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Energy flow in ecosystem.pptx
1. ENERGY FLOW IN
ECOSYSTEM
Dr. Preeti Kumari
Assistant Professor, Amity Institute of Applied Sciences,
Amity University, Jharkhand, India -834002.
2. INTRODUCTION
โข Energy flow in an ecosystem refers to the movement of
energy through various trophic levels, from producers to
consumers, and eventually to decomposers.
โข Primary Producers: They convert sunlight into chemical
energy through photosynthesis, storing it in organic
molecules like glucose. Eg. green plants, algae, or
photosynthetic bacteria.
โข Primary Consumers: Primary consumers, also known as
herbivores, obtain energy by consuming primary producers.
3. โข Secondary and Tertiary Consumers: Secondary consumers
are carnivores that obtain energy by feeding on herbivores.
Tertiary consumers are carnivores that feed on other
carnivores.
โข Decomposers: Break down dead organic matter and
returning nutrients to the environment. They release energy
through the process of decomposition, allowing it to re-
enter the ecosystem.
โข Understanding energy flow in ecosystems is essential for
studying ecological relationships, nutrient cycling, and the
4. MODELS OF ENERGY FLOW IN ECOSYSTEM
โข Lindeman (1942) was the first to propose a model based on the premise that
plants and animals can be arranged into trophic levels and that the laws of
thermodynamics apply to plants and animals.
โข He emphasized that the quantity of energy at each trophic level is determined by
the net primary production and the food energy conversion efficiency.
โข Following this, several models depicting energy transfer in ecosystems are
described.
5. LINEAR ENERGY FLOW MODEL OR SINGLE
CHANNEL ENERGY FLOW MODEL
โข Energy flow is characterized by its unidirectional or
one-way nature, commonly known as a single
channel flow.
โข To gain a better understanding of this concept,
let's examine the simplified diagram of the Single
Channel Energy Flow Model, as depicted in Figure.
6.
7. โข The diagram reveals two important aspects.
โข 1. The flow of energy is unidirectional and non-cyclic in nature.
โข 2. Energy decreases gradually at each trophic level.
8. PRODUCER CONSUMERS
[I- total energy input, LA โ light absorbed by plant cover, PG โ gross primary production, A โ total assimilation, PN โ
net primary production, P โ Secondary production, NU โ Energy not used (stored), NA โ Energy not assimilated by
consumers (egested), R โ respiration. Bottom line in the diagram shows the order of the magnitude of energy losses
expected at major transfer points, starting with a solar input of 3,000 Kcal per square meter per day. (After E.P. Odum,
1963)]
9. โข The linear energy flow model has significant implications.
๏ถ It highlights that shorter food chains tend to have more energy available at higher
trophic levels.
๏ถThis observation highlights the significance of taking into account the length and
complexity of food chains when evaluating energy availability in ecosystems.
10. Y-SHAPED OR DOUBLE CHANNEL ENERGY FLOW
MODEL
โข The double channel or Y-shaped energy flow model demonstrates how grazing
and detritus food chains work together in an ecosystem.
โข Functionally, the grazing food chain involves the direct consumption of living
plants by herbivores, which directly affects the plant population.
โข Decomposers have the opportunity to access the uneaten portion of plants after
death, which contributes to the detritus food chain.
โข Detritus food chain relies on the decomposition and utilization of dead organic
matter by detritivores and decomposers.
11. โข The importance of the grazing and detritus food chains may differ in different
ecosystems. In some cases, grazing is more important, while in others, detritus plays a
more significant role.
โข The Y-shaped energy flow model, as depicted in Figure, was first introduced by H.T.
Odum in 1956.
โข It illustrates the common boundary, light and heat flow, and the import, export, and
storage of organic matter within the ecosystem. Decomposers are represented in a
separate box, emphasizing their role in separating the grazing and detritus food
chains.
โข This separation in both time and space allows for a better understanding of the
distinct dynamics and interactions within each food chain.
12. Fig: The relationship between flow of energy through the grazing food chain and detritus
pathway.
13. Fig: A Y-Shaped or 2-channel energy flow diagram that separates a grazing food chain (Water column of vegetation
canopy) from a detritus food chain (Sediments and in soil).
14. โข In marine ecosystems, primary production in the open sea is limited,
and a major portion of it is consumed by herbivorous marine
animals.
โข Consequently, only a small fraction of primary production is available
for the detritus pathways.
โข In contrast, in forest ecosystems, a substantial amount of biomass is
produced, exceeding the capacity of herbivores to consume it all.
โข As a result, a significant proportion of the the detritus compartment
in the form of litter, making the detritorganic matter enters us food
chain more important in such ecosystems.
15. Fig: A Y-shaped energy flow model showing linkage between the grazing and detritus food
chains.
16. โข In conclusion, the Y-shaped or double channel energy flow model provides a
more comprehensive understanding of energy flow within ecosystems compared
to a simple linear chain model.
โข It considers the simultaneous functioning of grazing and detritus food chains,
acknowledges their interconnectedness, and highlights their varying importance
in different ecosystems.
โข It is more realistic representation of energy flow in ecosystems.
17. UNIVERSAL ENERGY FLOW MODEL
โข The Universal Energy Flow Model is a comprehensive framework that offers valuable
insights into the dynamics of energy flow within ecosystems.
โข This model has widespread applicability, as it can be used to understand the energy
dynamics of various living components, including plants, animals, microorganisms,
individuals, populations, and trophic groups.
โข Developed by E.P. Odum in 1968.
โข It allows us to visualize and analyze the intricate relationships between different
organisms and their energy interactions.
โข By depicting the energy flow using a series of interconnected boxes, this model provides a
comprehensive overview of how energy is obtained, utilized, and transferred within a
given system.
18. Fig.: Components for a โuniversalโ model of energy flow, I= input or ingested energy, NU= not used, A=
assimilated energy, P=production, R=respiration, B=biomass, G=growth, S=stored energy, E=excreted
energy.
19. โข The Universal Energy Flow Model offers a versatile and
comprehensive framework for understanding the complex dynamics
of energy flow within ecosystems.
โข By considering the energy inputs, utilization, and partitioning among
different components, this model provides valuable insights into the
interdependencies and interactions that govern energy flow in
nature.
Editor's Notes
Unlike the cycling of nutrients, such as carbon, nitrogen, phosphorus, and sulfur, which move in a cyclic manner and are reused by producers after passing through the food chain, energy is not recycled in the same way. In contrast, it flows from producers to herbivores, then to carnivores, and so on.
Green plants, or autotrophs, take in energy from the sun through photosynthesis and convert it into chemical energy. Plant tissues store this energy and then transform it into heat energy during metabolic activities. Afterwards, it is transferred to the next trophic level in the food chain. The solar energy captured by autotrophs does not return to the sun; instead, it travels through the ecosystem, reaching herbivores and subsequently consumers. The functioning of biological systems is dependent on this unidirectional flow of energy. The entire ecosystem would collapse without a primary energy source.
The transfer of energy from one trophic level to another causes a significant loss of heat through metabolic reactions. Additionally, the organisms utilize some of the energy at each trophic level for their various biological processes.
When considering the Single Channel Energy Flow Model, it becomes evident that the flow of energy in an ecosystem decreases significantly at each successive trophic level.
The reason for this reduction is energy losses in the form of heat or other unusable forms. Considering the total energy flow, which includes primary productivity and respiration, or focusing solely on secondary productivity, there is a gradual decrease in energy flow. For instance, out of the 3,000 Kcal of total light energy falling upon green plants, approximately 50% is absorbed, 1% is converted at the first trophic level, resulting in a net primary production of only 15 Kcal. As we move up the trophic levels, secondary productivity tends to be around 10% for successive consumer levels, although it may occasionally reach 20% at the carnivore level.
The first law of thermodynamics states that energy cannot be created or destroyed but can be converted from one form to another. In the context of energy transfer in ecosystems, there is a degradation of energy from a concentrated form, such as mechanical or chemical energy, to a dispersed form, primarily as heat.
The second law of thermodynamics emphasizes that energy transformations are never 100% efficient and are always accompanied by some loss of energy, predominantly in the form of heat.
Within the same ecosystem, both grazing and detritus food chains are interconnected in nature.
For example, the dead bodies of small animals that were once part of the grazing food chain become incorporated into the detritus food chain, as do the feces of grazing animals. This interconnectedness highlights the importance of both food chains in sustaining the overall functioning of the ecosystem.
Estimates for standing crops (shaded boxes) and energy flows compare a hypothetical coastal marine ecosystem (upper diagram) with a hypothetical forest (lower diagram).
The model considers two key energy inputs: I and A. The I component represents the ingested energy, which can vary depending on the organismโs role in the ecosystem.
