The document discusses energy flow through ecosystems. It describes how energy moves from primary producers like plants through primary, secondary and tertiary consumers, and finally to decomposers. It then summarizes several models used to represent energy flow, including the linear model showing a single direction of flow, the Y-shaped model accounting for both grazing and detritus food chains, and the universal model depicting comprehensive energy interactions within a system.

1. ENERGY FLOW IN
ECOSYSTEM
Dr. Preeti Kumari
Assistant Professor, Amity Institute of Applied Sciences,
Amity University, Jharkhand, India -834002.

2. INTRODUCTION
• Energy flow in an ecosystem refers to the movement of
energy through various trophic levels, from producers to
consumers, and eventually to decomposers.
• Primary Producers: They convert sunlight into chemical
energy through photosynthesis, storing it in organic
molecules like glucose. Eg. green plants, algae, or
photosynthetic bacteria.
• Primary Consumers: Primary consumers, also known as
herbivores, obtain energy by consuming primary producers.

3. • Secondary and Tertiary Consumers: Secondary consumers
are carnivores that obtain energy by feeding on herbivores.
Tertiary consumers are carnivores that feed on other
carnivores.
• 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.
• Understanding energy flow in ecosystems is essential for
studying ecological relationships, nutrient cycling, and the

4. MODELS OF ENERGY FLOW IN ECOSYSTEM
• 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.
• He emphasized that the quantity of energy at each trophic level is determined by
the net primary production and the food energy conversion efficiency.
• Following this, several models depicting energy transfer in ecosystems are
described.

5. LINEAR ENERGY FLOW MODEL OR SINGLE
CHANNEL ENERGY FLOW MODEL
• Energy flow is characterized by its unidirectional or
one-way nature, commonly known as a single
channel flow.
• 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.

7. • The diagram reveals two important aspects.
• 1. The flow of energy is unidirectional and non-cyclic in nature.
• 2. Energy decreases gradually at each trophic level.

8. PRODUCER CONSUMERS
[I- total energy input, LA – light absorbed by plant cover, PG – gross primary production, A – total assimilation, PN –
net primary production, P – Secondary production, NU – Energy not used (stored), NA – Energy not assimilated by
consumers (egested), R – 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. • The linear energy flow model has significant implications.
 It highlights that shorter food chains tend to have more energy available at higher
trophic levels.
This 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
• The double channel or Y-shaped energy flow model demonstrates how grazing
and detritus food chains work together in an ecosystem.
• Functionally, the grazing food chain involves the direct consumption of living
plants by herbivores, which directly affects the plant population.
• Decomposers have the opportunity to access the uneaten portion of plants after
death, which contributes to the detritus food chain.
• Detritus food chain relies on the decomposition and utilization of dead organic
matter by detritivores and decomposers.

11. • 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.
• The Y-shaped energy flow model, as depicted in Figure, was first introduced by H.T.
Odum in 1956.
• 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.
• 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. • In marine ecosystems, primary production in the open sea is limited,
and a major portion of it is consumed by herbivorous marine
animals.
• Consequently, only a small fraction of primary production is available
for the detritus pathways.
• In contrast, in forest ecosystems, a substantial amount of biomass is
produced, exceeding the capacity of herbivores to consume it all.
• 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. • 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.
• It considers the simultaneous functioning of grazing and detritus food chains,
acknowledges their interconnectedness, and highlights their varying importance
in different ecosystems.
• It is more realistic representation of energy flow in ecosystems.

17. UNIVERSAL ENERGY FLOW MODEL
• The Universal Energy Flow Model is a comprehensive framework that offers valuable
insights into the dynamics of energy flow within ecosystems.
• 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.
• Developed by E.P. Odum in 1968.
• It allows us to visualize and analyze the intricate relationships between different
organisms and their energy interactions.
• 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 ‘universal’ 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. • The Universal Energy Flow Model offers a versatile and
comprehensive framework for understanding the complex dynamics
of energy flow within ecosystems.
• 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.