UNIVERSITY OF NAIROBI 
                                                           
                            COLLEGE OF BIOLOGICAL AND PHYSICAL SCIENCES 
               
                                       FACULTY OF EXTERNAL STUDIES 
                                                           
                                                           
                                                           
                                                           
                                    BACHELOR OF EDUCATION (SCIENCE) 
                                                           
                                                           
                                                           
                                                           
                                                           
                                                           
                                                           
                                                           
               
                                         FUNDAMENTALS OF ECOLOGY 
                                                     (SZL 103) 
               
               
               
                                                     Written by 
                                                           
                                     Dr. Nathan Gichuki and Dr. John Githaiga 
                                                     Lecturers 
                                               Department of Zoology 
                                                           
               
               
               
               
               
              Published by                                          Published by 
              University of Nairobi                                 College of Education and  
              P.O. Box 30197                                        External Studies 
              Nairobi.                                              P.O. Box 30197 
                                                                    Nairobi. 
               
               
                                                           
               
               
                                                         1 
                   FUNDAMENTALS OF ECOLOGY 
                        (SZL 103) 
       Introduction 
       The purpose of this unit is to enable you acquire knowledge in ecology and appropriate skills for 
       teaching and undertaking research or further study in biological sciences.  During the course you 
       will be exposed to a wide range of indoor and outdoor activities, which are intended to help you 
       understand better the subject matter.     
        
       Ecology is the sub-discipline of biology that deals with the interactions of animals and plants in 
       their natural surroundings.  These surroundings are called the environment of the plant or the 
       animal.  That environment comprises the other living organisms (biotic environment) and the 
       non-living or physical environment.   
        
       Human beings are animals and hence interact with the physical environment, other animals as 
       well as plants.  These interactions are important for survival and successful reproduction of all 
       living things, including ourselves.  It is therefore important for us to understand how organisms 
       coexist and how their interactions affect us or are affected by our own activities. 
        
        In this unit, you will learn how to identify and describe different ecosystems of the world.  You 
       will also learn how land and water ecosystems function, especially how energy and matter are 
       transferred  from  plants  to  animals,  and  how  nutrients  are  recycled.    You  will  also  have  an 
       opportunity to learn about biological populations, their characteristics and interactions as well as 
       factors that influence their distribution and abundance.   
        
       In addition, you will study the process of ecological succession and how it is influenced by biotic 
       factors, environment and soil characteristics.  Before the end of the unit, you will learn wetlands, 
       forests and rangelands contribute to conservation of wild species of plants and animals, and their 
       significance to human welfare. 
        
       The course will be learned from lectures provided in this coursework book, weekly assignments 
       and practical work.  The materials provided in this text are sufficient but you are advised to do 
       further reading of the recommended textbooks for this course.  During your residential training, 
       you will have an opportunity to ask questions and seek clarification of any aspects of this unit 
       that you did not understand while studying on your own. 
        
       Objectives 
       At the end of this unit, you should be able to correctly: 
        1.  describe the structure of aquatic and terrestrial ecosystems 
        2.  discuss how energy flows and material is transferred in ecosystems 
        3.  describe and draw the cycles of water and major nutrients 
        4.  state the characteristics of biological populations 
        5.  describe the process of ecological succession and explain how it is  
          influenced by soil characteristics 
             6.  explain the significance of biological conservation 
        7.  acquire essential skills, attitudes, values and techniques that are relevant to the study  
          of ecology and the broader field of biology 
                          2 
                                                    COURSE OUTLINE 
                
                
                Lecture 1: What is ecology? Nature of ecology                                  4 
               Lecture 2: Natural selection and diversity of life histories                    7 
               Lecture 3: Sexual selection and speciation                                      10 
               Lecture 4: Evolution of life histories                                          14 
               Lecture 5: Basic structure and types of ecosystems                              18 
               Lecture 6: Bio-geochemical cycles                                               23 
               Lecture 7: Basic terminology and characteristics of biological populations      33 
               Lecture 8: Theories of population growth and interactions                       40 
               Lecture 9: Populations of humans, domestic animals and pests                    51 
               Lecture 10: Community structure and energetics                                  59 
               Lecture 11: Structure and function of aquatic ecosystems                        70 
               Lecture 12: Conservation of ecosystems and species                              84 
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                                                                                                
                
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