Environmental Science Lesson 1-10 PDF

Department of Distance and Continuing Education University of Delhi Ability Enhancement Course (AEC) Course Credit-2 ENVIRONMENTAL SCIENCE: THEORY INTO PRACTICE I As per the UGCF - 2022 and National Education Policy 2020  Editor...

Department of Distance and Continuing Education University of Delhi Ability Enhancement Course (AEC) Course Credit-2 ENVIRONMENTAL SCIENCE: THEORY INTO PRACTICE I As per the UGCF - 2022 and National Education Policy 2020  Editor Prof. Radhey Shyam Sharma Prof. Nibedita Khuntia Content Writers Dr. Mayank Pandey, Prof. Nibedita Khuntia, Dr. Sarthak Malhotra, Dr. Ashish Thomas, Dr. Ruchi Mishra, Dr. Pramod Kumar, Dr. Pallavi Saxena, Dr. Aniket Singh Academic Coordinator Mr. Deekshant Awasthi © Department of Distance and Continuing Education e-mail: [email protected] [email protected] Published by: Department of Distance and Continuing Education under the aegis of Campus of Open Learning/School of Open Learning, University of Delhi, Delhi-110 007 Printed by: School of Open Learning, University of Delhi Corrections/Modifications/Suggestions proposed by Statutory Body, DU/ Stakeholder/s in the Self Learning Material (SLM) will be incorporated in the next edition. However, these corrections/modifications/ suggestions will be uploaded on the website https://sol.du.ac.in. Any feedback or suggestions can be sent to the email- [email protected] © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I INDEX Lesson 1: Introduction to Environmental Studies.......................................... 1-21 1.1 Learning Objectives 1.2 Introduction 1.3 Components of Environment 1.4 Environmental Education 1.5 Difference between Environmental Science and Environmental Studies 1.6 Multi-disciplinary Nature of Environmental Studies 1.7 Scope and Importance of Environmental Studies 1.8 Important Landmarks in Environmentalism 1.9 Concept of Sustainability and Sustainable Development 1.10 Summary Lesson 2: Ecosystem: Concept, Structure, Pyramids and Succession......... 22-40 2.1 Learning Objectives 2.2 Introduction 2.3 Concept of Ecosystem 2.4 Structure of Ecosystem 2.5 Ecological Pyramids 2.6 Ecological Succession 2.7 Summary Lesson 3: Ecosystem: Biogeochemical Cycles, Functions, Energy Flow and Productivity........................................................ 41-59 3.1 Learning Objectives 3.2 Introduction 3.3 Biogeochemical Cycles 3.3.1 Atmospheric Nutrient Cycle 3.4 Functions i|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Ability Enhancement Course (AEC) 3.5 Energy Flow in an Ecosystem 3.6 Productivity 3.7 Homeostasis 3.8 Summary Lesson 4: Ecosystem: Types and Services.................................................... 60-73 4.1 Learning Objectives 4.2 Introduction 4.3 Types of Ecosystems 4.4 Ecosystem Services 4.5 Ecosystem Preservation and Conservation 4.6 Summary Lesson 5: Natural Resources: Land Resources............................................ 74-90 5.1 Learning Objectives 5.2 Introduction 5.3 Land Resources 5.4 Land Cover and Land Use Change 5.5 Land Degradation 5.6 Soil Erosion 5.7 Desertification 5.8 Deforestation 5.9 Impact of Mining and Dam Building 5.10 Steps for Sustainable Management of Land Resources 5.11 Summary 5.12 Glossary 5.13 Answers to In-text Questions 5.14 Self-Assessment Questions 5.15 References 5.16 Suggested Readings ii | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Lesson 6: Natural Resources: Water Resources........................................ 91-105 6.1 Learning Objectives 6.2 Introduction 6.3 Hydrological Cycle and Distribution of Water 6.4 Water Resources of India 6.5 Water Demand and Utilization 6.6 Emerging Water Resources Problems 6.7 Sustainable Water Management 6.8 Summary Lesson 7: Natural Resources: Energy Resources..................................... 106-128 7.1 Learning Objectives 7.2 Introduction 7.3 Growing Energy Needs 7.4 Sources of Energy 7.5 Renewable and Non-renewable sources of Energy 7.6 Energy Contents of Fossil Fuels 7.7 Nuclear Energy 7.8 Summary Lesson 8: Pollution: Air, Noise and Nuclear Pollution............................ 129-153 8.1 Learning Objectives 8.2 Introduction 8.3 Sources of Pollution 8.4 Classification of Pollution 8.5 Management of Environmental Pollution 8.6 Air Pollution 8.7 Noise Pollution 8.8 Nuclear Pollution iii | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Ability Enhancement Course (AEC) Lesson 9: Pollution: Water, Thermal and Soil Pollution......................... 154-174 9.1 Learning Objectives 9.2 Introduction 9.3 Water Pollution 9.4 Thermal Pollution 9.5 Soil Pollution Lesson 10: Solid Waste Management and Case Studies.......................... 175-189 10.1 Learning Objectives 10.2 Introduction 10.3 Types of Wastes 10.4 Waste Management 5 R Principles 10.5 Incineration, Composting and Landfill 10.6 Case Study: The London Smog 1952 10.7 Case Study: The Los Angeles Smog Episode 10.8 Case Study: The Bhopal Gas Disaster Episode 10.9 Case Study: Taj Mahal Issue 10.10 Case Study: The Ganga Pollution 10.11 Case Study: The Yamuna Pollution 10.12 Case Study: Chernobyl Disaster 10.13 Case Study: Fukushima Disaster 10.14 Case Study of Indore: Global Model for Waste Management 10.15 Summary iv | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I LESSON 1 INTRODUCTION TO ENVIRONMENTAL STUDIES Dr. Mayank Pandey Assistant Professor P.G.D.A.V College (Eve) University of Delhi STRUCTURE 1.1 Learning Objectives 1.2 Introduction 1.3 Components of Environment 1.3.1 Lithosphere 1.3.2 Hydrosphere 1.3.3 Atmosphere 1.3.4 Biosphere 1.4 Environmental Education 1.5 Difference between Environmental Science and Environmental Studies 1.6 Multi-disciplinary Nature of Environmental Studies 1.7 Scope and Importance of Environmental Studies 1.8 Important Landmarks in Environmentalism 1.9 Concept of Sustainability and Sustainable Development 1.10 Summary 1.11 Glossary 1.12 Answers to In-text Questions 1.13 Self-Assessment Questions 1.14 References 1.15 Suggested Readings 1|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.1 LEARNING OBJECTIVES After reading this lesson, you will be able:  to make the reader aware of the environment, its importance and its basic components.  to develop an understanding of the concept, scope and importance of the discipline of Environmental Studies.  to discuss the concept and necessity of a multidisciplinary approach to the subject.  to be aware of the historic milestones of environmentalism and environmental education.  to make the readers know about the origin of the concept of ‘Sustainability’ and ‘Sustainable Development’. 1.2 INTRODUCTION The term Environment is derived from the French word ‘Environ’ which literally means ‘surrounding’. Anything and everything which surrounds us i.e. all living beings or biotic components (microbes, plants and animals) and non-living or abiotic components (air, water, sunlight etc.) present in nature, form the environment. The Environmental Protection Act, of 1986 defines the Environment as “environment includes water, air and land and the inter- relationship which exists among and between water, air and land, and human beings, other living creatures, plants, micro-organism and property”. Interactions between the biotic and abiotic components lead to a functional ecosystem and sustainable life on the planet earth. We get all the basic goods and services (clean air and water, food, fodder, medicines, raw materials for industries, tourism etc.) from the environment. It is a well-known fact that anthropogenic activities and unsustainable consumption of natural resources by the human race have significantly damaged the environment and mother earth and the degradation is still going on at a fast pace. Therefore, it is our responsibility to protect the environment from getting degraded and polluted. Environmental education is indispensable to creating environmental awareness which ultimately will lead to environmental conservation. 1.3 COMPONENTS OF ENVIRONMENT Planet earth is the only known planet in the universe with a diversity of life. As earlier mentioned, life could have been possible on the planet only because of the healthy interactions between biotic and abiotic components in such a manner where the flow of energy and biogeochemical cycle follows a well-defined path. The planet earth is categorized 2|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I into different spheres which represent solid (rock/soil), liquid (water) and gaseous (air) phases. The overlapping zone of the three spheres, where life is available, is called the biosphere. A brief description of the spheres is given below: 1.3.1 Lithosphere (Greek: Lithos means rock) Earth’s structure can be stratified into outer crust, middle mantle and inner core regions (Fig. 1.1). Lithosphere is the outermost layer of the crust which represents the land mass of the planet. It consists of rocks, soil, sediments and minerals. Various geological structures or landforms like high mountains, plateaus, deep valleys and sea beds make the surface of the lithosphere uneven. Mount Everest is the highest point in the lithosphere. Various geological processes like weathering & erosion, volcanic eruptions, and biogeochemical cycles take place in the lithosphere. Different terrestrial ecosystems like forests, grasslands, deserts etc. are found in the lithosphere. Fig 1.1: Cross section of Lithosphere (Source: https://www.nationalgeographic.org/encyclopedia/lithosphere/) 3|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses ACTIVITY Take some time to think about the environmental damage you may have caused in the past day, week, or year as a result of your actions. You should then calculate how much destruction you will bring upon the planet during your lifetime if you keep doing what you're doing now. 1.3.2 Hydrosphere (Greek: Hydro means water) Hydrosphere represents water masses on the planet present in solid (ice cover, glaciers etc.), liquid (water bodies) and gaseous (water vapours) phases. Hydrosphere covers almost three-fourths of the total surface area of the earth. Oceans and seas represent marine ecosystem which contains 97 per cent of the total water content (having a very high concentration of salts) of the planet. The remaining 3 per cent of the water resources are freshwater present in the form of glaciers, rivers, lakes, ponds etc. (Fig 1.2). The hydrosphere is an integral part of the water cycle and plays a crucial role in maintaining normal climatic, meteorological, physical, chemical and biological functions on the planet. Oceans and seas are the largest sinks of carbon in the environment. Fig 1.2: Distribution of Water Resources on the Earth 1.3.3 Atmosphere The (Greek: Atmos means vapour) thin sheet of gaseous mixture which envelops the planet earth is called the atmosphere. The content of water vapour, the density of the air mass and 4|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I atmospheric pressure decrease rapidly with the increase in altitude. The composition of dry air is as follows: Table 1.1: Composition of dry air Component Volume (%) Nitrogen 78.084 Oxygen 20.946 Argon 0.934 Carbon Dioxide 0.040 Gases in traces Remaining The rate of change of temperature with the altitude is called the lapse rate. The atmosphere has been stratified into major four layers where temperature decreases (negative lapse rate) or increases (positive lapse rate). A brief description of atmospheric layers is as follows: Troposphere: the altitude of this layer varies from 16 km at the equator to 8 km at the poles. The largest percentage of the air mass is found in this region. The upper layer is called the tropopause. Temperature decreases with an increase in altitude (-6.40C per km) in this layer and varies from 150C (ground Level) to – 560C (tropopause). Stratosphere: temperature starts rising in this layer from tropopause (-560C) to stratopause (-20C) as ozone (O3) layering the upper stratosphere absorbs solar radiation and temperature rises. The ozone layer in this region absorbs harmful UV radiation, particularly UV-B radiation (280 nm to 315 nm), because of which life is possible on the earth’s surface. However, the ozone layer is depleting at a fast pace due to the presence of ozone-depleting substances (like chlorofluorocarbons- CFCs). Ozone holes are the places in the upper stratosphere where the concentration of ozone has depleted drastically. 5|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses Fig 1.3: Layers of atmosphere and temperature change with latitude (Source: Britannica Encyclopedia; https://www.britannica.com/science/ozone-layer) Mesosphere: temperature starts decreasing again and reaches -960C at the upper boundary of the layer i.e. mesopause. The density of air is very low and important chemical species found in this region are O2+ and NO+ which do not absorb much solar radiation. This causes the decline in ambient temperature in this region. Thermosphere: ionic oxygen atoms and other ions in this layer absorb short-wave solar radiation which increases the temperature in this layer rapidly from -960C (lower boundary) to 12000C (upper layer). 6|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Table 1.2: Layers of atmosphere and their composition (source: Environmental Chemistry by A K Dey) Layer Altitude Temperature Prominent Characteristics (km) Variation Chemical (0C) Species N2, O2, Ar, Troposphere 0 – 11 15 to (-56) Weather occurs CO2, H2O Stratosphere 11-50 (-56) to (-2) O3 Ozone Layer presence Mesosphere 50-85 (-2) to (-96) O2+, NO+ Meteors burn in this layer Thermosphere 85-500 (-96) to 1200 O2+, O+, NO+ Auroras occur here Fig 1.4: Biosphere (Source: Britannica Encyclopedia https://www.britannica.com/science/biosphere) 7|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.3.4 Biosphere (Greek: Bios means life) this is the self-regulating overlapping region of the atmosphere, lithosphere and hydrosphere in the environment where life sustainably exists and is nourished and flourishes by the healthy interaction between biotic (autotrophs and heterotrophs) and abiotic components (air, water, sunlight, soil, rock etc.) of the nature. IN-TEXT QUESTIONS 1. The lowest layer of the atmosphere is ______________. 2. The hydrosphere is the layer of gases surrounding to earth. True / False 3. Combination of Lithosphere, Hydrosphere and Atmosphere forms: a) Biosphere b) Troposphere c) Exosphere d) Core 4. The core of Earth is the part of Biosphere. True / False 5. The rate of change of temperature with the altitude is called _____________. 1.4 ENVIRONMENTAL EDUCATION In the second half of the twentieth century, global concerns were raised to make people environmentally aware. This was the time when it was recommended to design separate courses for environmental education and establish an independent and multidisciplinary discipline, commonly called Environmental Science or Studies. According to UNESCO (1971), the objectives of environmental studies are: Creating awareness about environmental problems among people. Imparting basic knowledge about the environment and its allied problems. Developing an attitude of concern for the environment. Motivating the public to participate in environmental protection and environmental improvement. Acquiring skills to help the concerned individuals in identifying and solving environmental problems. Striving to attain harmony with Nature. 8|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I UNESCO and UNEP jointly organized the first intergovernmental conference on environmental education in 1977 in Tbilisi, Georgia. The goals of the conference were: To foster clear awareness of and concern about, economic, social, political, and ecological interdependence in urban and rural areas; To provide every person with opportunities to acquire the knowledge, values, attitudes, commitment, and skills needed to protect and improve the environment; To create new patterns of behaviour of individuals, groups, and society as a whole towards the environment. The categories of environmental education objectives are: Awareness: to help social groups and individuals acquire an awareness and sensitivity to the total environment and its allied problems. Knowledge: to help social groups and individuals gain a variety of experiences, and acquire a basic understanding of, the environment and its associated problems. Attitudes: to help social groups and individuals acquire a set of values and feelings of concern for the environment and the motivation for actively participating in environmental improvement and protection. Skills: to help social groups and individuals acquire the skills for identifying and solving environmental problems. Participation: to provide social groups and individuals with an opportunity to be actively involved at all levels in working toward the resolution of environmental problems. Environmental Education in India: India also started taking significant steps to propagate environmental education. At the post-graduation level, environmental education was started by many central and state universities in India during 1985-2000. In 1991, Hon. Supreme Court of India gave a historical ruling to implement environmental education at all levels and gave directions to make Environmental Studies a compulsory paper for all the streams at undergraduate levels in Indian universities. At present, various short-term and regular courses on the environment and its various dimensions are being run in various universities in India. 9|Page © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.5 DIFFERENCE BETWEEN ENVIRONMENTAL SCIENCE AND ENVIRONMENTAL STUDIES Environmental Studies: Environmental study is a multidisciplinary subject which studies various dimensions (scientific, social, cultural, economic, political etc.) of the environment, its issues and challenges and tangible solutions in a holistic way. It studies the human- environment interaction and its results at the micro and macro level. Environmental Science strictly deals with the scientific aspects of the environment, its complex problems and the tangible solutions whereas Environmental Studies, in addition to the scientific aspects, also deals with the socio-economic, cultural, traditional, legislative and historical dimensions of the environmental issues. For example, suppose a river is getting polluted due to the discharge of untreated wastewater into the river. The student of Environmental Science will observe the causes, Physicochemical and biological changes within the river water, its effect on the aquatic and adjoining ecosystem and scientific mitigation measures for the river pollution. In addition to the above dimensions, Environmental Studies will also observe the impact of the pollution on the nearby population, their livelihood and culture etc. 1.6 MULTI-DISCIPLINARY NATURE OF ENVIRONMENTAL STUDIES Multidisciplinary means interaction of various subjects or disciplines. Environmental studies deal with all the aspects of biotic and abiotic components of the environment. Also, the Environment and environmental issues are complex in nature. Therefore, experts from different subjects or disciplines are required to understand different aspects of the environment. We may require expertise from different disciplines to resolve various environmental issues. The Multidisciplinary Nature of Environmental Studies may be understood by a small case study. Suppose a developmental activity (Dam, Mining, Highway etc.) is proposed within a given region. Before starting such projects, an Environmental Impact Assessment (EIA) is conducted to assess and mitigate the possible degradation of the environment and population living within the region. To effectively conduct the EIA, expertise from the following disciplines will be required: Life Sciences (Zoology and Botany): to assess the biodiversity richness and endemism of the given region and possible reversible or irreversible changes in the 10 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi Environmental Science: Theory into Practice I biological diversity of the region by anthropogenic activities. An expert from life sciences will also assess the ecosystem goods and services being provided by the nature in the specific region. Earth Sciences (Geology, Geography, Geochemistry etc.): Earth Sciences will study the details of geological and geographical terrain, soil/rock profile, tectonic and seismic activity in the region etc. Chemical Sciences: it will be helpful in understanding various chemical processes and reactions taking place in different matrices of the environment. It is also important to understand the fate and effect of pollutants on air, water, and soil. Anthropology, History and Archaeology: to assess the historical or archaeological importance of the monuments, tribal population, traditions or practices in a region or at the site of the construction. Social Sciences, Sociology and Economics: to assess the socio-economic stature of the population and possible changes the same with ongoing developmental projects. Law and Legal Aspects: expertise from a legal background is also required to satisfy different legal aspects during a developmental project activity (like land acquisition, relocation and rehabilitation etc.). Mathematics, Computer Modelling and Statistics: we need different statistical tools and models to statistically validate the obtained data from the study. Also, we are using numerous mathematical and computational models in day-to-day activities like meteorological predictions. Fig 1.5: Multidisciplinary Nature of Environmental Studies 11 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.7 SCOPE AND IMPORTANCE OF ENVIRONMENTAL STUDIES The multidisciplinary approach to the subject can be implemented in a wide range of applications and fields related to environmental awareness, education and conservation. Hence, the subject has a vast scope and the expert on the subject can serve in numerous ways in different spheres of society. Students may opt for the subject and make a professional career in Environmental Studies or Environmental Science. The experts and professionals of the subject are required and recruited in various sectors like: Academics: as discussed above, the subject has been introduced in numerous schools, colleges and universities in India and abroad, at school, under-graduation and post- graduation levels. The student may pursue the subject. Worldwide, a large number of dedicated departments, centres, universities and institutions have been established for the subject. An interested professional may join the teaching and academics and make the next generation aware of environmental issues and their tangible solutions. Many dedicated institutes, like WII Dehradun, FRI Dehradun, IIFM Bhopal etc., have been established to propagate education in specialized fields of the environment. Research & Development: research and post-doctoral works have been going on worldwide to understand the ecological mechanisms and to get cost-effective cutting- edge technologies to mitigate environmental issues and challenges. Industries: In order to effectively implement the environmental guidelines and technologies and to mitigate the environmental degradation directly or indirectly caused by the industries, a large number of industries have been recruiting environmental engineers/scientists/experts. Ministries and Agencies: ministry of environment and various environmental agencies & conventions of national and international repute frequently create vacancies for environmental experts. A few examples of such agencies are UNEP, IPCC, CITES, RAMSAR, USEPA etc. Non-governmental Organizations (NGOs) and Consultancy: a large number of national and international NGOs and consultancies are working as an extended hand to conserve the environment and its various components. Most of the NGOs and consultancies are old and have an experienced workforce. Some of the examples are the Bombay Natural History Society, IUCN, Conservation International, World Wide Fund for Nature, Wildlife Trust of India, Centre for Environmental Education, Centre for Science and Environment, Kalpavriksha, Madras Crocodile Bank Trust etc. 12 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Green Journalism: environmental awareness is indispensable for environmental conservation and media (print, electronic and social media) is the strongest medium to propagate the awareness. Green journalism is the term given when the media raises environmental issues and practical solutions suggested by experts on the subject. Environmental legislation and Green Advocacy: for effective environmental conservation, it is indispensable to have stringent legislative provisions and effective implementation of the same. Legal experts specialized in environmental law may act significantly in environmental conservation. In the last five decades, Environmental Studies or Environmental Science has emerged as an important multidisciplinary subject dealing with all the aspects of issues and challenges of the environment and it also suggests practical solutions to environmental problems. The subject is still evolving as environmental problems are also growing in intensity and magnitude at a fast pace. Anthropogenic activities have created the issues like pollution caused by conventional and emerging pollutants, biodiversity loss, global warming-climate change, growing global energy demands, utmost pressure on natural resources etc., which are causing serious threats to life on the planet. Environmental Studies have given tangible solutions to the environmental problems. Some of the prominent fields, that the subject addresses may be summarized as Environmental Education and Ethics, Ecosystem and ecology, Natural Resources Management, Energy Efficiency and Audit, Renewable sources of energy, Global warming-climate change, Biodiversity Conservation, Pollution monitoring and mitigation, Population and Environment, Waste management etc. Hence, it is necessary to make the newer generations aware of the basics and details of the subject. Resource Conservation advocated by Mahatma Gandhi The importance of resource conservation was an issue that Mahatma Gandhi thought deeply about. He pioneered the idea that “Earth provides enough to satisfy every man's needs, but not every man's greed.” at a time when few people understood how quickly the world's resources would be depleted. Most people at the time believed that the Earth's natural resources were infinite. Consequently, this was a novel idea that called for a radically different way of life. Gandhiji advocated for a minimalist lifestyle as a way to preserve the planet's limited resources. 13 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.8 IMPORTANT LANDMARKS IN ENVIRONMENTALISM In the western world, the first-ever concern about environmental degradation was raised after the publication of the book ‘Silent Spring’ by Rachael Carson in 1962. This book raised the issue of excessive use of chemical fertilizers and pesticides in the U.S. and its impact on different biotic and abiotic components of the environment. In 1970, the book ‘Limit to Growth’ by the Club of Rome attracted global attention. Ramsar Convention came into existence on 02nd February 1971 with the aim to conserve wetlands globally. Hence, World Wetlands Day is observed every year on 02nd February. In 1972, United Nations Conference on Human Environment was organized in Stockholm between 5th June – 16th June where India also presented its view on environmental degradation. In remembrance of this conference, World Environment Day is celebrated every year on 05th June. India started Project Tiger in 1973 to save its national animal of India. In between, India and the world witnessed the worst industrial disasters, Bhopal Gas Tragedy (02nd and 03rd December 1984) and Chernobyl Nuclear Disaster (26th April 1986), which taught many lessons to the globe. Vienna Convention (1985) and Montreal Protocol (16th September 1987) were signed to protect the Ozone layer from getting depleted by ozone-depleting substances (ODS). The concept of Sustainable Development was introduced to the world by Brundtland Commission Report (Our Common Future) in 1987. Intergovernmental Panel on Climate Change (IPCC) came into the existence in 1989 to formulate the framework to combat global warming-climate change. Agenda 21 was adopted at the Earth Summit in Rio de Janeiro in 1992. UN trio sister conventions (UNFCCC, UNCBD and UNCCD) were also signed in 1992. In 1997, Kyoto Protocol was signed to curb the emission of greenhouse gases responsible for global warming. The World Summit on Sustainable Development (Rio + 10) was conducted in 2002 in Johannesburg. 14 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi Environmental Science: Theory into Practice I Fig 1.6: Important Milestones in the history of Environmentalism 15 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses The Govt. of India took the initiative to form the International Solar Alliance (30 November 2015; headquartered at Gurugram, India) during the famous Paris convention of UNFCC, in order to motivate the tropical and sub-tropical countries to maximize the use of solar energy instead of the conventional sources of energy. A large number of organizations of national and international repute, working in the field of environmental awareness, education and conservation have also been established in the last century. IN-TEXT QUESTIONS 6. Who was the author of "Silent Spring"? 7. Ramsar Convention is related to a) Wetlands b) Ozone c) E-Waste d) Pesticides 8. World Environment Day is celebrated on _________ of every year. 9. In which year did Bhopal Gas Tragedy happened: a) 1984 b) 1982 c) 1972 d) 1994 10. Brundtland Commission's report was named as ________________. 1.9 CONCEPT OF SUSTAINABILITY AND SUSTAINABLE DEVELOPMENT It was the global perception that environmental conservation and economic development cannot be pursued together. With the onset of the 1980s, the world started finding the middle path so that long-term economic development may be pursued without harming the environment. With this aim, the United Nations established World Commission on Environment and Development (WCED), under the chairmanship of Geo Harlem Brundtland (former Prime Minister of Norway) in December 1983. Hence, this commission is commonly known as the Brundtland Commission. The task of the commission was to formulate “A global agenda for change”. Brundtland Commission submitted its report entitled “Our Common Future” in 1987 which gave the concept of Sustainable Development to the world. The report defines Sustainable Development as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” 16 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Sustainability (Latin: sustinere means to hold up) is a long-term idea that means making the entire world sustainable. However, sustainable development refers to pathways by which the goal of sustainability and a sustainable world can be achieved. Sustainable Development Goals (SDGs): these are the seventeen goals set as the ‘2030 agenda for sustainable development. It was adopted by the United Nations state members in 2015 as a blueprint for peace and prosperity for people and the planet, now and into the future.’ All the developed and developing countries have been called to achieve the goals by the global partnership. Society, environment and economy, are collectively considered the three pillars of sustainable development. When the three pillars harmonically interact with each other, sustainability and sustainable development is achieved. A brief description of the three pillars is given below: Environmental Sustainability: it means that we should consume environmental goods and services in a sustainable manner. Mahatma Gandhi, once rightly said, “Earth provides enough to satisfy every man’s need but not everyone’s greed”. The present rate of over-exploitation of natural resources exceeds manifolds the rate of replenishment of the same, which is causing environmental degradation at an exponential rate. Therefore, natural resources should be utilized sustainably. Sustainable Development Goals 6 (Clean Water and Sanitation), 7 (Affordable and Clean Energy), 13 (Climate Action), 14 (Life below Water) and 15 (Life on Land) indicate environmental sustainability. Social Sustainability: it defines a society as having fair and equal opportunities for its population with gender equality, good health and education facilities and people’s participation in nation-building. Sustainable Development Goals 3 (Good Health and Well-Being), 4 (Quality Education), 5 (Gender Equality), 7 (Affordable and Clean Energy), 16 (Peace, Justice and Strong Institutions) and 17 (Partnerships for the Goals) indicate social sustainability. Economic Sustainability: economic sustainability means the equitable distribution of resources. No one should be deprived of the basic needs to sustain a healthy life. Benefits should be earned from the resources but not at the cost of irreversible loss to the environment. Sustainable Development Goals 1 (No Poverty), 2 (Zero Hunger), 7 (Affordable and Clean Energy), 8 (Descent Work and Economic Growth), 9 (Industry, Innovation and Infrastructure), 10 (Reduced Inequalities), 11 (Sustainable Cities and 17 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses Communities) and 12 (Responsible Consumption and Production) indicates economic sustainability. The three pillars intersect each other giving the concept of a bearable, equitable and viable globe, which collectively forms a sustainable world.  Social Sustainability + Economic Sustainability = Equitable  Social Sustainability + Environmental Sustainability = Bearable  Economical Sustainability + Environmental Sustainability = Viable  (Social + Economical + Environmental) Sustainability = Sustainable Development IN-TEXT QUESTIONS 11. Sustainable Development Goal 1 is for “No Poverty”. True / False 12. Three Pillars of Sustainable Development are: ______________. 13. Sustainable Development Goal 5 is for _____________. 14. Zero Hunger is mentioned in Sustainable Development Goal _______. 15. Sustainable Development Goal 11 is for _________. Fig 1.7: Venn Diagram of Pillars of Sustainable Development 18 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Fig 1.8: Sustainable Development Goals (Source: https://www.un.org/sustainabledevelopment/blog/2015/12 /sustainable-development-goals- kick-off-with-start-of-new-year/) 1.10 SUMMARY Nature supports life. Man must realise the value of the environment and help to maintain it healthy and productive. The environment gave him this wonderful world. Before industrialization, urbanisation, and population increase, mankind's natural environment was healthy and robust. Nature refilled its scarce supplies. After modern civilization began, the health and efficiency of the natural environment began to deteriorate, to the point that nature has lost its potential to restore man-made resource losses. Environmentalists, geographers, and biologists worldwide work to restore a sustainable ecosystem. Environmental management, pollution regulations, recycling of non-biodegradable material, etc., require more attention. Present-day sustainability in nature requires careful utilisation of natural resources. Modern environmental concepts like biodiversity conservation and ecological balance require more discussion. Environmental studies educate us to utilise natural resources more effectively and live sustainably. It reveals the natural behaviour of organisms and their population and community interactions. 19 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1.11 GLOSSARY Atmosphere: a thin blanket of gaseous mixture which envelops the planet and is essential for the survival of biotic components on earth Biosphere: sphere on and around the earth having life Brundtland Commission: World Commission on Environment and Development, commonly known as the Brundtland Commission, gave the concept of sustainable development to the world. Environment: Every biotic and abiotic component that surrounds us forms the environment. Environmental Studies: Environmental study is a multidisciplinary subject which studies various dimensions (scientific, social, cultural, economic, political etc.) of the environment, its issues and challenges and tangible solutions in a holistic way. It studies the human- environment interaction and its results at the micro and macro level. Hydrosphere: depicts the area on earth covered with water Lithosphere: solid surface part of the earth Multidisciplinary: interaction of various subjects or disciplines to address a complex issue or subject. Sustainable Development: development that meets the needs of the present without compromising the ability of future generations to meet their own needs. 1.12 ANSWERS TO IN-TEXT QUESTIONS 1. Troposphere 9. 1984 2. False 10. Our Common Future 3. Biosphere 11. True 4. False 12. Society, Environment and Economy 5. Lapse Rate 13. Gender Equality 6. Rachel Carson 14. 2 7. Wetlands 15. Sustainable Cities and Communities 8. 5th June 1.13 SELF-ASSESSMENT QUESTIONS 1. What do you understand by the multidisciplinary nature of Environmental Studies? How does the multidisciplinary approach help to solve various environmental problems? 20 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi Environmental Science: Theory into Practice I 2. Describe the various components of the atmosphere. 3. Discuss important landmarks in the history of environmentalism in the World. 4. Discuss Sustainable Development. Write a short note on Sustainable Development Goals. 5. Define sustainable development, lithosphere, hydrosphere and biosphere. 1.14 REFERENCES 1. Dey, A. K. (1990). Environmental Chemistry. Wiley Eastern Ltd. 2. Bharucha, E. (2004). Textbook for Environmental Studies. University Grants Commission, New Delhi 1.15 SUGGESTED READINGS 1. Raven, P.H, Hassenzahl, D.M., Hager, M.C, Gift, N.Y., and Berg, L.R. (2015). Environment (8th Ed). Wiley Publishing, USA. Chapter 1 (Pages: 1-17); Chapter 2 (Pages: 22-23); Chapter3 (Pages: 40, 41); Chapter 4 (Pages: 64, 66). 2. Singh, J.S., Singh, S.P., and Gupta, S.R. (2017). Ecology, Environmental Science and Conservation. S. Chand Publishing, New Delhi. Chapter 1 (Page: 3-28). 21 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses LESSON 2 ECOSYSTEM: CONCEPT, STRUCTURE, PYRAMIDS AND SUCCESSION Prof. Nibedita Khuntia Maharaja Agrasen College University of Delhi STRUCTURE 2.1 Learning Objectives 2.2 Introduction 2.3 Concept of Ecosystem 2.4 Structure of Ecosystem 2.4.1 Biotic Components 2.4.2 Abiotic Components 2.5 Ecological Pyramids 2.6 Ecological Succession 2.7 Summary 2.8 Glossary 2.9 Answers to In-text Questions 2.10 Self-Assessment Questions 2.11 References 2.12 Suggested Readings 2.1 LEARNING OBJECTIVES After going through this lesson, you will be able 1. to know the concept, definition and structure of the ecosystem. 2. to distinguish between biotic and abiotic components of the ecosystem. 3. to understand the role of interaction among biotic and abiotic components. 3. to explain the different types of ecological pyramids. 4. to understand the term ecological succession. 22 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I 2.2 INTRODUCTION We are not alone in this world. We share our resources with other life forms. There are non- living things around us as well. Throughout our lifetime we keep on interacting with other living beings and non-living things and act as part of ecosystems. The study of the ecosystem includes a complete analysis of the structure, regulation and role of each component functioning there. Once we know it, in detail, the study of the ecosystem and its importance to the equilibrium of the environment will be understood easily. 2.3 CONCEPT OF ECOSYSTEM The ecosystem is the basic structural and functional unit of the environment. Both the living and non-living component of nature, when interact with each other to establish a stable living community, it is called an Ecosystem. That means there is a constant exchange of something between these living & non-living, which is called an Ecosystem. Without the living component, the establishment of an ecosystem is not possible and vice versa. Both are two sides of a coin or very much complementary to each other. The study of all the physical as well as biological processes including the distribution and abundance of living organisms and the interaction between them with their surrounding environment is known as the Ecosystem. In simpler words, if any environmental changes occur in the physical or abiotic factors, they, in turn, change the type and number of the organisms that are both the plants and the animals, present in that particular area. The ecosystem is very complex in nature and human beings are a part of ecosystem also. The theme of the ecosystem is “energy flow”. Sustenance of the ecosystem is possible due to the energy dependence as well as energy transfer between various components of an ecosystem may it be living or non-living. Examples of Ecosystems are terrestrial or land- based ecosystems, Aquatic or water-based ecosystems etc. 2.4 STRUCTURE OF ECOSYSTEM It is very easy to study or understand the structure of the ecosystem from the flow chart described (see Fig 2.1) below. 23 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 2.4.1. Biotic Components Biotic components are also divided into 3 categories based on their food-fed relationships (see Fig 2.2). (i) Producers: Producers are the autotrophs (auto means self, troph means to nourish) of the ecosystem. They are the green plants and green microorganisms that can make their own food material by using carbon dioxide and water in presence of sunlight with the help of chlorophyll present in them eg. all green plants, algae, cyanobacteria etc Fig 2.1: Schematic Representation of Structure of an Ecosystem (ii) Consumers: Consumers are the heterotrophs (hetero: not self troph to nourish) of an ecosystem. They depend on the producers of nature to get energy. Consumers are also different types like a) Primary Consumers – They are the herbivores who eat directly the autotrophs/plants. They cannot eat any animals eg grasshoppers, rabbits, goats etc. 24 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I b) Secondary Consumers – They cannot directly eat the producers of the ecosystem, that is the plants. They can eat only herbivores eg frogs, jackals, snakes etc c) Tertiary Consumers – They are carnivores in nature means they are meat eaters. Thus, they depend on secondary consumers for their food. They are top-level carnivores eg Tigers, Lions, Vulture, Kite etc. (iii) Decomposers: Decomposers are also to some extent heterotrophic in nature. They do not contain chlorophyll, so depend on other materials for food and energy. These organisms can grow on the dead and decaying materials of the environment. That is why they are known as the decomposers or saprophytes, or scavengers of nature or they can be called the detrivores (Detri means dead particulate organic material). They can live in any type of soil with organic waste. They play a very important role in the completion of the Biogeochemical Cycle in the environment eg Bacteria, Fungi, Earthworm etc. Fig 2.2: Relation between Producers, Consumers and Decomposers (Source: https://archive.bigelow.org/bacteria) 25 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses Table 2.1: Different biotic factors in consumer forms in different Ecosystems Sr.No. Type of Primary Consumer Secondary Tertiary Consumer Consumer Ecosystem 1 Grassland Grasshoppers, Frogs, Lizards, Hawks, Eagle, Ecosystem Rabbits, Deer, Sheep, Birds, Snakes Tiger etc Goats etc 2 Forest Ecosystem Leafhoppers, Bugs, Birds, Owls, Tiger, Lion etc Flies, Squirrels, Lizards, Insects, Deer, Fruit Wolves, bats, Nilgai, Jackals, etc. Elephants etc. 3 Desert Ecosystem Insects, Rats Birds, Scorpions, Snakes, Fox, Camel, Squirrel Fox, Jackal, Striped Hyena, Rattle Snakes, Sand Cats, Viper, Mongoose etc Saharan Cheetah, Eagles, Kites etc. 4 Pond or Lake Insects, Frogs, Insects, Larger Largest Fishes, Ecosystem Larvae, Beetles, fishes, Cranes, Water Snakes, Zooplanktons, Other Birds Hawks etc. Crustaceans etc 5 Marine Zooplanktons, Bigger Fishes, Giant Carnivorous Ecosystem Crustaceans, Small Mackerel etc Fish, Sharks, fishes Whales, Snakes, Hawks etc 2.4.2 ABIOTIC COMPONENTS These are the non-living factors in form of solids, liquids or gas found in nature (ice, water, moisture). They can be categorised into two types. I) Climatic factors: e.g Light, Temperature, Humidity, Rain etc. II) Edaphic factors: e.g Soil, Organic and Inorganic components of soil, Substratum etc. Let’s discuss the importance of each abiotic factor and its limitations in an ecosystem. 26 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I A. Climatic Factors A.1 Light It is an essential factor for all living organisms like producers, consumers as well as decomposers. In presence of the sunlight, plants can prepare their food material, which in turn is eaten by the heterotrophs & ultimately by the decomposers. Without sunlight, photosynthesis is not possible thus it is one of the most important abiotic factors of an ecosystem. Quantity, as well as the quality of light, has a different impact on different organisms. Let’s discuss: i) Importance of light for plants a) Chlorophyll production b) Distribution of plants: The vegetation or the types of plants that grow on the earth depend on the amount of sunlight they are getting. Thus the vegetation of temperate, tropical as well as Tundra regions is different from each other. c) Light thus decides the physiology of the plants of different regions. d) Temperature: When light increases, temperature also increases and vice versa. When temperature increases, the rate of transpiration in the plant increases. Thus, the absorption of water from the underground also increases. It clearly explains that temp also plays an important role and decides the type of plants to grow in a particular area. e) Stomatal Movement: The stomata are present in the leaves of the plants. They control the evaporation of water from a plant body. Thus, by opening and closing, stomata keep the plant body in a stable physiological status. f) Duration of Light: During the summer and winter months the types of flowers, and what we can observe in nature are different. The basic theory behind it is some plants that can bloom in the summer months are long days (based on the exposure to sunlight) plants and some are short-day plants (less exposure to sunlight or natural light). ii) Importance of Light for animals a) Metabolism: Light controls the physiology & metabolism of animals by affecting their enzymatic activity. 27 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses b) Vision: Without light, it is very difficult to see anything. So it is required by all animals. c) Pigmentation: The process of pigmentation on the skin colour depends on the natural light source. d) Reproduction: Different animals respond to different duration of light exposure for their breeding activities. e) Circadian Rhythm: Daily response of the animals toward the light condition is known as circadian rhythm. This is an important physiological action of all living organisms. Thus, it is a light-dependent process. A.2 Temperature: Temperature affects animals and plants in the following ways. i) Importance of temperature for plants a) Metabolism: Temperature increases physiological activity. Thus, the types of plants that grow in a desert ecosystem are different from the type of plants in a forest ecosystem and an aquatic ecosystem. b) On Growth & Development: Different types of plants need a different range of temperatures for their growth. Summer growing plants are different from winter season growing plants. This is self-explanatory. c) Thermal Stratification: The best example is an aquatic ecosystem. The organisms growing at the surface layer are different as they need more temperature and light than the organisms that grow at a deeper level in an aquatic ecosystem. ii) Importance of Temperature for Animals Based on the need for temperature, animals are categorised into two types. Like: a) Warm-Blooded or Endo- thermic animals b) Cold–Blooded or Ecto-thermic Animals Warm-blooded animals maintain their body temperature at a constant level. Their body temperature does not change with the environment's temperature. e.g: Mammals, Birds, etc. The body temperature of the organism when changes with the temperature of the environment, then they are known as Cold Blooded animals. e.g: Frogs c) Migration: Temperature is also a factor in the migration of animals. It is known as thermal migration. If temperature changes the locomotory animals 28 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I or birds may change their places for a temporary period & their comeback to their original ecosystem when the weather changes. A.3. Water: Life is never possible without water. So, water is a very important abiotic factor in an ecosystem. The amount of water present in an area decides the type of ecosystem to be developed there. In this regard sometimes aquatic ecosystems also develop e.g Pond & Lake ecosystems. If for a longer period, due to any reason, a huge amount of water got deposited & replenished repeatedly due to rainfall etc., then through the process of succession an aquatic ecosystem develops and gets established there. Besides photosynthesis & other metabolic activity plants needs water for the circulation of minerals throughout its body. Water is also an essential requirement of animals for their metabolic activity. Water regulates the body temperature of both plants and animals. Water in the form of rainfall is also needed by the ecosystem. It maintains the humidity & content of moisture in the atmosphere. The amount of rainfall also decides the kind of plants to grow over there. eg. Deciduous forests, Evergreen forests, Deserts etc. With the type of vegetation, different types of animals also started living in that particular geographic area. Water in form of humidity also affects plants and animals lives. Some plants can grow in a less humid area whereas some other plants need more moisture in their environment. Some plants can use atmospheric moisture directly from the environment e.g Epiphytes, Orchids, Lichens, Mosses etc. Some other needs it in liquid form from underground by the process of absorption eg: Higher plants. B. Edaphic Factors B.1. Soil: Soil is a natural resource and provides a platform for plants to grow and animals to dwell on it. Thus, the fertility and quantity of soil decide the type of vegetation in that area. To be more specific, the pH of the soil is the deciding factor. If the pH of the soil is less than 7, then it is acidic soil & if the pH is more than 7 it is alkaline. Thus, the acidity & alkalinity of the soil decides the number & kind of plants & animals to stay over there (Fig 2.3). But needless to say, neutral soil, i.e. when the pH ranges from 6.5 -7.5 is the preferred condition for most living organisms. 29 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses Fig 2.3: Schematic representation of different textures of the soil (Source: https://upload.wikimedia.org/wikipedia/commons/4/45/Horizons.gif) Soil is also associated with different kinds of minerals & nutrients. Some are required in more quantities and are called macronutrients and some are micronutrients which are required in small quantities. They also play a vital role in the development and sustenance of an ecosystem. The texture of the soil is also playing a key role. eg. Rocky areas, Swampy areas, Mining areas etc. Different textured soil will allow different types of biotic factors or organisms to grow and establish themselves in that ecosystem. ACTIVITY Enlist the biotic and abiotic components of an aquarium ecosystem. Also, write down the importance of each component in that ecosystem. 30 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I IN-TEXT QUESTIONS 1. The ecosystem is classified into biotic and __________ components. 2. Water is a type of biotic component. True/False 3. An example of an abiotic Component is : a) Horse b) Ashoka Tree c) Whale Fish d) Air 4. In the soil profile, R horizon stands for ____________________. 5. ____________ animals maintain their body temperature at a constant level. 2.5 ECOLOGICAL PYRAMIDS By now we are clear that the ecosystem can sustain itself if there is a balance between the producers, the consumer and the decomposers. Energy is a major link which binds all the above components in an ecosystem. Thus, there is a fixed position or level of a particular type of organism in an ecosystem. How we can know or decide on that position? To explain it, a graphical structure has been proposed by environmental biologists, known as a pyramid or Ecological Pyramid (Fig 2.4). An ecological pyramid is a graphical representation of the relationship between various trophic levels of organisms in a Food Chain. It was first designed by Charles Elton and is called Eltonian Pyramid or Food Pyramid. Ecological Pyramids are of three types: 1. Pyramid of Number 2. Pyramid of Biomass 3. Pyramid of Energy 1. Pyramid of Numbers: As the name says, in this type of pyramid number of organisms is counted and accordingly respective volume to each trophic level is allotted in the pyramid. Characteristic features of the pyramid of numbers are. i) The number of producers is higher in number than the consumers present in other trophic levels. ii) The number of individuals in each trophic level decrease when we go from bottom to top in a pyramid. 31 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses iii) Collectively the living organisms present in each of the trophic levels are known as standing crops. iv) Normally the pyramid of numbers is upright (Fig 2.5) e.g Grassland ecosystem, Aquatic ecosystem. v) Sometimes inverted pyramids (Fig 2.6) are also found in this case. vi) A mixed or spindle-shaped pyramid is also observed in the case of the forest ecosystem. Fig 2.4: Schematic representation of an Ecological Pyramid (Source: https://sites.google.com/site/vhs2015environmentalscience/biodiversity/ecological- pyramids) Fig 2.5: Upright Pyramid of Numbers (Source: https://www.pmfias.com/ecological-pyramids-pyramid-numbers-biomass-energy/) 32 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I 2. Pyramid of Biomass: Biomass is the total dry weight of the animals as well as plants present in the ecosystem at any point in time. Like a pyramid of numbers, it may be upright or inverted. In the case of a forest and grassland ecosystem, it is upright and in the cases of a pond ecosystem, inverted pyramids (Fig 2.7) are observed. The Fig shows the position of different organisms at different trophic levels. Fig 2.6: Inverted and Spindle-Shaped Pyramid of Numbers (Source: https://www.pmfias.com/ecological-pyramids-pyramid-numbers-biomass-energy/) Fig 2.7: Upright and Inverted Pyramid of Biomass (Source: https://www.tutorialspoint.com/environmental_studies/environmental_ studies_ecological_pyramid.htm) 3. Pyramid of Energy: As already mentioned, the Food Chain and Food Web systems have existed for energy requirements and energy transfer between the living organisms in an ecosystem. It is the most important type of ecological pyramid. The amount of energy 33 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses being transferred from the lower trophic level towards the upper ones become less and less. Thus, the longer the pyramid in height, the lesser will be the amount of energy to reach the organisms present at the topmost trophic level. Only 10% of the energy is transferred to the subsequent upper trophic level organisms (Fig 2.9). For example, if the producers generate a 1000 kilo-calorie amount of energy, the primary consumers will receive 100 kcal, the secondary consumer will get 10 kcal and only 1 kcal amount of energy will reach the tertiary or topmost level of consumers. In this way, a pattern of an upright Pyramid of Energy (Fig 2.8) will be developed for all types of ecosystems found in Nature. This is the universal formula. An energy pyramid can never be inverted or spindle-shaped found in other types of ecological pyramid structures. The shape of the pyramid of energy is not affected by the size, biomass, number or metabolic rate of the organisms. Some limitations are also observed in the studies of ecological pyramids. That can be described as follows: 1. The position of certain organisms is not fixed in one ecological pyramid. That may vary in the same or maybe in a different ecosystem. 2. There is no consideration of seasonal changes while studying the pyramids 3. The role of detrivores is not represented in an ecological pyramid. At last, it can be said that the pyramid of energy is very accurate and gives a true picture of the ecosystem. Fig 2.8: Structure of Pyramid of Energy 34 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi Environmental Science: Theory into Practice I Fig 2.9: Energy Flow 10% rule in an Ecosystem (Source: https://www.tutorialspoint.com/environmental_studies/ environmental_studies_ecological_pyramid.htm) IN-TEXT QUESTIONS 6. What is a graphical representation of the relationship between individuals at various trophic levels of a food chain called? 7. An energy pyramid can never be an inverted one. True/False 8. Only 10% of the energy is transferred to the subsequent upper trophic level organisms. True/False 9. Who formulated the ecological pyramids? a) Charles Darwin b) Raymond Lindemann c) Charles Elton d) Gregor Mende 10. Which pyramid depicts the numbers at each level? a) Pyramid of energy b) Circular pyramid c) Pyramid of age d) Pyramid of numbers 35 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 2.6 ECOLOGICAL SUCCESSION The ecological succession term was coined by Ragnar Hult (1885). Famous ecologist Clement defined Ecological Succession as “the natural process by which the same locality becomes successively colonised by different groups or communities of plants”. Characteristics of Ecological Succession: 1) The species types and the community change in an orderly process 2) The physical structure of a community changes by the biological action of the biological factors that grow there. 3) At last a stable ecosystem gets established in an area. Both biotic, as well as abiotic factors, interact there to establish equilibrium in that ecosystem. 4) Then the climax community gets established there, which in turn maintains an equilibrium with the environment. Fig 2.10: Schematic Representation of a Forest Succession (Source: https://upload.wikimedia.org/wikipedia/commons /4/41/Forest_succession_depicted_over_time.png) 36 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Causes of Ecological Succession a) Initial causes: It happens to the destruction of existing habitat. It is two types. i) Climatic Factors: e.g Soil Erosion, Soil deposition due to heavy wind, Continuous flood, Heavy rainfall, Fire, Drought, Land Slides, Oil Deposition etc. ii) Biotic Factors: e.g. Deforestation, Overgrazing, Jhum cultivation etc. b) Continuous Causes: It is responsible for the changes in the population composition in that area. The factors responsible for population compositions are migration for safety, migration due to urbanization, migration due to industrialization, migration for better life etc. c) Stabilizing Causes: Stabilization of an ecosystem happens due to the climatic condition of that area, availability of minerals, fertility of the land for agriculture as well as the growth of different types of producers for a continuous flow of food and energy as discussed earlier. The order of basic processes involved in succession is: nudation, invasion, completion and coaction, reaction, stabilization Types of Ecological Succession 1) Primary succession: It begins from the primitive substation where there was no living factor before. e.g Volcanic eruptions, Rocky Areas etc. 2) Secondary Succession: It begins from a previously sustained living matter, but the vegetation got damaged due to any climate factors like flood, fire, acid rain etc. 3) Autogenic Succession: (Auto means self or same, and genic means producing/causing) The developing plant community brings a change in the condition of a particular place, which is not suitable for them, but creates or produces an environment for the growth of a different community. It is a succession driven by the biotic components of an ecosystem. 4) Allogenic Succession: (It is caused by abiotic factors) In contrast to autogenic succession, allogenic succession is an abiotic factor-driven condition. The habitat of the ecosystem is changed due to volcanic eruptions, climate change, comet strikes, earthquakes, floods, drought etc. 5) Induced Succession: It is a man-made process, developed for the benefit of humankind. eg. Cultivation of Crops in a field. 37 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 6) Autotrophic Succession: When a place is rich in inorganic content & poor in organic matter, the development of a succession of plants over that area is called autotrophic succession. 7) Heterotrophic Succession: If a succession begins in an area which is rich in organic contents like forest litter, sewage etc, and dominated by saprophytes like fungi, mushrooms etc is called heterotrophic succession. 8) Retrogressive Succession: Sometimes due to heavy biological or biotic interferences, the succession goes backwards instead of progressing. e.g Forest community changes to shrubland or grassland or barren land due to deforestation and overgrazing. IN-TEXT QUESTIONS 11. Who coined the word Ecological Succession? a) Hult (1885) b) Reiter (1885) c) Haeckel (1869) d) Odum (1951) 12. Induced Succession is a man-made process. True/False 13. When succession goes backwards instead of progressing, it is known as ___________________. 14. The order of basic processes involved in succession is (a) invasion -> stabilization -> completion and coaction -> reaction -> nudation (b) nudation -> stabilization -> completion and coaction -> invasion -> reaction (c) invasion -> nudation -> completion and coaction -> reaction -> stabilization (d) nudation -> invasion -> completion and coaction -> reaction -> stabilization 2.7 SUMMARY The ecosystem is the study of living organisms with their surroundings. Thus, it’s an interdependence of biotic and abiotic factors in an area. The presence of only one factor cannot create an ecosystem. In an ecosystem positions of different organisms are different. This has been explained through ecological pyramids. The principle of the ecological pyramid depends on the food habit of the organisms present in that ecosystem. The development of a new ecosystem on barren land is known as succession. Sometimes reverse succession also happens when a well-functioning ecosystem may get destroyed due to some artificial i.e. man-made or due to natural calamities and gets converted into barren land. 38 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I 2.8 GLOSSARY Ecological Succession: the process by which the structure of a biological community evolves over time. Edaphic Factor: These are the aspects of the soil that affect the different kinds of organisms that live there. 2.9 ANSWERS TO IN-TEXT QUESTIONS 1. Abiotic 8. True 2. False 9. Charles Elton 3. Air 10. Pyramid of Numbers 4. Bedrock 11. Hult (1885) 5. Warm-blooded 12. True 6. Ecological Pyramid 13. Retrogressive Succession 7. True 14. (d) 2.10 SELF-ASSESSMENT QUESTIONS 1. What do you mean by an Ecosystem? 2. What are the ecological pyramids in an ecosystem? 3. Explain different types of ecological pyramids in an ecosystem. 4. What is the succession in an ecosystem? Explain in detail what you know about it. 5. Explain consumers, the pyramid of energy and the edaphic factor. 2.11 REFERENCES 1. Dey, A. K. (1990). Environmental Chemistry. Wiley Eastern Ltd. 2. Bharucha, E. (2004). Textbook for Environmental Studies. University Grants Commission, New Delhi 2.12 SUGGESTED READINGS 39 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 1. Raven, P.H, Hassenzahl, D.M., Hager, M.C, Gift, N.Y., and Berg, L.R. (2015). Environment, 9th Edition. Wiley Publishing, USA. Chapter 3 (Pages: 38-52); Chapter 4 (Pages: 53-62); Chapter 5 (Pages: 100-103); Chapter 6 (Pages: 106- 128). 2. Singh, J.S., Singh, S.P., and Gupta, S.R. (2017). Ecology, Environmental Science and Conservation. S. Chand Publishing, New Delhi. Chapter 13 (Pages: 307-323); Chapter 18 (Pages: 420-442); Chapter 28 (Pages: 747-769). 40 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I LESSON 3 ECOSYSTEM: BIOGEOCHEMICAL CYCLES, FUNCTIONS, ENERGY FLOW AND PRODUCTIVITY Prof. Nibedita Khuntia Maharaja Agrasen College University of Delhi STRUCTURE 3.1 Learning Objectives 3.2 Introduction 3.3 Biogeochemical Cycles 3.3.1 Atmospheric Nutrient Cycle 3.3.2 Edaphic Nutirient Cycle 3.4 Functions 3.4.1 Food Chain 3.4.2 Food Webs 3.5 Energy Flow in an Ecosystem 3.6 Productivity 3.7 Homeostasis 3.8 Summary 3.9 Glossary 3.10 Answers to In-text Questions 3.11 Self-Assessment Questions 3.12 References 3.13 Suggested Readings 3.1 LEARNING OBJECTIVES After going through this lesson, you will be able to 1. know the categories and their respective sub-categories of the biogeochemical cycle. 2. understand the working of the food chain. 3. distinguish between grazing and detritus food chains. 41 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses 4. give a schematic representation of the food web. 5. explain energy utilization in an ecosystem. 6. know the various concepts of productivity. 3.2 INTRODUCTION Function means the working of a particular ecosystem of a particular area. It includes the interlinking of organisms, their nutritional requirements, the circulation of nutrients, energy flow, and again decomposition of all the chemicals, both organic as well as inorganic and their release into the atmosphere. Mainly all these activities have been explained under three major categories as follows 1. Biogeochemical Cycle 2. Food chain and Food Web 3. Energy flow in the Ecosystem 4. Productivity 3.3 BIOGEOCHEMICAL CYCLES As the name indicates, in an ecosystem, both biological as well as physical components, pass/roll through the underground and above the ground to complete a cycle. Through Nutrient Cycling various, inorganic and organic compounds are formed and decomposed (normally forty elements are required by the living organisms in nature). These are also called nutrient cycles of the ecosystem. "Nature is self-sufficient by nature". Biogeochemical Cycle has been divided into two major categories atmospheric and edaphic cycling based on the types of substance they are dealing with. I) Atmospheric Nutrient Cycle a) Water Cycle b) Carbon Cycle c) Oxygen Cycle II) Edaphic Nutrients Cycle a) Nitrogen Cycle b) Sulphur Cycle c) Phosphorous Cycle 42 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I 3.3.1. Atmospheric Nutrient cycle a) Water Cycle: Water is an essential compound for photosynthesis in plants. Plants absorb water from the underground through the roots, to their upper or aerial parts. This water is used for the process of photosynthesis. Some water gets back to the atmosphere from the plant body through the process of transpiration and some are utilized by the plants for their metabolic activity (Fig 3.1). The driving force for a water cycle is solar radiation which is 15% of the total radiation reaching the earth. Though the radiation water gets evaporated from the surface of the waterbodies, it comes back to the surface of the earth as rain. Figure 3.1 clearly shows us how the cycling of this vital resource occurs on the earth. Fig 3.1: The Water Cycle (Source: https://upload.wikimedia.org/wikipedia/commons /9/94/Water_cycle.png) b) Carbon Cycle: Carbon Dioxide is an important gas present in nature. Plants need it for the process of photosynthesis to prepare the food material that is carbohydrates for its own as well as for heterotrophs. That means it gets locked into the organic matter through the process of photosynthesis. Carbon Dioxide is released into the atmosphere by the respiration of all the living organisms on the earth. Earth’s Crusts also release 43 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses carbon which is present in the forms of Calcium Carbonates (CaCO3) and Magnesium Carbonates (MgCO3) which come from the skeletons of marine organisms in the process of mineralization. By subsequent weathering, these Calcium Carbonates and Magnesium Carbonates get mixed with the soil and add to the soil nutrition. In this way ultimately these carbon-rich organic matters accumulate in the ecosystems. By the burning of fossil fuels, coal & wood large amount of carbon dioxide gets released into the atmosphere. These carbon dioxides get assimilated by the plants. The animals consume these carbohydrates, that is photosynthetic products. The carbohydrates consumed, in this way reach the heterotrophs. When these heterotrophs die, carbon again goes back to the earth’s crust. Through the process of respiration also carbon dioxide is released from the biotic components into the atmosphere (Fig 3.2). Fig 3.2: Carbon Cycle (Source: https://d32ogoqmya1dw8.cloudfront.net/ images/clean/literacy/tlp /carbocycle/carbon_cycle_diagram_1466775306722780178.jpg) 44 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I c) Oxygen Cycle: In the atmosphere, the dry air contains 20.94% of oxygen. Oxygen is required by all living organisms for respiration. It is also associated with moisture content. It is the simplest but inevitable nutrient cycle in ecosystems (Fig 3.3). 3.3.2. Edaphic Nutrient Cycle a) Nitrogen Cycle: It is a complex cycle that occurs in nature through various steps. About 79% of the atmospheric air is Nitrogen. It enters the biotic world and got assimilated then again goes back into the atmosphere. The following steps are involved in the completion of the Nitrogen cycle (Fig 3.4). Fig 3.3: Oxygen Cycle (Source: https://www.universetoday.com/61080/oxygen-cycle) A. Nitrogen enters the living organisms: Pure nitrogen gas cannot be used by green plants. Only Nitrate & Ammonium forms of Nitrogen can be utilized by them. Thus, nitrogen gas is first fixed into Nitrous oxide, Nitric oxide and Ammonium in nature. 45 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses The production of nitrates from nitrogen is called nitrification. The production of ammonia is called ammonification. 1. Nitrification: It can be done both in a non-biological (physical) and biological way. i) Non- Biological fixation of Nitrogen or Nitrification: During lightening, nitrogen gets combined with the oxygen in nature, this reaction needs a high amount of energy. ii) Artificially nitrogenous compounds are also get produced in industries. They are chemical fertilizers. Farmers use these fertilizers to enhance the yield of the crops and soil fertility. iii) Biological Nitrogen Fixation: As the name indicates biological nitrogen fixation is carried out by the living organisms known as nitrogen-fixing organisms. e.g Blue-green algae, Bacteria, Fungi etc. Fig 3.4.: Schematic Representation of Nitrogen Cycle (Source: https://en.wikipedia.org/wiki/ Nitrogen cycle #/media/File:Nitrogen_Cycle_2.svg) 46 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I Biological Nitrogen Fixation is of two types: i) Non-Symbiotic Nitrogen Fixation: It is carried out by organisms, that live freely in the soil or water. eg. Azobacter, Anabaena, Nostoc etc. ii) Symbiotic Nitrogen Fixation: Some microorganisms live inside the root nodules of different plants in a symbiotic association. They can fix atmospheric nitrogen. This process is called symbiotic nitrogen fixation. In the roots of the higher plants, primarily in legumes (beans, peas, soybeans), the nitrogen-fixing organisms form nodules, multiply inside these nodules and carry out the process of nitrogen fixation. eg. Bacteria, Rhizobium etc. The nitrogen gas from the atmosphere gets converted into Ammonia (NH3) which is then converted into amino acids. Amino acids are the building blocks of nucleic acids (DNA and RNA). Due to the symbiotic association legumes are regarded as a good biofertilizer for other crops which in turn reduces the use of chemical fertilizer in the crop fields. Without root nodules also some symbiotic associations are there for nitrogen fixation in nature. Example: (i) Anabaena – Azolla association (ii) Cycas Coralloid roots etc. B) Ammonification: Ammonification is an important step in the nitrogen cycle. It is the process of production of ammonia (NH3) or ammonium (NH4) compounds from the decomposition action of bacteria on organic matter. Thus, on the death and decay of the plants as well as animals the complex organic compounds are released into the soil where they are again decomposed into simpler compounds by the microorganisms and release energy. Examples of bacteria – Nitrosomonas bacteria, Nitrosococcus bacteria C) Nitrification: When ammonium gets converted into nitrates, it is called nitrification. Nitrates can be directly absorbed by plants & incorporated into proteins, nucleic acids & other nitrogenous organic compounds. Some nitrates may be stored in the humus of the soil, immobilized by the bacteria & some may reach into the waterbodies with the runoffs. D) Nitrogen Gas back to the Atmosphere: Through the process of denitrification, nitrogen gas goes back to the atmosphere. Some bacteria there can convert Nitrates (NO3) to Nitrites (NO2). They are called denitrifying bacteria e.g Pseudomonas. Ultimately Nitrates, Nitrites & gaseous Nitrogen are then released into the atmosphere. 47 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses b) Sulphur Cycle Fig 3.5: Schematic Representation of Sulphur Cycle Like other Nutrient Cycles, the movement of sulphur in the biosphere and the underground is called the “Sulphur Cycle” (Fig 3.5). Sulphur Cycle is a sedimentary type of nutrient cycle as the reserve pool is buried underground in rocks, minerals as well as sulphates (SO4) in sea sediments. Sulphur is found in nature in the following forms: Hydrogen sulphide (H2S), Sulphur dioxide (SO2), and Sulphates (SO4). Fig 3.6: Schematic representation of Sulphur Cycle in detail (Source: https://en.wikipedia.org/wiki/Sulfur_cycle#/media/File:SulfurCycle_copy.jpg) 48 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I It enters the living system as i) The soluble form is present in the soil and passes on to the plants through the plant's roots. ii) It is assimilated by the plant to synthesize protein, vitamins & some other important products. iii) Then the above compounds are passed to the animal bodies through the food chain. Within plants & animal bodies the organic sulphur is decomposed by aerobic bacteria into sulphate (SO4) or hydrogen sulphides (H2S). Hydrogen Sulphides then get converted into elemental sulphur by anaerobic bacteria (these bacteria do not require oxygen). In this way, sulphur gets back to the soil & sulphur cycle gets completed. Sulphur Dioxide (SO2) is also released into the atmosphere by vehicular exhaustion i.e. the burning of fossil fuels (Fig 3.6). Example: Petroleum, Coal etc. c) Phosphorus Cycle: In the ecosystem, more phosphorous is available in plants and animal bodies in comparison to the abiotic system. In the abiotic system phosphorous is abundant in rocks and other natural deposits, formed during geological processes. Phosphorous is desired for the structure of DNA, as coenzymes and for the conversion of foods to release usable energy. It is a simpler cycle. Fig 3.7: Schematic representation of Phosphorous Cycle (Source: https://en.m.wikipedia.org/wiki/File:Phosphorus_Cycle_copy.jpg) 49 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  All UG Courses The roots of the plants absorb Phosphorous present in a soluble form in the soil and assimilate it. Through the food chain, it then gets transferred to the animal bodies and by the death and decay of the plants and animals, or animal excreta it goes back to the atmosphere (Fig 3.7). The runoff from the soil and the loss of phosphorous to the sea is greater than the availability on it the land. Only 60,000 tons of phosphorous is returned to the soil through the birds, fishes of the sea and the algae. A major amount of phosphorus gets lost in the sea. IN-TEXT QUESTIONS 1. The driving force for a water cycle is solar radiation which is _________ of the total radiation reaching the earth. 2. Carbon Dioxide is released into the atmosphere by ___________ of all the living organisms on the earth. 3. In the atmosphere, the dry air contains _______________ of oxygen. 4. Only _________ and ammonium forms of Nitrogen can be utilized by green plants. 5. During lightening, nitrogen gets combined with the ____________ in nature, this reaction needs a high amount of energy. 3.4 FUNCTIONS 3.4.1. FOOD CHAIN The transfer of food energy from the source in plants through a series of organisms with repeated eating & being eaten is referred to or called the food chain. How the Food chain works: The green plants are the autotrophs or the producer of the ecosystem. With the help of chlorophyll, and by using CO2 and H2O from nature in presence of sunlight the plants can prepare their own food known as carbohydrates. The process is known as photosynthesis. Sunlight Plants CO2 + H2O + Chlorophyll Carbohydrates (Photosynthesis Process) 50 | P a g e © Department of Distance & Continuing Education, Campus of Open Learning, School of Open Learning, University of Delhi  Environmental Science: Theory into Practice I That’s why plants are called autotrophs (auto-self; troph means to nourish). Thus, plants are the first step in a food chain. The heterotrophs (hetero means other; troph means