Environment 2021-22 by PMF IAS 
             
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             The Final File will Included Protected Area Network and Major Flora and Fauna of 
                                                                                            India 
                                                                                                   
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                                                                                   Table of Contents                                                                                        rn Smar
            1.     Environment, Habitat and Ecosystem ........................................................................................... 51                                         Lea
                                                                                                                                                                                            –AS 
                   1.1. Environment .......................................................................................................................................... 51           F I
                   1.2. Habitat ................................................................................................................................................... 52      PM
               
                           1.2.1.  Difference Between Habitat and Environment ............................................................................................. 52 
                      1.3. Ecosystem .............................................................................................................................................. 53 
                           1.3.1.  Classification of Ecosystems .......................................................................................................................... 53 
                           1.3.2.  Difference Between Ecology, Environment, Habitat & Ecosystem ............................................................... 54 
                                          Q. Which one of the following is the best description of the term “ecosystem”? ..................................................... 57 
                      1.4. Components of an Ecosystem ............................................................................................................. 58 
                           1.4.1.  Abiotic Components ...................................................................................................................................... 59 
                                          Q. If a tropical rain forest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. 
                                          This is because ............................................................................................................................................................ 59 
                                          Major Limiting Factors ................................................................................................................................................ 60 
                           1.4.2.  Effect of Abiotic Components on Terrestrial Primary Producers (Plants) .................................................... 62 
                                          Light ............................................................................................................................................................................ 62 
                                          Frost ............................................................................................................................................................................ 62 
                                          Snow ........................................................................................................................................................................... 62 
                                          Temperature ............................................................................................................................................................... 62 
                           1.4.3.  Biotic Components ........................................................................................................................................ 63 
                                          Primary Producers or Autotrophs (Self-Nourishing) ................................................................................................... 63 
                                          Consumers or Heterotrophs or Phagotrophs (Other Nourishing) .............................................................................. 63 
                                          Macro Consumers ....................................................................................................................................................... 63 
                                          Micro Consumers or Saprotrophs (Decomposers or Osmotrophs) ............................................................................ 63 
              1.      Ecology – Principles and Organizations ....................................................................................... 64 
                      1.1. Levels of Organizations in Ecology ..................................................................................................... 64 
                           1.1.1.  Individual and Species ................................................................................................................................... 67 
                           1.1.2.  Population ..................................................................................................................................................... 67 
                           1.1.3.  Community .................................................................................................................................................... 67 
                                          Major Communities .................................................................................................................................................... 67 
                                          Minor Communities .................................................................................................................................................... 67           2 
                           1.1.4.  Ecosystem ..................................................................................................................................................... 68 
                                          Ecological Niche .......................................................................................................................................................... 68      t          
                                          Difference Between Niche and Habitat ...................................................................................................................... 69                      mar
                                          Q. Which one of the following terms describes not only the physical space occupied by an organism but also its                                                                      rn S
                                          functional role in the community of organisms? ........................................................................................................ 69                           Lea
                           1.1.5.  Biome ............................................................................................................................................................ 69                      AS –
                                          Ecotone ....................................................................................................................................................................... 69  F I
                                          Characteristics of Ecotone .......................................................................................................................................... 70            PM
               
                                          Ecocline ....................................................................................................................................................................... 71 
                                          Edge Effect – Edge Species ......................................................................................................................................... 71 
                           1.1.6.  Biosphere ...................................................................................................................................................... 72 
                       1.2. Principles of Ecology ............................................................................................................................ 73 
                           1.2.1.  Adaptation .................................................................................................................................................... 73 
                                          Examples of Adaptation .............................................................................................................................................. 74 
                           1.2.2.  Variation ........................................................................................................................................................ 75 
                                          Adaptive radiation ...................................................................................................................................................... 75 
                           1.2.3.  Speciation ...................................................................................................................................................... 76 
                           1.2.4.  Mutation ....................................................................................................................................................... 77 
                           1.2.5.  Natural Selection ........................................................................................................................................... 77 
                           1.2.6.  Evolution ....................................................................................................................................................... 77 
                           1.2.7.  Extinction ...................................................................................................................................................... 78 
                                          Q. The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the 
                                          discussion of (2018) .................................................................................................................................................... 78 
                                          Q. Which of the following are true? ........................................................................................................................... 79 
                                          Q. Choose the incorrect pairs ..................................................................................................................................... 79 
              2.       Functions of an Ecosystem ............................................................................................................. 80 
                       2.1. Ecological Succession ........................................................................................................................... 80 
                           2.1.1.  Stages in Ecological Succession ..................................................................................................................... 81 
                           2.1.2.  Primary Succession........................................................................................................................................ 81 
                                          Q. Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic 
                                          association of .............................................................................................................................................................. 82 
                                          Autotrophic and Heterotrophic succession ................................................................................................................ 82 
                           2.1.3.  Secondary Succession ................................................................................................................................... 83 
                                          Difference Between Primary and Secondary Succession ........................................................................................... 83 
                           2.1.4.  Autogenic and Allogenic Succession ............................................................................................................. 84                                              
                                          Q. In the grasslands, trees do not replace the grasses as a part of an ecological succession because of .................. 84                                                            3
                           2.1.5.  Succession in Plants ...................................................................................................................................... 84                                  t          
                           2.1.6.  Succession in Water ...................................................................................................................................... 85                                   mar
                       2.2. Homeostasis in Ecosystem ................................................................................................................... 86                                                        earn S
                           2.2.1.  Homeostasis .................................................................................................................................................. 87                                L
                                          Regulate ...................................................................................................................................................................... 87        IAS– 
                                          Conform ...................................................................................................................................................................... 87        F
                                          Migrate ....................................................................................................................................................................... 88       PM
              
                                        Suspend ...................................................................................................................................................................... 88 
             3.      Energy Flow Through an Ecosystem – Trophic Levels ................................................................ 88 
                      3.1. Food Chain ............................................................................................................................................ 89 
                          3.1.1.  Grazing food chain ........................................................................................................................................ 90 
                          3.1.2.  Detritus food chain ....................................................................................................................................... 90 
                                        Q. With reference to the food chains in ecosystems, which of the following kinds of organism is/are known as 
                                        decomposer organism/organisms? ............................................................................................................................ 91 
                                        Q. Which one of the following is the correct sequence of a food chain? ................................................................... 92 
                      3.2. Food Web .............................................................................................................................................. 93 
                          3.2.1.  Types of Biotic Interactions in a Food Web .................................................................................................. 94 
                                        Q. With reference to food chains in ecosystems, consider the following statements: .............................................. 98 
                      3.3. Ecological Pyramids .............................................................................................................................. 98 
                          3.3.1.  Pyramid of Numbers ..................................................................................................................................... 98 
                                        Pyramid of Numbers – Upright ................................................................................................................................... 99 
                                        Pyramid of Numbers – Inverted ............................................................................................................................... 100 
                          3.3.2.  Pyramid of Biomass ..................................................................................................................................... 101 
                                        Pyramid of Biomass – Upright .................................................................................................................................. 102 
                                        Pyramid of Biomass – Inverted ................................................................................................................................. 103 
                          3.3.3.  Pyramid of Energy ....................................................................................................................................... 104 
                                        Ecological Efficiency .................................................................................................................................................. 105 
                          3.3.4.  Limitations of Ecological Pyramids .............................................................................................................. 106 
                          3.3.5.  Biomagnification – Pollutants and Trophic Level ........................................................................................ 106 
                                        Bioaccumulation ....................................................................................................................................................... 107 
                                        Biomagnification ....................................................................................................................................................... 107 
             4.      Biogeo Chemical Cycling or Nutrient Cycling ........................................................................... 108                                                                       
                      4.1. Types of Nutrient Cycles .................................................................................................................... 109                                          4
                      4.2. Carbon Cycle (Gaseous Cycle) ........................................................................................................... 109                                               t          
                          4.2.1.  Steps in Carbon Cycle .................................................................................................................................. 110                        mar
                                        Q. Consider the following: ........................................................................................................................................ 111       rn S
                                        Q. Which one of the following is the process involved in photosynthesis? ............................................................. 112                                     Lea
                      4.3. Nitrogen Cycle (Gaseous Cycle) ........................................................................................................ 112                                                 IAS– 
                          4.3.1.  Nitrogen Fixing – Nitrogen to Ammonia (N  to NH ) .................................................................................. 113 
                                                                                                         2          3                                                                                                 F
                          4.3.2.  Nitrification – Ammonia to Nitrates ............................................................................................................ 114                                PM