Biological Sciences
Energy Flow in Ecosystem
Energy flow in ecosystems refers to the movement of energy through the food chain, from producers to consumers and decomposers. Producers, such as plants, capture energy from the sun through photosynthesis, which is then passed on to herbivores and then to carnivores. Energy flow is unidirectional, with energy being lost as heat at each trophic level, ultimately driving the functioning of the ecosystem.
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12 Key excerpts on "Energy Flow in Ecosystem"
eBook - ePub- Allan M. Jones(Author)
- 2006(Publication Date)
- Routledge(Publisher)
Basic ecological concepts and processesKey concepts- The laws of thermodynamics determine the transfer of energy through an ecosystem.
- Energy flow through an ecosystem is a one-way process while other materials recycle on various timescales.
- Energy transfer is subject to a variety of factors and there are various measures of efficiency.
- The concept of trophic (feeding) levels, food chains and food webs is important for the understanding of energy transfer and loss in any ecosystem.
- Feeding relationships are fundamental to the organisation and function of biological communities.
- Every system has three main components: the autotrophic primary producers, the secondary producers (mainly the herbivores and carnivores) and the decomposers.
- The biosphere interacts with three main physical compartments: the hydrosphere (water), the lithosphere (land) and the atmosphere.
- Materials have biogeochemical cycles, the main ones being the water cycle, carbon cycle, oxygen cycle and the nutrient (particularly nitrogen, phosphorus and sulphur) cycles.
Despite the diversity of living forms and their habitats (outlined in Chapter 2 ), there are a number of fundamental concepts and processes that apply to all ecosystems and the interactions of their components. Any ecosystem is a collection of interdependent components (subsystems), each with its own defined boundary. Each ecosystem has two basic requirements for its successful functioning, namely- the acquisition, transformation and transfer of energy and
- the gathering and the recycling of the materials necessary for life.
By understanding how these systems function, environmental science is better able to understand and predict the impacts of human activities on such systems. This chapter presents an overview of the key processes involved.3.1 Energy in ecosystems Energy comes in many forms, such as heat, light, sound and electricity, and all have in common the capacity to do work. All forms of energy fall into one of two categories:
eBook - PDF- Mahua Basu, Xavier Savarimuthu, SJ(Authors)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
It is the amount of energy that is received and transferred from organism to organism in an ecosystem that modulates the ecosystem structure. Energy flow refers to the amount of energy transferred through the food chain up the nutrient/ trophic level. Energy flow is alternatively known as calorific flow since energy input or the energy entering the ecosystem is measured in joules or calories. Sun is the biggest source of energy. Energy left unutilized in the ecosystem is ultimately lost as heat. When one organism feeds on another organism, both energy and nutrients are transferred through the food chain. The surplus or the leftover energy in an ecosystem is then devoured by the decomposers. While nutrients are recycled through an ecosystem, energy is simply lost over time. Energy flow in any ecosystem commence with the autotrophs that would trap the energy from sun. Herbivores feed on these autotrophs to transform the energy within the plant into their usable form. The carnivores then feed on these herbivores to obtain their energy, lastly, other top C 1 - 100 cal/m 2 C 2 - 10 cal/m 2 C 3 - 1 cal/m 2 Upright pyramid in all ecosystem P - 10,000 cal/m 2 Figure 4.8: Pyramid of energy 123 Ecosystems carnivores prey on the lower level carnivores. In each such step, energy from one trophic level is transferred to the next higher trophic level and every time some amount of energy is lost in the form of heat into the environment. This happens because each one utilizes part of the energy they obtain from the other one for their sustenance. The top consumer receives the least amount of energy. Earth is constantly hit by the radiation coming out of the sun about 93 million miles far-off which provides energy not only to the air, water and land, but also to the objects capable of absorbing energy; in simple words, radiant energy is transformed to heat energy. The winds and water currents are caused by unequal heating; i.e.
eBook - ePub- Gordon Dickinson, Kevin Murphy(Authors)
- 2007(Publication Date)
- Routledge(Publisher)
The energy captured by the ecosystem is transferred through different levels of the trophic structure of an ecosystem by consumption and predation. Ultimately all biological energy is converted to heat via respiration. However, this conversion can be postponed when energy is stored in the form of biodeposits (e.g. coal, oil). Decomposition processes, in which ecosystem detritus is broken down by the micro- and macro-organisms which have specialised in the consumption of dead organic matter, play a crucial role in ecosystem functioning. The detrital subsystem illustrates well the interaction between energy and material systems.The starting point for the flow of energy through the ecosystem is usually sunlight. The subsequent efficiency of energy capture and transfer through succeeding trophic levels is shown in Box 3.4 .Energy pyramids, food webs and stable isotopes
Most of the available energy not lost as heat is used, at each trophic level of an ecosystem, to support the operation of metabolic pathways within the organisms dominating that level. Pyramid diagrams can be constructed to show the amount of energy (or biomass, or numbers of organisms, which are approximate indicators of energy content) tied up in the biota of the ecosystem at each level (see Figures 3.2a –c ). These relationships are important in appreciating the spatial and temporal patterns of distribution of organisms in ecosystems.For example, this approach may be used to model how much energy there is available, in a given ecosystem, to support producers and consumers at different places and times.Figure 3.2 Pyramid diagrams depicting trophic relationships in ecosystems. See Box 3.4 for explanation of P, C1, C2 and C3 trophic levels (a) pyramids of individuals per ha in a Kentucky bluegrass grassland ecosystem; (b) pyramid of biomass (kg per ha) in a Wisconsin lake freshwater ecosystem; (c) pyramid of energy: energy flow (kJ per m2 per year) through Silver Springs, Florida: a wetland ecosystemPyramid models illustrate clearly how successive levels within the food chain (from producers to herbivores, to carnivores) support each other. They give a clear indication of ‘why big fierce animals are rare’ (Colinvaux 1980). Such animals are at the top of the energy pyramid, and there is simply not enough energy available up there to support a large biomass, or number, of top-level carnivores. This is especially so for warm-blooded homiothermic carnivores, such as tigers (Panthera tigris) or orcas (killer whales: Orcinus orca), which have a very high energy demand compared with cold-blooded poikilothermic carnivorous animals such as crocodiles (e.g. the Nile crocodile, Crocodylus niloticus) or sharks (see Chapter 5 ). All else being equal (though in practice it never is) we would expect to see a marine ecosystem being able to support a higher biomass of great white sharks (Carcharodon carcharias
eBook - PDF- Samantha Fowler, Rebecca Roush, James Wise(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
The speed at which an ecosystem recovers equilibrium after being disturbed is called resilience. Ecosystem resistance and resilience are especially important when considering human impact. The nature of an ecosystem may change to such a degree that it can lose its resilience entirely. This process can lead to the complete destruction or irreversible altering of the ecosystem. Food Chains and Food Webs A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another; the levels in the food chain are producers, primary consumers, higher-level consumers, and finally decomposers. These levels are used to describe ecosystem structure and dynamics. There is a single path through a food chain. Each organism in a food chain occupies a specific trophic level (energy level), its position in the food chain or food web. In many ecosystems, the base, or foundation, of the food chain consists of photosynthetic organisms (plants or phytoplankton), which are called producers. The organisms that consume the producers are herbivores: the primary consumers. Secondary consumers are usually carnivores that eat the primary consumers. Tertiary consumers are carnivores that eat other carnivores. Higher-level consumers feed on the next lower trophic levels, and so on, up to the organisms at the top of the food chain: the apex consumers. In the Lake Ontario food chain, shown in Figure 20.4, the Chinook salmon is the apex consumer at the top of this food chain. Chapter 20 | Ecosystems and the Biosphere 531 Figure 20.4 These are the trophic levels of a food chain in Lake Ontario at the United States–Canada border. Energy and nutrients flow from photosynthetic green algae at the base to the top of the food chain: the Chinook salmon. (credit: modification of work by National Oceanic and Atmospheric Administration/NOAA) One major factor that limits the number of steps in a food chain is energy.
eBook - PDF- Harold Morowitz(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
We are thus able to make contact between thermodynamics and the study of energy flow in ecology. So far we have dealt with rather general considerations of radiant and chemical energy. Other terms in the internal energy such as charge transfer, surface energy, and osmotic work are of major importance in biology. In the next chapter we present some approaches used to deal with these topics. BILIOGRAPHY Krebs, H. A., and Kornberg, H. L., Energy Transformations in Living Matter. Springer, New York, 1957. A detailed review of the relation of intermediary metabolism to bioenergetics. Lehninger, A. L., Biochemistry. Worth Publ., New York, 1975. This very extensive textbook of biochemistry details the metabolic pathways involved in bio-energetics and discusses various aspects of the subject. Morowitz, H. J., Energy Flow in Biology, Academic Press, New York, 1968. Much of this chapter comes from Chapter IV of this work. Slobodkin, L. B., Growth and Regulation of Animal Populations. Holt, New York, 1961. Chapter 12 discusses the efficiency of predator-prey energy conversions. Watt, B. K., and Merrill, A. L., Composition of Foods. U.S. Dept. of Agriculture, Washington, D.C., 1963. Contains extensive data on heats of combustion of a wide variety of biological materials.
eBook - PDF- Jose Galizia Tundisi, Takako Matsumura Tundisi(Authors)
- 2012(Publication Date)
- CRC Press(Publisher)
All organisms living on the Earth thus depend on the organic matter produced by plants through the process of photosynthesis. Primary production is not only pho-tosynthesis, however; it also includes chemo-autotrophic processes. Two factors are important in the study of energy flow: the efficiency of the process at each trophic level, and the structure/composition of the food web. In each ecosystem the food web may vary greatly, and so it is more accurate to refer to the dynamic food web, which includes the various processes of selective feeding and quantification. Organisms and ecosystems find themselves in a thermodynamic equilibrium : the energy received by ecosystems and organisms is used for growth and maintenance, or is stored. Degraded energy refers to that energy which is dissipated in heat and excre-tion products. The quantitative aspects (efficiency of processes, growth rates, saturation levels of photosynthesis) and qualitative aspects (selective feeding, main trajectory of the food network) can be studied in laboratories under controlled conditions. Transferring laboratory studies to actual field conditions is one of the major problems for greater understanding of food networks and efficiencies in ecosystems. In recent years, the use of huge experimental tanks (mesocosms) has to some extent facilitated the under-standing of qualitative and quantitative synecological processes. However, for certain organisms, the very limitations imposed by the nature of these mesocosms can cause problems and alter results. A large part of the quantitative methods used to study energy flow in aquatic systems was developed and standardized for comparative use during the International Biological Programme, and the series of IBP manuals on various techniques are useful as a basic reference (Worthington, 1975; Golterman et al ., 1978; Vollenweider, 1969, 1974).
eBook - PDFEcology
Principles and Applications
- J. L. Chapman, M. J. Reiss(Authors)
- 1998(Publication Date)
- Cambridge University Press(Publisher)
TWELVE Energy transfer 12.1 Energy and disorder Living organisms are highly organised. In order to survive and maintain this internal order organisms need supplies of the relevant nutrients, a source of energy and the ability to create a large amount of disorder outside themselves. This last requirement may sound rather odd, but the second law of thermodynamics states that the amount of disorder in a closed system, such as the universe, increases with time. For organisms to create order, as they do when they make new cells, they need energy and/or the ability to create disorder outside themselves. Respiration both releases energy and creates disorder as relatively large molecules, such as glucose, are broken down to smaller and therefore less ordered molecules, i.e. carbon dioxide and water. The trophic levels at which species feed have been considered in Chapter 11, and Chapter 13 will look at how organisms obtain the nutrients they need. This chapter aims to look quantitatively at how organisms obtain their energy and how they pass energy up a food chain. Because the vast majority of primary production in the world is the result of photosynthesis rather than chemosynthesis, we will first examine the environmental factors that determine the amount of photosynthesis in different communities. We will then see whether there are any ecological rules governing the transfer, or movement, of this energy up a food web through the trophic levels. 12.2 Primary production in terrestrial communities When autotrophs photosynthesise, they turn carbon dioxide and water into larger structural molecules which allow the plant to increase in size. Gross primary productivity is a measure of the total amount of dry matter made by a plant in photosynthesis. It is measured in units of dry weight per unit area per unit time.
eBook - PDFEcology
From Ecosystem to Biosphere
- Christian Leveque(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
Ecological pyramids were popular in the 1960s, but they are now much less so among ecologists. 11.5. FOOD WEB ORGANIZATION The nature and intensity of trophic relationships established between species living in an ecosystem play a central role in ecological theories. It is through these networks of interactions that matter and energy circulate in the ecosystem. 11.5.1. Trophic levels In order to live and reproduce, living things need a source of energy. Some, such as autotrophic organisms, draw from the abiotic environment the minerals necessary to synthesize their own organic substance by means of light energy from solar radiation. These primary producers include all the chlorophyllian plants (algae, macrophytes) as well as bacteria and protists. Autotrophs serve to feed herbivorous consumers, which transform plant organic matter composed of carbohydrates into animal matter that is relatively richer in nitrogenous organic substances. Herbivores themselves serve as prey for other consumers, the carnivores. All the animals as well as fungi and bacteria that draw their energy by consuming living or detritic organic matter are heterotrophic organisms. Finally, decomposers are organisms that mineralize dead organic matter to transform it into simple minerals that can again be assimilated by plants. 11.5.2. Food chains and food webs Matter and energy circulate constantly from primary producers to and then carnivores. In drawing these links of dependence of animals that eat some organisms before being eaten by others, we obtain what is called a food chain or food web, which diagrammatically describes the flows of matter or energy between different trophic levels, from autotrophic producers to terminal consumers. These are caricatures of nature that describe in a simplified manner who eats whom (Pimm, 1982).
eBook - PDFThe Hudson
An Illustrated Guide to the Living River
- Stephen P. Stanne, Roger G. Panetta, Brian E. Forist, Maija Liisa Niemisto(Authors)
- 2021(Publication Date)
- Rutgers University Press(Publisher)
They use budgets to track and describe the flow of energy and vital nutrients in ecosystems, the functional units en- compassing interacting living organisms and all aspects of the physical environment inhabited by these organisms. The study of relationships be- tween living organisms and their environments constitutes the science of ecology. In his classic Fundamentals of Ecology , Eugene Odum noted that the words “ecology” and “economics” have the same root—the Greek word oikos, meaning “house.” He pointed out that “eco- nomics deals with financial housekeeping and ecology deals with environmental housekeeping.” Perhaps the most basic item in a household bud- get is food, and the most important task of human housekeeping is keeping oneself or one’s family fed. The flow of food is also key to ecological house- keeping, and it is a good place to start discussion of Hudson River ecology. Food Chains: A Deli-Style Approach On a cloudless September morning the rising sun clears the hills along the Hudson’s eastern shore and shines down on the shallows of the Green Energy Flow and Nutrient Cycles in the Hudson | 17 Flat just north of Saugerties. Its rays light a bed of wild celery, the plant’s long, tape-like leaves gen- tly undulating in the current. On many leaves are green, hairlike growths of algae. As sunlight enters each algal cell, the cell’s photosynthetic machinery starts humming, converting light energy into the chemical energy of sugar and other molecules that build and maintain protoplasm. Nosing along one of the wild celery leaves is a half-inch long amphipod, browsing on the algae, digesting algal protoplasm, and converting it into animal tissue. The amphipod’s algal food also fuels muscular activity, as when the creature launches itself off the leaf, swimming away from the bright sun and toward a thicker, more shadowy patch of vegetation.
eBook - PDF- Fred D. Singer(Author)
- 2016(Publication Date)
- Cambridge University Press(Publisher)
486 Chapter 19 Ecosystem structure and energy fl ow eaten. Dead organisms and their products then enter the detrital food chain ( Figure 19.9 ). There are several important features of the detrital chain. First, detritivores are both competing with and preying upon decom-posers when they consume detritus. Second, both detritivores and decomposers are mortal, and thus add to the pool of dead organic matter if they die without being eaten. Lastly, detriti-vores that are eaten by consumers form an important linkage with the linear food chain described in Figure 19.8 . One feature shared by both food chains is that energy is lost on several paths as it moves through the ecosystem. Energy loss with each transfer A great deal of energy is lost to cellular respiration at all levels, with producers generally losing less than consumers. Energy is also lost in the linear food chain because much of the production is simply not consumed, and thus passes to the detrital chain. This can happen at any level; for example, not all of the herbivores (primary consumers) are eaten by secondary consumers, and their dead tissues pass to the detrital food chain. In addition, not all ingested organic matter can be used by consumers and is egested as feces, also passing on to the detrital chain (see Figure 19.9 ). As a consequence of all of these losses, there is much less energy available to each higher trophic level within an ecosystem. Energy and biomass pyramids The amount of energy available to one trophic level is a small fraction of what is available to the trophic level below it. This relationship, the trophic ef fi ciency , is equal to ( P N / P N 1 ) 100, where P N is equal to the production of one trophic level, and P N 1 is equal to the production of the trophic level below it. In a very early study, Howard Odum ( 1957 ), Eugene Odum ’ s brother and colleague, explored the freshwater ecosystem at the headwaters of Silver Springs, Florida.
eBook - PDF- David Pimentel(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Chapter 1 Energy Flow in the Food System DAVID PIMENTEL Department of Entomology Cornell University Ithaca, New York I. Introduction 1 II. Solar Energy III. Energy Flow in Hunter-Gatherer Societies 3 IV. Human-Powered Crop Production V. Draft Animal-Powered Crop Production VI. Mechanized Crop Production VII. Alternatives for Reducing Energy Inputs in Crop Production 10 A. Soil Nutrients and Alternative Fertilizers 10 B. Substitute Cultural Practices 12 C. Alternate Pest Control 3 D. Solar Crop Drying 4 E. Irrigation Water 4 VIII. Livestock Production 5 IX. Alternative Diets 7 X. Food Processing and Packaging 19 XI. Food Transport 21 XII. Preparing Food for Consumption 22 References 23 I. INTRODUCTION The ecological system of which man is a part is fundamentally a network of energy and mineral flows. Solar energy as well as plants that capture solar energy for use by the biological system and by man are essential to humans and to the ecosystem as a whole. At the same time, elements and minerals such as carbon, hydrogen, oxygen, nitrogen, phosphorous, potassium, and calcium provide the essential chemical structure of the diverse biological system of animals and plants. Basic to the survival of humans, other organisms, and plants are adequate supplies of food and water; these are both directly and indirectly related to the flow of energy and minerals through the ecosystem. To this end, the ecological system has evolved elaborate ways to conserve and recycle mineral resources. For many centuries man obtained his food like other animals, that is, as a hunter-gatherer. During this early period he was completely dependent on solar 1 FOOD A N D ENERGY RESOURCES Copyright © 1984 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-556560-7 2 David Pimentel energy. Nearly 500,000 years elapsed before man discovered fire and used wood as an energy source.
eBook - PDFThe Environment
Science, Issues, and Solutions
- Mohan K. Wali, Fatih Evrendilek, M. Siobhan Fennessy(Authors)
- 2009(Publication Date)
- CRC Press(Publisher)
115 Topics Solar Energy—the Driving Variable Laws of Thermodynamics Terrestrial Primary Productivity Photosynthetic Pathways Ecological Controls on Primary Productivity Aquatic Primary Productivity Secondary Productivity Bioaccumulation through Food Webs 7 Energy Flows and Ecosystem Productivity Solar Energy—the Driving Variable Thus far, we have studied the ingredients of life and where and under what conditions they operate. We now turn our attention to what drives the systems that produce the amazing diversity of life as we see it. The sun, directly and indirectly, sustains all life systems and drives all life processes. Those who model ecological systems refer to this energy as the “driving variable.” The energy reaching the Earth from sunlight, or solar energy, is captured and converted into chemical energy (photochemical energy) or into heat (thermal energy). The photochemical energy is captured by green plants, which use it to convert simple mole-cules (carbon dioxide, water, minerals) into complex ones such as carbohydrates, proteins, fats, and other compounds. The thermal energy warms up the earth, drives the water cycle, and provides currents of air and water. Regardless of the circumstances, all forms of energy continually move from something warmer (high-quality energy) to something cooler (low-quality energy)—never the reverse. The sunlight, or radiation, is thus continuously captured, con-verted, and reconverted, with changes brought about by a flow of energy. The science of energy transfer and transformation is thermodynamics. Thermodynamically, there are three types of systems: (1) isolated (or adiabatic) systems that can exchange neither energy nor matter with their surroundings, (2) closed sys-tems that can exchange energy but not matter, and (3) open systems that can exchange both energy and matter (von Bertalanffy 1950). The Earth is a closed system (see Figure 7.1), but its ecosystems are open systems.
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