Environmental Ecology

Topic-wise Strategy

1. Environmental Ecology 1

1. Defining Environmental Ecology 11.1 Environment 11.2 Ecology 1

2. Components of an Ecosystem 22.1 Biotic Components 22.2 Ecosystem Functions 22.3 Abiotic Components 3

3. Major Terrestial Ecosystems 43.1 Major Biomes of the World 4

4. Vertical orAltitudinal Biomes 65. Aquatic Ecosystems 66. Man-made Ecosystems 77. Interactions in an Ecosystem 78. Ecosystem Productivity 89. Bio-chemical Cycles 8

9.1 The Carbon Cycle 89.2 The Oxygen Cycle 99.3 The Nitrogen Cycle 99.4 The Phosphorus Cycle 109.5 The Water Cycle 109.6 The Sulphur Cycle 11

10.Ecological Succession 1111.Ecotoneand Edge Effect 11 Self–Evaluation Test 12

2. Biodiversity 131. Introduction 132. Types of Biodiversity 133. Types of Species 134. BiodiversityValue 14

4.1 Ecological Values 144.2 Economic Values 144.3 Cultural Values 14

5. Biodiversity Loss 156. Hotspots of Biodiversity 15

6.1 What is a Hotspot? 157. Indian BiodiversityHotspots 16

7.1 Indo-Burma (Eastern Himalayas) 177.2 Western Ghats (Sahyadri Hills) 177.3 The Himalayas - Western and Eastern

Himalayas (from part of Himalayan Global Biodiversity Hotspot) 17

7.4 Nicobar Islands – Part of the Sundaland Global Biodiversity Hotspot 18

8. Agro-ecological Zones 198.1 The Trans-Himalayan Region 198.2 The Himalayan Region 198.3 The Indian Desert 198.4 The Semi-Arid Region 198.5 The Western Ghats 198.6 The Deccan Peninsula 198.7 The Gangetic Plain 198.8 The Coastal Region 208.9 The North-East 208.10 The Indian Islands 20

9. TheWesternGhats 209.1 Threat Status 219.2 Madhav Gadgil Panel for Protection

of Western Ghats 2110.Biodiversity ofArid and

Semi-Arid Lands 2110.1 Hot Deserts and Semi-arid Region 2210.2 Cold Desert Region 22

11. InlandWater Biodiversity 2211.1 Wetlands 2211.2 Mangroves 2411.3 Coral Reefs 2411.4 Estuary 25

Self–Evaluation Test 26

Environmental Ecology 1-116

Contents

3. Biodiversity Conservation 27

1. Conservation of Biodiversity 271.1 Key Biodiversity Areas 27

2. In-situ ConservationMethods 272.1 Man and the Biosphere Programme (MAB) 272.2 Biosphere Reserves 272.3 Biosphere Reserves in India 282.4 India’s National REDD+ Strategy 2018 312.5 National Parks 31

3. Ex-situMethods of BiodiversityConservation 373.1 IUCN Red List Categories 37

4. Species Based Projects 384.1 Project Tiger 384.2 Project Elephant 394.3 Gharial Conservation 404.4 Rhinoceros 404.5 Hangul 404.6 Vulture 404.7 Great Indian Bustard (GIB) 414.8 Snow Leopard 414.9 Olive Ridley Turtle Conservation Project 414.10 Irrawaddy Dolphins 414.11 The Gangetic River Dolphin 41

5. Government Initiatives for BiodiversityConservation 435.1 National Biodiversity Action Plan (NBAP) 435.2 National Mission for a Green India (GIM) 435.3 Genetic Engineering Approval

Committee (GEAC) 445.4 Institutions for the Promotion of

Biodiversity in India 445.5 Legislative Measures 44

6. India’s InternationalCooperation in BiodiversityConservation 47

7. Other Recent Initiatives 507.1 Partnership for Action on Green Economy 507.2 Global Environment Facility 507.3 Global Wildlife Program 517.4 Secure Himalayas 517.5 TEEB-India Initiative 517.6 BIOFIN 51

7.7 TRAFFIC 517.8 South Asia Cooperative Environment

Programme 51 Self–Evaluation Test 52

4. Pollution and Its Control 53

1. Environmental Pollution and Its Control 53

2. Air Pollution 532.1 EffectsofAirPollutantsonClimate 552.2 Acid Rain 552.3 Smog 552.4 India’s Initiatives 552.5 Alternate Fuels 56

3. Water Pollution and its Control 573.1 India’s Initiatives 59

4. LandDegradationandSoil Pollution 614.1 Construction Activities 614.2 India’s Initiatives 62

5. Noise Pollution and its Control 625.1 India’s Initiatives 62

6. Radioactive Pollution 636.1 Sources of Radioactive Pollution 63

7. SolidWasteManagement (SWM) 637.1 Basic Concepts 637.2 Solid Waste Management Rules, 2016 647.3 How To Remove Toxic Waste? 65

8. Bio-medicalWaste 659. ElectronicWastes (E-Wastes) 66

9.1 E-Waste Management Rules, 2016 6610.HazardousWasteManagement 67

10.1 Hazardous and Other Wastes (Management & Transboundary Movement) Rules, 2016 67

11.Thermal Pollution and its Control 6712. Legislations for PollutionGovernance 68

12.1 The Environment (Protection) Act, 1986 6812.2 The Water (Prevention and Control

of Pollution) Act of 1974 and Amendment, 1988 68

12.3 The Water (Prevention and Control of Pollution) Cess Act of 1977 69

12.4 The Air (Prevention and Control of Pollution) Act of 1981 and amendment, 1987 69

12.5 The Public Liability Insurance Act, 1991 6912.6 Noise Pollution (Regulation and Control)

Rules, 2000 6912.7 Draft Coastal Regulation

ZoneNotification 6912.8 National Green Tribunal 70

13.Environment ImpactAssessment (EIA) 7013.1 AmendedEIANotification2009 71

14.SustainableDevelopment Initiatives 7114.1 Sustainable Development Goals (SDGs) 7114.2 National Hydrology Project 7114.3 Climate-Smart Agriculture (CSA) 7214.4 Organic Farming 7314.5 Bioremediation and its Types 7314.6 Phytoremediation 73

Self–Evaluation Test 74

5. Climate Change 75

1. What is ClimateChange? 752. ClimateChange&Vulnerability 753. Causes ofClimateChange 75

3.1 Natural Causes of Climate Change 753.2 Anthropogenic Causes of Climate Change 76

4. Impact and Consequences of ClimateChange 78

5. ClimateChangeand its Possible Impact on India 805.1 Observed Sea-level Rise and Future

Projections 806. MitigationMeasures 81

6.1 Steps Taken by India to Mitigate Climate Change 84

7. Major InternationalDevelopmentsRelated toClimateChange 847.1 Montreal Protocol 847.2 Vienna Convention 857.3 Kigali Agreement 857.4 The UN Framework Convention on

Climate Change (UNFCCC), 1992 857.5 Agenda 21, UNCED, 1992 857.6 Kyoto Protocol, 1997 85

7.7 Conference of Parties 877.8 Intergovernmental Panel on Climate

Change (IPCC) 908. India’s Actions onClimateChange 92

8.1 National Action Plan on Climate Change 928.2 Indian Network of Climate Change

Assessment (INCCA) 938.3 National Environment Policy, 2006 938.4 Energy Sector Initiatives 938.5 Renewable Energy Initiatives 938.6 UJALA Programme 958.7 Transport 958.8 Industry 95

9. Carbon Tax 96 Self–Evaluation Test 98

6. Major Environment Treaties 99

1. Antarctic Treaty 992. Basel Convention on theControl

of TransboundaryMovements ofHazardousWastes and their Disposal 99

3. Convention for theConservation ofAntarctic Seals 99

4. Convention on Biological Diversity 1005. Convention onWetlands of

International Importance Especially asWaterfowlHabitat (Ramsar) 100

6. Convention on the International Trade in Endangered Species of Wild Floraand Fauna (CITES) 100

7. InternationalConvention for theRegulation ofWhaling (ICRW) 100

8. International Tropical Timber Agreement, 2006 100

9. Kyoto Protocol to theUnited Nations FrameworkConvention onClimateChange 100

10.Protocol of 1978 Relating toInternationalConvention for Prevention of the Pollution from Ships, 1973 (MARPOL) 101

11. Protocol on Environmental Protection to theAntarctic Treaty 101

12.UnitedNationsConvention to CombatDesertification in ThoseCountries Experiencing Serious Drought and/orDesertification,Particularly inAfrica 101

13.UnitedNations Framework Convention onClimateChange 101

14.Convention onConservation of MigratorySpeciesofWildAnimals 102

15.International Union for Conservation ofNature (IUCN) 102

16.NairobiDeclaration 10217.ViennaConvention for the

Protection ofOzone Layer 102

18.Helsinki Declaration 10219.Bali Summit 10220.Montreal Protocol 10321.The Kigali Amendment to the

Montreal Protocol: Another GlobalCommitment to stop climate change 103

22.Nagoya Protocol 10323.RotterdamConvention 10324.UNClimateChangeConference-

Paris Agreement 10425.Cartagena Protocol on Biosafety 104Self–Evaluation Test 105

Practice Set 106

1Environmental Ecology

1. Defining environmental ecology

1.1 EnvironmentThe term environment describes the sum total of physical and biotic conditions influencing the responses of organisms. More specifically, the sum of those portions of the hydrosphere, lithosphere, and atmosphere into which life penetrates is the biosphere.

1.2 EcologyEcology as a discipline is focused on studying the interactions between an organism of some kind and its environment. An organism's niche includes everything affected by the organism. The word ecology is derived from the Greek word Oikos meaning habitation, and logos meaning discourse or study implying a study of the habitations of organisms. Ecology was first described as a sepearate field of knowledge in 1866 by the German Zoologist Ernst. We study ecology to learn how nature works. So ecology is a study to help scientists to achieve a new goal of developing methods to protect the natural world - physical environment. Haeckel, who invented the word Ecology for "the relation of the animal to its organic as well as its inorganic environment, particularly its friendly or hoslite relations to those animals or plants with which it comes in contact." In ecology, 'niche' refers to the role an organism or species play in its ecosystem.

Q. Which one of the following terms describe not only the physical space occupied by an organism, but also its functional role in the community of organisms?(a) Ecotone (b) Ecological niche(c) Habitat (d) Home range

(UPSC-2013)

Types of Ecology

Behavioral Ecology It deals with the study of the behavioral relationship between individuals of a species.

Community Ecology It deals with the study of the organised activity of a species.

Environmental Ecology It deals with the study of the relationship between the environment and species

Ecophysiology It examines how the physiological functions of organisms influence the way they interact with the environment, both biotic and abiotic

Population Ecology It studies the dynamics of populations of a single species

Ecosystem Ecology It deals with the study of the flows of energy and matter through the biotic and abiotic components of ecosystems

Systems Ecology It is an interdisciplinary field focusing on the study, development, and organisation of ecological systems from a holistic perspective

Landscape Ecology It examines processes and relationship in a spatially explicit manner, often across multiple ecosystems or very large geographical areas

Evolutionary Ecology It deals ecology in a way that explicitly considers the evolutionary histories of species and their interactions

Political Ecology It connects politics and economy to problems of environmental control and ecological change

Chapter 1 Environmental Ecology

The Ecology is the scientific study of the distribution, abundance and relation of organisms and their interactions with the environment. The scope of study include interactions of organisms with each other and with abiotic components of their environment.Thus, this chapter discusses the basic concept of environmental ecology, the interaction of biotic and abiotic components and different types of Ecosystem present on the Earth. Through this chapter, students will be able to understand:• MeaningofEnvironmentandEcology• TypesofEcology• Componentsofanecosystem–BioticandAbioticandUnderlinedConceptsRelatedtoThem• MajorBiomesoftheWorld• SalientFeaturesoftheAquaticEcosystem• InteractionamongSpeciesinanEcosystem• Concept of Bio-chemical Cycle and Understanding of Different Nutrient Cycles as Carbon, Oxygen, Nitrogen,

Water,etc.

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2. components of an ecosystemThere are two components of ecosystem; Living (Biotic) components and non-living (Abiotic) components. Living components are either producers or consumers. They are also called biotic components.

A biotic community cannot live in isolation. It lives in an environment, which supplies its material and energy requirements and provides other living conditions. The biotic community together with the physical environment forms an interacting system called the ecosystem.

Q. Which one of the following is the best description of the term 'ecosystem'?(a) A community of organisms interacting with one another.(b) That part of the Earth which is inhabited by living

organisms.(c) A community of organisms together with the

environment in which they live.(d) The flora and fauna of a geographical area.

(UPSC-2015)

An ecosystem can be natural or artificial, temporary or permanent. A large pond or an ocean, a small tract in a forest or a single log, a village, an aquarium or an artificial pond can all be regarded as ecosystems. Therefore, any structural and functional unit of the environment that can be identified and studied is called an ecosystem.

The study of an ecosystem is not only the description of the biotic community and its abiotic environment but also understanding of a whole network of relationships comprising the various exchanges and interactions between abiotic and biotic components.

2.1 Biotic ComponentsThe biotic component of an ecosystem consists of mainly three components: producers, consumers and decomposers.

List of Ecological Functional GroupsFunctional Group Definition and Examples

Producer or Autotrophs Usually, plants or cyanobacteria that are capable of photosynthesis. But these could be other organisms such as bacteria found near ocean vents that are capable of chemosynthesis.

Consumers or Heterotrophs

Animals which can be primary consumers (herbivorous) or secondary or teritiary consumers (carnivorous and omnivorous).

Decomposers or Detritivores

Bacteria, fungi and insects which decompose organic matters of all types and restore nutrients to the environment. The producers then consume the nutrients, completing the cycle.

Q. With reference to the food chains in eco-systems, which of the following kinds of organisms is/are known as decomposer organism/organisms?

1. Virus 2. Fungi 3. BacteriaSelect the correct answer using the codes given below.(a) 1 only (b) 2 and 3 only(c) 1 and 3 only (d) 1, 2 and 3 (UPSC-2013)

The green plants and photosynthetic bacteria which produce food in the form of carbohydrates, protein and fat by utilising solar energy are termed as producers. The animals and non-green plants which consume this energy or food are called consumers. The organisms like the fungi and some bacteria, which are incapable of producing their own food, live on the dead and decaying plants or animal are categorized as the decomposers.

Primary Producers are organisms in an ecosystem that produce biomass from inorganic compounds (autotrophs). In almost all cases these are photosynthetically active organisms (plants, cyanobacteria and a number of other unicellular organisms).

The herbivores such as goat, cattle, sheep which derive their energy or food directly from plants i.e., producers are known as the first order consumers. The carnivores such as tiger, lion, leopard which derive their food from primary consumers are termed as second order consumers.

2.2 Ecosystem FunctionsFood Chain : The food relation in its simplest form: grass-cattle-lion-microorganisms; representing a producer (grass), a primary consumer (cattle), a secondary consumer (lion) and a decomposer (micro organism) is called a food chain. Each step in the food chain represents a trophic level. Thus energy from the sun in the form of insolation enters the living world through photosysnthetic organisms and passes on from one organism to another in the form of food.Types of Food ChainsIn nature, basically two types of food chains are recognised – grazing food chain and detritus food chain.

1. Grazing Food Chain: This type of food chain starts from the living green plants goes to grazing herbivores, and on to carnivores. Ecosystems with such type of food chain are directly dependent on an influx of solar radiation.

2. Detritus Food Chain: This type of food chain goes from dead organic matter into microorganisms and then to organisms feeding on detritus (detrivores) and their predators. Such ecosystems are thus less dependent on direct solar energy. These depend chiefly on the influx of organic matter produced in another system. For example, such type of food chain operates in the decomposing accumulated litter in a temperate forest.

Q. With reference to food chains in ecosystems, consider the following statements :

1. A food chain illustrates the order in which a chain of organisms feed upon each other.

2. Food chains are found within the populations of a species.

3. A food chain illustrates the numbers of each organism which are eaten by others.

Which of the statements given above, is/are correct?(a) 1 only (b) 1 and 2 only(c) 1,2 and 3 (d) None

(UPSC-2013)

Food Web: In nature, the food relationship cannot be explained only in terms of a single food chain. A herbivore consumes many types of plant or its products. Similarly, many

3Environmental Ecology

other kinds of animals apart from lion derive food from herbivorous animals. Some animals like mosquito, ticks, mites and leeches are dependent on both herbivores and carnivores. Therefore, food chains are not isolated linear chains of trophic levels. Depending upon the availability and choice of food, different organisms at each level have food relationship with more than one organism at lower trophic levels. For example, a rat consumes various kinds of stems, roots, fruits and grams. The rat is consumed by snake which is eaten by a Hawk. The snake can feed on both rats and frogs. Thus a complex network of food chain exists and this is called a Food Web.

The multiplicity and complexity of food web is due to variability in tastes and preferences, availability and compulsion and several other factors at each trophic level. For example, Bengal tiger living in Sunderbans prefers to eat deer, but due to their unavailability they are forced to eat fish or crabs, which they don't eat in normal circumstances. They also have learned to swim efficiently.

Food Web

Ecological Pyramid : A common feature of food chain is that the members of food chain at the successive higher levels are smaller in number. For example in a forest the herbivorous deer are more abundant than the carnivorous lions. Thus, the number of organisms in one trophic level is higher than that at the next higher trophic level. When the number of organisms at each successive levels are plotted, they assume the shape of a pyramid called ecological pyramid.

When the number of organism at successive levels are plotted, they assumed the shape of a pyramid called Pyramid of Number. The amount of energy and materials transferred through food to higher levels become less and less. These parameters (energy and biomass) can be measured and graphically represented. These also assume the shape of pyramids. The pyramid of energy is always upright.

Pyramid of Energy in a Food Chain

Biomagnification

Biomagnification is the process in which toxins are concentrated in an organism as larger animals continue to eat smaller animals. This process moves toxins up the food chain to larger organisms and is of particular concern with regards to concentration of dangerous toxins in larger species.Bioaccumulation  occurs  within  a  trophic level, and is the increase in the concentration of a substance in certain tissues of organisms’ bodies due to absorption from food and the environment.Bioconcentration is defined as occurring when uptake from the water is greater than excretion.

The number of organism at any trophic level depends upon the availability of organisms which serve as food for the lower level. For example, the number of a particular herbivorous insect would increase if more plant food were available to them.

Subsequently, plenty of food would be available not only to its prey, say a common frog, but also to other animals like a bird which feeds on an insect as a second choice leading to an increase in their number. As a result of this increased predation, the number of herbivorous insects is decreased and this in turn would lead to a reduction in the number of the predators. Thus availability of food is the main factor which maintains the balance of nature.

2.3 Abiotic ComponentsAmong the abiotic factors the most important are climatic and edaphic factors. The climatic factor comprise of temperature, humidity, rainfall, snowfall, wave action, wind, pH etc. The edaphic factors include the soil and substratum. The important abiotic factors are as follows:-

(i) Temperature : Temperature is an essential ingredient for survival of an organism. The living organisms can survive only a narrow range of temperature which allows their metabolism. We have seen that increase or decrease in temperature causes extinction of organism if they are not able to tolerate this range of temperature. Therefore, for survival they must develop physiological adaptation to withstand extremes of temperature. Some organisms adopt hibernating (in winter) and aestivating (in summer) to keep themselves from the adverse effects of temperature. Some birds and mammals migrate to warmer place in winter to avoid extreme cold, which is essential for their survival. Similarly, some desert animals like snake, rats etc, live inside burrows to avoid the intense heat of the desert.

(ii) Rainfall : Waters which is an essential ingredient for survival of an organism. A large number of organisms live only in water, they are called aquatic organisms. The need of water varies

Environmental Ecology4

from one organism to another and therefore the distribution of organisms depends upon the extent of the need.

The spatial distribution of organism is directly related to the water or rainfall pattern. The tropical region of the world with high rainfall has the highest biodiversity; whereas, polar region with least precipitation with low level of biodiversity.

(iii) Sunlight : Sunlight is an essential ingredient for photo- synthetic organisms. Green plants contain chloroplast, which acts as photoreceptors to trap sunlight. These chloroplast trap chemical energy of sunlight and transform it in the form of carbohydrates. Apart from production of food, the light controls the rythem of functioning of a large number of organism, for example:- cockroaches, moths and bats which are active during the night.

The net amount of solar insolation is constant throughout the Earth's surface. The tropical region receive maximum amount of sunlight and therefore, produce maximum amount of gross primary product, whereas, the amount of sunlight decrease as one moves from equator to pole and so does photosynthetic activities.

(iv) Humidity : Humidity is a measure of the dampness of the atmosphere which varies greatly from place to place and even at a place at different time of a day. The actual amount of water vapour present in the air, which is expressed in grams per cubic metre, is called the absolute humidity. But more important from the point of view of weather studies is relative humidity.

This is the ratio between the actual amount of water vapour and the total amount of moisture the air can hold at a given temperature, expressed as a percentage. When the relative humidity reaches 100 percent, the air becomes completely saturated. Further cooling will condense the water vapour into clouds or rain. It is thus clear that when relative humidity is high, the air is moist, as in the equatorial regions. When it is low, the air is dry, as in the deserts.

The humidity in the atmosphere directly regulates the rate at which water evaporates from the body surface of land organisms by transpiration, perspiration and by other means. Different plants and animals shows various adaptations to withstand dry conditions and abnormal temperature.

(v) Wind : Wind blows due to a difference in pressure which arises mainly by differential solar insolation. Wind determines the rate of transpiration. Wind also helps in the dispersal of seeds and fruits in an ecosystem.

(vi) pH : pH is a measure of the activity of the (solvated) hydrogen ion. For survival of any organism an optimum pH range is needed. Some plants and animals require acidic condition (i.e., pH < 7), other need neutral (pH = 7) or alkaline (pH > 7) conditions. Therefore pH of the soil and water has a strong influence on the distribution of organisms. Acid rain with low pH kills many micro organisms in the soil.

(vii) Mineral Elements : Soil has four important components:- air, water, inorganic minerals and biotic component. The minerals present in soil are essential for the growth and survival of an organism. There are about 16 minerals which are essential for plant growth and development and therefore regarded as essential plant nutrient mineral. Their deficiency in soil causes stunted growth of plant.

(viii) Topography : Topography refers to surface configuration of an area (physical feature like hills, plants or slopes). It influences the distribution of organisms as evident by the difference in biodiversity of below mentioned places:

(a) The centre and edge of a pond or a stream,(b) Top side and under-side of a rock,(c) North and south face of a ridge or a wall usually inhabited

by different species of organism.Topographical effect may be direct or indirect. It also indirectly

affects other factors like wind, water current, light or wave action.(ix) Background : The background of the habitat at

(a specific place where an organism usually lives) also determines the distribution of animals by enabling them to camouflage against the colour, texture and pattern. For example–mimicry by Chameleon. Desert animals like the lion and the camel are sand-coloured.

3. major terrestial ecosystemsNatural ecological grouping of plants and animals occur over large areas. Each of these major terrestrial ecosystems or distinctive terrestrial areas with their group of climax plants and associated animals are called Biomes. Therefore, a biome is the largest terrestrial community. The nature and extent of biomes is determined by rainfall, temperature range, nature of soil barriers, latitude and altitude.

3.1 Major Biomes of the WorldI. Tropical Rain Forest Tropical rain forest comprises evergreen trees like Mahogany, Ebony, Green Heart, Cabinet wood and Dye wood. Climbing plants like Epiphytes and Parasitic plants that live on other plants are found.

Rainforests are populated with insects (like butterflies and beetles), arachnids (like spiders and ticks), worms, reptiles (like snakes and lizards), amphibians (like frogs and toads), birds (like parrots and toucans) and mammals (like sloths and jaguars). Different animals live in different strata of the rainforest.

The biome located in the equatorial region where the annual rainfall exceeds 200 cm is referred to as tropical rain forests.

Tropical rain forests are mainly located in South America, along the Amazon and Orinoco river basin, Congo basin of Africa, Malaysia and the East Indies. They cover one-eighth of our planet's surface but contain more than half of the earth's flora and fauna. They are rich in biodiversity

Equatorial Rain forest comprises of evergreen trees like-mahogany, ebony, green heart, cabind woods and dye woods.

Climbing plants live epiphytes and Parasitic plants that live on other plants are found.

World Map Showing Tropical Rain Forest Region

5Environmental Ecology

II. Tropical and Temperate Deciduous ForestThe deciduous forests are found in both tropical and temperate regions of north central Europe, eastern Asia and the eastern USA. Here, the annual precipitation varies from 100 cm to 200 cm. With the onset of autumn most of the trees and shrubs shed their leaves.

The climax vegetation here comprises broad-leaved hardwood trees such as oak, elm, birch, maple and hickory. The fauna includes salamanders, frogs, snakes, racoons, foxes and deer.

III. Tropical SavannaSavannas are warm climate plains characterized by coarse grass and scattered trees on the margins of tropics where rainfall is seasonal.

They are located mainly in South America, Africa and Asia. The climate is also prevalent in sections of Central America, Northern Australia and North America. The average rainfall varies from 100 to 150 cm. The savanna type of climate is characterized by an alternate hot, rainy season and cool, dry season. The monthly temperature is however between 70°F and 90°F for lowland stations.

The prevailing winds of the region are the trade winds, which  brings rain to the coastal districts. The savanna is characterized by tall grass and short trees. The grass is tall and coarse, growing 6 to 12 feet high. This biome supports the widest variety of hoofed herbivore species including the zebra, giraffe, elephant and several kinds of antelope, and kangaroos.

Savannas land also has many different tribes who are either cattle pastoralists like the Masai of the East African plateau or settled cultivator like the Hausa of Northern Nigeria. The landscape of Savanna regions is known as Parkland landscape because grasses are dotted with trees.

World Map Showing Savanna Type of Climate

IV. The GrasslandGrasslands are areas where the vegetation is dominated by grasses (Poaceae) and other plants. Grasslands occur naturally on all continents except Antarctica.

The principal grasslands include, the prairies of Canada and the USA, the Pampas of South America, the Steppes of Europe and Asia, the Velds of Africa, the Pustaz of Hungary and the Canterberry of New Zealand.

The annual rainfall in these grassland varies from 25 cm to 75 cm. The dominant plants species comprise short and tall grasses. These areas are less suitable for farming and are used for some form of ranching.

The region is dominated by nomadic and semi-nomadic peoples like the Kirghiz of the Asiatic Steppes, the Red Indians of North

America etc. The grassland has been ploughed up for extensive, mechanized wheat cultivation and is now the grainary of the world.

Pastoralism is another occupation of people living in this region. With the development of refrigerated ships in the late nineteenth century, the temperature grasslands became major pastoral regions, exporting large quantities of mutton, beef, wool, milk, butter and other dairy products.

Q. In the grasslands, trees do not replace the grasses as a part of an ecological succession because of(a) insects and fungi(b) limited sunlight and paucity of nutrients(c) water limits and fire(d) None of the above

(UPSC-2013)

V. The DesertDeserts cover about one fifth of the Earth's surface and occur where rainfall is less than 50 cm/year.

In other words, deserts are regions of low rainfall which may be hot like the hot deserts of the Sahara or temperate as the mid latitude deserts of Turkmanistan, Pategonia and Gobi. Deserts are characterized by extremely low rainfall and high evaporation rate. The aridity of the hot desert is mainly due to the effects of off-shore trade winds, hence they are also called Trade wind deserts. The temperate desert are rainless because of their interior location in the temperate latitudes.

The major hot deserts of the world are located on the western coasts of continents between latitudes 15° and 30° N and S. The major deserts of the world includes– Sahara, Thar, Australian desert, Kalahari, Namib, Mojave, Atacama, Patagonia, Turkistan and Gobi.

Desert has always been inhabited by different groups of inhabitants, such as Bedouin of Arab, the Bushmen of the Kalahari and the Bindibu of Australia. The Bushman and The Bindibu are nomadic hunters and food gatherers. The Bedouin of Arabia ride on horses and live in tents; the Tuaregs of the Sahara are camel riders and dwell in grass Zerbia, while Gobi Mongols ride on horse to herd their yaks and live in portable huts.

Q. Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?

1. Hard and waxy leaveas 2. Tiny leaves or no leaves3. Thorns instead of leavesSelect the correct answer using the codes given below.(a) 1 and 2 only (b) 2 only(c) 1 and 3 only (d) 1, 2 and 3

(UPSC-2014)

The sea of mineral wealth is a pull factor for desert economy. The gold mining of great Australian desert, diamond and copper mining of Kalahari desert has brought many people into desert.

VI. The Coniferous Forest or TaigaThe northern coniferous forest or Taiga extends as an east-west band across North America, Europe and Asia, just South of the Tundra. The average rainfall ranges from 10 to 35 cm and the average

Environmental Ecology6

temperatures are– 40°C in the winter to 20°C in the summer. The growing duration of plant is only about 150 days.

The predominant vegetation of Siberian climate is evergreen coniferous forest. It stretches across North America, Europe and Asia. The greatest single band of the coniferous forest is known as Taiga in Siberia. The taiga is absent in the southern hemisphere because of the narrowness of the southern continents in the high latitudes.

The climate of the Taiga is characterized by a bitter cold winter of long duration and a cool, brief summer.

Equator

Topic of cancer

Topic of Capricorn

World Map Showing Coniferous Forest

The Taiga climate is known for coniferous evergreen forest. The coniferous forest belts of Eurasia and North America are the richest source of softwood for use in building construction, furniture, timber industries, matches, pulp and paper. The world's greatest softwood producers are Scandinavian countries (Finland, Norway and Sweden), Canada, USA and Russia. Following major species in the coniferous forest:-• Pine, e.g. red pine, white pine• Fir e.g. Douglas fir • Black Spruce• Larch • Ferns• Mushrooms • Mosses• Fireweed • Giant sequoia

The presence of pure strands make coniferous forest a great advantage in commercial forest exploration. The soil of these regions is 'Podzol' which is acidic in nature.

VII. The TundraThe word tundra means north of the timberline. The tundra extends across Asia, Europe and North America generally above 60°N latitude. Tundra has plains characterized by snow, ice and frozen soil most of the year. The main limiting factors for life are poor light and extremely low temperature. Annual precipitation is generally below 25 cm. The snowfall is scanty.

The vegetation in north tundra is so sparse that it is also called an arctic desert. The biome is virtually treeless. It consists mainly of mosses, lichens, hedges, grass and small willow trees. Caribou, arctic hares, arctic foxes, reindeer, snow owl and migratory birds are common in this region. The tundra is a very delicate ecosystem and recovers from any disturbance very slowly.

Human activities in the tundra are largely confined to the coast. The few people who live in the tundra live a semi-nomadic life and have to adapt themselves to the harsh environment. The Eskimos Live in Greenland, northern Canada and Alaska. During winter time they live in compact igloos and in summer they live in portable tents of skins.

4. vertical or altituDinal Biomes

The series of biomes such as tropical rain forest, deciduous forest, coniferous forest, tundra and snow and ice are observed along the slopes of high mountain ranges like the Himalaya (Asia), Andes (South America) and the Rockies (North America). In these high rise mountain range the gradual change in the biome type follows the altitude rather than the latitude. This can be illustrated through the following diagram.

Ice and Snow coverBiodiversity increases

Ice and Snow

Coniferous forest

Coniferous forest

Deciduous forest

Deciduous forest

Equator

Tropical forest

Tropical forest

Tundra Pole

Tree line

Snow lineTundra

Tree line

Correlation Between Latitudinal Biomes With Altitudinal Biomes

The types of biome formation is highly dependent on temperature and precipitation rates (rainfall or snowfall). In the tropical mountain the sequence of communities from the base of the mountain to the snow line are as follows:• Tropical forest (called Terai in India),• Deciduous forest• Coniferous forest, and• Tundra.

5. aquatic ecosystems

There are many kinds of aquatic ecosystems that differ with regard to the abiotic factors.

The water along with aquatic organism community form aquatic ecosystem. The aquatic ecosystems range from open ocean to small temporary pond. They have conditions of salinity, depth and temperature fluctuation.

The adaptation of organisms to aquatic environments also vary in diversity and degree. Animals such as fish live exclusively in water. Some animals such as frog, crocodiles and aquatic birds are amphibious in nature. Some animals like the echinoderms (e.g. starfish) live only in saline water.

Planktons

This group includes both microscopic plants, like algae (phytoplankton) and animals, like crustaceans and protozoans (zooplankton), found in aquatic ecosystems. The locomotory power of the planktons is limited so that their distribution is controlled largely by currents in the aquatic ecosystems.

7Environmental Ecology

they carry, speed of flow, oxygen content, temperature, pH and other numerous chemical and physical conditions.

The rivers, specially big ones are generally perennial like  Ganges, Yamuna, Brahmaputra, Amazon, Nile etc. originating in springs, lakes or from melting of glaciers. The flow of water is swife therefore, floating populations of plankton are not found. In the lowland, the water often becomes muddy, resulting in abundance of phytoplankton and zooplankton.

6. man-maDe ecosystemsMan-made ecosystems include villages, cities, plantations, parks, fish tanks, aquarium and agricultural land. The agro ecosystems, the most important of the man-made ones, mainly comprise seasonal variety of one crop a few weeds and several animals. These ecosystems are highly efficient but are poor in diversity and are vulnerable to drought, floods, pests, diseases and pathogens. They are highly simplified in nature.

7. interactions in an ecosystemAll abiotic and biotic components of an ecosystem interact with each other and also with the subcomponents of its system. For example, man-animal interaction. These interactions determine the sustainability of the ecosystem. The major common type of interaction that prevail in ecosystem are:

(i) Mutualism : It is an interactions between two species that benefit both of them. For example — bee and a pollinating flower.

(ii) Predation : This is a direct food relation between two species of animals in which one animal (the predator) captures and feed on another (the prey). For example, relationship between lion and deer. A species such as the snake may be both a prey and a predator. Snake acts as a predator with frog and as prey with Hawk.

(iii) Scavenging : This is the direct food relationship where animals such as a vulture feed on other organisms, which have died naturally or have been killed by another animal. For example, the left over of lion's food is eaten by smaller animals such as jackals, hyenas and vultures.

(iv) Parasitism : This is an association of two species which results in the damage or harm to one and benefit to the other species. For example, Ticks, mites and lice are external parasites, whereas, parasites like malaria, microfilaria, tapeworm and roundworm are examples of internal parasites. They live in association with other species and benefit from them but also harming them at the same time.

(v) Symbiosis : This is an association of two species where both the partners benefit from one another. For example, lichens are composed of an algae and a fungus. The green algae synthesizes food for both; whereas, the fungus gives protection and raw materials for the preparation of food. The bacterium Rhizobium found in the root nodules of leguminous plants is another common example of symbiotic relationship. Here, the Rhizobium fixes atmospheric nitrogen which is used by the plant. In turn the plant supplies water, minerals and organic food to the bacterium.

(vi) Commensalism : Here only one organism is benefitted and mother is harneo. Ex — a spider buiding a web on a tree.

Q. What would happen if phytoplankton of an ocean is completely destroyed for some reasons?1. The ocean as a carbon sink would be adversely affected.2. The food chains in the ocean would be adversely

affected.3. The density of ocean water would drastically decrease.

Select the correct answer using the codes given below : (a) 1 and 2 only (b) 2 only(c) 3 only (d) 1, 2 and 3

(UPSC-2012) Q. Human activities in the recent past have caused the

increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of

1. its escape into the outer stratosphere. 2. the photosynthesis by phytoplankton in the oceans. 3. the trapping of air in the polar ice caps.

Which of the statement(s) given above is/are correct?(a) 1 and 2 (b) 2 only(c) 2 and 3 (d) 3 only (UPSC-2011)

Fresh Water EnvironmentThe fresh water environment is characterised by its low concentration of salt and mineral ions. The fresh water ecosystem consists of lakes, ponds, streams and rivers.

(i) Lakes and Ponds Ecosystem : Both lakes and ponds are characterised by stagnant fresh water bodies and occur practically in every biome. They also vary in their size from less than a hectare to thousands of hectares; like Victoria Lake of Africa, Lake Superior of USA and Caspian sea of Central Asia.

The shallow lakes have a rich accumulation of organic compounds and they are called Eutrophic lakes. They have rich circulation of nutrients such as phosphates. On the other hand, lakes with steep and rocky sides, are poor in circulating nutrients such as phosphates, and are called Oligotrophic lakes.

Oligotrophic lakes are those that are unproductive; net primary production is only between 50 and 100 milligrams of carbon per square metre per day, nutrients are in poor supply, and secondary production is less. Eutrophic lakes, on the other hand, are productive: net primary production is between 600 and 8,000 milligrams of carbon per square metre per day, nutrients are in good supply, and secondary production is high. Mesotrophic lakes are lakes of intermediate productivity: net primary production is between 250 and 1,000 milligrams of carbon per square metre per day. Models that relate levels of lake productivity to levels of nutrient input have been useful in controlling eutrophication in many temperate freshwater lakes. It was once thought that lakes evolved from states of oligotrophy to eutrophy, but this is now generally believed not to be the case. Instead, lake productivity reflects contemporary process of nutrient supply which is more than the historical events.

(ii) Streams and Rivers : Streams and rivers are free flowing fresh water bodies. They differ from each other in volume of water

Environmental Ecology8

This is a relationship between two species in which one lives attached to another but does not harm it. The attachment of the sedentary sea anemone to the body of an hermit crab and remora (a fish) to a shark are examples of commensalism.

(vii) Competition : This is a relationship which involves struggle among organisms for water, nutrients, space, sunlight or organic food. This results in elimination of the less fit or weaker species from the ecosystem. Competition occurs not only among individuals of a given species but also between member of two or more species. For example—trees, shrubs and herbs in a forest compete for light, water nutrients etc. Lion and tiger in a place compete for prey. This is a classic example of the survival of fittest theory given by Darwin.

8. ecosystem proDuctivity

Ecosystem Productivity refers to the rate of increase of biomass whereas production is the amount of biomass in a given unit area at a given time.

Plant and animal biomass may be measured and represented separately. R.H. Whittaker and G.M. Woodwell (1971) have measured the net primary productivity, world net primary production and biomass of plants of major natural ecosystems of the whole earth. Mean net primary productivity for the whole earth is 320 dry gram/m2/year whereas the mean values for the tropical rainforest, swamps and marshes and estuaries are 2000 dry grams/m2/year in each case. Very low net primary productivity is of extreme desert, rock and ice (3 dry grams/m2/year), desert scrub (70 dry grams/m2/year), open ocean (125 dry grams/m2/ year) and Tundra and Alpine ecosystems (140 dry grams/m2/year).

Q. Which one of the following is the correct sequence of ecosystems in the order of decreasing productivity?

(a) Oceans, lakes, grasslands, mangroves(b) Mangroves, oceans, grasslands, lakes(c) Mangroves, grasslands, lakes, oceans(d) Oceans, mangroves, lakes, grasslands

(UPSC-2013)

Q. In the context of ecosystem productivity, marine upwelling zones are important as they increase the marine productivity by bringing the:

1. decomposer microorganisms to the surface. 2. nutrients to the surface. 3. bottom-dwelling organisms to the surface. Which of the statement(s) given above is/are correct ?(a) 1 and 2 (b) 2 only(c) 2 and 3 (d) 3 only (UPSC-2011)

9. Bio-chemical cycles

The exchange of materials between the living and the non-living world is called the Cycle of Material. Cycles of material are classified into gaseous and sedimentary cycles. For Gaseous Cycles, the reservoir of materials is the atmosphere or water. The four major elements in the living organisms, carbon, hydrogen, oxygen and nitrogen, are predominately gaseous. In the sedimentary cycle involving minerals such as phosphorous, sulphur and calcium, the

reservoir is the lithosphere. The major cycles of material which are important to life are as follows:

9.1 The Carbon CycleCarbon is considered as the basis of life. All life is based on the element carbon. Carbon is the major chemical constituent of most organic matter, from fossil fuels to the complex molecules (DNA and RNA) that control genetic reproduction in organisms. Yet by weight, carbon is not one of the most abundant elements within the Earth's crust. In fact, the lithosphere is only 0.033% carbon by weight. In comparison, oxygen and silicon respectively make up 45.2% and 29.4% of the Earth's surface rocks.

There are five main sources of carbon in the world:(1) Organic molecules in living and dead organisms found in the

biosphere;(2) The gaseous carbon dioxide in the atmosphere; (3) Organic matter in soils; (4) In the lithosphere as fossil fuels and sedimentary rock

deposits such as limestone, dolomite and chalk; and(5) In the oceans as dissolved atmospheric carbon dioxide and

as calcium carbonate shells in marine organisms.

Q. Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth? 1. Volcanic action 2. Respiration 3. Photosynthesis  4. Decay of organic matterSelect the correct answer using the code given below. (a) 1 and 3 only (b) 2 only (c) 1, 2 and 4 only  (d) 1, 2, 3 and 4

(UPSC-2014)

Ecosystems gain most of their carbon dioxide from the atmosphere. A number of autotrophic organisms have specialised  mechanisms that allow for absorption of this gas into their cells. With the addition of water and energy from solar  radiation, these organisms use photosynthesis to chemically  convert the carbon dioxide to carbon-based sugar molecules. These molecules  can then be chemically modified by these organisms through the metabolic addition of other elements to produce more complex compounds like proteins, cellulose, and amino acids. Some of the organic matter produced in plants is passed down to heterotrophic animals through consumption.

Estimated Major Stores of Carbon on the Earth

Sink Amount in Billions of Metric Tons

Atmosphere 578 (as of 1700) - 766 (as of 1999)

Soil Organic Matter 1500 to 1600

Ocean 38,000 to 40,000

Marine Sediments and Sedimentary Rocks

66,000,000 to 100,000,000 (highest)

Terrestrial Plants 540 to 610

Fossil Fuel Deposits 4000

9Environmental Ecology

Carbon CycleThe Greenhouse gas effect has resulted in enhanced heat

energy in the atmosphere carbon dioxide plays a role in this process of Grennhouse Effect. As the sun grew more intense, several biological mechanisms gradually locked some of the atmospheric carbon dioxide into fossil fuels and sedimentary rock.

The Gaia hypothesis proposes that, organisms interact with their inorganic surroundings on Earth to form a self-regulating, complex system that contributes to maintaining the conditions for life on the planet. Topics of interest include how the biosphere and the evolution of life forms effect the stability of global temperature, ocean salinity, oxygen in the atmosphere and other environmental variables that affect the habitability of Earth.

9.2 The Oxygen CycleAlmost all living things need oxygen. They use this oxygen during the process of generating energy in living cells.

Just as water moves from the sky to the earth and back in the hydrologic cycle, oxygen is also cycled through the environment. Plants mark the beginning of the oxygen cycle. Plants are able to use the energy of sunlight to convert carbon dioxide and water into carbohydrates and oxygen in a process called photosynthesis.

CO2 + H2O + sunlight chlorophyll → O2 + carbohydrate

The Oxygen Cycle

This means that plants "breathe" in carbon dioxide and "breathe" out oxygen.

Animals form the other half of the oxygen cycle. We breathe in oxygen which we use to break carbohydrates down into energy in a process called respiration.

O2 + carbohydrate → CO2 + H2O + energyCarbon dioxide produced during respiration is breathed out

by animals into the air. So oxygen is created in plants and used up by animals, as is

shown in the picture above. But the oxygen cycle is not actually quite that simple. Plants must break carbohydrates down into energy just as animals do. During the day, plants hold onto a bit of the oxygen which they produced in photosynthesis and use that oxygen to break down carbohydrates. But in order to maintain their metabolism and continue respiration at night, the plants must absorb oxygen from the air and give off carbon dioxide just as animals do. Even though plants produce approximately ten times as much oxygen during the day as they consume at night, the night-time consumption of oxygen by plants can create low oxygen conditions in some water habitats.

9.3 The Nitrogen CycleNitrogen cycle is the process by which nitrogen is converted into its various chemical forms. Nitrogen is an essential constituent of proteins and nucleic acids that form the essential structural and functional components of a living organism. The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems. Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins and nucleic acids. The store of nitrogen found in the atmosphere, where it exists as a gas (mainly N2), plays an important role. This store is about one million times larger than the total nitrogen contained in living organisms. Other major stores of nitrogen include organic matter in soil and the oceans. Despite its abundance in the atmosphere, nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4

+) and the ion nitrate (NO3–). Most plants obtain the nitrogen

they need as inorganic nitrate from the soil solution. Ammonium is used less by plants for uptake because in large concentrations it is extremely toxic. Animals receive the required nitrogen they need for metabolism, growth and reproduction. They do this by consuming living or dead organic matter containing molecules composed partially of nitrogen.

The Nitrogen Cycle

In most ecosystems nitrogen is primarily stored in living and dead organic matter. This organic nitrogen is converted into inorganic forms when it re-enters the biogeochemical cycle via decomposition. Decomposers, found in the upper soil layer, chemically modifies the

Environmental Ecology10

to another molecule, driving an enzymatic reaction or cellular transport. Phosphorus is also the glue that holds DNA together, binding deoxyribose sugars together, forming the backbone of the DNA molecule. Phosphorus does the same job in RNA.

Again, the agent of getting phosphorus into trophic systems are plants. Plants absorb phosphorous from water and soil into their tissues, tying them to organic molecules. Once taken up by plants, phosphorus is available for animals when they consume the plants.

When plants and animals die, bacteria decomposes their bodies, releasing some of the phosphorus back into the soil.

The Phosphorus Cycle

Once in the soil, phosphorus can be moved 100s to 1,000s of miles from were they were released by riding through streams and rivers. So the water cycle plays a key role of moving phosphorus from ecosystem to ecosystem.

In some cases, phosphorus will travel to a lake, and settle on the bottom. There, it may turn into sedimentary rocks, limestone, to be released millions of years later. So sedimentary rocks acts like a reservoir, conserving much of the phosphorus for future eons. In Chile, Guano birds eat potassium rich fish from the Pacific Ocean. Guano droppings are collected to make phosphorus rich fertilizers.

9.5 The Water CycleWater is a recyclble resource. It can be used and re-used. Water also undergoes a cycle from the ocean to land and land to ocean.

The hydrological cycle describes the movement of water on, in, and above the earth. The water cycle has been working for billions of years and all the life on earth depends on it. Next to air, water is the most important element required for the existence of life on earth. The distribution of water on earth is quite uneven. Many locations have plenty of water while  others  have  very limited quantity. The hydrological cycle is the circulation of water within the earth's hydrosphere in different forms i.e., the liquid, solid and the gaseous phases. It also refers to the continuous exchange of water between the oceans, atmosphere, land surface and the organisms.

nitrogen found in organic matter from ammonia (NH3) to ammonium salts (NH4

+). This process is known as mineralisation and it is carried out by a variety of bacteria, actinomycetes and fungi.

Q. Which of the following adds/add nitrogen to the soil?1. Excretion of urea by animals2. Burning of coal by man 3. Death of vegetationSelect the correct answer using the codes given below.(a) 1 only (b) 2 and 3 only(c) 1 and 3 only (d) 1, 2 and 3

(UPSC-2013)

Almost all of the nitrogen found in any terrestrial ecosystem originally came from the atmosphere. Significant amounts enter the soil in rainfall or through the effects of lightning. The majority, however, is biochemically fixed within the soil by specialized microorganisms like bacteria, actinomycetes, and cyanobacteria. Members of the bean family (legumes) and some other kinds of plants form mutualistic symbiotic relationships with nitrogen fixing bacteria. In exchange for some nitrogen, the bacteria receives from plants carbohydrates. They special structures (nodules) in roots where they can exist in a moist environment. Scientists estimate that biological fixation globally adds approximately 165 million metric tonnes of nitrogen to ecosystems every year.

In 2011, study found that nitrogen from rocks may also be a significant source of nitrogen.

Humans activities have severely altered the nitrogen cycle. Some of the major processes involved in this alteration include:

• The application of nitrogen fertilisers to crops has caused increased rates of denitrification and leaching of nitrate into groundwater. The additional nitrogen entering the groundwater system eventually flows into streams, rivers, lakes and estuaries. In these systems, the added nitrogen can leads to eutrophication.

• Increased deposition of nitrogen from atmospheric sources because of fossil fuel combustion and forest burning. Both these processes release a variety of solid forms of nitrogen through combustion.

• Livestocks release a large amounts of ammonia into the environment from their wastes. This nitrogen enters the soil system and then the hydrologic system through leaching, groundwater flow, and runoff.

• Sewage waste and septic tank leaching.

Q. What can be the impact of excessive/inappropriate use of nitrogenous fertilisers in agriculture?1. Proliferation of nitrogen-fixing microorganisms in soil

can occur.2. Increase in the acidity of soil can take place.3. Leaching of nitrate to the ground-water can occur.Select the correct answer using the code given below:(a) 1 and 3 only (b) 2 only(c) 2 and 3 only (d) 1, 2 and 3 (UPSC-2015)

9.4 The Phosphorus CyclePhosphorus is the key to energy in living organisms, for it is phosphorus that moves energy from ATP (Adenosine Triphosphate)

11Environmental Ecology

Precipitation

Seepage

Lakes & Ocean

Evaporation

Run-Off

The Hydrological/Water (H2O) Cycle

About 97.25 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, seeps into the ground or a part of it becomes glacier.

Reservoir Percentage of the TotalOceans 97.25Ice Caps and Glaciers 2.05

Groundwater 0.68Lakes 0.01Soil Moisture 0.005Atmosphere 0.001

It is to be noted that the renewable water on the Earth is constant while the demand is increasing tremendously. This is resulting in water crisis areas in the world.

9.6 The Sulphur CycleProteins are not only made from carbon and nitrogen, but many important proteins also contain sulphur. Sulphur is also an important component of coenzyme A, which is used to produce energy in cellular respiration. So the availability of sulphur is essential in maintaining life.

H2S SO2

(Thiobacillus)Oxidation

(Desulfovibrio)Reduction

Sulfides in Soil

Sulfates in Soil

AminoCombustion

FossilFuels

Plants

AcidsDead Origanic Matter

Micoorganisms

Precipitationby Rain

The Sulphur Cycle

Just as plants can not convert Nitrogen into something useful in the nitrogen cycle similalry sulphur can not be utilised in its elemental form, they cannot utilise. Again, plants depend upon bacteria, in this case chemoautotrophic bacteria, which oxidizes elemental sulphur to sulfates, as in the following formula.

2S + H2O + 3O2 → 2H2SO4.

Once in the form of sulfate (H2SO4), plants can then incorporate the sulphur into proteins.

Sulphur shares other characteristics to the nitrogen cycle. 2H2SO4 can be converted into hydrogen sulfide (H2S) by sulphur bacteria, as can proteins when were broken down by decomposers.

10. ecological succession

Ecological  succession  is a series of progressive changes in the species that make up a community over time. Ecologists usually identify two types of succession, which differ in their starting points:• In primary succession, newly exposed or newly formed rock is

colonized by living things for the first time.• In secondary succession, an area that was previously occupied

by living things is disturbed, then re-colonized following the disturbance.

Succession is directional. Different stages in a particular habitat succession can usually be accurately predicted.

These stages, characterised by the presence of different communities, are known as ‘seres’.

Communities change gradually from one sere to another. The seres are not totally distinct from each other and one will tend to merge gradually into another, finally ending up with a ‘climax’ community.

Succession will not go any further than the climax community. This is the final stage. 

11. ecotone anD eDge effect

An ecotone acts as the boundary or barrier between two biomes. It is the area where two distinct types of environments merge and blend.

Ecotones could be the border where forestland and grassland meet or the boundary where wetlands meet prairie. Many things form a sharp boundary such as natural formations. The area where the land meets water such as where the mangrove fields meet the ocean is also considered an ecotone. The estuary between freshwater and saltwater is also a natural ecotone.

The influence of the two bordering communities on each other is known as the  edge effect. An ecotonal area often has a higher density of organisms of one species and a greater number of species than are found in either flanking  community. Some organisms need a transitional area for activities such as courtship, nesting, or foraging for food.

Environmental Ecology12

Self–Evaluation Test1. Consider the following statements about an ecotone:

1. It is the coinciding zone or a transition area between two or more ecosystems.

2. The ecotone may comprise of biodiversity which does not exist in the adjacent areas.

Select the correct answer using the codes given below:(a) 1 only (b) 2 only(c) Both 1 and 2 (d) Neither 1 nor 2

2. With reference to Ecological Pyramids, consider the following statements:1. In case a pyramid is upright it means that in an ecosys-

tem, producers are more in number and biomass than the herbivores, and herbivores are more in number and biomass than the carnivores.

2. In an ecological pyramid of sea, biomass at a lower tro-phic level is less as compared to the same at a higher level.

3. One of the major loopholes in a pyramid is that sapro-phytes or organisms living on dead organic matter are not given any place in it.

Select the correct answer using the codes given below:(a) 1 and 2 only (b) 2 and 3 only(c) 1 and 3 only (d) All of the above

3. Consider the following statements with regard to carbon cycle:1. Carbon cycling occurs at different levels involving

atmosphere, ocean and through living and dead organ-isms.

2. Decomposers do not contribute to the CO2 pool by any means.

Select the correct answer using the codes given below:(a) 1 only (b) 2 only(c) Both 1 and 2 (d) Neither 1 nor 2

4. Which of the following is the largest land biome?(a) Rainforest biome(b) Taiga biome(c) Grassland biome(d) Tundra biome

5. Which of the following constitute Detritivores?1. Earthworms2. Beetles3. Mussels

Select the correct answer using the codes given below:(a) 1 and 2 only (b) 2 and 3 only(c) 1 and 3 only (d) All of the above

6. Consider the following statements1. Bioaccumulation is the increase in concentration of a

pollutant from the environment to the first organism in a food chain.

2. Biomagnification is the tendency of the pollutants to concentrate as they move from one tropic level to the next.

Which of the statement (s) is/are incorrect?(a) 1 only (b) 2 only(c) Both 1 and 2 (d) Neither 1 nor 2

ANSWERS

1. (c) 2. (d) 3. (a) 4. (b) 5. (d) 6. (d)