viii Contents
3.2 Population Dynamics 28
3.3 Population Size Variation Models 29
3.3.1 Exponential Model 29
3.3.2 Logistic Model 30
3.4 Interactions between Two Populations 32
3.4.1 Symbiosis of Two Populations 32
3.4.2 Competition between Two Populations 33
3.4.2.1 Competition Models of Two Populations 34
3.4.3 Predator-Prey Interaction 35
3.4.3.1 Predator-Prey Interaction Models 37
3.5 Natural Selection and Evolution 40
3.6 Survival Strategies of Populations 41
3.7 The Human Population 43
3.7.1 The Changes of Human Populations 44
4 organisation at the Ecosystem Level
51
4.1 Energy Flow in the Ecosystem 51
4.1.1 Food Chains—Trophic Levels 52
4.1.2 The Role of Photosynthesis and Respiration 54
4.1.3 Ecosystem Energy Model 55
4.2 Limiting Factors in Various Environments 58
4.2.1 Primary Production 59
4.3 Biogeochemical Cycles 61
4.3.1 Water Cycle 64
4.3.2 Carbon Cycle 64
4.3.2.1 Main Features of the Cycle 64
4.3.2.2 Carbon Cycle Perturbations 66
4.3.3 Nitrogen Cycle 67
4.3.4 Oxygen Cycle 70
4.3.5 Phosphorous Cycle 71
4.3.6 Sulphur Cycle 73
4.4 Ecosystems’ Change in Time 73
4.4.1 Ecological Succession 73
4.4.2 Complexity and Stability of Ecosystems 74
4.5 Functions of Aquatic Ecosystems 77
4.5.1 Trophic and Other Characteristics
of Aquatic Ecosystems 77
4.5.2 Temperature Layering and Seasonal Inversions 78
4.5.3 Mathematical Model of a Lake 80