What organism most efficiently converts a given quantity of mass into heat?

What organism most efficiently converts a given quantity of mass into heat?

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Question I am trying to answer:

In the popular film The Matrix, heat given off by humans is harvested as an energy source. I wondered, if this were possible, would humans be a good organism to choose? Would any other organism be better?

Question I want to ask:

Many warm-blooded organisms produce heat by metabolism. Do different organisms produce different levels of heat for the same mass of input (food)? Is there any organism that directs energy flux into heat production more than any other organism?

A small hardy warm blooded omnivore that is easily tamed. I suggest rats.

Small: You don't want a lot of metabolic effort going into building bone and structure to support structure. Hardy: it needs to be survivable with little care. Warm blooded: You want to harvest energy from it. Easily tamed: The animal shouldn't try to escape its captivity.

All About Photosynthetic Organisms

Some organisms are capable of capturing the energy from sunlight and using it to produce organic compounds. This process, known as photosynthesis, is essential to life as it provides energy for both producers and consumers. Photosynthetic organisms, also known as photoautotrophs, are organisms that are capable of photosynthesis. Some of these organisms include higher plants, some protists (algae and euglena), and bacteria.

Key Takeaways: Photosynthetic Organisms

  • Photosynthetic organisms, known as photoautotrophs, capture the energy from sunlight and use it to produce organic compounds through the process of photosynthesis.
  • In photosynthesis, the inorganic compounds of carbon dioxide, water, and sunlight are used by photoautotrophs to produce glucose, oxygen, and water.
  • Photosynthetic organisms include plants, algae, euglena and bacteria



In an editorial in 1995, “Homage to the chromosome”, Joseph Gall wrote:

Biological organisms , unlike complex inanimate systems, contain information that regulates their day-to-day activities, and, more remarkably, lets them produce new organisms from single cells. That this information resides in the chromosomes was established 75 years ago … missing from the classical account, however, was any understanding of the nature of the information carried by the chromosomes. That gap was, of course, filled by later spectacular advances in molecular genetics, which showed that a gene is a segment of DNA whose linear sequence of nucleotides specifies the linear sequence of amino acids in the protein. … But just as a book is more than a random assortment of words, chromosomes are more than simple repositories of gene sequences. They must contain regulatory information for turning genes on and off and they must control their own replication, repair, packaging, as well as the complex movements they carry out during mitosis and meiosis. [ Gall, 1995 ]

Gall here expressed in a nutshell the achievements of genetic analysis together with its methodological successes and epistemological blind alleys.

Genetic analysis in the first decades of the twentieth century had to struggle for its independence [ Falk, 1995b ]. It achieved this to a large extent by concentrating its efforts on the phenomenological aspects of the mechanical causes of inheritance, by applying a strict reductionist methodology. By and large, genes (and their organization) were treated as intervening variables, or as hypothetical constructs, “because at the level at which the genetic experiment lie, it does not make the slightest difference whether the gene is a hypothetical unit, or whether the gene is a material particle” [ Morgan, 1935 ]. But the wider context was not neglected, whether in the search for their physico-chemical structure and function, or in their role in the evolution of populations and species.

At the time when genetics achieved its secure independence, Morgan asserted:

The story of genetics has become so interwoven with that of experimental embryology that the two can now to some extent be told as a single story. … today their interdependence is so obvious that the geneticists takes for granted the main outlines of the facts of embryology, and the embryologist is coming to realize his dependence on the evidence from genetics. [ Morgan, 1934 , 9]

The course opened by Beadle and Tatum's “one gene — one enzyme” and their analysis of metabolic pathways in Neurospora directed wide attention to the study of gene-function in the tradition of genetic analysis of discrete genes, rather than that of dealing with developmental systems. The presentation of the molecular basis of heredity with Watson and Crick's model of DNA, further directed research studies to gene function rather than to embryonic development and differentiation.

Benzer's detailed mapping of the gene and Yanofsky's demonstration on the colinearity of the gene sequence and the that of protein made the elucidation of the process of gene function more urgent. However, the next step was primarily a task of biochemistry of synthesizing proteins in the test tube [ Rheinberger, 1997 ]. Genetic analysis stepped in again with making sense of the processes of transcription and translation by providing a model of genetic regulation of gene action [ Jacob and Monod, 1961 ].

Many believed at the mid-1960s that molecular genetic analysis has exhausted itself [ Stent, 1968 ], but development and differentiation was not resolved by the molecular genetic analysis of gene regulation and the paradigm of Jacob and Monod [1961 ]. While molecular biologists encountered the complexity of eukaryotic gene organization, “classical” genetic analysis managed to improve its methodology and increasingly to analyze gene function in a system-context, thus addressing more relevantly the “classical” problems of embryology. It took some time for the molecular biologists to appreciate Lewis's breakthrough in providing a phenomenological model of genetic control of segmental differentiation (see Morange [2000 , 196]), but once obtained, genetic analysis of embryological development and differentiation became increasingly molecular.

Evelyn Fox Keller attributes these developments to the change of the mechanistic, lineal mode of thinking to that of the kibernetic, informational feedback era ( Keller [1995 2000 2002 ], and many others) that changed the image of the gene as an acting agent to that of an activated agent. There is no doubt that the ”informational” metaphor had an important role in genetic thought. It must however be kept in mind that this metaphor was far from the mathematical-kibernetic notion of information theory, which dealt with the probabilistic reliability of transmission of signs, with no reference to their semantic contents, whereas the information-metaphor of genetic analysis was crucially dependent on the comparison and transmission of semantic information, as obtained by the methodology of hybridization, whether that of living organisms or that of DNA and/or RNA nucleotide sequences. More importantly, Keller ignores the internal developments in the conceptions and techniques of the sciences involved. Both Development Systems Analysis (see Oyama [1985 ]), and the notion of Punctuated Evolution (see Eldredge and Gould [1972 ]), which played major roles in the new organismal-look, were engendered far away from the foci of molecular-biology, by avid opponents of the information notion. By the time computing algorithms and machines for analysis of very large number of data became available the information metaphor was long forgotten in molecular biology.

Keller is right in pointing at Goldschmidt, who “was typically grandiose, leaning always toward overarching generalization”, unrelentingly insisted on embryological development as systems of interacting and coordinated reactions: “[H]is search was precisely for the dynamic properties of such systems (Zusammenspiel der Reaktionen). To Goldschmidt gene action meant that genes were both catalysts and catalyzed, actors and ‘reacting substances’” [ Keller, 1995 , 15-16]. However, to the “American geneticist” Sturtevant's rephrasing of the problems in terms of ”chain of reactions into their individual links”, had an immense appeal, because, as Keller says, “Once the problem of development is translated into the question of how genes produce their effects, the task is immediately — and almost miraculously — simplified” [ Keller, 1995 , 16]. The problem was not that of switching the notion from “gene action” to that of “gene activation”. It was one of overcoming the reductionist paradigm of genetic analysis that was immanent to the genetic theory of inheritance for de Vries, but largely pragmatic and instrumental to Morgan and his associates.

If genetic determinism became stereotypic, this was to a large extent due to its experimental success. But genetic analysis advanced toward a system's perspective from within. To a large extent, the sheer amount of reductionist data that needed integration led to the sublimation of instrumental reductionism of genetic analysis. Methods were developed toward the beginning of the twenty-first century in relation to the sequencing effort of the complete human genome (see, e.g., Sulston and Ferry [2002 ]). Many were based on the principles of analysis of the hybridability of nucleotide sequences. The price for such collections of huge amounts of data was inevitably the reduced reliability of individual data. This was overcome in the genome sequencing effort by repeatedly sequencing of any segment. However, for other purposes, like that of building “proteomes” (the total yield of proteins synthesized by cells) or the “interactome” (the total pattern of protein-interactions in given cells) (see, e.g., Perkel [2004 ]) the lack of accuracy of individual data was often amply compensated for by the algorithms developed for looking for bulk-effects (based on tens of thousands of individual data) of patterns of production and interaction.

Essay on Ecosystem: Meaning and Components

Read this essay to learn about ecosystem. After reading this essay you will learn about: 1. Meaning of Ecosystem 2. Components of Ecosystem 3. Productivity 4. Diversity 5. Ecosystem Goods and Services 6. Homeostasis.

  1. Essay on the Meaning of Ecosystem
  2. Essay on the Components of Ecosystem
  3. Essay on Ecosystem Productivity
  4. Essay on Ecosystem Diversity
  5. Essay on Ecosystem Goods and Services
  6. Essay on Homeostasis in Ecosystem

Essay # 1. Meaning of Ecosystem:

An ecosystem is a system formed by the interactions of a variety of individual organisms with each other and with their physical environment. Ecosystems are nearly self-contained so that the exchange of nutrients within the system is much greater than exchange with other system.

An ecosystem, thus, is not entirely a biological entity. Any complete description of an ecosystem must include the physical environment as well as the biological components and the interactions between the two. Ecosystems are of diverse types-mostly natural, but there are a few which are man-made or modified by man’s activity.

Essay # 2. Components of Ecosystem:

An ecosystem is not entirely a biological entity. The biological or biotic components of an ecosystem include both living organisms and products of these organisms. Thus microbes, all categories of plants and animals as well as their waste products are included in the ecosystems.

The non-biological or abiotic components include climatic and edaphic features, in particular climatic components like sunlight, temperature, air and water supply along with soil component such as soil nutrients which are very important contributing factors of ecosystem operation.

The biotic components are broadly categorized as producers, and consumers of different classes viz. herbivores (animals that eat plants), carnivores (animals that eat flesh of other animals), omnivores (animals that consume both plants and animals as available) and lastly scavengers (animals that eat dead plant and animal matters).

In addition there are decomposer classes, which include mostly saprophytic organisms that help in nutrients and element recycling process.

They are heterotrophic organisms that feed solely on dead organic matter, i.e., saprophytes. The bulk of the saprophytic decomposition is carried out by bacteria, fungi and protozoans. Imagine that a piece of organic Utter falls to the floor of a forest.

In a typical sequence, microscopic bacteria or fungi will excrete chemicals, called enzymes, that break down the complex chemical compounds in the object Some of the breakdown products are absorbed as food, whereas others are left behind.

These serve as a food supply for other organisms that carry the decomposition one step further. Eventually the waste products of the final line of decomposers are energy-poor mineral nutrients that are reabsorbed, and thus recycled, by plants — Fig. 5.1.

Essay # 3. Ecosystem Productivity:

During the process of production and consumption, energy is passed along, or flows, from one organism to another. For example, solar energy is converted to chemical energy within the leaves of green plants. The leaves can then be eaten by some herbivore, and the herbivore may, in turn, be eaten by a carnivore.

Consider a hypothetical ecosystem that receives 1,000 Kilocalories of light energy in a given day (Fig. 5.2). Most of this energy is not absorbed at all. Some is simply reflected back into space. Of the energy that is absorbed, most is stored as heat or used for evaporation of water. A small amount is assimilated by plants.

The productivity in an ecosystem are of two kinds—primary productivity and secondary productivity. The primary productivity of an ecosystem is the rate at which organic matter is produced during photosynthesis.

Some amount of photosynthetic material is subsequently utilized for respiratory purpose. The initial photosynthetic product which is formed at first is called gross primary productivity which is expressed as Kcal/m 2 /yr.

Only about half of the gross productivity accumulates as new plant matter, because the rest of the chemical energy is metabolized by the plant’s own respiration and released to the environment as heat. The net gain in plant matter is called the net primary productivity.

Thus the Net primary productivity = Gross primary productivity – Plant respiration

On the whole, productivity depends on a variety of factors such as sunlight, temperature, rainfall and the availability of nutrients. The total quantity of organic matter present at any one time in an ecosystem is called the biomass.

The biomass equals the total organic matter gained through net primary productivity over a period of time minus the quantity of material that is consumed and lost during respiration by animals. Let us return to the hypothetical ecosystem that receives 1,000 Kcal of sunlight (Fig. 5.2).

Although the efficiency of energy transfer varies from ecosystem to ecosystem, as an average value, of the 1,000 Kcal absorbed, only about 12 Kcal are utilized during photosynthesis. Of these 12 Kcal, 2 Kcal are used for plant respiration and about 10 Kcal are stored in the plant tissue as energy-rich material, which animals can use for food.

1,000 Kcal of sunlight → 988 Kcal lost to the environment + 12 Kcal stored as plant tissue.

The net primary productivity of various ecosystems varies distinctly. Among them tropical rain forests are most productive and rock, ice and sandy areas are least productive ecosystems (Table 5.2).

The variation in global patterns of primary production illustrates the range and variety of ecosystem character and functioning. The main factors affecting global patterns of primary production are light, heat, water, carbon dioxide and oxygen, and nutrient elements.

Occupying most of the Earth’s surface, the oceans provide an excellent example of how productivity varies with regional conditions. In the oceans there are very well-mapped and predictable patterns of primary productivity (Table 5.3).

Russian oceanographic research work during the 1960s defined five main productive regions of the oceans. In general, productivity is highest where there is a strong circulation of water, with upwelling currents brining deep water to the surface.

Nutrient concentrations tend to the greater in deep waters due to the continuous rain of material from shallow waters, down past the euphotic zone (where autotrophs can recycle the nutrients into the food chain). High productivity is commonest in shallow waters, where plants can grow to larger sizes.

Human impacts upon primary production are very important in many ecosystems. The broad pattern of natural environmental factors which control primary production at a global scale is shown in Table 5.4. This, however, provides only a generalized overview of ecosystem productivity (at biome level). The pattern of influence of the major limiting factors shown is frequently different at regional or local scales.

Secondary productivity is defined as the rate of formation of new organic matter by heterotrophs of the net primary productivity available in a forest, herbivores (e.g. insects, deer) eat only about 1-3%.

In grassland, as much as 15% of the vegetation may be eaten by herbivores. In the ocean, 80% of the net primary productivity is consumed by herbivores. Very little of the plant matter that is consumed is actually converted to animal tissue.

In terms of energy content, the conversion is only about 10 per cent. To summarise, although there are large variations from ecosystem to ecosystem, as a generalisation, for every 10 Kcal of plant tissue available to herbivores, about 1 Kcal will be eaten, and only about 0.1 Kcal will be stored in the form of body weight.

Carnivores that eat herbivores are likewise inefficient in converting food to body weight, so the energy available to the carnivore is even less. It is obvious, then, that the amount of usable energy decreases, as it is transferred from sunlight to plants to animals.

Thus there is a decreasing quantity of energy available at each trophic level. As a consequence, there will be a decreasing mass of organisms at each level. This relationship can be shown as Fig. 5.3 and called “energy pyramid”.

I. Food Chain and Food Webs:

The flow of food energy in an ecosystem progress through a food chain in which one step follows another—primary consumers eat producers, secondary consumers eat primary consumers, and so on. Within any ecosystem there are two major food chains, the grazing food chain and the detrital food chain (Fig. 5.4).

The two-food chains are distinguished by their source of energy or food for the initial consumers. In grazing ecosystems autotrophs, or living plant tissues, are the primary source of energy for the initial consumers, the herbivores. In the detrital food chain, the initial consumers, primarily bacteria and fungi, use dead organic matter, detritus, as their source of energy.

Ii. Grazing Food Chains:

The grazing food chain is the one more obvious to us. Cattle grazing on pastureland, deer browsing in the forest, rabbits feeding in old fields, and insect pests feeding on garden crops represent the basic consumer groups of the grazing food chain.

Although highly conspicuous, the grazing food chain is not the major food chain in terrestrial and many aquatic ecosystems. Only in some aquatic ecosystems do the grazing herbivores play a dominant role in energy flow.

Voluminous data exist on phytoplankton productivity, filtration rates by grazing zooplankton, and production efficiencies of zooplankton. Few data, however, are available on the flow of energy, rate of grazing, biomass turnover rates for phytoplankton, and turnover of zooplankton biomass within the same aquatic system.

In terrestrial systems, a small proportion of primary production goes by way of the grazing food chain. Over a three year period, only 2.6 per cent of net primary production of a yellow-poplar forest was used by grazing herbivores, although the holes made in the growing levels resulted in a loss of 7.2 per cent of photosynthetic surface.

Iii. Detrital Food Chains:

The detrital food chain is common to all ecosystems, but in terrestrial and littoral ecosystems it is the major pathway of energy flow.

In yellow-poplar (Liriodendron tulipifera) forests, 50 per cent of gross primary production goes into maintenance and respiration, 13 per cent is accumulated as new tissue, 2 per cent is consumed by herbivores, and 35 per cent goes to the detrital food chain.

Two-thirds to three-fourths of the energy stored in a grassland ecosystem that is un-grazed by cattle is returned to the soil as dead plant material, and less than one-fourth is consumed by herbivores.

Of the quantity consumed by herbivores, about one- half is returned to the soil as feces. In the salt march ecosystem, the dominant grazing herbivore, the grasshopper, consumes just 2 per cent of the net production available to it.

Iv. Supplementary Food Chains:

Other feeding groups, such as the parasites and scavengers, form supplementary food chains in the community. Parasitic food chains are highly complicated because of the life cycle of the parasites. Some parasites are passed from one host to another by predators in the food chain.

External parasites (ectoparasites) may move from one host to another. Other parasites are transmitted by insects from one host to another through the blood-stream or plant fluids.

However, natural systems are rarely so orderly and linear. Many organisms occupy several trophic levels simultaneously.

For example, a raven can be a primary consumer when it eats corn, a secondary consumer when it eats grasshoppers, and a tertiary consumer if it manages to catch a shrew or small snake. In addition, ravens will eat dead animals and are, therefore, also scavengers.

In nearly all natural ecosystems, the patterns of consumption are so complicated that the term food web is more descriptive because there are many cross-links connecting the various organisms (Fig. 5.5).

Once food is eaten, its energy follows a variety of pattern through the organisms. Not all food can be fully digested and assimilated. Hair, feathers, insect exoskeletons, cartilage and bone in animal foods and cellulose and ligin in plant foods cannot be digested by most animals. These materials are either egested by defecation or regurgitated in pellets of indigested remains.

Organisms use most of the food energy that they assimilate into their bodies to fulfil their metabolic requirements:

Performance of work, growth and reproduction. Because biological energy transformations are inefficient, a substantial proportion of metabolized food energy is lost, unused, as heat. Organisms are no different from man-made machines in this respect.

Most of the energy in gasoline is lost as heat in a car’s engine rather than being transformed into the energy of motion. In natural communities, energy used to perform work or dissipated as heat cannot be consumed by other organisms and is forever lost to the ecosystem.

Assimilated energy that is not lost through respiration or excretion is available for the synthesis of new biomass through growth and reproduction. Populations lose some biomass by death, disease or annual leaf drop, where they enters the detritus pathways of the food chain.

The remaining biomass is eventually consumed by herbivores or predators and its energy thereby enters the next higher trophic level in the community (Fig. 5.6).

V. Energetic Efficiencies:

The movement of energy through the community depends on the efficiency with which organisms consume their food resources and convert them into biomass. This efficiency is referred to as the food chain or ecological efficiency.

Ecological efficiencies are determined by both internal, physiological characteristics of organisms and their external, ecological relationships to the environment. To understand the biological basis of ecological efficiency, one must dissect the individual link of the food chain into its component parts (Fig. 5.7).

Ecological efficiency depends on the efficiencies of three major steps in energy flow exploitation, assimilation and net production (Table 5.5).

The product of the assimilation and net production efficiencies is the gross production from efficiency—the percentage of the exploitation and gross production efficiencies is the food chain or ecological efficiency—the percentage of available food energy in prey converted into consumer biomass.

The measurement of energy flow through an entire community is a complex and virtually impossible task. Yet the total flux of energy and the efficiency of its movement determine the basic trophic structure of the community, number of trophic levels, relative importance of detritus and predatory feeding, steady state values for biomass and accumulated detritus and turnover rates of organic matter in the community.

Each of these properties, in turn, influences the inherent stability of the community.

The study of energy transformation by plants and animals does, however, provide a useful insight into the basis of ecological efficiency and the trophic structure of the community.

Plants are terrible predators as they harness light energy, animals, however, have different problems—they have feeding ability and thus consume organic mass and energy assimilation takes place thereafter. Energy flow between trophic levels represents the sum of the feeding activities of many species.

Individual populations usually consume only a small fraction of available food resources. Carnivores, seed-eaters and aquatic herbivores are most efficient the commonest species consume 10 to 100% of the food available to them. Terrestrial herbivores usually consume only 1 to 10% of the leafy vegetation.

Essay # 4. Ecosystem Diversity:

Ecosystem varies widely, with respect to both its biotic and abiotic composition and their interactions. Broadly speaking, habitat wise there are two major categories of ecosystem, viz., terrestrial or land ecosystem or biome and aquatic ecosystem. Each of them, again, is divided into several ecosystem types depending on atmospheric temperature, rainfall and soil or substrate nature.

The habitat condition varies widely from coastal areas, to mountains, deserts, hills, and alluvial plains in both tropical and subtropical zones. Habitat wise, major land ecosystems are thus depicted in the Fig. 5.8. The major ecosystem types in terrestrial habitat are these-grassland, rain forest, deciduous forest, mountain, desert, coastal, alpine and glacier zones etc.

Two major abiotic factors regulate the plant community structure in terrestrial habitat viz., rainfall and temperature. The major plant communities were tropical rain forest, temperate rain forest, tropical seasonal forest, temperate forest, thorn forest or savanna, woodland or grassland, taiga, desert and tundra zones.

The distributional pattern of major terrestrial biomes are given in Fig. 5.9. The overall topography and biotic composition of each of the zones described above are quite unique and distinguishable one from another (Fig. 5.10). In many cases human interference on such ecosystems leads to alteration of climate, landscape and so also the composition of species.

Though plants were widely adapted to climatic changes, yet major climatic factors govern the successional pattern of biological species in different habitat zones. Three distinctive successional profiles of plant communities is depicted in Fig. 5.11, to show the influence of climatic gradients on community formation.

With respect to aquatic ecosystem there were quite a good number of diversities. The major types were lake, open sea, coastal water, coral habitats, rivers, ponds, reservoir and swampy region etc. The life forms vary widely in each of the ecosystem zones.

Even within a single ecosystem zone there are distinctive regions where, due to variation of ecological niche, species composition varies widely in diversities and density. Two clear examples of species distribution in a lake and in ocean are depicted in separate figures i.e., Figs. 5.12 and 5.13.

A lake is a large water body mostly static or rarely having a flow system. From biological viewpoint, a lake has a number of layers:

1. Compensation level, the depth at which light energy is just sufficient for photosynthesis to balance the respiratory needs of primary producers.

2. Euphotic zone, this layer lies above the compensation level.

3. Profoundal zone, this layer lies below the compensation level.

Within the Euphotic zone, again, there are two subdivisions—the shallow littoral zone, deeper limnetic zone. The phytoplankton’s are mostly dominant in limnetic zone and abundant in littoral zone. There are occasional blooms also. Zooplanktons and swimming nektons are also abundant in limnetic zone.

The profoundal zone, by definite, lacks sufficient light per photosynthesis (i.e., < 1% of total incident light), it is, therefore, dominated by consumers. This zone has greater amount of debris i e more of organic load. The most productive lakes are those with a large littoral zone in relation to their volume.

Here, sunlight reaches most of the lakes waters, providing an energy source for the primary producers in addition to significant warming during the growing season.

Shallowness of the water allows the development of a large biomass of lightly productive rooted aquatic plants. Phytoplankton blooms are characteristic because of high inorganic nutrient concentrations produced as bottom micro-organisms degrade large volumes o organic matter.

Since profoundal waters have low oxygen concentrations, stagnation of bottom water is relatively frequent. Such shallow, highly productive lakes are termed Eutrophic lake.

In contrast, Oligotrophic lakes are much less productive. An oligotrophic lake is usually deep and steep-sided, with a narrow littoral zone. Concentrations of inorganic nutrients are low, and so is phytoplankton density. Blooms are rare, for the intense competition for nutrients keep population levels low.

Dissolve oxygen is high in the hypolimnion its large volume, low temperatures and low input of organic matter serve to keep oxygen depleting microbes in check. Cold water bottom pushes such a lake trout or landlocked salmon find suitable habitats in the profoundal zone.

Essay # 5. Ecosystem Goods and Services:

Each and every ecosystem provides a number of goods and services to mankind directly or indirectly. These includes material supply like food, fiber, fuel, medicines and bio-chemicals or it helps in control of flood, erosion, habitat protection, waste recycling, recreation and so on. An example of provisioning of goods and services of estuarine ecosystem is shown in Table 5.6.

Essay # 6. Homeostasis in Ecosystem:

Ecosystems are capable of self-maintenance and self-regulation as are their component populations and organisms.

Thus cybernetics—the science of controls, has important application in ecology, especially since man increasingly tends to disrupt natural controls or attempts to substitute artificial mechanisms for natural ones. ‘Homeostasis‘ is the term generally applied to the tendency for biological systems to resist change and to remain in a state of equilibrium.

However, the control depends on ‘feedback’, either in positive or negative ways. The positive feedback is deviation accelerating, while negative feedback is deviation counteracting. Both natural and man-made activities induced the changes in the ecosystem, but regulated feedback mechanism tends to resist the same thus, somewhat, homeostasis is maintained.

In every ecosystem, there are three basic components:

Inputs, internal cycling and output, those are influenced by soil & climate. The input of nutrients to the ecosystem depends on the type of biogeochemical cycle.

Nutrients with a gaseous cycle, such as carbon and nitrogen, enter the ecosystem via the atmosphere. In contrast, nutrients such as calcium and phosphorus have sedimentary cycles, with inputs dependent on the weathering of rocks and minerals.

Primary productivity in ecosystems depends on the uptake of essential mineral (inorganic) nutrients by plants and their incorporation into living tissues. Nutrients in organic form, stored in living tissues, represent a significant proportion of the total nutrient pool in most ecosystems.

As these living tissues senescence, the nutrients are returned to the soil or sediments in the form of dead organic matter.

Various microbial decomposers transform the organic nutrients into a mineral form, a process called mineralization, and the nutrients are once again available to the plants for uptake and incorporation into new tissues. This process is called internal cycling and is an essential feature of all ecosystems. It represents a recycling of nutrients within the ecosystem.

The export of nutrients i.e., output from the ecosystem represents a loss that must be offset by inputs if a net decline is not to occur. Export can occur in a variety of ways, depending on the nature of the specific biogeochemical cycle.

Carbon is exported to the atmosphere in the form of CO2 via the process of respiration by all living organisms. Likewise, a variety of microbial and plant processes result in the transformation of organic and inorganic nutrients to a gaseous phase that can subsequently be transported from the ecosystem in the atmosphere.

Examples of these processes will be provided in the following sections, which examine specific biogeochemical cycles. A generalized model is shown in Fig. 5.25. The feedback systems as available in internal cycling balances the homeostasis of ecosystem.

Adding sodium produces material that is most efficient at converting heat to electricity

In the production of power, nearly two-thirds of energy input from fossil fuels is lost as waste heat. Industry is hungry for materials that can convert this heat to useful electricity, but a good thermoelectric material is hard to find.

Increasing the efficiency of thermoelectric materials is essential if they are to be used commercially. Northwestern University researchers now report that doping tin selenide with sodium boosts its performance as a thermoelectric material, pushing it toward usefulness. The doped material produces a significantly greater amount of electricity than the undoped material, given the same amount of heat input.

Details of the sodium-doped tin selenide—the most efficient thermoelectric material to date at producing electricity from waste heat—will be published Nov. 26 by the journal Science.

The Northwestern development could lead to new thermoelectric devices with potential applications in the automobile industry, glass- and brick-making factories, refineries, coal- and gas-fired power plants, and places where large combustion engines operate continuously (such as in large ships and tankers).

Most semiconducting materials, such as silicon, have only one conduction band to work with for doping, but tin selenide is unusual and has multiple bands the researchers took advantage of these bands. They showed they could use sodium to access these channels and send electrons quickly through the material, driving up the heat conversion efficiency.

"The secret to our material is that multiband doping produces enhanced electrical properties," said Mercouri G. Kanatzidis, an inorganic chemist who led the multidisciplinary team. "By doping multiple bands, we are able to multiply the positive effect. To increase the efficiency, we need the electrons to be as mobile as possible. Tin selenide provides us with a superhighway—it has at least four fast-moving lanes for hole carriers instead of one congested lane."

Kanatzidis, a Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, is a world leader in thermoelectric materials research. He is a corresponding author of the paper.

To produce a voltage, a good thermoelectric material needs to maintain a hot side—where the waste heat is, for example—while the other side remains cool. (A voltage can be harvested as power.) Less than two years ago, Kanatzidis and his team, with postdoctoral fellow Lidong Zhao as protagonist, identified tin selenide as a surprisingly good thermoelectric material it is a poor conductor of heat (much like wood)—a desirable property for a thermoelectric—while maintaining good electrical conductivity.

Kanatzidis' colleague Christopher M. Wolverton, a computational theorist, calculated the electronic structure of tin selenide. He found the electrical properties could be improved by adding a doping material.

"Tin selenide is very unusual, not only because of its exceedingly low thermal conductivity, but also because it has many conduction lanes," said Wolverton, a senior author of the paper and professor of materials science and engineering in the McCormick School of Engineering and Applied Science. "Our calculations said if the material could be doped, its thermal power and electrical conductivity would increase. But we didn't know what to use as a dopant."

Sodium was the first dopant the researchers tried, and it produced the results they were looking for. "Chris' computations opened our eyes to doping," Kanatzidis said. He and Zhao successfully grew crystals of the new doped material.

The researchers also were pleased to see that adding sodium did not affect the already very low thermal conductivity of the material. It stayed low, so the heat stays on one side of the thermoelectric material. Electrons like to be in a low-energy state, so they move from the hot (high-energy) side to the cool side. The hot side becomes positive, and the cool side becomes negative, creating a voltage.

"Previously, there was no obvious path for finding improved thermoelectrics," Wolverton said. "Now we have discovered a few useful knobs to turn as we develop new materials."

The efficiency of waste heat conversion in thermoelectrics is reflected by its "figure of merit," called ZT. In April 2014, the researchers reported that tin selenide exhibits a ZT of 2.6 at around 650 degrees Celsius. That was the highest ZT to date—a world record. But the undoped material produced that record-high ZT only at that temperature. (There is a ZT for every temperature.)

The new doped material produces high ZTs across a broad temperature range, from room temperature to 500 degrees Celsius. Thus, the average ZT of the doped material is much higher, resulting in higher conversion efficiency.

"Now we have record-high ZTs across a broad range of temperatures," Kanatzidis said. "The larger the temperature difference in a thermoelectric device, the greater the efficiency."


Life depends upon the building up and breaking down of biological molecules. Catalysts, in the form of proteins or RNA, play an important role by dramatically increasing the rate of a chemical transformation––without being consumed in the reaction. The regulatory role that catalysts play in complex biochemical cascades is one reason so many simultaneous chemical transformations can occur inside living cells in water at ambient conditions. For example, the 10‑enzyme catalytic breakdown and transformation of glucose to pyruvate in the glycolysis metabolic pathway.

Chemically Assemble Organic Compounds

Part of the reason that synthesis reactions (chemical assembly) can occur under such mild conditions as ambient temperature and pressure in water is because most often, they occur in a stepwise, enzyme‑mediated fashion, sipping or releasing small amounts of energy at each step. For example, the synthesis of glucose from carbon dioxide in the Calvin cycle is a 15‑step process, each step regulated by a different enzyme.

Transform Chemical Energy

Life’s chemistry runs on the transformation of energy stored in chemical bonds. For example, glucose is a major energy storage molecule in living systems because the oxidative breakdown of glucose into carbon dioxide and water releases energy. Animals, fungi, and bacteria store up to 30,000 units of glucose in a single unit of glycogen, a 3‑D structured molecule with branching chains of glucose molecules emanating from a protein core. When energy is needed for metabolic processes, glucose molecules are detached and oxidized.

Transform Radiant Energy (Light)

The sun is the ultimate source of energy for many living systems. The sun emits radiant energy, which is carried by light and other electromagnetic radiation as streams of photons. When radiant energy reaches a living system, two events can happen. The radiant energy can convert to heat, or living systems can convert it to chemical energy. The latter conversion is not simple, but is a multi‑step process starting when living systems such as algae, some bacteria, and plants capture photons. For example, a potato plant captures photons then converts the light energy into chemical energy through photosynthesis, storing the chemical energy underground as carbohydrates. The carbohydrates in turn feed other living systems.


Phylum Plantae (“plants”): Angiosperms, gymnosperms, green algae, and more

Plants have evolved by using special structures within their cells to harness energy directly from sunlight. There are currently over 350,000 known species of plants which include angiosperms (flowering trees and plants), gymnosperms (conifers, Gingkos, and others), ferns, hornworts, liverworts, mosses, and green algae. While most get energy through the process of photosynthesis, some are partially carnivores, feeding on the bodies of insects, and others are plant parasites, feeding entirely off of other plants. Plants reproduce through fruits, seeds, spores, and even asexually. They evolved around 500 million years ago and can now be found on every continent worldwide.


For the first half of Earth’s life to date, oxygen was all but absent from an atmosphere made mostly of nitrogen, carbon dioxide, and methane. The evolution of animals and life as we now know it owe everything to photosynthesis .

About 2.5 billion years ago, cyanobacteria —the first organisms that used sunlight and carbon dioxide to produce oxygen and sugars via photosynthesis—transformed our atmosphere. Later, algae evolved with this ability, and about 0.5 billion years ago, the first land plants sprouted.

Algae, plankton, and land plants now work together to keep our atmosphere full of oxygen.

The Strategy

Photosynthesis occurs in special plant cells called chloroplast s, which are the type of cells found in leaves. A single chloroplast is like a bag filled with the main ingredients needed for photosynthesis. It has water soaked up from the plant’s roots, atmospheric carbon dioxide absorbed by the leaves, and chlorophyll contained in folded, maze-like organelles called thylakoid s.

Chlorophyll is the true catalyst of photosynthesis. Cyanobacteria, plankton, and land plants all rely on this light-sensitive molecule to spark the process.

Chlorophyll molecules are so bad at absorbing green light that they reflect it like tiny mirrors, causing our eyes to see most leaves as green. It’s usually only in autumn, after chlorophyll degrades, that we peep those infinite shades of yellow and orange produced by carotenoid pigment s.

The process of photosynthesis in plants involves a series of steps and reactions that use sunlight, water, and carbon dioxide to produce sugars that the plant uses to grow. Oxygen is released from the leaves as a byproduct.

The Strategy

But chlorophyll’s superpower isn’t the ability to reflect green light—it’s the ability to absorb blue and red light like a sponge. The sun’s blue and red light energizes chlorophyll, causing it to lose electrons, which become mobile forms of chemical energy that powers plant growth. The chlorophyll replenishes its lost electrons not by drinking water but by splitting it apart and taking electrons from the hydrogen, leaving oxygen as a byproduct to be “exhaled”.

The electrons freed from chlorophyll need something to carry them to where they can be put to use, and two molecules ( ATP and NADPH ) work much like energy transport buckets. They bring the electrons to the space outside of the thylakoid folds but still inside the chloroplast “bag.” In this area, called the stroma , the energy brought by the molecular buckets forces carbon dioxide to combine with other molecules, forming glucose . After these reactions occur, the buckets—now empty of electrons—return to the thylakoid folds to receive another batch from sunlight-stimulated chlorophyll.

When plants have enough sunlight, water, and fertile soil, the photosynthesis cycle continues to churn out more and more glucose. Glucose is like food that plants use to build their bodies. They combine thousands of glucose molecules to make cellulose , the main component of their cell walls. The more cellulose they make, the more they grow.

The Potential

Nature, through photosynthesis, enables plants to convert the sun’s energy into a form that they and other living things can make use of. Plants transfer that energy directly to most other living things as food or as food for animals that other animals eat.

Humans also extract this energy indirectly from wood, or from plants that decayed millions of years ago into oil, coal, and natural gas. Burning these materials to provide electricity and heat has, through overexploitation, led to dire consequences that have upset the balance of life on Earth.

What if humans could harness this power in a different way? Imagine green chemistry that’s catalyzed by sunlight instead of having to mine for heavy metals like copper, tin, or platinum. Think of the potential that chemical processes requiring little heat have to reduce energy consumption. With a better understanding of photosynthesis, we may transform agriculture to consume less water and preserve more land for native plants and forests. As we continue to grapple with climate change, listening to what plants can teach us can shine a light down a greener path.

Examples of Autotrophs


Plants, with very few exceptions (such as the venus fly trap which can eat insects) are photoautotrophs. They produce sugars and other essential ingredients for life by using their pigments, such as chlorophyll, to capture photons and harness their energy. When plants are consumed by animals, animals are then able to use that energy and those organic materials for themselves.

Green Algae

Green algaes, which may be familiar to you as pond scum, are also photoautotrophs. Green algae may in fact bear a great resemblance to the first common life form on Earth – cyanobacteria, a green bacteria that grew in mats and began the process of turning Earth into a world with an oxygen atmosphere.

”Iron Bacteria” – Acidithiobacillus ferrooxidans

The bacterium Acidithiobacillus ferrooxidans obtains energy from ferrous iron. In the process, it converts the iron atoms from a molecular form where they cannot be dissolved in water to a molecular form where they can.

As a result, Acidithiobacillus ferrooxidans has been used to extract iron from ores that could not be extracted through conventional means.

The field of biohydrometallurgy is the study of using living organisms to obtain metals by dissolving them in water, where they can be further processed.

Pros and Cons of Fermentation

With oxygen, organisms can use aerobic cellular respiration to produce up to 36 molecules of ATP from just one molecule of glucose. Without oxygen, some human cells must use fermentation to produce ATP, and this process produces only two molecules of ATP per molecule of glucose. Although fermentation produces less ATP, it has the advantage of doing so very quickly. It allows your muscles, for example, to get the energy they need for short bursts of intense activity. Aerobic cellular respiration, in contrast, produces ATP more slowly.

Myth: lactic acid build-up can cause muscle fatigue and a burning sensation in muscles. The soreness is thought to be due to microscopic damage to the muscle fibers.

Reality: The statement about lactic acid causing the burn in the muscle has no solid experimental proof. Alternate hypotheses suggest that through the production of lactic acid, the internal pH of the muscle decreases, triggering contraction in muscle due to the activation of motor neurons.

What type of food might an organism that lives its entire life in interstellar space eat?

Unfortunately, the creature you describe is so far from reality and the laws of physics that we are pretty much 100% in the realm of magic.

First off, let's talk eyesight. The metaphor of a baseball at 0.1 m isn't quite good enough. Let's take a look at the most likely food source, a comet. Comets themselves are not light sources. They get their light from a nearby star. A absolute-best-case-scenario for our creature is a comet or asteroid at 110 AU, which is right on the edge of interstellar space. Unfortunately for our poor creature, at that distance comets have no tail. They only get a tail when they get into the inner solar system, so they look like small asteroids at a distance.

There's a decent number of 100 km in diameter asteroids (larger than that, they're extremely rare). Assuming it was a sphere, that'd give it a frontal surface area of about 8×10 9 m 2 . At a distance of 110 AU, that covers 3×10 &minus17 steradians. Doing the math with our own Sun's luminosity, that's about 9×10 8 watts of energy hitting the asteroid.

Now let's re-radiate that energy out, so that our creature can see it. You mention its ability to travel across the galaxy, which is thousands of light years wide. Let's give it an easy morsel: it's only 1 light year away (10 16 m). We can do some more math here, to determine that the intensity of the light 1 light year away is 8×10 &minus25 W/m 2 .

This is a tiny amount of light. Let's try to put a number on it. The most likely band to be looking at is the hydrogen gap, where hydrogen absorbs the least, 27 cm. At this frequency, a photon has about 10 &minus24 J. This means, on average, a 1.2-square meter detector will see about 1 photon per second from our comet! This creature is going to have to be massive! So massive that eating comets is going to be a pretty paltry diet.

That's also assuming a very nice cool detector that can pick up those photons. It's going to have to be near a whopper of a thruster. A single hydrogen atom at 50% the speed of light had to be given 2.3×10 &minus11 J of energy. Let's pretend the creature harnesses pure antimatter to store energy. That amount of energy would take the annihilation of 2.6×10 &minus28 kg of matter and antimatter to produce. Coincidentally, a hydrogen atom is 1.6×10 &minus27 kg, so basically for every 6 hydrogen atoms in your creature, you need a corresponding pair of hydrogen/anti-hydrogen atoms to be used as fuel. Given that you also want to slow down, this basically says the creature is physically impossible because its energy needs are too high, even given perfect hardware. (None of these "thrusters." You'd never make them efficient enough.)

The energy requirements of the bio luminescence is even more of a problem. And, of course, there's the issue that any light you see from a mate 10 light years away is now 10 years old.

Your best bet is to remove the insanely fast movement, ignore the eye sight, and do what Lostinfrance recommended: have it consume interstellar hydrogen. Of course, you'd still need to dip into planetary systems from time to time to get more materials besides hydrogen. There's not much else out there. I'd also make them live for a few billion years to solve the issue of finding a mate.

Give it the ability to generate a vast magnetic field, making it a living Bussard ramjet. Then it could scoop up and "eat" interstellar hydrogen. It wouldn't exactly have a digestive system, more a combustion chamber.

Unfortunately the poor thing might get hungry even so.

Note: I am not saying this is realistic, just that this is how I could see it working. Well, this is as close to what your thinking about you can get IMO while not being totally impossible.

Perhaps your creature evolved to go into a dormant, VERY energy-conservative state known as hibernation while in interstellar space. It goes from star system to star system at some fraction of the speed of light by slingshotting itself off of multiple gas giants in each system (most systems have 1 or two of them it seems). Your creature would not be able to survive solely on junk available in interstellar space because it is to sparse.

Once it reaches the Kuiper belt of a system, though, it would have (depending on size) enough minerals to survive and would come out of hibernation.

Animal itself would likely just float around with minimal control as to the direction it is going (so as to conserve energy). This could happen by the animal evolving some sort of biological thruster system to propel it in the desired direction. I imagine that this animal would gain minerals from asteroids and comets and gain energy by absorbing radiation/sunlight in a process similar to photosynthesis. Otherwise it would absorb what was needed from passing comets and asteroids and dispose of the junk in the universal waste-disposing system: crapping.

You can look at a Baleen Whale to get an idea of its behavior patterns. Baleen whales essentially swim around with their mouths open, swallowing anything useful that come in (plankton, small fish) and getting rid of everything else.

tldr: You need an ocean in space.

As many other answers have stated, this isn't within the realm of known physics. Accelerating anything substantial to .5c takes a ridiculous amount of energy, let alone something that does so with the biological equivalent of rocket engines. Forget thrusters and go with something more exotic like pushing on the quantum virtual vacuum. Now on to your real question. What to eat.

Whatever this creature's method of locomotion, it's going to need massive amounts of energy. Unfortunately for our friendly neighborhood space whales, space is big[citation needed] and there's not much in it[dubious-discuss]. In order to harvest the amount of energy required, it's going to take an entire ecosystem.

This makes an intuitive sense when you think about it. It would be impossible for only one type of creature to have evolved on Earth, every part of the planet depends on every other part to produce its food in some way, shape or form. Plants absorb energy from the sun and concentrate it, herbivores eat those plants, carnivores eat those herbivores, then ultimately microorganisms eat the carnivores when they die and supply nutrients the plants need to keep harvesting sunlight (if you cite this explanation for any formal discussion of biology, you have only yourself to blame). So we need a similar ecosystem in space to support your space whales.

You could have swarms of plankton-like creatures that cluster around stars and soak up sunlight, and maybe others that feed on raw materials in planets (probably gas giants) and asteroids. Then perhaps a chain of other creatures eat those and concentrate their energy, and these whales are the apex predator of the system (as @oberron mentioned). In fact, it's probably better to think of these as space sharks instead of whales, because no whale on Earth is capable of accelerating its massive bulk very quickly (that would take more energy than they're capable of harvesting from plankton alone). I'd also save the high-end acceleration for migratory purposes, when food runs low in one solar system they need to boost on over to another, risking their energy reserves on the bet that there's more food there. Once accelerated they could go into a sort of hibernation where they turn off most body functions until they get where they're going or sense food somewhere, and just coast along in the meantime.

The moral of the story is there isn't enough energy just floating around in space as we know it to make this possible, so you're going to have to flesh out your ecosystem to make it work in some plausible way. Time to create more creatures!

Let me start by looking at the rockets.

If it's capable of reaching a speed of c/2 - and then slowing back down so as not to have a very 'impacting' arrival, it needs to have a delta-V of c, which requires its fuel to be expelled at light speed. (Where does that energy come from?) And even then the half lightspeed feat will require ejecting exactly 100% of its mass (at light speed) by the time it has slowed down.

If you tone it down to reasonable levels, the key point remains energy management. All non-extinct forms of life do their energy management well. This thing is going to require immense levels of energy just for propulsion. So after you tone it down sufficiently, you're going to be looking at something that eats stars. Maybe not whole (how big are they supposed to be?), but the delicious stuff would be well below the surface. (Do they sun-dive for their food? See also the huge velocities things would have as they impact the sun, just from the sun's gravity.)

This brings thermodynamics into the picture, as they will need to tame the high heat levels of not just the dive/eating but keeping and digesting their food. Who needs bioluminescence anyway?

Alternatively it would need to eat through huge amounts of matter to extract fissionables. Or have a magic matter-to-energy conversion thing that would be quite desired by all intelligent space-faring species, to the point of hunting them whenever they were seen, unless they learned to make their own.

Also, why does it need that pressurization? It'll need a membrane sturdy enough to survive high-velocity dust and keep things from falling off. But beyond that, the pressure fluid is probably useless extra mass that will eat into its energy budget.

What if it's made wholly of antimatter? Its food source of regular matter would therefore be quite tasty indeed (and extremely energetic) provide it had a means to properly ingest it (some sort of magnetics) so it doesn't simply collide and burn. Its food? (plot twist time) the unfortunate craft of all the space-faring species' who discover a strange, moving object in interstellar space and send a big rocket to investigate.

This is a tuffy, Let's ditch most of the science and hit specific problems.

It can't eat in the normal way. There is just nothing to eat. Photosynthesis gives us a decent model, but stars are really far a part, a space turnip isn't going to make it much further from the sun then earth is. So let's look at what is more "available" then light. Gamma Radiation, X-Ray Radiation, and the like. So basically "Radiation" is a food source. It could work, but it wouldn't give very much energy.

It defecates I don't see this happening. It would have to "use" almost 100% of the energy that it collects. See the section on thrusters though.

It moves Well, ok, so long as it doesn't move much, sure why not. If it moves too much you have an energy problem again. I would say it would be ok to "spasm" every once in a long while.

It grows Sure, why not. The problem is growing takes more energy then maintaining. With such a rare food intake, that precious energy probably can't go too much to growing.

It ejects eggs, attracts mates, and has sex in interstellar space Unless your writing space whale porn, let this one go. For all known lifeforms, sexual reproduction is a energy intensive task. Even plants, and they let someone else do all the work. Super abstract, all the energy of making an egg and a sperm, then finding a mate, sharing it, and hatching it, that's quite a bit of waste. Have them produce a-sexually. It's "easier". Once they reach a certain size, they split. In this case the "mother" split would need to die in 90% of the cases. Only if it was really lucky would the mother bit get to live.

It has skin that pressurizes its insides so that its insides are pressurized even when the organism lives in the vacuum of space. Why, There is no need for this. In this odd lifeforms, it's insides don't need air-pressure. It can evolve ways around that.

It has thrusters on its back that it can eject fuel out of to change its velocity. This is another odd one. I think you might be better off with "farts to change direction" There is not a lot in space, so where are you going to get this fuel. Assuming that this thing eats "radiation" it's gonna need a lot of it. You can get some propulsion by "emitting radiation" but not as much as your going to need. Look to satellites' magnetic engines for your best, currently known bet, and do something like that.

It is capable of accelerating to 50% the speed of light relative to the rest of the galaxy in 3 months allowing it to cover astronomical distances in search of food and mates. First, that's horribly slow. That's 8 years between star systems. The good news is, that as long as you don't care about slowing down, I suppose it's doable. It can speed up really really slowly, absorbing the radiation of a star as it gets closer, smashing into it, destroying it, and absorbing some matter in the process. Then fart propel it's self in a minor coarse correction, leaving behind a decimated ruin or a solar system.

Its eyesight is so good that it can see an object the size of Saturn from as far as Earth as a human seeing a baseball at a distance of 0.1m. Yeah, that's pretty crappy on interstellar terms. Using the normal analogy of Sol to Alpha century when both are the size of grapefruit, you would need to see that grapefruit from across the US. The good news is that because it eats "radiation" it doesn't have to "see" just has to point it's self at the most tasty radiation it can. And because it only has minor fart propulsion, it's not going to get a bunch of choices.

It has bioluminescence that allows it to be seen by potential mates. Unless it can light up brighter then a star, no it doesn't. It simply won't work. You can make it shiny though as a side effect of absorbing the "radiation".

You would have a MASSIVE lifeform, that basically, breaks wind in a single direction, hoping to find enough "Radiation" to sustain it's self. It wouldn't be very smart, it doesn't have the energy for that. Every 200 billion years or so it would clone it's self, without slowing down mind you, let out a massive fart (of radiation) and change direction by 0.0000001 degrees.

The creature would need to live near forever, it would be HUGE and would wipe out any solar system it came near.

Which plant is the most effective at converting CO2 to Oxygen?

Photosynthetic efficiency is the proper term for this and it's actually measured as sunlight to biomass. The reason is because the same amount of CO2 + (other stuff 1 ) = O2 + (other stuff 1 ), so efficient is always 1-to-1 ratio if you measure CO2 to O2 conversion.

In any case, the most efficient plant is sugar cane at around 7%. However, plants are put to same by algae have efficiency rations of up to 30%.

1 I know "other stuff" this is not very scientifically accurate but I'm trying to simplify things.

The high photosynthetic efficiency of sugar cane is also a reason why it is commonly used to make ethanol.

I don't know if the % of light energy that falls on a leaf is the critical factor in practice.

Well it's hard to speculate on relevant criteria. I would suggest that algae is a huge leg up because it can easily create 100% surface coverage over a given area for a bare minimum of biomass- leaving much energy left over.

That is, if you want the bio-energy. The question of oxygen generation. probably someone thinking of a biodome space station. In which case algae will be the clear winner, given the very high surface-to-mass ratio, short life cycle, and overall simplicity. Photonic efficiency is just a bonus.

Are these also the fastest converters or is this another property?

What plant that can be grown indoors in a household is most effective? (Im guessing sugar cane won't flourish in pots.)

I was always told spider plants are good for this, but online the suggestion always seems to be mother in laws tongue and arecia palm

So theoretically what would produce more oxygen? The amazon or a sugar cane field the size of the amazon.

I took the post to mean efficiency as a ratio of "CO2 conversion per unit of time to plant biomass".

Here, trees would seem to be rather inefficient, due to a low proportion of their biomass being dedicated to photosynthesis, while ferns, mosses and grasses would be better.

Do you have any data on that ratio?

Thank you for not lumping plants and algae together.

Does anyone know whether light, traveling slower in water, causing its bending, refraction,and filtering effects prior to impacting algae, results in an easier, more focused, and larger area of worthwhile light impacting the algae, enabling a greater efficiency of photosynthesis, or if it's just some fucky biological thing that makes it more effective?

Follow up question: wouldn't a plant with a larger green surface area convert more CO2 to O2?

Does the efficiency measurement take into account the amount of carbon dioxide released as a byproduct of cellular respiration process?

As everyone should know, if they don't already, is that the same plants that produce oxygen during the day, produce carbon dioxide at night.

This said, the amount of carbon dioxide produced by the plant species should also be taken into account to calculate a "real" efficiency score.

I.E. - how much oxygen is produced subtracted by the about of carbon dioxide is produce

Theoretically, if Sugar Cane has a higher conversion ratio for CO2 to O2, but also has a higher conversion ratio from O2 to CO2, then it will balance out, maybe even make it less "efficient" then some other species of plant.