Paper         : 12 Principles of Ecology 
                                                                                                                                   Module      : 21 Types of Ecosystems: Aquatic Ecosystem - 
                                                                                                                                                                                   Fresh Water Ecosystem: Part 1                                                                                                    
                                                                                                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                                         Development Team 
                                                                                                                                                 Principal Investigator                                                                                          :            Prof. Neeta Sehgal  
                                                                                                                                                                                                                                                                              Department of Zoology, University of Delhi 
                                                                                                                                                               
                                                                                                                                               Co-Principal Investigator  :  Prof. D.K. Singh 
                                                                                                                                                                                                                                                                             Department of Zoology, University of Delhi 
                                                                                                                                                 Paper Coordinator                                                                                               :            Prof. D.K. Singh 
                                                                                                                                                                                                                                                                              Department of Zoology, University of Delhi 
                                                                                                                                                 Content Writer                                                                                                  :            Dr. Sushma Bhardwaj , Deshbandhu College, DU                                                        
                                                                                                                                                                                                                                                                       Ms. Harshita Mishra, Research Scholar, DU 
                                                                                                                                                  
                                                                                                                                               Content Reviewer                                                                                                 :            Prof. K.S. Rao 
                                                                                                                                                                                                                                                                             Department of Botany, University of Delhi 
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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                                                                                                                                                                          Principles of Ecology 
                                                ZOOLOGY                                                                                                                   Aquatic Ecosystem – Fresh Water Ecosystem: Part 1 
                                                                             
                                                                                                                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                             
                                                                                                                                                                                                                                                  Description of Module 
                                                                            Subject Name                                                                                                                            ZOOLOGY 
                                                                            Paper Name                                                                                                                              Principles of Ecology 
                                                                            Module Name/Title                                                                                                                       Types of  Ecosystems 
                                                                            Module Id                                                                                                                               M21:  Aquatic Ecosystem: Freshwater Ecosystem: Part 1 
                                                                            Keywords                                                                                                                                Ecosystem,  Freshwater  ecosystem,  limnology,  lake,  river, 
                                                                                                                                                                                                                    stream 
                                                                             
                                                                            Contents 
                                                                            1.                     Learning Objectives  
                                                                            2.                     Introduction   
                                                                            3.                     Structure of Ecosystem  
                                                                                                   3.1. Trophic Structure of the Ecosystem   
                                                                                                   3.2. Components of Ecosystem   
                                                                            4.    Types of Ecosystem  
                                                                            5.    Freshwater Ecology   
                                                                                                   5.1. Freshwater Habitat   
                                                                                                   5.2.  Types of Freshwater Habitat   
                                                                                                   5.3.  Limiting Factors of Freshwater Ecosystems   
                                                                                                                           5.3.1.  Temperature   
                                                                                                                           5.3.2.  Transparency  
                                                                                                                           5.3.3.  Current   
                                                                                                                           5.3.4.  Concentration of respiratory gases  
                                                                                                                           5.3.5.  Concentration of biogenic salts   
                                                                                                                           5.3.6.  Isolation due to land barriers   
                                                                                                                           5.3.7.  Osmoregulation  
                                                                            6.                     Summary   
                                                                             
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                                                                                                                                                                          Principles of Ecology 
                                                ZOOLOGY                                                                                                                   Aquatic Ecosystem – Fresh Water Ecosystem: Part 1 
                                                                             
                                                                                                                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                            1. Learning Objectives                                                                                                                                                                                                         
                                                                            After the end of this module you will be able to  
                                                                                                Understand the structure, function and composition of  an ecosystem 
                                                                                                Differentiate between ecosystem, ecology and environment 
                                                                                                List the different type of ecosystems and their characteristics. 
                                                                                                Know the characteristics of  Freshwater Ecosystem 
                                                                                                Explain the limiting factors of Freshwater Ecosystem 
                                                                            2. Introduction 
                                                                            Any assemblage of plants and animals able to exist within an area will in time, form a biotic 
                                                                            community. In this community, the different species tend to interact with one another and to 
                                                                            modify the conditions of life within which each exists. They therefore develop the inter-
                                                                            relationships and inter-dependences which constitutes an ecosystem. All ecosystems of the 
                                                                            earth, together, form the biosphere. The biosphere is that portion of the earth within which 
                                                                            life exists. It includes all oceans and freshwater, lower layers of the atmosphere and the outer 
                                                                            skin of the earth‘s crust- the rocks and soil of the earth‘s surface. 
                                                                            The term ecosystem was proposed by A.G. Tansley in 1935, who defined it as ‗the system 
                                                                            resulting  from  integration  of  all  the  living  and  non-living  factors  of  environment‘.  An 
                                                                            ecosystem  is  an  overall  integration  of  whole  mosaic  of  interacting  organisms  and  their 
                                                                            environment. It is normally an open system with a continuous, but variable, influx and loss of 
                                                                            materials and energy. It is a basic, functional unit with no limits of boundaries, consisting of 
                                                                            both  biotic  and  abiotic  components  interacting  with  each  other,  both  necessary  for 
                                                                            maintenance of life upon earth. Therefore, it represents the highest level of energy based 
                                                                            ecological interaction. 
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                                                                                                                                                                          Principles of Ecology 
                                                ZOOLOGY                                                                                                                   Aquatic Ecosystem – Fresh Water Ecosystem: Part 1 
                                                                             
                                                                                                                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
                                                                                                                                                                                                                                                    Fig.1: Schematic Representation of an Ecosystem 
                                                                                                                                                                                                                                                                                                                                                             
                                                                            3. Structure of Ecosystem 
                                                                            3.1. Trophic Structure of the Ecosystem 
                                                                            Based on the trophic structure (trophe = ‘nourishment‘), ecosystem is two layered.  
                                                                            1.                    Autotrophic (―self-nourishing‖) Stratum is the upper layer, also called the ‗green belt‘ of 
                                                                                                  chlorophyll containing plants. This stratum is predominated by fixation of light energy, 
                                                                                                  use of simple inorganic substances, and the buildup of complex substances.  
                                                                            2.                    Heterotrophic  (―other-  nourished‖)  Stratum  is  the  second  layer,  also  known  as  the 
                                                                                                  ―brown belt‖ of soil and sediments, decaying matter, roots, etc. This level is dominated 
                                                                                                  by the use, rearrangement and decomposition of complex materials. 
                                                                            3.2. Components of Ecosystem 
                                                                            Living organisms and their non-living environment are in-separable and interact with each 
                                                                            other in an ecosystem (Fig. 2). Therefore, they constitute the two major components of an 
                                                                            ecosystem: 
                                                                               a.  Abiotic (Non- Living) component          b.   Biotic (Living) component 
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                                                                                                                                                                          Principles of Ecology 
                                                ZOOLOGY                                                                                                                   Aquatic Ecosystem – Fresh Water Ecosystem: Part 1