Introduction
The sun is the major source of energy. Energy provides the ability to work. The use of energy in any biological process is inevitable. In the process of photosynthesis, solar energy is converted into potential energy, which is stored in plant tissues. Through assimilation, the potential energy is converted into heat energy. This energy is transferred from the plant kingdom to the animal kingdom. Thus energy is transmitted from one food chain to another food chain. So energy flows into the ecosystem through food. The functionality of the ecosystem depends on this energy flow. Energy flow in the ecosystem is the process of transferring converted solar energy from one body to another in the ecosystem (1) & (4).
Definition
The process by which solar energy flows in the form of potential energy at different trophic levels in the food chain is called energy flow. The primary source of energy in the ecosystem is solar energy. This energy is converted and transferred from the producer to the body of different consumers.
As an example, solar energy is converted into potential energy in the body of a green plant. Later when a herbivore takes that green plant as food, that potential energy is gradually spread through the food to different trophic levels in the ecosystem (3). & (5).
Sun as the source of energy flow
Hydrogen gas in the sun is converted to helium through a fusion reaction as a result, a huge amount of energy is produced. This energy is constantly emitted from the sun as electromagnetic waves. These electromagnetic waves emitted from the sun contain waves of different wavelengths and frequencies. About 90% of the total energy emitted from the sun is ultraviolet and infrared wavelengths. The plants usually absorb more red and blue rays. Of the amount of solar energy that falls on the earth, 34% goes back into space. Of the remaining 66%, 10% is absorbed by the ozone layer, atmospheric water vapor, and various gases. A tiny fraction of the solar energy (0.02%) falling on the earth’s surface is used by green plants for photosynthesis. That is, the earth’s ecosystem depends on a tiny fraction of solar energy (3). & (6).
Characteristics of energy flow
There are some features of the energy flow of the ecosystem. These are
- The primary source of energy flow in the ecosystem is the sun. Without the sun, the ecosystem would be destroyed.
- The energy flow of the ecosystem is always one-way. That is after solar energy passes from the body of the autotrophs to the body of the various consumers, it does not return to the body of the producer again.
- There is no rotation of the energy flow of the ecosystem.
- In the food chain, the amount of energy gradually decreases during the transfer of energy from one food layer to another.
- The first and second formulas of thermodynamics are completely acceptable in the energy flow of ecosystems.
- The flowing energy is never destroyed, only transformed (1) & (5).
Steps of energy flow
The energy flow of the ecosystem occurs in three steps. Such as
- Absorption of energy.
- Use of energy.
- Transference of energy.
1. Absorption or source of energy
The sun is the main source of energy in the ecosystem. About 30% of the sunlight is radiated from the sun to the earth. Only 0.02% of it is bound as potential energy in the body of the green plant. Green plants convert solar energy (0.02%) into potential energy with the help of chlorophyll and in the presence of sunlight.
The amount of energy stored in the food produced during photosynthesis is called gross primary production or GPP. From this gross primary production, the green plant uses some amount of energy for its own needs. The amount of energy that remains after the use of green plants for their own needs is called net primary production or NPP. Energy is transferred from the producer level to the consumer level of the food chain for gross primary production. Thus the process of acquiring energy in the ecosystem is organized (2) & (6).
2. Use of energy
Only the primary consumer accepts the gross primary production energy of green plants or producers. Thus the energy (GPP) of the primary consumer is absorbed by the secondary consumer and the energy (GPP) of the secondary consumer is confined to the tertiary consumer. This process involves the use of energy between various types of consumers from the producer. The transfer of energy from the ecosystem never happens completely. Most of the energy that an organism absorbs is used to produce body heat and for various physiological functions. Only the remaining energy is transmitted to the next trophic level (2) & (6).
3. Transference of energy
From the gross primary production, some energy comes out of the organism in the form of excretory substances. The remaining energy is then periodically transferred from the producer to the various consumers in the ecosystem. This type of energy transfer can be observed in the food chain of any type of ecosystem (2) & (6).
Laws of energy exchange in energy flow
In order to maintain the ecological balance in the environment, the laws of thermodynamics must be followed. The energy flow of the ecosystem is actually controlled by thermodynamic formulas. The formulas for thermodynamics are
1. First laws
The first law of thermodynamics states that energy is transformed but that energy cannot be created or destroyed.
For example, green plants convert solar energy into potential energy by making food with the help of sunlight in the process of photosynthesis. This energy then flows through the ecosystem and is stored in the animal body or exits the ecosystem (4) & (6).
2. Second laws
The second law of thermodynamics states that heat energy is lost during the transfer of energy from one level to another in an ecosystem. The flow of this energy stops after it has flowed up to a certain level.
There is no 100% conversion of energy in the food pyramid. There is always some amount of energy loss. In 1942, scientist Raymond Lindeman explained this feature of the energy flow of the ecosystem by his famous 10% law. He said that as the trophic level rises, its supply decreases with the transfer of energy. And 10% of the energy in the food chain is used to build the body at every level.
For example, if a rabbit eats 1000 gm of green plants, then 100 gm of that food is used for its various physiological functions and body heat production. If a hawk eats that rabbit as food, only 10 gm of energy is transferred to the hawk’s body, according to Lindeman’s 10% law (4) & (6).
Unidirectional flow of energy in the ecosystem
The flow of energy in the ecosystem does not rotate like other elements of the environment. The flow of energy between living elements is always unidirectional in the ecosystem. This is because there are various interchangeable forms of energy the transformation of which is controlled by the law of thermodynamics. Green plants or producers bind solar energy to their bodies. After the energy from the producer goes to the body of the different consumers that energy no longer returns to the body of the producer. Thus energy flows from the primary consumer to the secondary consumer. And the energy of the secondary consumer flows into the body of the tertiary consumer (3).
Models of energy flow
Ecologists have presented different models of energy flows in different ecosystems. Two of these models are described below.
1. The single-channel energy flow model
Of total incoming solar energy, 118761gm kcal/ cm²/ year remains unused. Thus the total production by the producer is 111gm kcal/ cm²/ year. 21% of the total energy (23gm kcal/ cm²/ year) is used for the digestion and absorption of organisms which is used for their growth. 17% of the total production of energy is taken up by herbivores.
3.4% of the total production goes to the decomposition level. And the remaining amount of unused energy is 79.5% (70gm kcal/ cm²/ year). In the case of herbivores, the amount of energy expended by respiration is higher than that of producers. Most of the energy (60%) absorbed by carnivores is used for digestion and growth. Two things are known from the above model. First, the flow of energy is always one-way. So if the supply of solar energy is stopped, the entire ecosystem will be destroyed. Second, some energy is lost as energy flows from one food layer to another (2) & (4).
2. Y-shaped model
Scientists Odum studied the flow of energy in the ecosystem of a river called Silver Spring in the United States and discovered the Y-shaped model. Green algae, diatoms, bacteria, etc. are the primary producers of this ecosystem. Snails, fish, and many invertebrates are the primary consumers of this ecosystem. The big fish is the secondary consumer of this ecosystem. The tertiary consumers of this ecosystem are three species of fish and some parasites (2) & (4).
Importance of energy flow
The ecological balance of the environment is maintained by the energy flow of the ecosystem. Producers convert solar energy into potential energy by photosynthesis. A portion of this energy is stored in the body of the plant. The remaining energy is used for the growth and development of the plant. Everything in the ecosystem is controlled by energy. This energy flows from the producer to different trophic levels in the food chain. So without this energy flow, the producers and consumers of the ecosystem will be destroyed. The food chain will be destroyed. The whole ecosystem will be severely damaged. Even the ecosystem may be destroyed (3).
