In an ecological system, energy flows from one organism to another through the process of predation, where one organism consumes another. The transfer of energy from one organism to another through predation is a crucial component of the flow of energy through an ecosystem.
At the base of the energy pyramid are producers, which are organisms that produce their own energy through photosynthesis or chemosynthesis. Producers, such as plants, algae, and some bacteria, convert sunlight or chemical energy into organic matter, which they use to fuel their own growth and reproduction.
Primary consumers, also known as herbivores, are organisms that feed on producers. They obtain energy by consuming plants or algae. Secondary consumers, or carnivores, are organisms that feed on primary consumers. Tertiary consumers, or top carnivores, are organisms that feed on secondary consumers.
As energy is transferred from one organism to another through the food chain, some energy is lost in the form of heat. This is known as the 10% rule, which states that only about 10% of the energy consumed by one trophic level is passed on to the next.
Energy flow through an ecosystem is an important factor in determining the health and productivity of the ecosystem. The flow of energy through an ecosystem can be disrupted by factors such as habitat destruction, pollution, and climate change, which can have negative impacts on the species that depend on it.
The simple definition of energy is the capacity to do work. In physical science, we have studied basically two laws for energy: first law of thermodynamics and second law of thermodynamics.
Credit: Arild Vågen, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons
Application of the Laws of Thermodynamics in Ecological Ecosystems
The first law of thermodynamics, also known as the law of conservation of energy, states that energy can be converted from one form to another but is neither created nor destroyed. For example, light energy from the sun can be converted into heat or potential energy from food, but none of it is destroyed. The second law of thermodynamics, also known as the law of entropy, states that no process involving an energy transformation will spontaneously occur unless there is a degradation of energy from a concentrated form into a dispersed form. For example, a hot object spontaneously disperses its heat into cooler surroundings. The essential characteristics of thermodynamics are possessed by the organisms, ecosystems, and the entire ecosphere. The organisms and ecosystems are open and non-equilibrium thermodynamic systems that continuously exchange energy and matter with the environment to decrease internal entropy but increase external entropy.
- The light energy is transformed within the ecological systems as only a tiny portion of the light energy from the sun is converted into food energy by the plants through photosynthesis, and the rest passes out of the plant, the ecosystem, and the ecosphere.
- The concentrated form of energy (food energy stored in plants) is always less than the dispersed form of energy (solar rays) because of the heat dispersal during the conversion process.
- The light energy absorbed by the earth’s surface is balanced by the heat energy emitted by the earth’s surface as invisible heat radiation.
- The first law of thermodynamics can be explained as the light energy absorbed by the land and water on the earth’s surface, which causes hot and cold areas by conversion of light energy into heat energy. Then, it leads to the flow of air, i.e., conversion of heat energy into kinetic energy, which drives the windmills and performs work such as the pumping of water against the force of gravity, then the kinetic energy gets converted into potential energy.
- The second law of thermodynamics can be explained as the light energy produced by the sun gets evenly distributed in the solar system in the form of heat energy which results in an ultimately dispersed state. This degradation process is found to be also called “the running down of the solar system’.
- The food energy produced by the plants through the photosynthesis process represents potential energy which, when consumed by the animals, gets converted from a state of high-quality power to a form of low quality. In this way, the biological world obtains its potential chemical energy of food from the organic substances produced by the photosynthesis of plants or the chemosynthesis of microorganisms. The animals then convert a large of the consumed chemical potential power of food into heat energy and enable a small part of it as the chemical potential energy of new cytoplasm. When the energy is transferred from one organism into another, a larger part of the energy is degraded into heat. In this process, the entropy is not all negative.
- In an ecosystem, the respiration of the highly ordered biomass is known as the ‘dissipative structure’ according to the non-equilibrium hypothesis.
- The transfer of energy from one food chain to another in an ecosystem is known as “energy flow,” which is one way and according to the entropy law.
- Energy is a standard measure for all ecosystems, whether natural or designed by humans.
Units of energy
There are two basic units of energy quantity: potential energy units (independent of time) and power or rate units (energy-time units):
The units of potential energy are calorie or gram-calorie (cal or gcal), kilocalorie or kilogram-calorie (kcal), British thermal unit (BTU), joule (J), foot-pound and kilowatt-hour (KWh).
The units of power are watt (W) and horsepower (hp).
Solar Energy (Radiation) and the Ecosystem
Solar energy drives all biological and ecological systems. The solar radiation emitted by the sun consists of three components: visible light and two invisible components: shorter wave ultraviolet light and more extended wave infrared light. The solar radiation reaching the earth’s surface comprises about 10% ultraviolet, 45% visible, and 45% infrared light.
On the earth’s surface, only a minimal amount of visible light is absorbed by plants for photosynthesis which they convert into more concentrated energy of organic matter to be utilized by the biotic components of the ecosystem. Rest components of the sunlight pass throughout the ionosphere, atmosphere, clouds, water, vegetation, etc.
The solar radiation reaching the earth’s surface is in the middle range of the spectrum from near-infrared to ultraviolet.
The vegetation absorbs the blue and red visible light and far infrared light strongly, the green light less strongly, and the near-infrared light very weakly.
The vegetation reflects the green and near-infrared light whose spectral bands are used by ecologists in aerial and satellite remote sensing and photography to study the patterns of natural vegetation, crop condition, presence of diseased plants, and disturbed landscapes.
The short-wave ultraviolet radiation (less than 0.3 micrometers) is stopped by the ozone layers in the outer atmosphere. “Ozone holes” is a popular name denoting the damage to the protective ozone layer caused due to the chemical degradation by chlorofluorocarbons resulting in an increased risk of skin cancer. Thus, ozone layer depletion has become a matter of great concern.
At a temperature above absolute zero, thermal radiation is emitted by any surface or object of the environment, like soil, water, vegetation, clouds, etc. They radiate a significant amount of heat energy downward into the ecosystems. Due to this, the temperature on a cloudy winter night often remains higher than on a clear night.
The biomass absorbs more thermal radiation than solar radiation, which causes daily variation and is ecologically significant. Due to this, in deserts or alpine Tundra, the daytime fluctuation is significantly higher than the nighttime fluctuation. In contrast, in deep water or the interior of a tropical forest, the total radiation energy can remain constant during the 24-hour period.
ü In mountainous or hilly countries like Nepal, Bhutan, China, India, etc., the south-facing slopes receive more solar radiation than the north-facing slopes, resulting in a remarkable difference in the microclimate and distribution of vegetation pattern.
The energy dissipations of solar radiation into the biosphere is comprised of reflected energy (30%), direct conversion to heat (46%), evaporation precipitation energy (23%), wind, waves, and currents energy (0.2%), and energy for photosynthesis (0.8%).
The components of solar radiation are measured with the help of solarimeters. The instruments that are used to measure the total fluctuation of energy at all wavelengths are known as radiometers. There are two surfaces in the net radiometer: upward and downward which records the difference between the solar and thermal energy fluxes.
Productivity of the Ecosystem
The primary productivity of an ecological system can be understood as the rate at which the radiant energy is converted to organic substances by the photosynthetic and chemosynthetic activity of producers like green plants and microorganisms. It comprises of the four successive steps explained as follows:
- Gross primary productivity (GPP): It is the total rate of photosynthesis so also known as ‘total photosynthesis’ which includes the organic matter used up in the respiration during the period of measurement.
- Net primary productivity (NPP): It is also known as ‘net assimilation’ as it is the rate of storage of organic matter in plant tissues that exceeds the respiratory use by the plants during measurement period. The relation can be mathematically presented as:
Gross primary productivity = Net primary productivity + Amount of Plant Respiration
i.e. GPP = NPP + R
- Net community productivity: It is the rate of storage of organic matter not used by the heterotrophs during the period of growing season or a year. The relation can be mathematically presented as:
Net community productivity = Net primary productivity – Heterotrophic consumption
- Secondary productivity: It is the rate of energy storage at consumer levels. The secondary productivity cannot be divided into gross and net amounts as the consumers consume the food materials already produced with respiratory use and transport the food energy to different tissues by one overall process. The total energy flow of the heterotrophs (consumers) is analogous to the gross primary productivity, therefore, in the case of heterotrophs, the total energy flow is known as assimilation not production.
Measurement of Primary Production
The best method of estimating primary production is a measurement of gaseous exchange- oxygen production and carbon dioxide uptake. Measuring gaseous exchange is most easily done, whereas much more difficult in water. The daily changes in oxygen concentration can be measured in standing water like ponds, lakes, and oceans to estimate both gross and net production. The diurnal changes in oxygen concentration can be measured in flowing water by upstream and downstream methods. In marine environments, the changes in carbon dioxide are measured by using the radioactive isotope of carbon. Mostly, the measurement of the productivity of land vegetation is done by estimation of net production obtained by summing annual leaf, trunk, and root growth.
Similarly, the primary production of large landscapes, regions, and around the globe are very closely estimated by combining remote sensing of the color of the landscape by satellite with “ground truth” measurements. The bright or dark green color of the terrestrial landscape or water indicates very productive ecosystems. The yellow-green color of the land indicates a moderate level of productivity, whereas the brown color indicates a very low level of productivity, and the clear blue color of the water indicates a low level of productivity. The quantitative values of productivity are obtained by matching the color with local quantitative measurements on the surface. Aerial or satellite infrared photography has also been found to be very effective for the measurement of productivity. The brighter infrared light indicated a more productive landscape. In this, too, the quantitative values of productivity are obtained by calibrating the remote sensing with local quantitative measurements on the ground.
Energy flow or Energy Subsidy
The rate of primary production becomes high in both natural and cultivated ecosystems when the physical factors like water, nutrients and climate are favorable and the auxiliary energy from outside the system reduces maintenance costs. The auxiliary energy can be any such secondary energy that supplements the sun and allows the plants to store and pass on more substances produced by photosynthesis. The examples of energy subsidies are wind and rain in a rainforest, tidal energy in an estuary, fossil fuel used in the cultivation of crops, etc. The energy subsidy like tides help in bringing nutrients to marsh grass and food to oysters as well as taking away waste products which helps the organisms from saving their energy from these works and use more of their production for growth.
Ecological Pyramids
Ecological Pyramids can be defined as the relationship between numbers, biomass, and energy flow (metabolism) at the biotic community level, which is shown graphically. In ecological pyramids, the first or producer trophic level forms the base, and the successive trophic levels include the layers.
The Pyramid of Numbers is inverted, where the individual producers are more prominent in number than the average consumers, like in temperate deciduous forests. The Pyramid of Biomass is also inverted, where the respective producers are smaller in number than the average consumers, like in aquatic communities dominated by planktonic algae. Finally, the Pyramid of Energy is always upright in shape.
The ecological rule says that the Pyramid of Numbers mainly promotes the importance of tiny organisms, whereas the Pyramid of Biomass mainly promotes the importance of large organisms. In comparison to both, the energy flow gives a more suitable index for comparison of all the components of the ecosystem.
A Universal Energy Flow Model
The universal energy flow model applies to all the living components of the ecosystem, like plants, animals, microorganisms, individuals, populations, or trophic groups. These models depict food chains or the bioenergetics of an entire ecosystem.
Two methods can use the universal energy flow model:
- This model might be helpful to represent a species population, in which the appropriate energy inputs and links with the other species would be shown as a standard species-oriented food web illustration.
- This model might be helpful to represent a discrete energy level in which the biomass and energy channels illustrate all or part of many populations supported by the same energy source. For example, foxes obtain a part of their food by eating plants and fruits, whereas another part is by eating small herbivorous small mammals like rabbits and field mice
The energy of the food chains and food webs
The foundations of science of ecological energetics was laid by Lindemann in 1942. The concept of food chains and food webs was explained by him considering the efficiency of transfer between the trophic levels- from incident radiation received by a community through its capture by green plants in photosynthesis to its use by herbivores, carnivores and decomposers.
The simple meaning of food chain is ‘to eat and to be eaten’. In broad sense, food chain can be defined as the transfer of food energy from its source in the plants or autotrophs through a series of organisms that consume and are consumed. At each transfer of food energy, a high proportion of the potential energy is lost in the form of heat. Thus, greater amount of energy is available to the population if the food chain is shorter or if the organism is nearer to the producer trophic level. When the quantity of energy declines with each transfer, the quality or concentration of the energy that is transferred increases. There are basically two types of food chain: the grazing food chain and the detritus food chain.
- The grazing food chain starts from a green plant base, goes to grazing herbivores (plant eaters) and then to carnivores (animal eaters).
- The detritus food chain starts from nonliving organic matter to micro-organisms and then to detritivores and their predators.
Simply, food web is known as the interconnecting pattern of the food chains in an ecosystem. In the natural communities, the green plants occupy the first level (the producer trophic level), the herbivores occupy the second level (the primary consumer trophic level), the primary carnivores occupy the third level (the second consumer trophic level), and the secondary consumers occupy the fourth level (the tertiary consumer trophic level). A given species population can occupy one or more trophic levels depending on the source of the energy absorbed.
Frequently Asked Questions on Energy flow in Ecological System
How does energy flow in an ecosystem?
Energy flow occurs in an ecosystem in a single direction i.e. unidirectional. The organisms of one trophic level (energy level) pass their energy to organisms of next trophic level. The cycling of energy and nutrients has been maintaining the ecosystem. Firstly, the solar energy is used by the plants to produce food energy. The food energy produced by the producers is passed to the consumers, scavengers and decomposers.
What is the flow of energy in an ecosystem called?
The flow of energy in an ecosystem is called food chain. Energy flow occurs through an ecosystem in only direction from one trophic level to another trophic level. The organisms use most of their energy in the trophic levels. The organism utilize the energy for growth, locomotion, heat and reproduction.
What is energy flow explain with diagram?
Energy flows through different trophic levels in an ecosystem. In the first trophic level, the primary producers like green plants utilize the solar energy from the sun to produce food energy in the form of organic materials by the process of photosynthesis. In the second trophic level, the herbivores consume the plants and plant products.
How does energy move through the environment?
Energy moves through different trophic levels in the environment. At first trophic level, the solar energy is taken up by the producers or autotrophs to prepare food. So, the ultimate source of energy is the sun in all ecosystems except deep sea hydrothermal ecosystem. Among the total light rays incident by the sun, not whole is utilized but only 50% is used up and rest is reflected back into the space by the earth’s atmosphere. Photosynthetically Active Radiation (PAR) is the effective radiation in which the sunlight is absorbed maximum and it is active photosynthetically. Among the 50 % PAR, only 2-10 % is utilized which means that very less energy of the sun is required to drive the photosynthesis process. Thus, the solar energy is never a limiting factor in the ecosystem because only less amount of solar energy is required for the life processes.
Energy moves in the ecosystem through food chain and food web. The producers i.e. green plants produce their own food by photosynthesis. The primary consumers at the second trophic level feed upon the producers as they are herbivores which feed upon grasses and green plants only for energy. The secondary consumers are carnivores at the third trophic level which feed upon the primary consumers to derive energy. The tertiary consumers are top carnivores representing the higher trophic level which feed upon the secondary consumers. Similarly, in the aquatic food chain, the phytoplanktons are producers which are eaten up by the zooplanktons (primary consumers or herbivores). The zooplanktons are eaten up by the small fishes (carnivores or secondary consumers) which are again eaten up by the large fishes (top carnivores or tertiary consumers). Therefore, there is a unidirectional flow of energy from producer to consumer to primary consumers to secondary consumers to tertiary consumers. In this way, the different species of plants and animals are linked to one another through food chains. In this process, the amount of energy transfer gradually decreases. In the detritus food chain, the decomposers or saprophytes like fungi, bacteria, molds, worms, etc. decompose or break down the dead plants and animals in the soil which becomes nutrients for the soil and it is taken up by the plants for their growth. In this way, the energy never finishes or gets lost in the ecosystem but energy flows or transfers from one trophic level to another.
The interlocking pattern or interconnection of food chains is known as food webs. For example, a bird eats leaves and plant parts behaving as an herbivore whereas it also eats insects behaving as a carnivore. Similarly, an herbivore (E.g.: goat) is taken by the carnivores or top carnivores or man for food energy. Here, the bird and goat are participating in two different trophic levels of food chains at the same time forming a food web.
The standing crop (dry weight) is the total number of biomass at each trophic level. The number of trophic level is limited in each food chain because only 10 % of energy is transferred from one trophic level to another and 90% of the energy is lost during the transfer. (Lindeman’s 10 percent law)
How important is the energy flow of an ecosystem?
The energy flow is important to an ecosystem due to the following reasons:
i. It helps to maintain balance in all the types of ecosystem.
ii. The producers are able to synthesize their food only in the presence of the light energy from the ultimate source i.e. the sun.
iii. The herbivores cannot live without obtaining food energy from the producers.
iv. The carnivores get energy by feeding upon the herbivores.
v. The top carnivores obtain food energy by feeding upon the carnivores.
vi. Due to the detritus food chain, the energy is transferred from the dead and decaying organisms to the plants through the medium of nutrient rich soil.
Why are plants important to the energy flow in an ecosystem?
Plants are important to the energy flow in an ecosystem as they belong to the first trophic level in the food chain and ecological process. The plants synthesize their own food with the help of sunlight as a result of which, they are able to serve as a food source to the plant-eating herbivores.
What is energy flow and its importance?
Energy flow is the flow of energy through living organisms in an ecosystem being transferred through different trophic levels. Its importance is maintenance of ecological balance. The producers photosynthesize their food energy in the presence of sunlight. They store some part of that energy in their plant body whereas utilize the remaining part for their growth and development. Later, they are consumed by the herbivores, then that energy is passed on to carnivores and finally to the top carnivores.
What is energy flow model?
The energy flow model was proposed by Lindeman (1942) assuming that plants and animals can be arranged into the trophic levels and there is input and also loss of energy at each trophic level. The law of thermodynamics applies in the energy flow model for both plants and animals.
How do humans affect energy flow in ecosystems?
Humans affect energy flow in ecosystems by modification of the natural land into urban city areas, resulting in the degradation of habitat of flora and fauna, as a whole biodiversity. When resources are scarce, the particular resource-dependent species cannot reside for long in that ecosystem, either it dies or migrate to new places where it can find its basic resources for life. This disturbs the ecological balance.
What is energy flow and transfer?
Energy flow and transfer is the movement of energy along the food chain from one trophic level to another. The other name for energy flow is calorific flow.
Why energy flow through an ecosystem is one way?
The energy flow through an ecosystem is one way because the transfer of energy in the form of organic food energy starts from producers to consumer to primary consumers to secondary consumers to tertiary consumers i.e. in a unidirectional pattern.
How does energy move through an ecosystem quizlet?
The energy move through an ecosystem in one way pattern. The plants make their food utilizing sunlight. The herbivores consume the plants and obtain energy. The carnivores get energy by feeding upon the herbivores. The top carnivores obtain food energy by consumption of the carnivores. In this way, the energy flows out through an ecosystem.
How do humans affect the ecosystems?
Humans affect the ecosystems by their activities like rapid deforestation, over exploitation of natural resources by increasing human population, pollution of land, water and air, construction activities hampering the biota and the ecosystems, etc. Human activities badly affect the ecosystem by disturbing the food chain, biogeochemical cycles and ecological balance. The humans clear off the forests and grasslands in the name of development, enhancement of agricultural land, construction of buildings and factories, etc
Are humans important to the ecosystem?
Humans are important to the ecosystem as they are the intelligent creatures on the earth who can play a vital role to protect and conserve the threatened biodiversity. The proper utilization of natural resources is also a must for the proper functioning of the ecosystem. This can be done by the human beings. The moderate level of human disturbances can play an important role in the ecological successions.
How human activities destroy the ecosystem?
Human activities destroy the ecosystem as mentioned in the following points:
The overpopulation growth increases the act of rapid deforestation to fulfill the demand of expansion of human settlements, agricultural land, factories and basic infrastructures of development like education, health, transportation facilities, road, drinking water, etc.
The humans overexploit the natural resources which may lead to the vulnerability of resources and also severe impact on the biota and ecosystem due to the absence or scarcity of particular resources.
The rapid urbanization, industrialization and modernization results in the increasing pollution of air, water, soil and land. The air becomes polluted with the smoke and greenhouse gases emitted by the increasing number of vehicles, fossil fuel burning and industries. The water becomes polluted by the drainage and sewage from households, garbage dumped carelessly on land carried to the river, streams by surface runoff of rainwater, toxic chemicals from industries, etc. This severely affects the aquatic ecosystem and the inhabitant aquatic flora and fauna. The land becomes polluted with the overuse of chemical fertilizers, pesticides and insecticides used in the agricultural land. Solid wastes coming out from residents, hotels, hospitals, factories, etc. become a big hazard to the land ecosystem. The noise pollution emitted by construction works, human recreational activities, etc. also becomes a great health problem.
Due to the over deforestation, the biodiversity decreases and the valuable species of wildlife lose their habitat. This drives them to the danger of extinction.
The increasing rate of pollution has been leading to over greenhouse effect and ozone layer depletion. As a result, the climate change and global warming have become a serious issue in the present world.
What are the two general principles of energy flow?
The two general principles of energy flow are:
a) The food chains are short and in each food chain, the trophic levels are limited as the loss of energy is progressively higher for higher trophic levels.
b) The living organisms at progressively higher trophic levels receive energy from more than one source. So, the higher trophic levels are found to be less distinct than the lower trophic levels.
Why is energy 90 lost?
Energy 90 lost means that 90% of energy is lost during the transfer of organic food energy from one trophic level to the next higher trophic level.
What is definition of energy?
Energy is what helps the ecosystem exist and function properly. Energy enters in all the ecosystems as light and is gradually utilized and lost back into the environment in the form of heat.
Which is the largest ecosystem on earth?
Hydrosphere is the largest ecosystem on earth as it covers around 71 % of the earth’s surface.
What happens to energy and matter in an ecosystem?
Energy and matter flow or transfer from one trophic level to another in an ecosystem. The nutrient energy and living matter are transferred from the producers to the consumers (primary to secondary to tertiary) and then decomposed by the decomposers. In this way, the nutrient energy and organic matter mix with the soil which is taken up by the plants and the cycle continues.
Which way does energy flow and how does eating an organism result in energy transfer?
Energy flows is unidirectional i.e. follows single pattern. Eating an organism results in energy transfer as the primary consumers or herbivores obtain nutrient energy from the plants, then, it is transferred progressively to the secondary consumers and tertiary consumers.
How do you transfer energy?
Energy can be transferred by the radiation and mechanical action. For example, the plants obtain energy for photosynthesis by solar radiation. The herbivores obtain food from plants by mechanical breakdown of food and so do the consumers.
How do you make an energy flow diagram?
Solar Energy →Producer→ Primary consumer → Secondary consumers
↓
Producer ← Nutrient energy ←Decomposers ←Top Carnivores
How is energy flow through an ecosystem related to trophic structure?
Energy flow through an ecosystem is related to trophic structure as in the ecosystem, energy flow occurs from the sun to the first trophic level (producers), then to the second trophic level (primary consumers), followed by the third trophic level (secondary consumers) and finally to the highest trophic level (tertiary consumers). During this energy movement along the trophic levels, the energy becomes lost as metabolic heat when the organisms from one trophic level are consumed by the organisms from another trophic level. The amount of energy transferred between the trophic levels is measured by Trophic level transfer efficiency (TLTE).