Energy in Ecosystem pattern of flow of energy through the ecosystem and food chain.

Energy in Ecosystem pattern of flow of energy through the ecosystem and food chain.
20103429 (Mozakkir Azad) ESE-2105 Ecology.pdf

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Jatiya Kabi Kazi Nazrul Islam University
Assignment on: Energy in ecosystem pattern of flow of energy through the
ecosystem and food chain

Course Name: Ecology
Course Code: ESE-2105

DATE OF SUBMISSION: November 6, 2022
SUBMITTED BY:
MOZAKKIR AZAD
Roll no: 20103429
Session: 2019-2020
2
nd
Year 1
st
Semester
Department of Environmental Science and Engineering
Jatiya Kabi Kazi Nazrul Islam University
SUBMITTED TO:
MD. RAKIBUL HASAN
Assisstant Professor
Department of Environmental Science and Engineering.
Jatiya Kabi Kazi Nazrul Islam University
Trishal, Mymensingh

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Content:

No Topics Page No.
1. Introduction 04
2. Ecosystem 05
2.1 Energy Flow 05
2.2 Energy flow in Ecosystem 07
3. Energy flow through the Ecosystem 08
4.1 Food Chain 12
4.2 Food Chain Theory 15
4.3 Food Web 15
4.4 Food Web Theory
17
4.5 Tropic Level 19
5. Conclusion 22
6. References 23

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Figure:

No Topic Page

01 Fate the solar radiation incident 05
02 Flow the energy at different level of Ecosystem 07
03 Energy flow models 10
04 Y shape/double channel Energy flow model 12
05 Food Chain 13
06 Food web in a grassland Ecosystem 16
07 Tropic level Process 22












1. Introduction:

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An ecosystem is a structural and functional unit of nature and it comprises abiotic and biotic
components. Abiotic components are inorganic materials- air, water and soil, whereas biotic
components are producers, consumers and decomposers. Each ecosystem has characteristic
physical structure resulting from interaction amongst abiotic and biotic components. Species
composition and stratification are the two main structural features of an ecosystem. Based on
source of nutrition every organism occupies a place in an ecosystem. Productivity,
decomposition, energy flow, and nutrient cycling are the four important components of an
ecosystem. Primary productivity is the rate of capture of solar energy or biomass production of
the producers. It is divided into two types: gross primary productivity (GPP) and net primary
productivity (NPP). Rate of capture of solar energy or total production of organic matter is
called as GPP. NPP is the remaining biomass or the energy left after utilisation of producers.
Secondary productivity is the rate of assimilation of food energy by the consumers. In
decomposition, complex organic compounds of detritus are converted to carbon dioxide, water
and inorganic nutrients by the decomposers. Decomposition involves three processes, namely
fragmentation of detritus, leaching and catabolism. Energy flow is unidirectional. First, plants
capture solar energy and then, food is transferred from the producers to decomposers.
Organisms of different trophic levels in nature are connected to each other for food or energy
relationship forming a food chain. The storage and movement of nutrient elements through the
various components of the ecosystem is called nutrient cycling; nutrients are repeatedly used
through this process. Nutrient cycling is of two types—gaseous and sedimentary. Atmosphere
or hydrosphere is the reservoir for the gaseous type of cycle (carbon), whereas Earth’s crust is
the reservoir for sedimentary type (phosphorus). Products of ecosystem processes are named
as ecosystem services, e.g., purification of air and water by forests. The biotic community is
dynamic and undergoes changes with the passage of time. These changes are sequentially
ordered and constitute ecological succession.
Succession begins with invasion of a bare lifeless area by pioneers which later pave way for
successors and ultimately a stable climax community is formed. The climax community
remains stable as long as the environment remains unchanged.


2. Ecosystem:

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An ecosystem is a geographic area where plants, animals, and other organisms, as well
as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic
or living, parts, as well as abiotic factors, or nonliving parts. Biotic is the
factors include plants, animals, and other organisms. Abiotic is the
factors include rocks, temperature, and humidity. Every factor in an ecosystem depends on
every other factor, either directly or indirectly. A change in the temperature of
an ecosystem will often affect what plants will grow there, for instance. Animals that depend
on plants for food and shelter will have to adapt to the hanges, move to another ecosystem,
or perish. Ecosystems can be very large or very small. Tide pools, the ponds left by
the ocean as he tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a
kind of algae, which uses photosynthesis to create food. Herbivores such as abalone eat
the seaweed. Carnivores such as sea stars eat other animals in the tide pool, such as clams
or mussels. Tide pools depend on the changing level of ocean water. Some organisms, such
as seaweed, thrive in an aquatic environment, when the tide is in and the pool is full.
Other organisms, such as hermit crabs, cannot live underwater and depend on the shallow
pools left by low tides. In this way, the biotic parts of the ecosystem depend on abiotic
factors.

The whole surface of Earth is a series of connected ecosystems. Ecosystems are often
connected in a larger biome. Biomes are large sections of land, sea, or
atmosphere. Forests, ponds, reefs, and tundra are all types of biomes, for example. They're
organized very generally, based on the types of plants and animals that live in them. Within
each forest, each pond, each reef, or each section of tundra, you'll find many
different ecosystems.

2.1 Energy flow:
The chemical energy of food is the main source of energy required by all living organisms.
This energy is transmitted to different trophic levels along the food chain. This energy flow is
based on two different laws of thermodynamics:
 First law of thermodynamics, that states that energy can neither be created nor
destroyed, it can only change from one form to another.

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 Second law of thermodynamics, that states that as energy is transferred more and
more of it is wasted.
It states that every energy transformation involves degradation or dissipation of energy from a
concentrated to a dispersed form due to metabolic functions, so that only a small part of energy
is stored in the biomass. Light falling on the plants is trapped by the producers in the presence
of Mg++containing green pigment called chlorophyll and is used in assimilating the organic
food called glucose by the process of photosynthesis. By photosynthesis, radiant energy of
sunlight is transformed into potential energy of foodstuffs. Evidences show that only a part of
energy is trapped by the producers while the rest of energy is dissipated.
The energy conserving efficiency is– 1.15% for grasslands, 0.9% for Savannah, 0.8% for mixed
forests, 5% for modern crops and 10-20% for sugarcane field. The green plants or producers
breakdown a part of organic food in respiration to obtain chemical energy for various body
functions and overcoming entropy. Dissipation of energy occurs as heat. The remaining energy
is used in the synthesis of plant biomass called net photosynthesis which is then available to
the next trophic level of food chains.
This loss is not due to the inefficiency of the photosynthetic mechanism of the plants but due
to the operation of second law of thermodynamics.The total biomass manufactured by plants
during photosynthesis is called gross primary productivity of an ecosystem and is symbolized
as PG. On average, it is about 1-5 percent energy of incident radiations, i.e. 2-10 percent of
photosynthetic active radiation (PAR). A part of it is used by the plants themselves for
respiration (R), while the remaining biomass is called net primary productivity (PN). It is also
called apparent photosynthesis. On average, it is about 0.8-4 per cent energy of incident
radiations, i.e. 1.6-8 per cent of PAR. So it can be represented as
PN = PG – R.

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Figure 01 : Fate of solar radiation incident on plant canopy
2.2 Energy Flow in Ecosystem:

The energy flow in the ecosystem is one of the major factors that support the survival of such
a great number of organisms. For almost all organisms on earth, the primary source of energy
is solar energy. It is amusing to find that we receive less than 50 per cent of the sun’s effective
radiation on earth. When we say effective radiation, we mean the radiation, which can be used
by plants to carry out photosynthesis.
Most of the sun’s radiation that falls on the earth is usually reflected back into space by the
earth’s atmosphere. This effective radiation is termed as the Photosynthetically Active
Radiation (PAR). Overall, we receive about 40 to 50 percent of the energy
having Photosynthetically Active Radiation and only around 2-10 percent of it is used by plants
for the process of photosynthesis. Thus, this percent of PAR supports the entire world as plants
are the producers in the ecosystem and all the other organisms are either directly or indirectly
dependent on them for their survival. The energy flow takes place via the food chain and food
web. During the process of energy flow in the ecosystem, plants being the producers absorb
sunlight with the help of the chloroplasts and a part of it is transformed into chemical energy
in the process of photosynthesis. This energy is stored in various organic products in the plants
and passed on to the primary consumers in the food chain when the herbivores consume
(primary consumers) the plants as food. Then conversion of chemical energy stored in plant
products into kinetic energy occurs, degradation of energy will occur through its conversion
into heat.

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Then followed by the secondary consumers. When these herbivores are ingested by carnivores
of the first order (secondary consumers) further degradation will occur. Finally, when tertiary
consumers consume the carnivores, energy will again be degraded. Thus, the energy flow is
unidirectional in nature. Moreover, in a food chain, the energy flow follows the 10 percent law.
According to this law, only 10 percent of energy is transferred from one trophic level to the
other; rest is lost into the atmosphere. This is clearly explained in the following figure and is
represented as an energy pyramid.

3. Energy flow through the Ecosystem:

Figure 02: Flow of energy at different level of ecosystem

According to Raymond Lindeman (1942) “The basic process in the trophic dynamics is the
transfer of energy from one part of the ecosystem to another”. All function, and indeed all life,
within an ecosystem depends upon the utilization of an external source of energy, solar
radiation. Portion of this incident energy is transformed by the process of photosynthesis into
the structure of living organisms.”The amount of energy at trophic level is determined by the
net primary production (NPP) and the efficiency at which food energy is converted into
biomass. The plants use 15 to 70 percent of assimilated energy for the maintenance which is
not available to the consumers. The herbivores and carnivores are comparatively more active
as compare to plants which uses more assimilated energy for the maintenance. So, the
productivity at each trophic level lies between 5 to 20 percent that of the level below it. The
percentage of energy which is transferred from one trophic level to the next trophic level is

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called as ecological efficiency. In general, secondary producers utilize 55% to 75% of
assimilated energy in maintenance. Temperature and moisture are two components of the
habitat and the type of species determine the maintenance cost. The dry and hot regions require
higher maintenance cost, irrespective of the species.
[Primary production is the rate of organic biomass growth or accumulation by plants. Primary
production is commonly split into two components, gross primary productivity (GPP) and net
primary productivity (NPP). Gross primary productivity is the overall rate of biomass
production by producers, whereas net primary productivity is the remaining fraction of biomass
produced after accounting for energy lost due to cellular respiration and maintenance of plant
tissue. Thus, NPP = GPP – respiration.]


The 10 Percent Energy Law:
The transfer of the energy in the food chain is limited; and hence, the number of trophic levels
in the food chain is limited. There is only 10% of the transfer of energy from each lower trophic
level to the next/higher trophic level. This law, known as the 10% energy law, was proposed
by Raymond Lindeman. The primary consumers do not acquire 100% of the energy transfer
from the plants/producers; some of the energy of the sun is consumed by the plants during the
process of photosynthesis.







Ecological efficiency can be defined as the product of efficiencies in which organisms exploit
their food resources and convert them into biomass for next higher trophic level. As biological

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production is almost consumed, the overall exploitation efficiency remains 100 percent,
whereas, ecological efficiency is dependent on two factors: the proportion of assimilated
energy incorporated in growth, storage and reproduction. The first proportion is called as
assimilation efficiency and second is net production efficiency. The product of the assimilation
efficiency and net production efficiencies is called as gross production efficiency. It is the
proportion of food energy that is transformed into consumer biomass energy. Net production
efficiency of plants is the ratio of net production to gross production.

Energy flow models:








Figure 03: Energy flow models
1. The single / linear channel model: The single or linear channel energy flow model is one
of the first published models pioneered by H. T. Odum in 1956. This model depicts a
community boundary and, in addition to light and heat flows, it also includes import, export
and storage of organic matter. There is loss of energy at every successive trophic level; also a
corresponding decline in biomass. However, it does not specify any correlation between the
biomass and energy. The connection between biomass and energy content may vary according
to different conditions. For example, one gram of algae may be equivalent to several grams of
forest leaves, due to the fact that the production rate of algae is higher than the forest leaves.
The higher biomass of the organism does not necessary indicate the higher productivity. Energy
flow in the system balance the energy out flows as required by the First law of thermodynamics

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and each energy transfer is accompanied by loss of energy ( in the form of unavailable heat
energy (respiration) as stated by second law of thermodynamics. The energy flow is
significantly reduced at each successive trophic level. Thus, at each transfer of energy from
one trophic level to another trophic level, major part of energy (90%) is lost in the form of heat
or any other form
2. Y- shaped/ Double channel model: Y- shaped model shows a common boundary, light and
heat flow as well as import, export and storage of organic matter. In this model of energy flow,
grazing and detritus food chain are sharply separated. It is more practical than simple linear
chain energy model as: i) It confirms the basic stratified structure of ecosystem ii) It separates
the grazing food chain from detritus food chain (Direct consumption of living plants and
utilization of dead organic matter respectively) in both time and space. iii) Macro consumer
(animals) and micro consumers (bacteria & fungi) differ greatly in size-metabolism relations.

In Y-Shaped model one arm represents the grazing food chain and the other arm represents
detritus food chain. The two arms differ fundamentally in such a way that they can influence
primary producers. For Example, in marine bay, the energy flow through grazing food chain is
larger than the energy flow via detritus food chain. Whereas reverse is true for forest food chain
where 90% or more of net primary production is normally utilized in detritus food chain. Thus,
in marine ecosystem the grazing food chain is the major pathway of energy flow whereas in

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the forest ecosystem, the detritus food chain is more important. In grazing chain, herbivore feed
on living plant, therefore they directly affect the plant population. What they not eat is
available, after death, to the decomposer. As a result, decomposers are not able to directly
influence the rate of supply of their food. The Y-shaped model further indicates that the two
food chains are in fact, under natural conditions, not completely isolated from one another. For
example, dead bodies of small animals that were once part of grazing food chain become
incorporated in the detritus food chain as do the feces of grazing food animals. The importance
of two food chains may differ in different ecosystem, in some cases, grazing is more important
and in others, detritus is more important.









Figure 04: Y-Shaped/ double Channel Energy Flow Model

4.1 Food Chain:
A food chain is simply a feeding relationship in which food energy is transferred from a given
source through a series of species each of which eats the one before itself in the chain. This
repeated series of eating and being eaten is always initiated with green plants. Green plants
receive their energy from the sun.
A very simple food chain may be represented as :

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Each successive level of nourishment as represented by the links of the food chain is known
as trophic level. Plants form the first trophic level namely the producer trophic level. Then
come the consumer levels. These comprise the herbivores (the primary consumers), the
carnivores and parasites (secondary and tertiary consumers etc.). At each level when the energy
transfer occurs, a large proportion of the potential energy present in the chemical bonds of the
food species is lost as heat. Because of this phenomenon the number of steps in a food chain
is, usually, limited to four or five. It has been found that the shorter the food chain (or the
nearest the organisms is to the beginning of the chain) the greater the available energy that can
be converted into biomass (living weight) utilised in cellular respiration.

In a two-step food chain of more of the potential energy initially available per unit of corn
reaches man than if the corn is fed to pigs and the swine are eaten by man (Fig.).

Figure 05. : Food chain
Types of Food Chain:

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 Parasitic food chains
 Grazing food chains
 Detritus food chains
Grazing food chain It starts from green plants and ends with carnivores passing through
herbivores.
Detritus food chain The organic wastes, exudates, and dead matter derived from the grazing
food chain are generally termed detritus. The energy contained in the detritus is not lost to the
ecosystem; rather it serves as the source of energy for a group of organisms (detritivores) which
constitute the detritus food chain.
In the predatory type of food chains smaller organisms are eaten by larger organisms. In the
parasitic food chains largest organisms are eaten by smaller species. The term saprophytic is
given to a food chain where dead organic matter is fed upon by fungi such as mushrooms and
finally bacteria.
Example of some Food Chain:
Food Chains on Land-
 Grass → Grass Hopper → Frog → Snake → Peacock/Falcon
 Vegetation → Rabbit → Fox → Wolf → Tiger
 Vegetation → Insect → Predator Insect → Insectivorous Bird → Hawk.
Food Chains in Water -(Pond)
 Phytoplankton → Zooplankton → Small Crustaceans → Predator Insects → Small
Fish → Larger Fish → Crocodile.
 Phytoplankton → Zooplankton → Small Crustaceans → Predator Insects → Small
Fish → King Fisher/Stork.

4.2 Food chain theory:

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Based on the modelling approach by Lotka (1925) and Volterra (1926), who were the first to
study population dynamics with the help of differential equations, Rosenzweig and MacArthur
(1963) related the “green world hypothesis” to mathematical reasoning. Rosenzweig and
MacArthur investigated general properties of predator-prey relationships and developed a
theoretical basis for concepts such as predator control and primary in productivity
(Rosenzweig & MacArthur 1963, Rosenzweig 1971, reviewed in Fretwell 1987). It took
another 15 years until Fretwell (1977) and Oksanen et al. (1981) developed a general
framework for bottom-up and top-down control in food chains with more than three trophic
levels. Food chain theory predicts an alternating pattern of bottom-up versus top-down control
from the top trophic level to the bottom (Fretwell 1977). Top consumers are assumed to be
only limited by food supply and thereby control their prey (the sub-terminal species along the
food chain), which in turn releases the prey of the sub-terminal species from predation pressure.
This pattern then repeats itself alternatingly down the food chain. Concordantly, in each food
chain the top trophic level and all levels in even distance from the top are bottomup controlled
(i.e. their equilibrium abundance/biomass increases with enrichment of the primary producers),
whereas all trophic levels in odd distance to the top are top-down controlled (i.e. are kept at a
constant level unaffected by enrichment. Furthermore,
Oksanen et al. (1981) predicted a lengthening of the food chain with increasing enrichment,
i.e. successful establishment of a next higher trophic level requires sufficient productivity at
the base of the food chain Assembly sequence of successive trophic levels along an enrichment
gradient with RResource, P-Primary producer, H-Herbivore, CCarnivore. Arrows next to
circles indicate the equilibrium response of the corresponding trophic level to enrichment,
indicating either increase (upward arrows) or no change (horizontal arrows).

4.3 Food Web:
Food web is a network of food chains which become interconnected at various trophic levels
so as to form a number of feeding connections amongst the different organisms of a biotic
community. A food web is simply the total set of feeding relationships in a biotic community.
The advantage of having such complex web of feeding relationships in the community is that

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it gives stability to the ecosystem. Even if one or more of these relations is altered, the
community will remain stable.

Figure 06. : Food web in a grassland ecosystem
Energy Flow Model:
 First, the energy flows one way, i.e., from producers through herbivores to carnivores;
it cannot be transferred in the reverse direction.
 Second, the amount of energy flow decreases with successive trophic levels.Producers
capture only a small fraction of solar energy (1-5 per cent of total solar radiation), and
the bulk of unutilized energy is dissipated mostly as heat.
Part of the energy captured in gross production of producers is used for maintenance of their
standing crop (respiration) and for providing food to herbivores (herbivory).

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The unutilized net primary production is ultimately converted to detritus, which serves as
energy source to decomposers. Thus, energy actually used by the herbivore trophic level is
only a small fraction of the energy captured at the producer level.On an average, in different
ecosystems, the herbivores assimilation or productivity approximates 10 per cent of gross
productivity of producers.

4.4 Food web theory:

While food chain theory has given much insight into the consequences of trophic linkages,
the study of many other central trophic interactions requires the incorporation of parallel
pathways of energy flow. Food web modules consisting of only a few interacting species have
been extensively used to explore the dynamical consequences of central ecological
interactions (defined in Fig. 2) such as resource competition, shared (‘apparent’) predation,
intraguild predation, and their interplay. In the context of food webs with purely exploitative
interactions, competition is always an indirect effect mediated through at least one intermediate
compartment (sensu Abrams et al. 1996). Therefore, competition can be either mediated
through a basal resource, referred to as ‘exploitative competition’ (Fig. 2a), or through a shared
predator, referred to as ‘apparent competition’ (Fig. 2b).

Fig. 2. Food web modules illustrating
resource (R), b) apparent competition, two consumer species sharing a common predator (TC)
c) diamond module, a combination of modules a and b, d) intraguild-predation, a top consumer
(TC) competing with its prey (C) for a shared resource (R). With pure exploitative competition
for a single limiting resource stable coexistence between competitors is not possible. The
superior resource competitor, being able to persist at the lowest resource levels (R*), will
always exclude the inferior one by suppressing resource levels below the minimum
requirements of its competitor (‘R*-rule’, Tilman 1980). Similarly, with pure apparent
competition the species, which can sustain the highest predator levels P*, and thus the highest
predation pressure (‘P*-rule’, Holt et al. 1994), will exclude all more vulnerable prey (Holt et
al. 1994). In contrast, if the resource and apparent competition modules are combined, two prey
species sharing a common predator and a common limiting resource, the interaction of both

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processes can enable coexistence (Fig. 2c). Due to its shape, the corresponding food web
module is referred to as ‘diamond’ web. A necessary condition for coexistence in the diamond
web is that both competitors face an intrinsic competitionpredation trade-off, i.e. the superior
resource competitor is also more vulnerable to predation.
Through a gradual shift in competitive advantage from the superior resource competitor at
low resource enrichment levels towards the less vulnerable competitor at high enrichment
levels, coexistence becomes possible over a range of intermediate enrichment levels (Holt et
al. 1994, Leibold 1996). Insights from the ‘diamond’ module have been very influential on
both empirical and theoretical studies of predator mediated coexistence (reviewed in Chase et
al. 2002).
Another important and ubiquitous trophic interaction is omnivore, i.e. the feeding on
resources/prey from more than one trophic level (Polis & Strong 1996, McCann & Hastings
1997). Omnivore introduces links between non-adjacent trophic levels, resulting in a reticulate
food web structure (Polis & Strong 1996). The smallest reticulate food web with omnivore is
the intraguild predation module (IGP) consisting of an intrigued predator being involved in
competition for a shared resource with its intrigued prey. A necessary condition for coexistence
in the IGP module is that the intrigued prey is the superior resource competitor, which implies
that it can persist with the resource alone at low levels of resource enrichment; stable
coexistence of intraguild predator and prey may then be possible at intermediate levels of
enrichment, whereas the intraguild prey is often excluded at high levels of enrichment (Holt &
Polis 1997, Diehl & Feißel 2000). Within the range of stable coexistence the dominant
interaction shifts from resource competition between intraguild prey and predator to apparent
competition between resource and intraguild prey along an enrichment gradient. This shift is
accompanied by a decrease in the intraguild prey and an increase in the intraguild predator,
which leads to the exclusion of the intraguild prey at higher enrichment levels. The intraguild
predation web does not allow a clear comparison with trophic cascade theory, because the
trophic level of the intraguild predator is at a non-integer trophic level above the trophic level
of the intraguild prey. This holds true for omnivores in general and was one major criticism
concerning the applicability of trophic cascade theory to real ecosystems (Polis & Strong
1996). The above examples already highlight the potential for indirect effects mediated through
multiple, parallel energy pathways to shape community dynamics and suggest a complex
interplay with external forcing such as the availability of production limiting nutrients. Several

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extensions of the above food web modules including more trophic levels and more links
between them, have been explored (e.g. Leibold 1996, Grover 1997, Abrams 1993,
Hulot et al. 2000, Hulot & Loreau 2006). Still, a comprehensive framework for the prediction
of bottom-up and top-down responses in food webs with alternative energy pathways, similar
to the one established for simple, linear food chains (Fretwell 1977, Oksanen et al. 1981), is
so far missing. Such a framework will be developed.

4.5 Tropic level:
Energy flow is a fundamental process which occurs in all ecosystems. Energy is defined as the
capacity to do work. It is the basic force responsible for all metabolic activities. The flow or
movement of energy through a series of organisms in an ecosystem is called energy flow. The
energy flows from producer to top consumers in unidirectional form. The study of trophic level
interaction in an ecosystem gives an idea about the energy flow through the ecosystem. As all
organisms require energy to do work this energy is obtained from the chemical energy of food
which they consume. This chemical energy is obtained, by the producers which has the ability
to convert solar energy to chemical energy. Trophic level interaction Trophic level interaction
deals with how the members of an ecosystem are connected on the basis of their nutritional
needs.Organisms are either producers or consumers in terms of the energy flow through the
ecosystem. Energy flows through the trophic level from producers to subsequent trophic level-

• In the first trophic level Plants acts as producers. They take energy from sunlight and convert
it into organic material through the process of photosynthesis. Thus, the plants are primary
producers.
• At the second trophic level, the herbivores feeds on plants. This gives them energy. Most of
this energy is used up in performing metabolic functions such as breathing, food digestion, the
growth of tissues, maintaining body temperature and blood circulation.

• At the next trophic level come carnivores. Carnivores feed on the herbivores and derive
energy for their growth and sustenance. Large predators are present in subsequent trophic levels

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and they derive their energy by consuming smaller carnivores. Some organisms like human
beings consume both plants (producers) and animals for their food. There is loss of some
energy in the form of heat at each trophic level and thus in each trophic level the energy level
decreases. Organisms that can fix radiant energy utilizing inorganic substances to produce
organic molecules are called autotrophs/producers. Plants are examples of autotrophs.
Heterotrophs are organisms that cannot obtain energy from abiotic sources and rely on energy-
rich organic molecules synthesised by autotrophs. Consumers are those that obtain energy from
living organisms and decomposers are those that obtain energy from dead organisms. At each
trophic level (also called feeding level), heat energy is released thereby reducing the amount
of energy passing onto each level. That means energy is degraded. The flow of energy is also
only unidirectional. At the last level, all organisms die and become detritus or food for
decomposers. Here, the last remnants of energy are extracted and released as heat energy, while
the inorganic nutrients are returned to the soil or water only to be taken up again by primary
producers. The energy is lost or released while the inorganic nutrients are recycled. The
ultimate source of energy is the sun. Ultimately, all energy in ecosystems will get They take
energy from sunlight and convert it into organic material through the process of photosynthesis.
This takes place at the first trophic level and plants are primary producers. At the second trophic
level are herbivores who use plants as food. This gives them energy. Most of this energy is
used up in performing metabolic functions such as breathing, food digestion, the growth of
tissues, maintaining body temperature and blood circulation. At the next trophic level come
carnivores. Carnivores feed on the herbivores and derive energy for their growth and
sustenance. Large predators are present in subsequent trophic levels and they derive their
energy by consuming smaller carnivores. Some organisms like human beings consume both
plants (producers) and animals for their food.At each trophic level (also called feeding level),
heat energy is released thereby reducing the amount of energy passing onto each level. That
means energy is degraded. The flow of energy is also only unidirectional. At the last level, all
organisms die and become detritus or food for decomposers. Here, the last remnants of energy
are extracted and released as heat energy, while the inorganic nutrients are returned to
the soil or water only to be taken up again by primary producers. The energy is lost or released
while the inorganic nutrients are recycled. The ultimate source of energy is the sun. Ultimately,
all energy in ecosystems will get lost as heat

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Energy flows through an ecosystem in only one direction. Energy is passed from organisms
at one trophic level or energy level to organisms in the next trophic level. Which organisms
do you think are at the first trophic level (Figure below)?

Figure 07 : Tropic Level Process

Most of the energy at a trophic level – about 90% – is used at that trophic level. Organisms
need it for growth, locomotion, heating themselves, and reproduction. So animals at the
second trophic level have only about 10% as much energy available to them as do organisms
at the first trophic level. Animals at the third level have only 10% as much available to them
as those at the second level.


5. Conclusion:

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Sun is the ultimate source of energy. An ecosystem is a functional unit with energy flowing
among abiotic components very effectively. Energy flow in an ecosystem is always
unidirectional. Energy in an ecosystem is never destroyed but is converted from one form
to another.

What is the 10 per cent law of energy flow? Only 10% of energy is passed to the successive
trophic level. The sun’s energy is available to the organisms at higher trophic levels since
the sun is the only natural source of energy provided at higher trophic levels. If any links
in a food chain or food web (interconnected food chains) are removed, efficient energy
flow will not occur. A food chain describes the passage of energy between trophic
levels. A food web is a set of interconnected and overlapping food chains. Food webs
are interconnected, such as nearby land and a marine food webs.













6. Reference:

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f
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