Environmental Science Study Material PDF

Ability Enhancement Compulsory Course (AECC) Environmental Science For All UG Courses Semester I/II Study Material : 1 (Lesson 1 to 9) SCHOOL OF OPEN LEARNING University of Delhi Editors Prof. Radhey Shyam Sharma Dr. Nibedita Khuntia Ability Enhancem E ent Compu ulsory Courrse (AECCC) Enviironmentall Science (For All Undergradu U uate Coursees) Semesterr I/II Stuudy Materiaal 1 (Unit: 1 – 4; Lesson: 1-9) Editorss Prof. Radhey Shyaam Sharmaa Departmentt of Environnmental Stuudies Un niversity off Delhi AND Dr. Nibedita K Khuntia Mahaaraja Agraseen College Un niversity off Delhi Lesson Writeers List Lesson Author Title Paage No. 1 Dr. Mayaank Pandey Introducction to Envvironmentall Studies 1-15 2 Dr. Nibeddita Khuntiaa Ecosysttem: Structuure of Ecosyystem 166-30 3 Dr. Nibeddita Khuntiaa Ecosysttem: Functioon of the Eccosystem 311-47 4 Dr. Sarthhak Malhotrra Ecosysttem: Types of Ecosysteems and 488-58 Ecosysttem Servicees 5 Dr. Ashissh Thomas Natural Resources:: Land Resoource 599-71 6 Dr. Ruchhi Mishra Natural Resources:: Water Ressources 722-82 7 Dr. Pram mod Kumar Natural Resources:: Energy Reesources 833-103 8 Dr. Rajw want Kaur Biodiveersity 1004-118 9 Dr. Nehaa Sharma Biodiveersity Conseervation Straategies 1119-128 Cou urse Co-ord dinator Dr. Janmejoy J K Khuntia Asssociate Proofessor School of Open Learning Unniversity off Delhi Delhi - 1100007 School of Open Learning 5, Cavaalry Lines, University U o Delhi, Deelhi-1100077 of LESSON-1 INTRODUCTION TO ENVIRONMENTAL STUDIES Dr. Mayank Pandey Assistant Professor, P.G.D.A.V. College (Eve), University of Delhi INTRODUCTION The term Environment is derived from 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 the nature, form the environment. The Environmental Protection Act, 1986 defines 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 the industries, tourism etc.) from the environment. It is a well-known fact that the 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 create environmental awareness which ultimately will lead to environmental conservation. LEARNING OBJECTIVES  To make the reader aware about the environment, its importance and basic components.  To develop an understanding about the concept, scope and importance of the discipline Environmental Studies  To discuss the concept and necessity of multidisciplinary approach of the subject.  Readers will be aware of the historic milestones of the environmentalism and environmental education  To make the readers know about the origin of the concept of ‘Sustainability’ and ‘Sustainable Development’. 1. Components of Environment Planet earth is the only known planet in the universe having 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 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: Lithosphere: (Greek: Lithos means rock) Earth’s structure can be stratified into outer crust, middle mantle and inner core regions (Fig. 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, plateau, deep valleys and sea beds make the surface of lithosphere uneven. Mount Everest is the highest point on the lithosphere. Various geological processes like weathering & erosion, volcanic eruptions, biogeochemical cycles take place at the lithosphere. Different terrestrial ecosystems like forests, grasslands, deserts etc. are found on the lithosphere. Figure 1: Cross section of Lithosphere (Source: https://www.nationalgeographic.org/encyclopedia/lithosphere/) Hydrosphere: (Greek: Hydor means water) Hydrosphere represents water masses on the planet present in solid (ice cover, glaciers etc.), liquid (water bodies) and gaseous (water vapors) phases. Hydrosphere covers almost three-fourth of the total surface area of the earth. Oceans and seas represent marine ecosystem which contains 97 percent of the total water content (having very high concentration of salts) of the planet. Remaining 3 percent of the water resources are freshwater present in the form of glaciers, rivers, lakes, ponds etc. (Figure 2). 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 sink of carbon in the environment. ‐2‐ Figure 2: Distribution of Water Resources on the Earth Atmosphere: (Greek: Atmos means vapor) the thin sheet of gaseous mixture which envelops the planet earth is called atmosphere. Content of water vapor, density of the air mass and atmospheric pressure decreases rapidly with the increase in altitude. The composition of dry air is as follows: Table 1: Composition of dry air Component Volume (%) Nitrogen 78.084 Oxygen 20.946 Argon 0.934 Carbon di oxide 0.04 Gases in traces Remaining The rate of change of temperature with the altitude is called lapse rate. The atmosphere has been stratified into major four layers where temperature decreases (negative lapse rate) or increases (positive lapse rate). Brief description of atmospheric layers is as follows:  Troposphere: the altitude of this layer varies from 16 km at equator to 8 km at poles. Largest percentage of the air mass found in this region. The upper layer is called tropopause. Temperature decreases with increase in altitude (-6.4 0C per km) in this layer and varies from 15 0C (ground Level) to – 56 0C (tropopause).  Stratosphere:temperature starts rising in this layer from tropopause (-56 0C) to stratopause (-2 0C)as ozone (O3) layerin the upper stratosphere absorbs solar radiation and temperature rises. Ozone layerin this region absorbs harmful UV radiation, particularly UV-B radiation (280 nm to 315 nm), because of which life is possible on 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.  Mesosphere: temperature starts decreasing again and reaches at -96 0C at the upper boundary of the layer i.e. mesopause. 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. ‐3‐  Thermosphere: ionic oxygen atoms and other ions in this layer absorb short wave solar radiation which increases the temperature in this layer rapidly from -96 0C (lower boundary) to 1200 0C (upper layer). Table 2: Layers of atmosphere and their composition (Source: Environmental Chemistry by A.K. Dey) Layer Average Altitude Temperature Variation Prominent Chemical (km) (0C) Species Troposphere 0 - 11 15 to (-56) N2, O2, Ar, CO2, H2O Stratosphere 11-50 (-56) to (-2) O3 Mesosphere 50-85 (-2) to (-96) O2+, NO+ Thermosphere 85-500 (-96) to 1200 O2+, O+, NO+ Figure 3Layers of atmosphere and temperature change with latitude (Source: Britannica Encyclopedia; https://www.britannica.com/science/ozone-layer) ‐4‐ Biosphere:(Greek: Bios means life) this is the self-regulating overlapping region of atmosphere, lithosphere and hydrosphere in the environment where life sustainably exists, nourished and flourished by the healthy interaction between biotic (autotrophs and heterotrophs) and abiotic components (air, water, sunlight, soil, rock etc.) of the nature. Figure 4: Biosphere (Source: Britannica Encyclopedia; https://www.britannica.com/science/biosphere) 2. 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 course for environmental education and establish an independent and multidisciplinary discipline, commonly called as Environmental Science or Studies. According to UNESCO (1971), the objectives of environmental studies are:  Creating the 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 public to participate in environment protection and environment improvement. ‐5‐  Acquiring skills to help the concerned individuals in identifying and solving environmental problems.  Striving to attain harmony with Nature. UNESCO and UNEP jointly organized first intergovernmental conference on environmental education in 1977 at 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 behavior 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 experience in, 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 resolution of environmental problems. Environmental Education in India: India also started taking significant steps to propagate environmental education. At post-graduation level, the environmental education was started by many central and state universities in India during 1985-2000. In 1991, Hon. Supreme Court of India gave historical ruling to implement environmental education at all the levels and gave directions to make Environmental Studies a compulsory paper for all the streams at under-graduate levels in Indian universities. At present, various short-term and regular courses on environment and its various dimensions are being run in various universities in India. 3. Difference between Environmental Science and Environmental Studies Environmental Studies: Environmental studies is multidisciplinary subject which studies about 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 micro and macro level. ‐6‐ 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 discharge of untreated wastewater into the river. The student of Environmental Science will observe the causes, physico-chemical and biological changes within the river water, its effect on 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. 4. Multidisciplinary 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, Environment and environmental issues are complex in nature. Therefore, expertise from different subjects or disciplines is required to understand different aspects of the environment. We may require expertise from different disciplines to resolve various environmental issues. 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 to 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 biological diversity of the region by the 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 about 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, soil and  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. ‐7‐  Social Sciences, Sociology and Economics: to assess the socio-economic stature of the population and possible changes the same with on-going developmental projects.  Law and Legal Aspects: expertise from 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. Figure 5: Multidisciplinary Nature of Environmental Studies 5. Scope and Importance of Environmental Studies The multidisciplinary approach of the subject can be implemented in wide range of applications and fields related to the environmental awareness, education and conservation. Hence, the subject has a vast scope and the expert of the subject can serve in numerous ways in different spheres of the society. Students may opt 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, large number of dedicated departments, centers, universities and institutions have been established for the subject. An interested professional may join the teaching and academics and make the next generation aware about the environmental issues and its 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. ‐8‐  Research & Development: research and post-doctoral works have been going on worldwide to understand the environmental 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 the environmental experts. Few of the 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 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.  Green Journalism: environmental awareness is indispensable for the environmental conservation and media (print, electronic and social media) is the strongest medium to propagate the awareness. Green journalism is the term given when media raises the environmental issues and its practical solutions suggested by the experts of the subject.  Environmental legislation and Green Advocacy: for an effective environmental conservation, it is indispensable to have stringent legislative provision 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 the environmental problems. The subject is still evolving as the 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 the natural resources etc., which are causing serious threats to the life on the planet. Environmental Studies has given tangible solutions to the environmental problems. Some of the prominent fields, which 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 about the basics and details of the subject. ‐9‐ 6. Important landmarks in Environmentalism In the western world, first ever concern about the environmental degradation was raised after 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, book ‘Limit to Growth’ by the Club of Rome attracted the 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 at Stockholm between 5th June – 16th June where India also presented its view on environmental degradation. In the remembrance of this conference, World Environment Day is celebrated every year on 05th June. India started Project Tiger in 1973 to save is national animal of India. In between, India and the world witnessed worst industrial disasters, Bhopal Gas Tragedy (02nd and 03rd December, 1984) and Chernobyl Nuclear Disaster (26th April, 1986), which taught many lessons to globe. Vienna Convention (1985) and Montreal Protocol (16th September 1987) were signed to protect the Ozone layer from getting depleted by the 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. The Agenda 21 was adopted in the Earth Summit at 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 down the emission of greenhouse gases responsible for the global warming. The World Summit on Sustainable Development (Rio + 10) was conducted in 2002 at Johannesburg. 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 one century. ‐ 10 ‐ Figure 6: Important Milestones in the history of Environmentalism 11 7.Concept of Sustainability and Sustainable Development It was the global perception that the environmental conservation and economic development cannot be pursued together. With the onset of 1980s, the world started finding the middle path so that the 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. 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.” 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 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 planet, now and into the future.’ All the developed and developing countries have been called to achieve the goals by global partnership. Society, environment and economy, collectively considered as 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 the 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, the 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) indicates environmental sustainability.  Social Sustainability: it defines a society 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) indicates social sustainability.  Economic Sustainability: economic sustainability means the equitable distribution of the 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 12 environment. Sustainablee Developm ment Goals 1 (No Pooverty), 2 (Zero Hun nger), 7 (Aff ffordable annd Clean Ennergy), 8 (D Descent Wo ork and Ecconomic Grrowth), 9 (IIndustry, Innoovation andd Infrastruccture), 10 (Reduced ( Inequalities) I ), 11 (Susttainable Citties and Commmunities) and 12 (R Responsible Consumption and Prroduction) iindicates ecconomic susttainability. The thrree pillars intersect i eaach other giiving the concept of bearable, b eqquitable and d viable globe, which w collecctively form ms sustainabble world.  Social Susttainability + Economiic Sustaina ability = Eq quitable  Social Susttainability + Environm mental Susstainability = Bearable  Economicaal Sustainability + Ennvironmental Sustainaability = Viiable  (Social + Econom mical + Environme E ental) Susstainabilityy = Susttainable Developmeent o Pillars off Sustainable Developm Figgure7: Vennn Diagram of ment Figu ure 8: Sustaainable Dev velopment Goals G (Sourcee: https://ww ww.un.org/ssustainableddevelopmennt/blog/20155/12/sustainnable-develo opment- gooals-kick-off ff-with-start--of-new-yeaar/) 13 QUESTIONS FOR PRACTICE One-word answer type Question 1. Title of the Brundtland Commission Report was _____________ 2. Number of Sustainable Development Goals are _______ 3. World Environment Day in observed every year on _________ 4. Lowest layer of the atmosphere is _________ 5. Bhopal Gas Tragedy took place on _______________ Answers: 1- Our Common Future; 2- Seventeen; 3- 05th June; 4- Troposphere; 5- 02nd – 03rd December, 1984 Match the following A. Silent Spring 1. Stratosphere B. Sustainable Development 2. 1972 C. Ozone layer 3. Wetlands Conservation D. UN Conference on Human Environment 4. Brundtland Commission E. Ramsar Convention 5. Rachael Carson Answers: A- 5; B- 4; C- 1; D- 2; E- 3 Short answer type Question  Define sustainable development  Define Biosphere Long answer type Question  What do you understand by the multidisciplinary nature of Environmental Studies? How the multidisciplinary approach is helpful in solving various environmental problems?  Describe the various components of atmosphere  Discuss Sustainable Development. Write a short note on Sustainable Development Goals. 14 GLOSSARY  Atmosphere: thin blanket of gaseous mixture which envelops the planet and 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 studies is multidisciplinary subject which studies about 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 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 15 LESSION-2 ECOSYSTEM: STRUCTURE OF ECOSYSTEM Dr. Nibedita Khuntia Assistant Professor, Maharaja Agrasen College, University of Delhi. 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. LEARNING OBJECTIVES After going through this lesson, you will be able to 1. Know the concept, definition and structure of ecosystem. 2. Distinguish between biotic and abiotic components of ecosystem. 3. Explain the different types of ecological pyramids. 4. Understand the term ecological succession. 1. CONCEPT OF ECOSYSTEM Ecosystem is the basic structural and functional unit of the environment. Both the living and non-living component of the nature, when interact with each other to establish a stable living community, it is called as Ecosystem. That means there is a constant exchange of something between these living & non-livings, is called an Ecosystem. Without the living component, 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 ecosystem includes complete analysis of the structure, regulation and the role of each and every component functioning there. Once we know it, in detail, the study of the ecosystem and its importance to the equilibrium of environment will be understood easily. 2. DEFINITION OF ECOSYSTEM The study of all the physical as well as biological processes including the distribution and abundance of living organisms and the interaction in between them with their surrounding environment is known as 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 is both the plants and the animals, present in that particular area. 16 The ecosystem is very complex in nature and human beings are a part of the ecosystems also. The theme of the ecosystem is “energy flow”. Sustenance of 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: Terrestrial or land-based ecosystem, Aquatic or water-based ecosystems etc. 3. STRUCTURE OF ECOSYSTEM It is very easy to study or understand the structure of ecosystem from the flow chart described (Fig.1) below. ECOSYSTEM BIOTIC COMPONENTS ABIOTIC COMPONENTS LIGHT PRODUCERS CLIMATIC FACTORS TEMPERATURE CONSUMERS WATER DECOMPOSERS EDAPHIC FACTOR SOIL Fig.1.Schematic Representation of Structure of an Ecosystem 3.1. BIOTIC COMPONENTS Biotic components are also divided into 3 categories basing upon their food-fed relationships (Fig.2). 3.1.1. PRODUCERS: Producers are the autotrophs (auto means self, troph means to nourish) of the ecosystem. They are the green plants and green microorganisms who can make their own food material by using carbon dioxide and water in presence of sunlight with the help of chlorophyll present in them. Ex. All green plants, Algae, Cyanobacteria, 17 3.1.2. CONSUMERS: Consumers are the heterotrophs (hetero-not self troph to nourish) of an ecosystem. They depend on the producers of the 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. Ex. Grasshoppers, Rabbits, Goats. b) Secondary Consumers – They cannot directly eat the producers of the ecosystem, that is the plants. They can eat only herbivores. Ex. Frogs, Jackal, Snakes c) Tertiary Consumers – They are carnivores in nature means they are the meat eaters. Thus, they depend on the secondary consumer for their food. They are the top-level carnivores. Ex. – Tigers, Lions, Vulture, Kite 3.1.3. DECOMPOSERS: Decomposers are also to some extent heterotrophic in nature. They do not contain chlorophyll, so depend on other material for food and energy. These organisms can grow on the dead and decay materials of the environment. That is why they are known as the decomposers or saprophyte, or scavengers of the nature or they can be called as 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 for the completion of the Biogeochemical Cycle in the environment. Ex. Bacteria, Fungi, Earthworm Sr.No. Type of Primary Consumer Secondary Tertiary Consumer Consumer Ecosystem 1 Grassland Grasshoppers, Rabbits, Frogs, Lizards, Hawks, Eagle, Tiger Ecosystem Deer, Sheep, Goats etc Birds, Snakes Etc 2 Forest Leafhoppers, Bugs, Flies, Birds, Owl, Tiger, Lion etc Ecosystem Squirrels, Insects, Deer, Lizards, Wolves, Fruit bats, Nilgai, Jackals, etc. Elephants etc. 3 Desert Insects, Rats Birds Camel, Scorpions, Fox, Snakes, Fox, Striped Ecosystem Squirrel Jackal, Rattle Hyena, Sand Cats, Viper, Snakes, Mongoose Saharan Cheetah, Eagles, etc Kites etc. 18 4 Pond or Insects, Frogs, Larvae, Insects, Larger Largest Fishes, Water Lake Beetles, Zooplanktons, fishes, Cranes, Snakes, Hawks etc. Ecosystem Crustaceans etc Other Birds 5 Marine Zooplanktons, Crustaceans, Bigger Fishes, Giant Carnivorous Fish, Ecosystem Small fishes Mackerel etc Sharks, Whales, Snakes, Hawks etc Table-1: Different living organisms or biotic factors in consumer forms in different Ecosystems Fig.2. Relation between Producers, Consumers and Decomposers Ref: https://archive.bigelow.org/bacteria 19 3.2. ABIOTIC COMPONENTS: These are the non-living factors in form of solid, liquid or gas found in the nature (ice, water, moisture). They can be categorised into 2 types. I) Climatic factors Ex. Light, Temperature, Humidity, Rain etc. II) Edaphic factors Ex. Soil, Organic and Inorganic components of the soil, Substratum etc. Let’s discuss importance of each abiotic factors and their limitations in an ecosystem. 3.2.1. CLIMATIC FACTORS 3.2.1.1. Light – It is an essential factor for all the living organisms like producers, consumers as well as decomposers. In presence of the sunlight plants are able to prepare their food material, which in turn eaten by the heterotrophs & ultimately by the decomposers. Without sun light photosynthesis is not possible thus it is one of the most important abiotic factors of an ecosystem. Quantity as well as quality of light has different impact on different organism. Let’s discuss. i) Importance of light for plants a) Chlorophyll production b) Distribution of plants: The vegetation or the types of plants grow on the earth depends on the amount of sunlight they are getting. Thus the vegetation of temperate, tropical as well as Tundra regions are different from each other. c) Light thus decides the physiology of the plants of different regions. d) Temperature: When light increases, temperature also increase and vice versa. When temperature increases rate of transpiration in the plants 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 keeps the plant body in a stable physiological status. f) Duration of Light: During summer and winter months the type of flowers, what we can observe in the nature are different. The basic theory behind it is some plants can bloom in summer months are long day (basing on the exposure to the sun light) plants and some are short day plants (less exposure to sunlight or natural light). 20 ii) Importance of Light for animals a) Metabolism: Light controls the physiology & metabolism of animals by affecting it’s enzymatic activity. 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 color 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 towards the light condition are known as circadian rhythm. This is an important physiological action of all the living organisms. Thus, it is a light dependent process. 3.2.1.2 Temperature: Temperature affects animals and plants in following ways. i) Importance of temperature for plants a) Metabolism: Temperature increase the physiological activity. Thus, the types of plants grow in a desert ecosystem are different from the type of plants of a forest ecosystem and an aquatic ecosystem. b) On Growth & Development: Different types of plants need different range of temperatures for their growth. Summer growing plants are different from winter season growing plants. This is self-explanatory. c) Thermal Stratification: Best example is an aquatic ecosystem. The organism growing at surface layer are different as they need more temperature and light than the organisms grow at a deeper level in an aquatic ecosystem. ii) Importance of Temperature for Animals Basing on need of the 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 temperature. Ex. 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. Ex. Frogs c) Migration: Temperature is also a factor for migration of animals. It is known as thermal migration. If temperature changes the locomotory animals or birds may change their places for a temporary period & them comeback to their original ecosystem when the weather changes. 21 3.2.1.3. 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 for ex. Pond & Lake ecosystems. If for a longer period of time, 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 get established there. Beside for photosynthesis & other metabolic activity plants needs water for circulation of minerals throughout its body. Water is also an essential requirement of the animals for their metabolic activity. Water regulates the body temperature of both plants and animals. Water in forms of rainfall also needed by the ecosystem. It maintains the humidity & content of moisture in the atmosphere. Amount of rainfall also decides the kind of plants to grow over there. Ex. Deciduous forest, Evergreen forest, 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 animal lives. Some plants can grow in less humid area where some other plants need more moisture in their environment. Some plants can use atmospheric moisture directly from the environment. Ex. Epiphytes, Orchids, Lichens, Mosses etc. Some other needs it in liquid form from underground by the process of absorption. Ex. Higher plants. 3.2.2. EDAPHIC FACTORS 3.2.2.1. Soil: Soil is a natural resource and provides platform for the plants to grow & animals to dwell on it. Thus, the fertility and quantity of soil decides the type of vegetation in that area. To be more specific, pH of the soil is the deciding factor. If pH of the soil is less than 7, then it is acidic soil & if pH is more than 7 it is alkaline. Fig.3: Schematic representation of different texture of the soil (Ref:https://upload.wikimedia.org/wikipedia/commons/4/45/Horizons.gif) 22 Thus, the acidity T a & alkalinity a off the soil decides d the number & kind of plantsp & animals to stay over thhere (Fig.3)). But needless to say, neutral soiil, i.e. when n the pH ranges from m 6.5 -7.5 iss the preferrred conditio on for most of the livingg organism.. Soil is also associated with different kinds off minerals & nutrients.. Some are required r in more quuantity, are called maccronutrient and some are micronnutrients wh hich are required inn a small quantity. TheyT also play a vittal role in developm ment and sustenance of an ecosyystem. Texture of the soil is also playinng a key ro ole. For ex. Rocky areeas, Swamp py areas, Mining areas etc. Different teextured soil will allow different ty ypes of biotiic factors orr organisms to grow and establissh in that eccosystem. 4. ECO OLOGICAL L PYRAMIIDS By noww we are cleear that the ecosystem can sustain ns itself, if there t is a bbalance betw ween the produceers, the connsumer andd the decom mposers. En nergy is a major m link wwhich bindss all the above components c s in an ecosyystem. Thuss, there is a fixed positiion or level of a particu ular type of orgaanisms in ann ecosystem m. How we can know or decide that t positioon? To expllain it, a graphiccal structuree has been proposed p byy the enviro onmental bioologists, knnown as pyrramid or Ecologiical Pyramid (Fig.4). Fig.4: Schem matic repressentation of an Ecologgical Pyram mid mids) (Ref:htttps://sites.google.com/sitte/vhs2015ennvironmentallscience/bioddiversity/ecological-pyram Definitiion: An ecoological pyrramid is a graphical g reepresentatioon of the reelationship between b various trophic levvels organism ms in a Foood Chain. It was first f designeed by Charlees Elton andd are called Eltonian Pyyramid or F Food Pyram mids. Ecologiical Pyramids are threee types: 1. Pyrramid of Nuumber 23 2. Pyramid of Biomass 3. Pyramid of Energy A. Pyramid of Numbers: As the name says, in this type of pyramid number of organisms are counted and accordingly respective volume to each trophic level is allotted in the pyramid. Characteristic features of pyramid of number are. 1) Number of producers are higher in number than the consumers present in other trophic levels. 2) Number of individuals in each trophic level decrease when we go from bottom to top in a pyramid. 3) Collectively the living organisms present in each of the trophic levels are known as standing crop. 4) Normally the pyramid of number is an upright (Fig.5) one Ex. Grassland ecosystem, Aquatic ecosystem. 5) Sometimes inverted pyramids (Fig.6) are also found in this case. 6) A mixed or spindle shaped pyramid is also observed in case of forest ecosystem. Fig.5: Upright Pyramid of Numbers (Ref: https://www.pmfias.com/ecological-pyramids-pyramid-numbers-biomass-energy/) 24 Fig.6: Inverted and Spindle Shaped Pyramid of Numbers (Ref: https://www.pmfias.com/ecological-pyramids-pyramid-numbers-biomass-energy/) B. Pyramid of Biomass: Biomass is the total dry weight of the animals as well as plants present in the ecosystem at any point of time. Like pyramid of numbers it may be upright one or inverted one. In case of a forest and grass land ecosystem it is upright and in cases of a pond ecosystem inverted pyramids (Fig.7) are observed. Fig.7: Upright and Inverted Pyramid of Biomass Ref:https://www.tutorialspoint.com/environmental_studies/environmental_ studies_ecological_pyramid.htm The figures show the position of different organisms in different trophic levels. 25 C. Pyramid of Energy As already mentioned, the Food Chain and Food Web systems are existed for the energy requirement and energy transfer between the living organisms in an ecosystem. It is the most important type of ecological pyramid. The amount of energy being transferred from the lower trophic level towards the upper ones become less and less. Thus, longer the pyramid in height, lesser will be the amount of energy to reach the organisms present in the topmost trophic level. Only 10% of the energy is being transferred to the subsequent upper trophic level organisms (Fig.9). For example, if the producers generate 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 to the tertiary or topmost level of consumers. In this way a pattern of upright Pyramid of Energy (Fig.8) will be developed for all types of ecosystems found in the Nature. This is the universal formula. Energy pyramid can never be an inverted one or spindle shaped found in other types of ecological pyramid structure. The shape of the pyramid of energy is not affected by the size, biomass, number or the metabolic rate of the organisms. Fig.8: Structure of Pyramid of Energy 26 Fig.9: Energy Flow 10% rule in an Ecosystem. (Ref:https://www.tutorialspoint.com/environmental_studies/environmental_studies_ecological_pyramid.htm) Some limitations are also observed in the studies of ecological pyramids. That can be described as follows: 1. The position of certain organisms are not fixed in one ecological pyramid. That may vary in same or may be in a different ecosystem. 2. There is no consideration of seasonal changes, while studying the pyramids 3. Role of detrivores are 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. 5. ECOLOGICAL SUCCESSION Ecological succession term was coined by 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 changes in an orderly process 2) The physical structure of a community changes by the biological action of the biological factors grow there. 27 3) At last a stable ecosystem m gets estabblished in an n area. Withh both biotiic as well ass abiotic facctors interaccting there to establish equilibrium m in that ecoosystem. 4) Thhen the cliimax commmunity getts establish hed there, which in turn main ntain an equuilibrium with w the enviironment. Scheematic Reprresentation of a Forest Successionn (https:///upload.wikkimedia.org//wikipedia/commons/4 4/41/Forest__successionn_depicted_o over_ti me.png:) Causess of Ecologiical Successsion a) Initial causess: It happens for the destruction off an existingg habitat. It is two types. i)) Climatiic Factors: E Soil Eroosion, Soil deposition Ex. d d to heavy due y wind, Conntinuous floood, Heavy rainfall, Fire, Drrought, Lannd Slides, Oil Depositio on etc. iii) Biotic Factors: F Ex. Defforestation, Over grazinng, Jhum cu ultivation ettc. b) Coontinuous Causes: C It is i responsibble for the changes c in population p ccompositionn in that areea. The facctors responnsible for population p compositioons are, miigration forr safety, miigration duee to urbanizzation, miggration due to industrialization, m migration foor better life fe etc. 28 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 growth of different types of producer for a continuous flow of food and energy as discussed earlier. Types of Ecological Succession 1) Primary succession: It begins from the primitive substation where there was no living factor before. Ex. Volcanic eruptions, Rocky Areas etc. 2) Secondary Succession: It begins from a previously sustained living matters, 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 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 eruption, climate change, comet strike, earthquake, flood, drought etc. 5) Induced Succession: It is a man-made process, developed for the benefit of the humankind. Ex. Cultivation of Crops in a field. 6) Autotrophic Succession: When a place is rich in inorganic content & poor in organic matter, the development of succession of plants over that area is called as 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 backward instead of progressing. Ex. Forest community changes to a shrub land or grassland or to a barren land due to deforestation and overgrazing. LEARNING OUTCOME Ecosystem is the study of living organisms with its surroundings. Thus, it’s an interdependence of biotic and abiotic factors in an area. Presence of only one factor cannot create an ecosystem. In an ecosystem position of different organisms are different. This has been explained through ecological pyramids. The principle of ecological pyramid depends on the food habit of the organisms present in that ecosystem. The development of a new 29 ecosystem on a barren land is known as succession. Sometimes reverse succession also happen that is a well-functioning ecosystem may get destroyed due to some artificial i.e. manmade or due to some natural calamities and gets converted into a barren land. Some Important Terms used in the Lesson Allogenic Succession Ecological Pyramid Autogenic Succession Ecological Succession Autotrophs Ecosystem Autotrophic Succession Edaphic Factors Abiotic Components Heterotrophic Succession Biotic Components Heterotrophs Biomass Induced Succession Climatic Factors Primary Succession Decomposers Retrogressive Succession Detrivores Secondary Succession PRACTICE QUESTIONS I. Multiple Choice Questions: 1. Which one of the following is a biotic factor in an ecosystem. a) Oxygen, b) Soil, c) Rocks, d) Lizard 2. ---------------- is an autotroph. a) Fungi, b) Tiger, c) Rabbit, d) Algae 3. Which one of the following is decomposer in an ecosystem. a) Squirrel, b) Insects, c) Earthworms, d) Lizard Ans-1(d), 2(d), 3(c) II. Write Short Notes on: 1. Consumers 2. Pyramid of Energy 3. Water as an abiotic factor III. Long Questions: 1. What do you mean by an Ecosystem. 2. What are the ecological pyramids in an ecosystem. 3. What is succession in an ecosystem. Explain in detail what you know about it. 30 LESSION-3 ECOSYSTEM: FUNCTION OF THE ECOSYSTEM Dr. Nibedita Khuntia Assistant Professor Maharaja Agrasen College University of Delhi INTRODUCTION Function means the working of a particular ecosystem of a particular area in. 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 to 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 LEARNING OBJECTIVES After going through this lesson, you will be able to 1. Know the categories and their respective sub-categories of biogeochemical cycle. 2. Understand working of food chain. 3. Distinguish between grazing and detritus food chain. 4. Give schematic representation of food web. 5. Explain energy utilization in an ecosystem. 6. Know the various concepts of productivity. 3.1 BIOGEOCHEMICAL CYCLE As the name indicates, in an ecosystem, both biological as well as physical components, passing/rolling 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 the nature). This is also called as nutrient cycles of the ecosystem. "Nature is self-sufficient by nature". Biogeochemical Cycle has been divided into two major categories like atmospheric and edaphic cycling based on the types of the substance they are dealing with. 31 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 3.1.1. Atmospheric Nutrient cycle a) Water Cycle: Water is an essential compound for the photosynthesis in plants. Plants absorb water from the underground through the roots, to its 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 its metabolic activity(Fig.1). The driving force for a water cycle is the solar radiation which is 15% of the total radiation reaching on the earth. Though the radiation water gets evaporated from the surface of the waterbodies, it comes back to the surface of earth as rain. The above figure clearly teaches us how the cycling of this vital resource occurs on the earth. Fig.1: The Water Cycle (Ref: https://upload.wikimedia.org/wikipedia/commons /9/94/Water_cycle.png) 32 b) Carbon Cycle: Carbon Dioxide is an important gas present in the nature Plants needs 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 released to the atmosphere by respiration of all the living organisms on the earth. Earth’s Crusts also releases carbon which is present in forms of Calcium Carbonates (CaCO3) and Magnesium Carbonates (MgCO3) which comes 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. Fig.2: Carbon Cycle (Ref: https://d32ogoqmya1dw8.cloudfront.net/images/clean/literacy/tlp /carbocycle/carbon_cycle_diagram_1466775306722780178.jpg 33 By burning of fossil fuel, coal & wood large amount of carbon dioxide get released to the atmosphere. These carbon dioxides get assimilated by the plants. The animals consume these carbohydrates, that is the photosynthetic products. The carbohydrates consumed, in this way reach to the heterotrophs. When these heterotrophs die, carbon again goes back to earth’s crust. Through the process of respiration also carbon dioxide released from the biotic components to the atmosphere (Fig.2). c) Oxygen Cycle: In the atmosphere the dry air contains 20.94% of oxygen. Oxygen is required by all the living organisms for respiration. It is also associated with the moisture content. It is the simplest but inevitable nutrient cycle in the ecosystems (Fig.3). Fig.3: Oxygen Cycle (Ref:https://www.universetoday.com/61080/oxygen-cycle) 3.1.2. Edaphic Nutrient Cycle: a) Nitrogen Cycle: It is a complex cycle occurs in nature through various steps. About 79% of the atmospheric air is Nitrogen. It enters to the biotic world and got assimilate then again goes back to the atmosphere. Following steps are involved for the completion of Nitrogen cycle (Fig.4). A. Nitrogen enters to the living organisms: Pure nitrogen gas cannot be used by the green plants. Only Nitrate & Ammonium forms of Nitrogen can be utilized by them. 34 Thus, nitrogen gas first fixed into Nitrous Oxides, Nitric Oxides and Ammonium in the nature. The production of nitrates from nitrogen is called nitrification. Production of ammonia is called ammonification. 1. Nitrification: It can be done both by non-biological (physical) and biological way. i) Non- Biological fixation of Nitrogen or Nitrification: During lightening, nitrogen gets combined with the oxygen in nature as this reaction needs a high amount of energy. ii) Artificially nitrogenous compounds also get produced in industries. They are the chemical fertilizers. Farmers use these fertilizers to enhance the yield of the crops and soil fertility. iii) Biological Nitrogen Fixation: As name indicates biological nitrogen fixation is carried out by the living organisms known as nitrogen fixing organisms. Ex. Blue-green algae, Bacteria, Fungi etc. Biological Nitrogen Fixation are of two types. i) Non-Symbiotic Nitrogen Fixation: It is carried out by organisms, who live freely in the soil or water. Ex. Azobacter, Anabaena, Nostoc etc. ii) Symbiotic Nitrogen Fixation: Some microorganisms live inside the root nodules of different plants in a symbiotic association. They have the capacity to 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. Ex. Bacteria, Rhizobium etc. The nitrogen gas from the atmosphere gets converted into Ammonia (NH3) which in 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 association are there for nitrogen fixation in the nature. Example:(i) Anabaena – Azolla association (ii) Cycas Coralloid roots etc. 35 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 Fig.4.: Schematic Representation of Nitrogen Cycle (Ref:https://en.wikipedia.org/wiki/ Nitrogen cycle #/media/File:Nitrogen_Cycle_2.svg) C) Nitrification: When ammonium gets converted into nitrates, it is called nitrification. Nitrates can be directly absorbed by the 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. 2) Nitrogen Gas back to the Atmosphere: Through the process of denitrification nitrogen gas goes back to the atmosphere. Some bacteria are there, who can convert Nitrates (NO3) to Nitrites (NO2). 36 They are called denitrifying bacteria. Ex. Pseudomonas Ultimately Nitrates, Nitrites & gaseous Nitrogen then released to the atmosphere. b) Sulphur Cycle Fig.5: Schematic Representation of Sulphur Cycle Like other Nutrient Cycles, the movement of sulphur in the biosphere and the underground is called “Sulphur Cycle” (Fig.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 found in nature in following form. i) Hydrogen sulphide (H2S) ii) Sulphur dioxide (SO2) iii) Sulphates (SO4) It enters to the living system as i) Soluble form presents in the soil and pass on to the plants through the plants roots. 37 ii) It is assimilated by the plant to synthesize protein, vitamins & same other important products. Fig.6:Schematic representation of Sulphur Cycle in detail (Ref:https://en.wikipedia.org/wiki/Sulfur_cycle#/media/File:SulfurCycle_copy.jpg) iii) Then the above compounds passed to the animal bodies through food chain. Within plants & animal bodies the organic sulphur decomposed by aerobic bacteria to 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 to the atmosphere by vehicular exhaustion i.e. the burning of fossil fuels (Fig.6). Example: Petroleum, Coal etc. j) Phosphorus Cycle: In the ecosystem, more phosphorous is available in plants and animal bodies in comparison to the abiotic system. In 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. Roots of the plants absorb Phosphorous present in a soluble form in the soil and assimilate it. Through 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.7). 38 The runoff from the soil and the loss of phosphorous to the sea is greater than the availability of it to 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 to the sea. Fig.7: Schematic representation of Phosphorous Cycle Ref:https://en.m.wikipedia.org/wiki/File:Phosphorus_Cycle_copy.jpg 3.2.1. FOOD CHAIN Definition: 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 as food chain (Odum, 1971). How 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) That’s why plants are called autotrophs (auto-self; troph-to nourish) Thus, plants are the first step in a food chain. 39 The heterotrophs (hetero= other; troph = to nourish) are the organisms who depends on the autotrophs for food and energy. Heterotrophs are two types – Herbivores and Carnivores Herbivores are the herb/plant eaters. They can only eat the green plants/autotrophs. Ex. Grasshoppers, Rabbits, Goats etc. Carnivores are the meat eaters in an ecosystem. They cannot have the ability to eat herbs. For example, Frogs, Snakes, Hawks, Lions, Tigers. Thus, in an ecosystem a chain like structure is found based on “-to eat and being eaten “scheme, which is also called “Pray- Predator relationship” in an ecosystem (Fig.8). Plants (Autotrophs) Herbivores (Heterotrophs ) Carnivores (Heterotrophs) or Plants Primary consumers Secondary consumer Tertiary consumers Fig.8: Schematic representation of a Food Chain (Ref:https://www.ck12.org/biology/food-chain/lesson/Food-Chains-and-Food-Webs-BIO/) Types of Food Chain: Two types of food chains are observed in different ecosystems, known as 1. Grazing Food Chain 2. Detritus Food chains 40 Grazing Food Chain – It is recognized by the starting level organisms of a food chain. They are the living green plants. Then if we see the examples, in a grassland ecosystem the chain will be starting with Greengrass, then Grasshoppers, then Frogs then Snakes then Hawks as shown in the above figure. Detritus Food Chain – Here the starting point is dead plants or animals. This type of Food chain does not depend on the sunlight. Ex- Dead plants and animals, Scavengers, Micro organism This should be noted that the Grazing and Detritus Food Chain perform independent to each other but different parts of a single ecosystem. More energy is transferred in a grazing food chain than in a detritus one. Combinedly the grazing and the detritus Food chain complete the nutrient cycle in an ecosystem. 3.2.2. FOOD WEBS In a natural system the linear structured food chain does not happen always. Sometimes, if a particular species is absent in a particular area, that species is replaced by another species so that the “to eat and to be eaten” system will be maintained. For example, in a grassland ecosystem, if frogs will remain constant and for the eagle, food will also be available. Fig.9: Schematic representation of a Food Web (Ref:https://www.tutorialspoint.com/environmental_studies /environmental_ studies _functions_of_ecosystem.htm 41 Additioon to this, inn Nature, a more compplicated nettwork of foood chains iss existed which w are interconnnected. Thhat is knownn as Food Webs W (Fig.9)). Thoughh Food Webbs are very complex inn nature. It playsp a signnificant rolee in the balaance and stabilityy of an Ecosystem. If deer d will bee eliminated d from the nature, n thenn number off grasses i will invadde to the crooplands. In turn area off the croplannds will be reduced will inccrease, and it resultinng reduced products. p Siimilarly, the upper trop phic level animals a likee tigers willl not get their foood and will die ultimattely. So, the Food Web networkingg is an impoortant creatiion of the naature to maaintain and sustain s a balancee in the ecossystems. 3.3. EN NERGY FL LOW IN AN N ECOSYS STEM According to first law of therrmodynamics, energy cannot be created c or ddestroyed. It I can be transferrred from onne form to another. a In an eccosystem thhe energy geets fixed or in other woords in preseence of sunlight the au utotrophs or the producers p prrepare their food materrial. The hetterotrophs get g their foood / energy from f the autotropphs that is the t plants. Energy is required r by all the livinng organism ms to perform their work orr metabolism m (Fig.10). Fig.10: Relationsh hip between n producerr, consumerr and decom mposers 42 Energy utilization in an ecosystem occurs in two ways. i) Quantity of solar energy the plants receive from the sun for photosynthesis ii) Quantity of energy flow occurs from the plants to the consumers. This behaviour of energy transaction in an ecosystem is known as energy flow. Energy flow occurs in two models within the ecosystem a) Single Channel Energy Flow Model b) Y- Shaped Energy Flow Models a) Single Chain Energy Flow Model: This type of energy flow works as per the food chain of the ecosystem. For example, in a grassland ecosystem, grasses are the producers. They fix carbon dioxide2 from the atmosphere and produce carbohydrates as the gross productivity. It is a one-way direction of energy flow. This clearly indicates that, if the food chain is longer in length then the energy reaches to the top carnivores are less and if the food chain is a shorter one, more energy will be available to the topmost trophic level organisms. b) Y – Shaped Energy Flow Model: In nature besides the single chain model, another way of energy transfer is found. Food web shows the realistic picture of flow of energy which is more complex with more combinations. The Y-model explains the connection between a grazing & a detritus food chain (Fig.11). Fig. 11: Y – Shaped Energy Flow Model Ref:https://eco-intelligent.com/2016/11/17/y-shaped-model-of-energy-flow-who-eats-whom- in-nature/ In this above figure at every stage the two food chains are linked. The herbivores can be eaten up by the decomposer or the top predator in the detritus food chain. The other links are, when 43 the herbivore or the top predator died. They get decomposed by the decomposer and again used up as nutrients by the plants. In a nutshell, in balanced ecosystem hardly anything goes to the waste. Sometimes, the decomposers are also eaten up by the top predators of grazing food chain. Ex. Earthworms in a grassland ecosystem can be eaten up by the hawks or eagle. It is called so, because it looks like the English alphabet ‘Y’. 3.4. PRODUCTIVITY Concept of Productivity: The amount of organic matter i.e. the food prepared by a plant is known as productivity. When it is measured at any unit time, it is known as rate of productivity of that ecosystem. Productivity are of following types A. Primary Productivity B. Secondary Productivity C. Net Productivity A. Primary Productivity: The productivity is the production capability of a plant. Thus, primary productivity is always associated with the autotrophs or the photosynthetic organisms i.e. the green plants. Some of the microorganisms also can carry out this process and are known as photosynthetic microorganisms. Thus, primary productivity is the rate of fixation of solar energy from the sun by the photosynthesis activity of the organisms. Primary Productivity are 2 types 1. Gross Primary Productivity (GPP) 2. Net Primary Productivity (NPP) 1. Gross Primary Productivity: It is the total rate of photosynthesis or food production by a photosynthetic organism. It depends on the chlorophyll content of a plant. Thus, it is calculated as amount of CO2 fixed per gram of chlorophyll per one hour. This can be represented as GPP = amount of CO2 /gm Chl / hr. 2. Net Primary Productivity (NPP): We know, energy is required for each activity they do, by the living organisms. Thus, for respiration work, plants also need energy. So, the energy what was fixed during photosynthesis is being used here. As a result, the remaining energy after loss in the respiration utilization is known as the Net Primary Productivity. In simple words NPP = GPP – Respiration energy B) Secondary Productivity: This is related to the heterotrophs in contrast to the Primary Productivity. Secondary Productivity is the energy stored at consumer level. Ecologist 44 Odum (1971) prefer to use the term assimilation rather than production at this level. Secondary production is not a fixed level of energy utilization of production rather moves from one consumer level to the other through the food chain. C) Net Productivity: Net Productivity is the storage energy of the consumers. That means it is the energy which remains in the body of the consumer after utilization in respiration or any other work done by the consumer. Thus, it can be measured as the biomass. Net productivity can be expressed as production of carbon mg/meter2/day. It can then be calculated how much energy per/biomass of the consumer gets in a year. HOMEOSTASIS Definition of Homeostasis is “The ability to maintain a constant internal environment in response to the environment changes”. This is an unique principle of biology. In the same way natural ecosystems are also capable of maintaining their internal regulations i.e. self-regulations or self-maintenance at any point of time. This is called as stable steady state of an ecosystem (Homeo means same, stasis means standing) Odum (1971) defined Homeostasis as the tendency of an natural ecosystem to resist change and to remain in state of equilibrium, which implies that within an ecosystem there is always stays a balance between the production, consumption as well as decomposition and in all the living organisms within a particular ecosystem in a particular time follow this kind of equilibrium. LEARNING OUTCOME The abiotic factors in an ecosystem maintains a dynamic role. Different components of the atmosphere, like oxygen, hydrogen, carbon, nitrogen, Sulphur etc. cannot be used by the living organisms in their elemental form. Thus, these elements form different compounds as nutrients for the living world. In that way a cycle of “elements to compounds and again back to elemental form” happens in the nature. That cycle is known as Biogeochemical Cycle. Each organism has a place in an ecosystem pyramid. That is based on their food habit. This characteristic can be easily understood by the food chain of an ecosystem. But if one of the organisms if absent in an ecosystem. Then some other organism with same kind of food choice will replace that place. Thus, the chain of” to eat and to be eaten” habit remain maintained. So, in instead of only one chain, a web like structure found for the self- sustenance of an ecosystem. That is known as Food Web. Energy Flow is the theme of the ecosystem. Through different channels energy flow occurs between the producers, consumers and decomposers. We know that the external environment or climate has an impact on the living organisms, growing in that area. But side by side the Nature also provided a system to them that, the internal environment or the system within the body of the living organisms do not change with the disturbances of the outside environment. This is a gift of the Nature to the biotic factors of an ecosystem and called as Homeostasis. 45 Some Important Terms used in the Lesson Ammonification Net Productivity Biogeochemical Cycle Nitrification Carbon Cycle Nitrogen Cycle Detritus Food Chain Oxygen Cycle Edaphic Nutrients Cycle Phosphorous Cycle Energy flow Primary Productivity Secondary Productivity Food chain Sulphur Cycle Food Web Water Cycle Grazing Food Chain PRACTICE QUESTIONS III. Multiple Choice Questions: 1. Pray – Predator relationship is found in a) Food chain, b) Atmosphere c) Rocks, d) Homeostasis 2. ---------------- is a Primary Producer. a) Fungi, b) Tiger, c) Rabbit, d) Green Plant 3. Match the following: A B a. Autotrophs v. Living organisms b. Y-Shaped Model w. Carbon Cycle c. Detritus Food Chain x. Green grasses d. Biological nitrogen fixation y. Dead and Decay material e. Atmospheric Nutrient Cycle z. Energy Flow in an Ecosystem Answers: Q.1.a; Q.2.d; Q.3. a-x; b-z; c-y; d-v; e-w 46 II. Short Questions: 1. Food Chain 2. Food Web 3. Homeostasis III. Long Questions: 1. What are the nutrient cycle found in an ecosystem. 2. Nitrogen Cycle: Explain in detail. 3. Describe the Food Chain and Food Web in an ecosystem, with proper examples. 4. How energy flows in an Ecosystem. 47 LESSON-4 TYPES OF ECOSYSTEMS AND ECOSYSTEMSERVICES Dr. Sarthak Malhotra Assistant Professor, Dyal Singh College (Eve), University of Delhi INTRODUCTION Ecosystems can range from small water bodies to an ocean, similarly on land from a patch of woods to a forest. Ecosystems can be natural or anthropogenic (human-created like farmlands). Broadly Ecosystem is classified into terrestrial and aquatic ecosystems, which are further classified into several kinds. Ecosystem sustains mankind on earth by providing various products and services. There are several kinds of ecosystem services which maintain the basic functioning of the planet. Due to the exploitation of resources by ever-growing human population ecosystems are getting degraded. Therefore it is essential to understand various concepts of preservation, conservation and restoration of ecosystem. Learning Objectives After going through this unit, you will be able to 1. Understand the importance and types of various ecosystems. In addition to this threat to these ecosystems and conservation strategies. 2. Understand concepts of ecosystem services 3. Understand ecosystem preservation and conservation strategies 4. Basics of ecosystem restoration 1. TYPES OF ECOSYSTEMS Tundra, Forest, Grassland, Desert, Aquatic (ponds, streams, lakes, rivers, oceans, estuaries); importance and threats with relevant examples from India I. Terrestrial Ecosystems: Diverse kinds of terrestrial ecosystems are present on the earth. Both climate and relative contribution of general plant life-forms (trees, shrubs, and grasses) contributes to the diversity. 1. Forest Ecosystem: Forest ecosystem mainly consists of community of plants, animals and microorganism and their non-living environment functioning collectively to exchange material and energy, where trees, shrubs, climbers and ground cover forms the main component. Due to the expansion of human settlements and industrial areas since the last century, the pristine forest is only left in protected areas like National Parks and Wildlife Sanctuaries. The appearance of different types 48 of forest differs greatly from each other. Each forest type forms a habitat for a community of animals that are specifically adapted to live in it. Forest ecosystem also consists of abiotic or non-living component which includes factors like temperature, rainfall, topography, soil properties, etc. Due to the variation of these abiotic factors biotic or living components of the forest also vary in different types of forest. Forests also differ in their plant communities in response to the type of soil. Forest Types in India: Forests in India can be broadly classified into coniferous forests and broadleaved forests. In addition to this, forest is also classified according to the kind of tree species they have which includes evergreen, deciduous, xerophytic or thorn trees, mangroves, etc. Forests are usually named after the most abundant species of trees such as Sal or Teak forests. In many cases, a forest is named after the first three or four most abundant tree species. Coniferous forests are found in the high-altitude Himalayan mountain ranges. These ranges remain snow-covered for many months of the year with the temperature dipping below zero. These forests usually have tall trees with downward sloping branches so that the snow can slip off the branches. Coniferous forest has trees having needle-like leaves. Many trees are gymnosperms which have cones instead of seeds. Pine and deodar trees are found in the Himalayan coniferous forest. Many animals are found adapted to these types of forests. Animal species found in coniferous forests include wild goat, sheep and Himalayan black bear. Some rare species of animals are also found in this forest which includes snow leopard, hangul and Himalayan brown bear. Broadleaf forests are a category of forest further classified into evergreen forests, deciduous forests, thorn forests, and mangrove forests. Evergreen forests are found in the Western Ghats, North Eastern India and the Andaman and Nicobar Islands. These regions receive a high amount of rainfall during long monsoon period. Evergreen forests in southern India receives two monsoons. Trees in evergreen forest keep shedding some leaves throughout the year instead of having a dedicated dry leafless phase as in a deciduous forest. This is why the evergreen forest appears green throughout the year. Evergreen forests have dense canopy because of a high number of trees are present adjacent to each other with their branches overlapping. Due to this less amount of sunlight reaches the forest floor where some shade loving plants grow. Species richness in the evergreen forest is highest. Several orchids and ferns are found in these forests. High diversity of mammals, reptiles, insects are found adapted to these forests. Some of the animals found in the evergreen forest of North-eastern India, Western Ghats and Andaman and Nicobar Islands include tiger, leopard, sambar, Malabar pied hornbill and tree 49 frogs. Rare animals like Pigmy Hog and Lion tailed macaque are also found in the evergreen forests. Deciduous forests are found in the regions with a moderate amount of rainfall during the monsoon season. Deciduous forests are found in central highlands and Deccan peninsula. These forests have a specific season in which trees shed their leaves. On the onset of monsoon, they regain their leaves. Appearance of these forest vary with the season. These forests have thick undergrowth as light easily reaches the floor. Teak (Tectona grandis), Sal (Shorea robusta) and Ain (Terminalia elliptica) are some examples of trees found in the deciduous forests of India. Animals like tiger, cheetal, barking deer, flycatchers and hornbills are also found in the deciduous forests of India. Thorn and scrub forests are found in the semi-arid and arid regions of India. These are regions of low and very low annual rainfall. Here trees are distributed sparsely and are surrounded by grasslands. Xerophytic plants

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