks. In the atmosphere, some birds fly at heights up to 6.8 mi (11 km) or more. On land, microscopic biomes exist from sea level to the highest mountain areas. There are several main ecosystems within the biome of the land, including forests, deserts, grasslands, and wetlands.
No matter how the biosphere is subdivided, all living organisms are interrelated in some way. Within the biosphere and its biomes are regional and local ecosystems. Each of these ecosystems consists of living organisms and the non-living components upon which they depend. The living organisms depend upon one another as parts of the food web. The food web has a hierarchy: producers (organisms that make food), consumers (organisms that consume producers), and decomposers (organisms that recycle dead organisms). Local ecosystems are parts of the regional ecosystem and, in turn, are components in the biomes and global biosphere.
Biosphere and Earth History
The biosphere has existed and continued to expand, with brief lapses, over most of the 4.6-billion-year history of Earth. It is not known exactly when life arose on Earth, but it is a consensus view that life was probably in existence by about 3.8 billion years ago. The diversity of life has increased over time, both in the number of different groups of organisms and the complexity of some of the groups.
The biosphere has experienced some crises during Earth history in which large numbers of organic groups have been extinguished over a brief span of time. These events are called mass extinctions and represent episodes of reorganization of ecosystems and biomes of Earth. For example, the mass extinction that claimed the dinosaurs and many other species about 65 million years ago was such an event. There have been about four such other events in Earth history over the past 500 million years.
Impacts and Issues
Biosphere is a term associated with some biology experiments that have been conducted over the past few decades. Biosphere 2 (so named because the Earth is viewed as Biosphere 1) was a large laboratory experiment in Arizona. Bios-3 was an experimental facility operated by the government of the former Soviet Union in the late 1960s. Biosphere J is a more recent Japanese experiment. The biospheres were restricted environments where a local ecosystem was simulated.
WORDS TO KNOW
: Well-defined terrestrial environment (e.g., desert, tundra, or tropical forest). The complex of living organisms found in an ecological region.
: The hard, outer shell of Earth that floats upon the softer, denser mantle.
: The time-ordered mass of fossils (mineralized impressions of living creatures) that is found in the sedimentary rocks of Earth. The fossil record is one of the primary sources of knowledge about evolution and is also used to date rock layers (biostratigraphy).
: The totality of water encompassing Earth, comprising all the bodies of water, ice, and water vapor in the atmosphere.
: The rigid, uppermost section of Earth's mantle, especially the outer crust.
Earth's biosphere necessarily changes in response to climatic change. Climate change can spur migrations and relocations of many organisms. Likewise, climate change can spell doom for species that cannot adapt to such changes. The demise of species opens the way for new species to arise to fill those niches. As the fossil record shows, over the long span of geological time, many species have adapted, become extinct, or arisen as a result of climatic change.
See Also Biodiversity; Extinction; Gaia.
BIBLIOGRAPHY
Books
Lovelock, James. Gaia:A New Look at Life on Earth. Oxford, UK: Oxford University Press, 2000.
Parry, M. L., et al, eds. Climate Change 2007: Impacts, Adaptation and Vulnerability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.
Web Sites
Pidwirny, Michael. “Fundamentals of Physical Geography. Chapter 9: Introduction to the Biosphere.” PhysicalGeography.net, 2007. < http://www.physicalgeography.net/fundamentals/chapter9.html> (accessed November 30, 2007).
David T. King Jr .
Biosphere
Biosphere
Earth's biosphere is the sphere of life around the planet. Its organisms interact with their environment and each other, maintaining conditions on the planet conducive to life. Light from the Sun causes plants and algae to photosynthesize and thereby produce the oxygen that animals and microbes need. As a by-product of their respiration, animals and microbes in turn provide carbon dioxide, which plants require to grow. The oxygen atoms are used over and over again within the biosphere's oxygen cycle. There are many such cycles in a biosphere, with many creatures depending on other creatures for their survival.
Why Build a Biosphere for People?
At current estimates, it would cost around $22,000 to launch a medium pepperoni pizza to the International Space Station. For short space missions of less than two years it is cost effective to take along everything that is needed, as if one were embarking on a camping trip. But longer missions require that the crew grows their own food and that all the oxygen, water, and waste is recycled. The longer the mission away from Earth, the more complete the recycling has to be.
On the space shuttle and the International Space Station, everything that the astronauts and cosmonauts need is taken with them. To maintain a habitable environment within the spacecraft a physical-chemical life support system is used; equipment removes the carbon dioxide and other contaminants from the atmosphere and produces oxygen and water. These systems are efficient and compact, but they require that consumables be brought from Earth. For example, when the carbon dioxide is removed from the atmosphere it is vented to space or stored. This means that the oxygen contained in that carbon dioxide is no longer available for human consumption and that a source of oxygen must be supplied.
For a mission such as a long-term base on Mars, a life support system is required in which almost everything is recycled and reused and nothing is thrown away—a regenerative system. Systems that use living organisms to perform life support system functions are called bioregenerative life-support systems. Earth has such a bioregenerative system—the biosphere.
Biosphere 2
In Arizona, scientists built an artificial biosphere, called Biosphere 2. An eight-person crew lived inside the 1.28-hectare (3.15-acre) hermetically sealed structure for two years from 1991 to 1993. They produced their own food and recycled the atmosphere, water, and waste using a bioregenerative life support system.
Biosphere 2 had a mini rain forest, savanna, desert, marsh, and ocean, as well as a farm and a human habitat. The habitat housed the crew quarters, dining room, kitchen, medical facility, and an analytical laboratory for testing that the air was safe to breathe and that the water was safe to drink. There was also a machine shop for making and repairing equipment, such as water pumps, and the Command Room, with videoconferencing, Internet connections, phones, and a station to monitor the environment of each area in the biosphere.
Just as Earth's biosphere has cycles, so do bioregenerative life support systems. In Biosphere 2 the crew ate the same carbon molecules over and over again and breathed the same oxygen. Following is an example of how a water molecule might move through the biosphere.
After drinking a glass of water, a crew member excretes the water molecule as urine. The crew member flushes it into the wastewater treatment system, a specially designed marsh lagoon where plants and microbes work together to purify the water. Once the treatment cycle is complete, the water irrigates the farm crops. After soaking into the soil, the water molecule that the crew member drank is absorbed by the roots of a wheat plant and is later transpired through its leaves. The water molecule is now in the atmosphere, and after passing through a dehumidifying or condensing heat exchanger that maintains the temperature in the biosphere, the water is removed from the atmosphere and placed in a holding tank. A crew member preparing dinner goes into the kitchen and turns on the faucet. Out comes the water molecule, which becomes part of the evening soup. And so on it goes, around and around and around.
Biosphere 2 was the first attempt at a fully bioregenerative life support system. It demonstrated that such a system could be used to support human life on another planet. Someday people will inhabit other planets, and bioregenerative systems will play a key role in allowing that to happen.
see also Closed Ecosystems (volume 3); International Space Station (volumes 1 and 3); Living in Space (volume 3); Living on Other Worlds (volume 4); Mars Bases (volume 4).
Jane Poynter
Bibliography
Eckart, Peter. "Bioregenerative Life Support Concepts." In Spaceflight Life Support and Biospherics. Torrance, CA: Microcosm Inc.; Dordrecht, Netherlands: Kluwer Academic, 1996.
Marino, Bruno D., and H. T. Odum. "Biosphere 2: Introduction and Research Progress." Ecological Engineering 13, nos. 1-4 (1999):4-14.
Purves, William K., Gordon H. Orians, and H. Craig Heller. Life: The Science of Biology, 6th ed. New York: W. H. Freeman, 2001.
Wieland, P. O. Living Together in Space: The Design and Operation of the Life Support Systems on the International Space Station. Marshall Space Flight Center, Huntsville AL: National Aeronautics and Space Administration, 1998.
Cabins See Capsules (Volume 3).
Biosphere
Biosphere
The biosphere is that part of Earth that contains life. This worldwide ecosystem ( a area in which living things interact with each other and the environment) is made up of the land, water, and atmosphere that support life, and includes every part of Earth where life exists. Its many parts are linked together by nutrient cycles.
The biosphere can be described as all of the world's ecosystems, or the worldwide ecosystem. As such, it consists of Earth's lithosphere, atmosphere, and hydrosphere. The lithosphere includes all of Earth's surface layers of solid substances like soil and rocks. The atmosphere is the envelope of gases or air that completely surround the planet. The hydrosphere includes all of the lakes, rivers, and oceans on its surface. All of the elements and forces in these three spheres are constantly part of the many chemical, biological, and physical processes that make the entire "bio-sphere" or "life-sphere" what it is. To date, no other planet besides Earth has been discovered that contains a biosphere or living world.
EDUARD SUESS COINS THE TERM BIOSPHERE
The term biosphere was first used by the Austrian geologist Eduard Suess (1831–1914) in 1875 to describe that part of the Earth that contains life. This concept had little impact on the scientific community until it was discussed by the Russian mineralogist, Vladimir I. Vernadsky (1863–1945) in his 1926 book. Vernadsky argued that in order to study the biosphere, scientists from many fields like geology, chemistry, and biology had to work together.
Earth's biosphere can be considered to be thousands of feet thick—from the bottom of the oceans to about 30,000 feet (9.144 kilometers) above sea level. However, given the size of the entire Earth, this is a fairly thin layer. In fact, most of the life that does exist within the biosphere can be found in the narrow band just below sea level to about 20,000 feet (6.096 kilometers) up. That height is about the limit for animals and most plants to live. Scientists consider Earth's biosphere a closed system in which the only thing ever added is sunlight. Living things in the biosphere need energy and nutrients and an appropriate environment in order to live and reproduce. The Sun is the ultimate energy source for the biosphere, and its light energy is captured by green plants that use the process of photosynthesis to change light energy into chemical energy. This energy then passes through the biosphere from plants to other organisms and then to others again. It is eventually either lost in the form of heat to the environment or stored for a long time in organic molecules, such as carbon atoms are locked in coal underground. The biosphere can, therefore, be seen as a group of tightly interconnected recycling systems and subsystems that affect and influence each other.
THE BIOSPHERE CONSIDERED AS A GLOBAL CONCEPT
The global concept of the biosphere has become increasingly useful and important as technology allows the world to be considered in a truly global way. Spacecraft can not only provide images of the entire globe, but also can monitor the many systems that make up Earth's total environment. Today, therefore, the term biosphere is used most often when discussing the health of Earth. Current research focuses on the effects that human activities have on the health of the global environment (the biosphere). The pressures and demands of increasing populations have resulted in two major threats to the biosphere's well-being: the loss of natural resources and the effects of pollution. As more and more of the natural environment is destroyed, such as the continuing destruction of tropical rain forests, many scientists fear that the balance of nature may be so upset that it may permanently harm or change the biosphere. Many also fear that the pollution by-products of everyday modern life could become too great for the biosphere to bear and may permanently damage its systems. Activities such as fuel consumption (burning coal, oil, and gas) and the use of fertilizers could increase the levels of carbon dioxide, nitrogen, and phosphorous in the atmosphere and seriously alter the natural balance of the life-sustaining biosphere.
The concept of the biosphere is also at the center of a scientific debate as to whether Earth and its biosphere should be considered a living organism with self-regulating mechanisms. Called the "Gaia hypothesis," this idea was first put forth in the late 1970s by the British scientist, James Lovelock (1919– ), who argued that the biosphere is able to create and maintain the environment that most favors its own stability—as long as it is left alone. Lovelock argued that by tampering with and sometimes altering Earth's environmental balancing systems, humans are placing themselves and their planet at risk. He and his followers argue that such phenomena as global warming, or the greenhouse effect (caused by too much carbon dioxide in the atmosphere), and ozone depletion from pollution (the resulting decrease in protection from harmful ultraviolet radiation from the Sun, are evidence of a growing risk. Whether the Gaia hypothesis is right or wrong, it has been very useful in generating concern and research about people's influence on the worldwide ecosystem known as the biosphere.
[See alsoPhotosynthesis; Respiration ]
biosphere
bi·o·sphere / ˈbīəˌsfi(ə)r/ • n. the regions of the surface, atmosphere, and hydrosphere of the earth (or analogous parts of other planets) occupied by living organisms.DERIVATIVES: bi·o·spher·ic / ˌbīəˈsfi(ə)rik; -ˈsfer-/ adj.