Food Chains and Food Webs

Food Chain:

• Ecosystems have an hierarchy of feeding relationships (trophic levels) that determine the pathway of energy flow in the ecosystem. The energy flow in the ecosystem can be illustrated as a Food chain.

• Sun is the ultimate source of energy in ecosystems. Producers or autotrophic organisms convert the solar energy into chemical or organic energy during photosynthesis. 

• This is the source of food for heterotrophic organisms and these animals may in turn be eaten by other animals. In this way energy is transferred through series of organisms. Such a sequence is called food chain or grazing link in the ecosystem. 

• Each stage of the food chain is known as a trophic level. Producers occupy the first trophic level. The second trophic level is occupied by the primary consumers and third is occupied by secondary consumers and so on.

• In some ecosystems, as much as 80% of primary production is not eaten by primary consumers. Instead, decomposer organisms consume plant materials. This type of food chain is konwn as detrital food chains, (eg. Tropical forest ecosystems).

Producers, Consumers and Decomposers

The biotic community of any ecosystem can be divided simply into producers, consumers and decomposers.

Producers:

Producers or autotrophs are organisms that make their own organic material from simple inorganic substances. For most of the biosphere the main producers are photosynthetic plants and algae that synthesis glucose from carbon dioxide and water. The microscopic algae and blue-green bacteria are the main producers in an aquatic ecosystem and are known as phytoplankton. 

The glucose produced is used both as an energy source and combines with other molecules from the soil to build biomass. It is this biomass that provides the total theoretical energy available to all non photosynthesising organisms in the ecosystem.

Energy flow in the Ecosystem

The study of energy flow through the ecosystem is called energitics. It includes energy transformation which occurs in the ecosystem. It involves;

1. Quantity of energy reaching to the ecosystem.
2. Quantity of energy trapped by green plants and its conversion of chemical energy.
3. Quantity and path of energy flow from the green plants to organisms of different trophic level.

From sun's, energy which reach to the earth, 40% is reflected immediately from the clouds or dusk etc. 15% is absorbed and converted into heat energy. 45% penetrates to the earth's surface. Out of it 5% is converted into chemical energy by photosynthesis. 

Autotrophs capture the solar energy and provides to the other organisms in the ecosystem. The chemicals found in living organisms are derived from abiotic components (air, water, soil) and they return back by decomposition. Bacteria and fungi bring about decomposition, obtaining energy from waste products and dead organisms in the process.

The Transformation of Energy

The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate.

The prophet Isaah said "all flesh is grass", earning him the title of first ecologist, because virtually all energy available to organisms originates in plants. Because it is the first step in the production of energy for living things, it is called primary production. Herbivores obtain their energy by consuming plants or plant products,carnivores eat herbivores, and detritivores consume the droppings and carcasses of us all. 

Concept of an Ecosystem

The term ecosystem genaerally refers to all biotic and abiotic components and their interarction with each other, in some defined area. The ecosystem was proposed by A. G. Tansley in 1935. An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. There are many examples of ecosystems; a pond, a forest, an estuary, a grassland. The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.

Multidisciplinary Nature of Environmental Studies

The science of Environment studies is a multidisciplinary science because it depends on various disciplines like chemistry, physics, medical science, etc. It is the science of physical phenomena in the environment. It is inherently a multidisciplinary field that draws upon not only its core scientific areas, but also applies knowledge from other non-scientific studies such as economic, law and social science.

Renewable and Non-renewable Resources

A natural resource may be defined as any material given to us by nature which can be transformed in a way that it becomes more valuable and useful. For an example wood is used for making furniture. Yarn obtained from cotton is used for weaving cloth. Likewise, various machine, tools and household goods are made of metals. Now furniture, clothes, machine, tools are more valuable than their raw form i.e. wood, cotton and metal, respectively. Thus, water, minerals, forests, wildlife as well as human beings are resources. 

Renewable and Non-renewable Resources

Basically the natural resources are are classified into two types;

1. Renewable Resources
2. Non-renewable Resources.

Expected Questions: Unit 01

• Define environment.

• Discuss the scope of environment.

• Write a note on the importance of environment studies.

• Write a note on the need of public awareness about environment.

• What is Environment? Discuss the scope of Environment.

• Describe the importance of environment studies.

• “The need for public awareness about environment is of vital importance.” Discuss.

• Explain the multidisciplinary nature of environmental studies.

• Write a short note on Chipko Movement or Appiko Movement.

Scope and Importance of Environmental Studies

The environment studies enlighten us, about the importance of protection and conservation of our indiscriminate release of pollution into the environment. At present a great number of environment issues, have grown in size and complexity day by day, threatening the survival of mankind on earth. We study about these issues besides and effective suggestions in the Environment Studies. 

Environment studies have become significant for the following reasons:

1. Environment Issues Being of International Importance:

Meaning and Definition of ES

The word environment is derived from the French word environner, meaning to encircle or surrounding. It can be defined as the circumstances or conditions that surround an organism or group of organisms. The term environment is considered as a composite term fro the condition in which organisms live and thus consists of air, water, food and sunlight which are basic needs of life organisms.

Environmental Study is the study of the interactions among the physical, chemical and biological components of the environment; with a focus on pollution and degradation of the environment related human activities; and the impact on biodiversity and sustainability from local and global development. 

E.S Second Semester Syllabus

Unit 1: Multidisciplinary Nature of Environmental Studies

• Definition and Meaning
• Scope and Importance
• Multidisciplinary Nature of ES
• Need for Public Awareness
• Environmental Awareness Movements
• Expected Questions

Unit 2: Natural Resources

• Renewable and non-renewable resources 
• Natural resources and associated problems;

1. Forest Resource: 
2. Water Resources: 
3. Mineral Resources: 
4. Food Resources: 
5. Energy Resources: 
6. Land Resources:

• Role of an individual in Conservation of Natural Resources
• Equitable use of Resources for Sustainable Lifestyle

Unit 3: Ecosystems

• Concept of an Ecosystem
• Structure and Function of an Ecosystem.
• Producers, Consumers and Decomposers
• Energy Flow in the Ecosystem
• Ecological succession.
• Food Chains and Food Webs
• Ecological Pyramids.
• Introduction, Types, Characteristic Features, Structure and Function of the following Ecosystems;

                   a) Forest ecosystem

                   b) Grassland ecosystem

                   c) Desert ecosystem

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

Unit 4: Biodiversity and Its Conservation

• Introduction – Definition: genetic, species and ecosystem diversity.
• Biogeographical classification of India
• Value of biodiversity: consumptive use, productive use, social, ethical, aesthetic and option values
• Biodiversity at global, National and local levels.
• India as a mega-diversity nation
• Hot-spots of biodiversity.
• Threats to biodiversity: habitat loss, poaching of wildlife, man-wildlife conflicts.
• Endangered and endemic species of India
• Conservation of biodiversity: In-situ and Ex-situ conservation of biodiversity.

Unit 5 : Environmental Pollution

1. Definition, Cause, effects and control measures of ;

• Air pollution
• Water pollution
• Soil pollution
• Marine pollution
• Noise pollution
• Thermal pollution
• Nuclear hazards

2. Solid waste Management : Causes, effects and control measures of urban and industrial wastes.

3. Role of an individual in prevention of pollution.

4. Pollution case studies.

5. Disaster management: floods, earthquake, cyclone and landslides.

Unit 6: Social Issues and the Environment

• From Unsustainable to Sustainable development
• Urban problems related to energy
• Water conservation, rain water harvesting, watershed management
• Resettlement and rehabilitation of people; its problems and concerns. Case Studies
• Environmental ethics: Issues and possible solutions.
• Climate change, global warming, acid rain, ozone layer depletion, nuclear accidents and holocaust. Case Studies.
• Wasteland reclamation.
• Consumerism and waste products.
• Environment Protection Act.
• Air (Prevention and Control of Pollution) Act.
• Water (Prevention and control of Pollution) Act.
• Wildlife Protection Act.
• Forest Conservation Act.
• Issues involved in enforcement of environmental legislation.
• Public awareness.

Unit 7: Human Population and the Environment

• Population growth, variation among nations
• Population explosion – Family Welfare Programme VII
• Environment and human health
• Human Rights
• Value Education
• HIV/AIDS
• Women and Child Welfare
• Role of Information Technology in Environment and human health
• Case Studies