Ecosystem [Environmental Studies Notes for BCOM/BA/BSC 2nd SEM CBCS Pattern]

Unit 3: Ecosystems (Classes: 10; Marks: 17)

Environmental Studies Notes for BCOM/BA/BSC 2nd SEM CBCS Pattern CBCS Pattern

A. Concept of an ecosystem.

B. Structure and function of an ecosystem.

C. Producers, consumers and decomposers.

D. Energy flow in the ecosystem.

E. Ecological succession.

F. Food chains, food webs and ecological pyramids.

G. Introduction, types, characteristics features, structure and function of the following ecosystem:

a. Forest ecosystem

b. Grassland ecosystem

c. Desert ecosystem

d. Aquatic ecosystems (ponds, streams, lakes, rivers, oceans, estuaries)


Meaning and Definition of Ecosystem

The term “Eco – system” was proposed for the first time by A.G. Tanslay in 1935. “Eco” means the environment and “system” means a set of interacting inter-dependent living and non-living components.

According to Tanslay, Ecosystem is defined as the system resulting from the integration of all the living and non-living factor of the environment. It has both structure and function. The structure is related to species diversity and the function is related to the flow of energy and cycling of materials through the structural components.

Thus, any unit that includes all the organisms in a green area interact with the physical environment, so that a flow of energy leads to a clearly defined tropic structure, biotic diversity and material cycle that is exchange of material and energy both living and Non-living components within the system is known as Ecosystem.

An eco-system may be as small as a pond, a crop land or as large as an ocean, forest or desert. Each unit of eco-systems are linked with each other. An eco-system represents the highest level of ecological integration, which is energy based and the functional units are capable of energy transformation, accumulation and circulation.

Structure of an Ecosystem

The structure of an ecosystem refers to the physical and biological components that make up the ecosystem. Ecosystems are made up of living organisms, such as plants, animals, and microorganisms, as well as non-living components, such as air, water, and soil. The structure of an ecosystem can be divided into different levels of organization, which include:

1. Individual organisms: These are the basic units of any ecosystem. They include all living things, such as plants, animals, fungi, and microorganisms, that interact with each other and their environment.

2. Populations: Populations are groups of organisms of the same species that live in a particular area. Populations interact with each other through competition for resources, mating, and other activities.

3. Communities: A community is made up of different populations of organisms that live in the same area and interact with each other. Communities can be divided into different groups based on the types of organisms present, such as a forest community or a marine community.

4. Ecosystems: An ecosystem is a community of living and non-living components that interact with each other. Ecosystems can be small, such as a pond, or large, such as a biome, which is a large area with similar climate and vegetation.

5. Biosphere: The biosphere is the sum total of all ecosystems on Earth. It includes all living things and their environments.

Functions of Ecosystem

The principle functions or the steps involved in the operation of eco-system are as follows:

(i) Trapping of solar energy by the producer.

(ii) Preparation of organic materials from the inorganic once by the producers.

(iii) Consumption of producers by consumers.

(iv) After the death of producers and the complex organic compounds.

(v) Smaller compounds are me to chemical finally covered into inorganic hydrates from by Transformers which process of may be suitable for reuse by chemical producer.

Components of ecosystem

1. Producers: Producers are organisms that produce their own food using energy from the sun through a process called photosynthesis. The most common producers in terrestrial ecosystems are plants, while in aquatic ecosystems, they can include algae and phytoplankton. They are also called autotrophs.

2. Consumers: Consumers are organisms that obtain energy and nutrients by feeding on other organisms. There are three main types of consumers: herbivores, carnivores, and omnivores. Herbivores eat only plants, carnivores eat only other animals, and omnivores eat both plants and animals. Consumers are also called heterotrophs.

3. Decomposers: Decomposers are organisms that break down dead organic matter and recycle the nutrients back into the ecosystem. Decomposers include bacteria, fungi, and worms. They are important for maintaining the balance of nutrients in the ecosystem.

4. Abiotic factors: Abiotic factors are the non-living components of an ecosystem, including temperature, water, air, soil, and sunlight. These factors influence the distribution and abundance of organisms in an ecosystem.

5. Biotic factors: Biotic factors are the living components of an ecosystem, including plants, animals, and microorganisms. These factors interact with each other and with abiotic factors to shape the structure and function of the ecosystem.

Energy flow of Eco-system

Energy flow is a fundamental process in an ecosystem that describes the movement of energy through living and non-living components of the ecosystem. Energy flow is essential for the functioning of an ecosystem and is critical to understanding the interactions between different organisms and their environment.

The energy flow in an ecosystem can be described through the concept of trophic levels, which are the different feeding positions in a food chain. The trophic levels are classified into producers, consumers, and decomposers. Producers are at the bottom of the trophic level, and they convert sunlight into food through the process of photosynthesis. Consumers are organisms that consume other organisms to obtain their energy, and decomposers are organisms that break down dead organic matter and recycle the nutrients back into the ecosystem.

The energy flow through the trophic levels follows the laws of thermodynamics, which state that energy cannot be created or destroyed, but it can be transformed from one form to another. In an ecosystem, the energy from the sun is transformed into organic matter by the producers, which is then consumed by the consumers. However, not all the energy that is consumed by the consumers is converted into biomass; some of it is lost as heat during respiration and movement, and some is used for growth and reproduction.

The energy flow through the ecosystem can be represented using an ecological pyramid. An ecological pyramid is a graphical representation of the trophic levels, which shows the relative amount of energy, biomass, or number of individuals at each trophic level. The ecological pyramid is always pyramid-shaped because there is less energy available at higher trophic levels, due to the loss of energy at each step of the food chain.

The flow of energy through an ecosystem has important implications for the stability and sustainability of the ecosystem. The energy flow determines the number of organisms that an ecosystem can support and the availability of resources, such as food and water, to different organisms. Changes in the energy flow, such as the introduction or removal of a species, can have significant impacts on the entire ecosystem. For example, the over-harvesting of a species at the top of the food chain can result in the collapse of the entire ecosystem.

In conclusion, the energy flow is a critical process in an ecosystem, and understanding it is essential for the management and conservation of ecosystems. The energy flow through the trophic levels is critical for maintaining the balance and stability of the ecosystem and for ensuring the survival of the organisms within it.

In order to have a clear out understanding about energy flow, the following points are to be focused:

(i) The quality of solar energy reaching an eco-system per unit area per unit time.

(ii) The efficiency of producer in solar energy trapping and its bioconversion into chemical energy.

(iii) The use of this converted chemical from of energy by the consumer.

(iv) The total input of energy in the form of food and its efficiency of Assimilation.

(v) The loss through respiration heat, excretion.

(vi) The gross net production.

Living organisms can use energy mainly in two forms:

(A) Radiant Energy: It is the light energy coming from the Sun.

(B) Fixed energy: It is the potential energy stored in various organic substance which can be broken down in order to release their energy content.

The undirectional energy flow in eco-system takes place in the following manner.

The green plants trap solar energy through chlorophyll and convert the fame to chemical energy, which is stored in carbohydrates and other organic molecules. Such a process of conversion of solar energy into chemical energy along with the simultaneous produce of organic molecules from inorganic sources is known as primary production.

The total quantity of solar energy converted into chemical energy by green plant is known as Gross primary production. A portion of gross production is used by the producers for their various metabolic activities. The remainder of energy after utilisation is called Net primary production.

In case, the gross production becomes equal to energy required for metabolic activities. Then their shall be no change in energy content, but if the gross production is lesser than energy required for metabolic activities, the bio-mass will undergo degradation, However, if the gross production is more than energy required for metabolic activities, there will be accumulation of biomass.

In an ecosystem, flow of energy usually occurs in the sequence of: Sun ® Producer ® Herbivore ® Carnivore ® Decomposer.

Herbivores, carnivores, and omnivores are consumers. Herbivores are primary consumers. Carnivores and omnivores are secondary consumers.

Ecological Succession

Ecological succession refers to the gradual process of change in the species structure of an ecological community over time. This process happens as a result of natural disturbance or human interference such as forest fires, floods, or land use changes. The succession process is divided into two main types: primary succession and secondary succession.

I. Primary Succession

Primarysuccession occurs in areas where there was no previous soil or vegetation. This may happen on bare rock surfaces or newly formed volcanic islands. The following are the stages of primary succession:

a) Pioneer Stage: The first stage of primary succession is the pioneer stage, which involves the colonization of barren land by pioneer species. These are typically small plants, lichens, or mosses that can grow on bare rock surfaces.

b) Herbaceous Stage: In the next stage, herbaceous plants such as grasses and ferns start to colonize the area. These plants can grow in shallow soil that is formed by the decay of pioneer species.

c) Shrubs and Small Trees: As the soil becomes more developed, shrubs and small trees start to grow. These plants can tolerate harsh conditions such as drought and strong winds.

d) Climax Community: The final stage of primary succession is the climax community. This is a stable, diverse community of plants and animals that can survive in the area without any major disturbances. The species composition of the climax community varies depending on the climate and soil conditions.

II. Secondary Succession

Secondary succession occurs in areas where there was previous soil and vegetation, but it has been disturbed or destroyed. The following are the stages of secondary succession:

a) Pioneer Species: The first stage of secondary succession is similar to primary succession, where pioneer species such as grasses and weeds begin to colonize the area.

b) Shrubs and Small Trees: As the soil becomes more developed, shrubs and small trees start to grow. These plants can tolerate harsh conditions such as drought and strong winds.

c) Young Forest: As the shrubs and small trees continue to grow, a young forest develops. This forest has a mixture of species, and there is an increase in plant and animal diversity.

d) Mature Forest: The final stage of secondary succession is the mature forest, which has a stable, diverse community of plants and animals. The species composition of the mature forest is different from the climax community of primary succession because it is influenced by the history of the disturbance.

Food chains, food webs and ecological pyramids.

Food chain

The green plants synthesis food using solar energy and various inorganic constitution of eco-system. The food manufactured by the green plants is utilised by themselves and also by the Herbivorous. The Herbivorous are consumed by some carnivorous animals. In this way one form of life is supported by the other form. Thus, food from one trophic level reaches the other trophic level and chain is established which is known as food chain.

A food chain may be defined as the transfers of energy and nutrient from the source in plants through series of organisms with repeated process of eating and being eaten.

It is estimated that only about 10% of the potential energy available at the preview trophic level is being available to an organism. The efficiency of a food chain is, therefore dependent on the number of trophic levels or links in a food chain. The shorter of food chain more is the amount of energy available to the last trophic levels in an eco-system in all the eco-system energy moves as per the indirection given below:

a) Sun>Producer> Consumer>Decomposer.

b) Sun > Autotroph> Heterotroph.

Food chain are of three types:

i) Grazing or Predator food chain.

ii) Parasitic food chain.

iii) Saprophytic or ditritus food chain.

Food web

In eco-system, normally the food chain never operates as isolated sequences but are inter-connected with one another foaming some sort of inter- locking pattern such a complicated network of the food relationship and inter relationship is called as food web. The concept of food web is useful for analysis of community under natural condition, the food chain may not be arranged clearly.

That is a particular organism may not occupy the trophic level in every food chain. It may simultaneously behave as a secondary a Tertiary or a top consumer. Hence, it the food chain are inter-connected with one another through different types of organisms of different trophic levels. Food levels maintain the stability of the eco-system. The greater number of alternative more stable is the community of living thing.

A food levels in a grassland eco-system is seen to consist of as many as five dinner food chains as shown below:

i) Grass>Grass Hopper>Hawk.

ii) Grass>Grass Hopper>Lizard>Hawk.

iii) Grass> Rabbit>Hawk.

Iv) Grass>Mouse>Hawk.

v) Grass>Mouse>Snake>Hawk.

vi) Grass>Insect>Firoz>Snake>Hawk.

Ecological Pyramid

Since a lot of potential energy is lost as heat at each step in the food chain, the organism in each trophic level pass lesser energy to the next trophic level than they received, because of such flow out of available energy in food chain, the trophic structure and function of successive trophic levels may be represented graphically by means of ecological Pyramid. In another words, an ecological pyramid may be defined as diagrammatic representation of flow of energy at each trophic level in an eco-system.

The higher step in the ecological pyramid, are of three general types:

1) Pyramid of numbers: It shows the numbers of individuals’ organisms at each level.

2) Pyramid of biomass: It shows the total day weight and other suitable measures of the total living matter.

3) Pyramid of energy: It shows the rate of energy flow and productivity and successive trophic levels.

Environmental Studies  MCQs  Multiple Choice Questions and Answers

Top 100 Environmental Studies MCQs

Environmental Studies  Chapterwise  Notes

Unit 1: Introduction to Environmental Studies

Unit 2: Ecosystems

Unit 3: Natural Resources: Types, Renewable and Non-renewable Resources

Unit 4: Biodiversity and Conservation (Available in DTS App – Only for Members)

Unit 5: Environmental Pollution

Unit 6: Social Issues and the Environment

Unit 7: Environmental Policies & Practices

Unit 8: Human Communities and the Environment

Unit 9: Field work

Environmental Studies  Question Papers 

➡ Dibrugarh University 2022

➡ Gauhati University 2022

➡ Assam University 2019  2021

➡ Kolkata University (Coming Soon)

Environmental Studies  Solved Question Papers  

➡ Dibrugarh University 2022

Leave a Comment

error: Content is protected !!