Download Elements of Ecology (8th Edition)

Elements of
Ecology
Eighth Edition
Thomas M. Smith
University of Virginia
Robert Leo Smith
West Virginia University, Emeritus
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Smith, T. M. (Thomas Michael)
Elements of ecology / Thomas M. Smith, Robert Leo Smith.—8th ed.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-321-73607-9
1. Ecology. I. Smith, Robert Leo. II. Title.
QH541.S624 2011
577—dc22
2011015962
ISBN 10: 0-321-73607-9; ISBN 13: 978-0-321-73607-9 (Student edition)
ISBN 10: 0-321-74286-9; ISBN 13: 978-0-321-74286-5 (Professional copy)
ISBN 10: 0-321-88454-X; ISBN 13: 978-0-321-88454-1 (Books a la Carte)
2 3 4 5 6 7 8 9 10—DOW—15 14 13 12 11
Contents
Preface xv
Chapter 1
The Nature of Ecology 1
1.1 Ecology Is the Study of the Relationship between Organisms
and Their Environment 2
1.2 Organisms Interact with the Environment in the Context
of the Ecosystem 2
ECOLOGICAL ISSUES: Ecology Has Complex Roots 3
1.3
1.4
1.5
Ecological Systems Form a Hierarchy 4
Ecologists Study Pattern and Process at Many Levels 5
Ecologists Investigate Nature Using the Scientific Method 6
QUANTIFYING ECOLOGY 1.1: Classifying Ecological Data 8
1.6
Models Provide a Basis for Predictions 9
QUANTIFYING ECOLOGY 1.2: Displaying Ecological Data: Histograms
and Scatter Plots 10
1.7 Uncertainty Is an Inherent Feature of Science 12
1.8 Ecology Has Strong Ties to Other Disciplines 12
1.9 The Individual Is the Basic Unit of Ecology 13
Summary
13
•
Study Questions
14
•
Further Readings
14
PART 1 The Physical Environment 16
Chapter 2
Climate
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
18
Earth Intercepts Solar Radiation 19
Intercepted Solar Radiation Varies Seasonally 21
Air Temperature Decreases with Altitude 22
Air Masses Circulate Globally 25
Solar Energy, Wind, and Earth’s Rotation Create Ocean Currents 26
Temperature Influences the Moisture Content of Air 27
Precipitation Has a Distinctive Global Pattern 27
Topography Influences Regional and Local Patterns of Precipitation 30
Irregular Variations in Climate Occur at the Regional Scale 30
Most Organisms Live in Microclimates 32
ECOLOGICAL ISSUES: Urban Microclimates 33
Summary 34 • Study Questions 35 • Further Readings
Chapter 3
35
The Aquatic Environment 36
3.1
Water Cycles between Earth and the Atmosphere 37
ECOLOGICAL ISSUES: Groundwater Resources 38
3.2
3.3
3.4
3.5
3.6
3.7
3.8
Water Has Important Physical Properties 39
Light Varies with Depth in Aquatic Environments 41
Temperature Varies with Water Depth 42
Water Functions as a Solvent 44
Oxygen Diffuses from the Atmosphere to the Surface Waters 45
Acidity Has a Widespread Influence on Aquatic Environments 46
Water Movements Shape Freshwater and Marine Environments 47
iii
3.9 Tides Dominate the Marine Coastal Environment 48
3.10 The Transition Zone between Freshwater and Saltwater Environments
Presents Unique Constraints 49
Summary
Chapter 4
50
•
Study Questions
51
•
Further Readings
51
The Terrestrial Environment 52
4.1 Life on Land Imposes Unique Constraints 53
4.2 Plant Cover Influences the Vertical Distribution of Light 54
QUANTIFYING ECOLOGY 4.1: Beer’s Law and the Attenuation of Light 56
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
Soil Is the Foundation upon Which All Terrestrial Life Depends 57
The Formation of Soil Begins with Weathering 58
Soil Formation Involves Five Interrelated Factors 58
Soils Have Certain Distinguishing Physical Characteristics 59
The Soil Body Has Horizontal Layers, or Horizons 60
Moisture-Holding Capacity Is an Essential Feature of Soils 61
Ion Exchange Capacity Is Important to Soil Fertility 62
Basic Soil Formation Processes Produce Different Soils 63
Summary
65
•
Study Questions
66
•
Further Readings
67
PART 2 The Organism and Its Environment 68
Chapter 5
Ecological Genetics: Adaptation and Natural Selection 70
5.1 Adaptations Are a Product of Natural Selection 71
5.2 Genes Are the Units of Inheritance 72
5.3 The Phenotype Is the Physical Expression of the Genotype 72
5.4 Genetic Variation Occurs at the Level of the Population 73
5.5 Adaptation Is a Product of Evolution by Natural Selection 73
5.6 Several Processes Can Function to Alter Patterns of Genetic
Variation 77
QUANTIFYING ECOLOGY 5.1: Hardy–Weinberg Principle 78
5.7
5.8
Natural Selection Can Result in Genetic Differentiation 80
Adaptations Reflect Trade-offs and Constraints 81
FIELD STUDIES: Beren Robinson 82
5.9 Organisms Respond to Environmental Variation at the Individual
and Population Levels 86
ECOLOGICAL ISSUES: The Ecology of Antibiotic Resistance 88
Summary 89 • Study Questions 90 • Further Readings 90
Chapter 6
Plant Adaptations to the Environment 92
6.1 Photosynthesis Is the Conversion of Carbon Dioxide into Simple
Sugars 93
6.2 The Light a Plant Receives Affects Its Photosynthetic Activity 94
6.3 Photosynthesis Involves Exchanges between the Plant
and Atmosphere 95
6.4 Water Moves from the Soil, through the Plant, to the Atmosphere 95
6.5 The Process of Carbon Uptake Differs for Aquatic and Terrestrial
Plants 98
6.6 Plant Temperatures Reflect Their Energy Balance with the Surrounding
Environment 98
6.7 Carbon Gained in Photosynthesis Is Allocated to the Production of Plant
Tissues 99
6.8 Constraints Imposed by the Physical Environment Have Resulted
in a Wide Array of Plant Adaptations 101
iv
6.9
Species of Plants Are Adapted to Different Light Environments 101
QUANTIFYING ECOLOGY 6.1: Relative Growth Rate 104
6.10 The Link between Water Demand and Temperature Influences Plant
Adaptations 106
FIELD STUDIES: Kaoru Kitajima 108
6.11 Plants Vary in Their Response to Environmental Temperatures 112
6.12 Plants Exhibit Adaptations to Variations in Nutrient Availability 113
6.13 Wetland Environments Present Unique Constraints on Plant
Adaptations 115
Summary
Chapter 7
116
•
Study Questions
118
•
Further Readings
118
Animal Adaptations to the Environment 119
7.1 Size Imposes a Fundamental Constraint on the Evolution of
Organisms 120
7.2 Animals Have Various Ways of Acquiring Energy and Nutrients 122
7.3 Animals Have Various Nutritional Needs 125
7.4 Mineral Availability Affects Animal Growth and Reproduction 126
7.5 Animals Require Oxygen to Release Energy Contained in Food 127
FIELD STUDIES: Martin Wikelski 128
7.6 Regulation of Internal Conditions Involves Homeostasis
and Feedback 130
7.7 Animals Exchange Energy with Their Surrounding Environment 130
QUANTIFYING ECOLOGY 7.1: Heat Exchange and Temperature
Regulation 132
7.8 Animals Fall into Three Groups Relative to Temperature Regulation 133
7.9 Poikilotherms Depend on Environmental Temperatures 134
7.10 Homeotherms Escape the Thermal Restraints of the Environment 135
7.11 Endothermy and Ectothermy Involve Trade-offs 136
7.12 Heterotherms Take on Characteristics of Ectotherms
and Endotherms 138
7.13 Torpor Helps Some Animals Conserve Energy 138
7.14 Some Animals Use Unique Physiological Means for Thermal Balance 139
7.15 Maintenance of Water Balance for Terrestrial Animals Is Constrained
by Uptake and Conservation 140
7.16 Animals of Aquatic Environments Face Unique Problems in Maintaining
Water Balance 141
7.17 Buoyancy Helps Aquatic Organisms to Stay Afloat 142
7.18 Daily and Seasonal Light and Dark Circles Influence Animal
Activity 142
7.19 Critical Day Lengths Trigger Seasonal Responses 143
7.20 Activity Rhythms of Intertidal Organisms Follow Tidal Cycles 144
Summary
145
•
Study Questions
147
•
Further Readings
147
PART 3 Populations 148
Chapter 8
Properties of Populations 150
8.1
8.2
8.3
8.4
8.5
8.6
Organisms May Be Unitary or Modular 151
The Distribution of a Population Defines Its Spatial Location 151
Abundance Reflects Population Density and Distribution 153
Determining Density Requires Sampling 156
Populations Have Age Structures 156
Sex Ratios in Populations May Shift with Age 158
v
8.7 Individuals Move Within the Population 158
8.8 Population Distribution and Density Change in Both Time and Space 160
ECOLOGICAL ISSUES: Human-Assisted Dispersal 162
Summary 163 • Study Questions 163 • Further Readings
Chapter 9
164
Population Growth 165
9.1 Population Growth Reflects the Difference between Rates of Birth
and Death 166
QUANTIFYING ECOLOGY 9.1: Derivatives and Differential Equations 167
QUANTIFYING ECOLOGY 9.2: Exponential Model of Population Growth 168
9.2 Life Tables Provide a Schedule of Age-Specific Mortality
and Survival 169
9.3 Different Types of Life Tables Reflect Different Approaches to Defining
Cohorts and Age Structure 170
QUANTIFYING ECOLOGY 9.3: Life Expectancy 171
9.4 Life Tables Provide Data for Mortality and Survivorship Curves 172
9.5 Birthrate Is Age-Specific 173
9.6 Birthrate and Survivorship Determine Net Reproductive Rate 174
9.7 Age-Specific Mortality and Birthrates Can Be Used to Project Population
Growth 174
9.8 Stochastic Processes Can Influence Population Dynamics 176
9.9 A Variety of Factors Can Lead to Population Extinction 177
9.10 Small Populations Are Susceptible to Extinction 177
Summary
Chapter 10
178
•
Study Questions
179
•
Further Readings
179
Life History 181
10.1 The Evolution of Life Histories Involves Trade-offs 182
10.2 Reproduction Involves Both Benefits and Costs to Individual
Fitness 182
10.3 Age at Maturity Is Influenced by Patterns of Age-Specific
Mortality 183
10.4 Reproductive Effort Is Governed by Trade-offs between Fecundity
and Survival 185
10.5 There Is a Trade-off between the Number and Size of Offspring 188
QUANTIFYING ECOLOGY 10.1: Interpreting Trade-offs 190
10.6 Species Differ in the Timing of Reproduction 190
10.7 An Individual’s Life History Represents the Interaction between
Genotype and the Environment 192
10.8 Mating Systems Describe the Pairing of Males and Females 193
10.9 Acquisition of a Mate Involves Sexual Selection 194
10.10 Females May Choose Mates Based on Resources 195
FIELD STUDIES: Alexandra L. Basolo 196
10.11 Patterns of Life History Characteristics Reflect External Selective
Forces 198
Summary
Chapter 11
200
•
Study Questions
201
•
Further Readings
201
Intraspecific Population Regulation 202
11.1
The Environment Functions to Limit Population Growth 203
ECOLOGICAL ISSUES: The Human Carrying Capacity 204
11.2
Population Regulation Involves Density Dependence 206
QUANTIFYING ECOLOGY 11.1: The Logistic Model of Population
Growth 207
11.3
vi
Competition Results When Resources Are Limited 207
11.4 Intraspecific Competition Affects Growth and Development 208
11.5 Intraspecific Competition Can Influence Mortality Rates 210
11.6 Intraspecific Competition Can Reduce Reproduction 212
FIELD STUDIES: T. Scott Sillett 214
11.7
11.8
11.9
11.10
11.11
11.12
High Density Is Stressful to Individuals 216
Dispersal Can Be Density Dependent 216
Social Behavior May Function to Limit Populations 217
Territoriality Can Function to Regulate Population Growth 217
Plants Preempt Space and Resources 219
Density-Independent Factors Can Influence Population Growth 219
Summary
Chapter 12
220
•
Study Questions
221
•
Further Readings
222
Metapopulations 223
12.1 Four Conditions Define a Metapopulation 224
12.2 Metapopulation Dynamics Is a Balance between Colonization
and Extinction 226
QUANTIFYING ECOLOGY 12.1: Equilibrium Proportion of Occupied
Patches 227
12.3 Patch Area and Isolation Influence Metapopulation Dynamics 227
12.4 Habitat Heterogeneity Influences Local Population Persistence 230
12.5 Some Habitat Patches May Function as the Major Source
of Emigrants 230
12.6 Certain Factors Can Function to Synchronize the Dynamics
of Local Populations 231
12.7 Species Differ in Their Potential Rates of Colonization
and Extinction 232
12.8 The Concept of Population Is Best Approached by Using
a Hierarchical Framework 233
Summary
234
•
Study Questions
235
•
Further Readings
235
PART 4 Species Interactions 236
Chapter 13
Species Interactions, Population Dynamics, and Natural
Selection 238
13.1 Species Interactions Can Be Classified Based on Their Reciprocal
Effects 239
13.2 Species Interactions Influence Population Dynamics 240
13.3 Species Interactions Can Function as Agents of Natural Selection 241
13.4 The Nature of Species Interactions Can Vary Across Geographic
Landscapes 245
13.5 Species Interactions Can Be Diffuse 245
13.6 Species Interactions Influence the Species’ Niche 246
13.7 Species Interactions Can Drive Adaptive Radiation 248
Summary
Chapter 14
249
•
Study Questions
249
•
Further Readings
250
Interspecific Competition 251
14.1 Interspecific Competition Involves Two or More Species 252
14.2 There Are Four Possible Outcomes of Interspecific Competition 252
14.3 Laboratory Experiments Support the Lotka–Volterra Equations 253
QUANTIFYING ECOLOGY 14.1: Interpreting Population Isoclines 255
14.4 Studies Support the Competitive Exclusion Principle 256
14.5 Competition Is Influenced by Nonresource Factors 256
vii
14.6 Temporal Variation in the Environment Influences Competitive
Interactions 257
FIELD STUDIES: Katherine N. Suding 258
14.7 Competition Occurs for Multiple Resources 260
14.8 Relative Competitive Abilities Change along Environmental
Gradients 261
QUANTIFYING ECOLOGY 14.2: Competition under Changing Environmental
Conditions: Application of the Lotka–Volterra Model 263
14.9 Interspecific Competition Influences the Niche of a Species 266
14.10 Coexistence of Species Often Involves Partitioning Available
Resources 267
14.11 Competition Is a Complex Interaction Involving Biotic and Abiotic
Factors 270
Summary
Chapter 15
270
Predation
•
Study Questions
271
•
Further Readings
272
273
15.1 Predation Takes a Variety of Forms 274
15.2 Mathematical Model Describes the Basics of Predation 274
15.3 Model Suggests Mutual Population Regulation 276
15.4 Functional Responses Relate Prey Consumed to Prey Density 277
15.5 Predators Respond Numerically to Changing Prey Density 280
15.6 Foraging Involves Decisions about the Allocation of Time
and Energy 281
QUANTIFYING ECOLOGY 15.1: A Simple Model of Optimal Foraging 283
15.7
15.8
15.9
15.10
15.11
15.12
Foragers Seek Productive Food Patches 284
Risk of Predation Can Influence Foraging Behavior 285
Coevolution Can Occur between Predator and Prey 285
Animal Prey Have Evolved Defenses against Predators 285
Predators Have Evolved Efficient Hunting Tactics 289
Herbivores Prey on Autotrophs 289
FIELD STUDIES: Rick A. Relyea 290
15.13 Plants Have Evolved Characteristics That Deter Herbivores 292
15.14 Plants, Herbivores, and Carnivores Interact 294
15.15 Predators Influence Prey Dynamics through Lethal and Nonlethal
Effects 294
Summary
Chapter 16
296
•
Study Questions
297
•
Further Readings
297
Parasitism and Mutualism 298
16.1 Parasites Draw Resources from Host Organisms 299
16.2 Hosts Provide Diverse Habitats for Parasites 300
16.3 Direct Transmission Can Occur between Host Organisms 300
16.4 Transmission between Hosts Can Involve an Intermediate
Vector 301
16.5 Transmission Can Involve Multiple Hosts and Stages 301
16.6 Hosts Respond to Parasitic Invasions 301
16.7 Parasites Can Affect Host Survival and Reproduction 303
16.8 Parasites May Regulate Host Populations 303
16.9 Parasitism Can Evolve into a Mutually Beneficial Relationship 305
16.10 Mutualisms Involve Diverse Species Interactions 305
ECOLOGICAL ISSUES: Plagues Upon Us 306
16.11 Mutualisms Are Involved in the Transfer of Nutrients 307
FIELD STUDIES: John J. Stachowicz 308
viii
16.12
16.13
16.14
16.15
Some Mutualisms Are Defensive 311
Mutualisms Are Often Necessary for Pollination 311
Mutualisms Are Involved in Seed Dispersal 312
Mutualisms Can Influence Population Dynamics 313
QUANTIFYING ECOLOGY 16.1: A Model of Mutualistic Interactions 314
Summary 315 • Study Questions 316 • Further Readings 316
PART 5 Community Ecology 318
Chapter 17
Community Structure 320
17.1 The Number of Species and Their Relative Abundance Define
Diversity 321
17.2 Numerical Supremacy Defines Dominance 323
17.3 Keystone Species Influence Community Structure Disproportionately
to Their Numbers 323
17.4 Food Webs Describe Species Interactions 324
17.5 Species within a Community Can Be Classified into Functional
Groups 324
17.6 Communities Have a Characteristic Physical Structure 326
17.7 Zonation Is Spatial Change in Community Structure 328
17.8 Defining Boundaries between Communities Is Often Difficult 329
17.9 Two Contrasting Views of the Community 331
QUANTIFYING ECOLOGY 17.1: Community Similarity 332
Summary 333 • Study Questions 334 • Further Readings 334
Chapter 18
Factors Influencing the Structure of Communities 335
18.1
18.2
The Fundamental Niche Constrains Community Structure 336
Species Interactions Are Diffuse 337
FIELD STUDIES: Sally D. Hacker 338
18.3
Food Webs Illustrate Indirect Interactions 340
QUANTIFYING ECOLOGY 18.1: Quantifying the Structure of Food Webs:
Connectance 341
18.4 Food Webs Suggest Controls of Community Structure 344
18.5 Species Interactions along Environmental Gradients Involve Both Stress
Tolerance and Competition 345
18.6 Environmental Heterogeneity Influences Community Diversity 348
18.7 Resource Availability Can Influence Plant Diversity within
a Community 349
Summary
Chapter 19
351
•
Study Questions
352
•
Further Readings
352
Community Dynamics 353
19.1
Community Structure Changes Through Time 354
ECOLOGICAL ISSUES: American Forests 356
19.2 Primary Succession Occurs on Newly Exposed Substrates 358
19.3 Secondary Succession Occurs after Disturbances 358
19.4 The Study of Succession Has a Rich History 360
19.5 Succession Is Associated with Autogenic Changes in Environmental
Conditions 361
19.6 Species Diversity Changes during Succession 363
19.7 Succession Involves Heterotrophic Species 364
19.8 Systematic Changes in Community Structure Are a Result of Allogenic
Environmental Change at a Variety of Timescales 365
ix
19.9 Community Structure Changes over Geologic Time 367
19.10 The Concept of Community Revisited 369
Summary
Chapter 20
371
•
Study Questions
372
•
Further Readings
373
Landscape Dynamics 374
20.1 Environmental Processes Create a Variety of Patches
in the Landscape 375
20.2 Transition Zones Offer Diverse Conditions and Habitats 377
20.3 Patch Size and Shape Are Crucial to Species Diversity 378
20.4 The Theory of Island Biogeography Applies to Landscape Patches 382
20.5 Landscape Connectivity Permits Movement between Patches 384
20.6 The Metapopulation and Metacommunity Are Central Concepts
in the Study of Landscape Dynamics 385
20.7 Frequency, Intensity, and Scale Determine the Impact
of Disturbances 385
FIELD STUDIES: Nick M. Haddad 386
20.8 Various Natural Processes Function as Disturbances 388
20.9 Human Disturbance Creates Some of the Most Long-Lasting
Effects 390
20.10 The Landscape Represents a Shifting Mosaic of Changing
Communities 391
Summary
391
•
Study Questions
392
•
Further Readings
393
PART 6 Ecosystem Ecology 394
Chapter 21
Ecosystem Energetics 396
21.1 The Laws of Thermodynamics Govern Energy Flow 397
21.2 Energy Fixed in the Process of Photosynthesis Is Primary
Production 397
21.3 Temperature, Water, and Nutrients Control Primary Production
in Terrestrial Ecosystems 398
21.4 Temperature, Light, and Nutrients Control Primary Production
in Aquatic Ecosystems 401
21.5 External Inputs of Organic Carbon Can Be Important in Aquatic
Ecosystems 403
21.6 Energy Allocation and Plant Life-Form Influence Primary
Production 404
21.7 Primary Productivity Varies with Time 405
21.8 Primary Productivity Limits Secondary Production 406
ECOLOGICAL ISSUES: Human Appropriation of Net Primary
Productivity 408
21.9 Consumers Vary in Efficiency of Production 408
21.10 Ecosystems Have Two Major Food Chains 410
21.11 Energy Flows through Trophic Levels Can Be Quantified 411
FIELD STUDIES: Brian Silliman 412
21.12 Consumption Efficiency Determines the Pathway of Energy Flow
through the Ecosystem 414
21.13 Energy Decreases in Each Successive Trophic Level 415
Summary
Chapter 22
416
•
Study Questions
417
•
Further Readings
417
Decomposition and Nutrient Cycling 419
22.1 Most Essential Nutrients Are Recycled within the Ecosystem 420
22.2 Decomposition Is a Complex Process Involving a Variety
of Organisms 421
x
22.3 Studying Decomposition Involves Following the Fate of Dead
Organic Matter 423
QUANTIFYING ECOLOGY 22.1: Estimating the Rate of Decomposition 424
22.4
Several Factors Influence the Rate of Decomposition 425
FIELD STUDIES: Edward A. G. (Ted) Schuur 428
22.5 Nutrients in Organic Matter Are Mineralized During Decomposition 430
22.6 Decomposition Proceeds as Plant Litter Is Converted into Soil Organic
Matter 432
22.7 Plant Processes Enhance the Decomposition of Soil Organic Matter
in the Rhizosphere 434
22.8 Decomposition Occurs in Aquatic Environments 434
22.9 Key Ecosystem Processes Influence the Rate of Nutrient Cycling 436
ECOLOGICAL ISSUES: Nitrogen Fertilizers 437
22.10 Nutrient Cycling Differs between Terrestrial and Open-Water Aquatic
Ecosystems 438
22.11 Water Flow Influences Nutrient Cycling in Streams and Rivers 440
22.12 Land and Marine Environments Influence Nutrient Cycling
in Coastal Ecosystems 441
22.13 Surface Ocean Currents Bring about Vertical Transport of Nutrients 443
Summary
Chapter 23
443
•
Study Questions
444
•
Further Readings
445
Biogeochemical Cycles 446
23.1 There Are Two Major Types of Biogeochemical Cycles 447
23.2 Nutrients Enter the Ecosystem via Inputs 447
23.3 Outputs Represent a Loss of Nutrients from the Ecosystem 448
23.4 Biogeochemical Cycles Can Be Viewed from a Global Perspective 448
23.5 The Carbon Cycle Is Closely Tied to Energy Flow 448
23.6 Carbon Cycling Varies Daily and Seasonally 450
23.7 The Global Carbon Cycle Involves Exchanges among the Atmosphere,
Oceans, and Land 451
23.8 The Nitrogen Cycle Begins with Fixing Atmospheric Nitrogen 452
23.9 The Phosphorus Cycle Has No Atmospheric Pool 454
23.10 The Sulfur Cycle Is Both Sedimentary and Gaseous 455
ECOLOGICAL ISSUES: Nitrogen Saturation 457
23.11 The Global Sulfur Cycle Is Poorly Understood 458
23.12 The Oxygen Cycle Is Largely under Biological Control 459
23.13 The Various Biogeochemical Cycles Are Linked 460
Summary
461
•
Study Questions
462
•
Further Readings
463
PART 7 Ecological Biogeography 464
Chapter 24
Terrestrial Ecosystems 466
24.1 Terrestrial Ecosystems Reflect Adaptations of the Dominant Plant
Life-Forms 468
QUANTIFYING ECOLOGY 24.1: Climate Diagrams 470
24.2 Tropical Forests Characterize the Equatorial Zone 471
24.3 Tropical Savannas Are Characteristic of Semiarid Regions with
Seasonal Rainfall 474
24.4 Grassland Ecosystems of the Temperate Zone Vary with Climate
and Geography 476
24.5 Deserts Represent a Diverse Group of Ecosystems 479
24.6 Mediterranean Climates Support Temperate Shrublands 482
xi
24.7 Forest Ecosystems Dominate the Wetter Regions
of the Temperate Zone 484
24.8 Conifer Forests Dominate the Cool Temperate and Boreal Zones 486
24.9 Low Precipitation and Cold Temperatures Define the Arctic Tundra 488
Summary
Chapter 25
490
•
Study Questions
492
•
Further Readings
492
Aquatic Ecosystems 493
25.1 Lakes Have Many Origins 494
25.2 Lakes Have Well-Defined Physical Characteristics 494
ECOLOGICAL ISSUES: Dams: Regulating the Flow of River Ecosystems 496
25.3 The Nature of Life Varies in the Different Zones 497
25.4 The Character of a Lake Reflects Its Surrounding Landscape 498
25.5 Flowing-Water Ecosystems Vary in Structure and Types of Habitats 499
25.6 Life Is Highly Adapted to Flowing Water 501
QUANTIFYING ECOLOGY 25.1: Streamflow 502
25.7 The Flowing-Water Ecosystem Is a Continuum of Changing
Environments 504
25.8 Rivers Flow into the Sea, Forming Estuaries 504
25.9 Oceans Exhibit Zonation and Stratification 506
25.10 Pelagic Communities Vary Among the Vertical Zones 507
25.11 Benthos Is a World of Its Own 508
25.12 Coral Reefs Are Complex Ecosystems Built by Colonies of Coral
Animals 509
25.13 Productivity of the Oceans Is Governed by Light and Nutrients 510
Summary
Chapter 26
511
•
Study Questions
513
•
Further Readings
513
Coastal and Wetland Ecosystems 514
26.1 The Intertidal Zone Is the Transition between Terrestrial and Marine
Environments 515
26.2 Rocky Shorelines Have a Distinct Pattern of Zonation 515
26.3 Sandy and Muddy Shores Are Harsh Environments 517
26.4 Tides and Salinity Dictate the Structure of Salt Marshes 518
26.5 Mangroves Replace Salt Marshes in Tropical Regions 519
26.6 Freshwater Wetlands Are a Diverse Group of Ecosystems 520
26.7 Hydrology Defines the Structure of Freshwater Wetlands 523
ECOLOGICAL ISSUES: The Continuing Decline of the Wetlands 524
26.8
Freshwater Wetlands Support a Rich Diversity of Life 526
Summary
Chapter 27
526
•
Study Questions
527
•
Further Readings
527
Large-Scale Patterns of Biological Diversity 528
27.1 Earth’s Biological Diversity Has Changed through Geologic Time 529
27.2 Past Extinctions Have Been Clustered in Time 530
27.3 Regional and Global Patterns of Species Diversity Vary
Geographically 530
27.4 Species Richness in Terrestrial Ecosystems Correlates with Climate
and Productivity 532
27.5 In Marine Environments, There Is an Inverse Relationship between
Productivity and Diversity 533
27.6 Species Diversity Is a Function of Processes Operating at Many
Scales 534
QUANTIFYING ECOLOGY 27.1: Quantifying Biodiversity: Comparing Species
Richness Using Rarefaction Curves 535
Summary 536 • Study Questions 537 • Further Readings 537
xii
PART 8 Human Ecology 538
Chapter 28
Population Growth, Resource Use, and Sustainability 540
28.1 Sustainable Resource Use Is a Balance between Supply and
Demand 542
28.2 Sustainability Can Be Indirectly Limited by Adverse Consequences
of Resource Use 544
28.3 Sustainability Is a Concept Learned from Natural Ecosystems 544
28.4 Agricultural Practices Vary in the Level of Energy Input 544
28.5 Swidden Agriculture Represents a Dominant Form of Agriculture
in the Wet Tropics 545
28.6 Industrialized Agriculture Dominates the Temperate Zone 546
28.7 Different Agricultural Methods Represent a Trade-off between
Sustainability and Productivity 548
28.8 Sustainable Agriculture Depends on a Variety of Methods 549
28.9 Sustainable Forestry Aims to Achieve a Balance between
Net Growth and Harvest 551
FIELD STUDIES: Deborah Lawrence 552
28.10 Exploitation of Fisheries Has Lead to the Need for Management 556
28.11 Fisheries Management Requires an Ecosystem Approach 558
28.12 Economics Are a Key Factor Governing Resource Management 560
Summary
Chapter 29
562
•
Study Questions
564
•
Further Readings
564
Habitat Loss, Biodiversity, and Conservation 565
29.1 Habitat Destruction Is the Leading Cause of Current Species
Extinctions 566
29.2 Human-Introduced Invasive Species May Threaten Many Native
Species 568
29.3 Species Differ in Their Susceptibility to Extinction 571
29.4 Identifying Threatened Species Is Critical to Conservation Efforts 572
29.5 Regions of High Species Diversity Are Crucial to Conservation
Efforts 572
ECOLOGICAL ISSUES: Wolf Reintroduction, Restoration,
and Management 575
29.6 Protecting Populations Is the Key To Conservation Efforts 576
29.7 Reintroduction Is Necessary to Reestablish Populations of Some
Species 577
29.8 Habitat Conservation Functions to Protect Whole Communities 579
29.9 Habitat Conservation Involves Establishing Protected Areas 579
29.10 Habitat Restoration Is Often Necessary in Conservation Efforts 582
29.11 Environmental Ethics Is at the Core of Conservation 583
Summary
Chapter 30
584
•
Study Questions
585
•
Further Readings
586
Global Climate Change 588
30.1 Greenhouse Gases Influence Earth’s Energy Balance and Climate 589
30.2 Atmospheric Concentration of Carbon Dioxide Is Rising 589
30.3 Tracking the Fate of CO2 Emissions 591
30.4 Atmospheric CO2 Concentrations Affect CO2 Uptake by Oceans 591
FIELD STUDIES: Erika Zavaleta 592
30.5 Plants Respond to Increased Atmospheric CO2 594
30.6 Greenhouse Gases Are Changing the Global Climate 596
xiii
30.7
Changes in Climate Will Affect Ecosystems at Many Levels 598
ECOLOGICAL ISSUES: Who Turned Up the Heat? 602
30.8 Changing Climate Will Shift the Global Distribution
of Ecosystems 604
30.9 Global Warming Would Raise Sea Level and Affect Coastal
Environments 605
30.10 Climate Change Will Affect Agricultural Production 606
30.11 Climate Change Will Directly and Indirectly Affect Human
Health 607
30.12 Understanding Global Change Requires the Study of Ecology
at a Global Scale 609
Summary
References R-1
Glossary G-1
Credits C-1
Index I-1
xiv
610
•
Study Questions
611
•
Further Readings
612
Preface
The first edition of Elements of Ecology appeared in 1976 as a short version of Ecology and
Field Biology. Since that time, Elements of Ecology has evolved into a textbook intended for use
in a one-semester introduction to ecology course. Although the primary readership will be students majoring in the life sciences, in writing this text we were guided by our belief that ecology
should be part of a liberal education. We believe that students who major in such diverse fields
as economics, sociology, engineering, political science, law, history, English, languages, and the
like should have some basic understanding of ecology for the simple reason that it impinges on
their lives.
New for the Eighth Edition
For those familiar with this text, you will notice a number of changes in this new edition of
Elements of Ecology. In addition to updating many of the examples and topics to reflect the
most recent research and results in the field of ecology, we have made a number of changes in
the organization and content of the text. An important objective of the text is to use the concept
of adaptation through natural selection as a framework for unifying the study of ecology, linking pattern and process across the hierarchical levels of ecological study: individual organisms,
populations, communities, and ecosystems. Many of the changes made in previous editions have
focused on this objective, and the changes to this edition continue to work toward this goal.
Life History Patterns Chapter Returned to Part Three
Despite all previous efforts, we feel that we did not fully meet this objective in the discussion of populations (Part Three) in the seventh edition. In hindsight, we believe that this
shortcoming was a result of our decision to move the presentation of Life History from Part
Three (Populations) to Part Two (The Organisms and Its Environment) in the sixth edition. By
moving Life History to Part Two we were trying to maintain the theme of trade-offs and constraints in the evolution of characteristics that is developed in Chapter 6 (Plant Adaptations to
the Environment) and Chapter 7 (Animal Adaptations to the Environment). However, it is the
discussion of life histories, specifically the discussion of adaptations relating to age-specific patterns of survival and fecundity (reproduction), that provide a direct link between natural selection and population dynamics. For this reason, we have returned the chapter on Life History to
Part Three (Populations). The chapter now follows Chapter 10 (Population Growth). In addition,
we have revised the materials that are presented to make explicit the links between life history
characteristics and population dynamics using the framework of life tables that is developed in
Chapter 10 (Population Growth).
Restructured Part Four: Species Interactions
Another major change that we have introduced in the eighth edition to emphasize the concept of
adaptation through natural selection as a framework for unifying the study of ecology is in the restructured presentation of Part Four, Species Interactions. In previous editions, Part Four consisted
of three chapters that introduced the four major species interactions of competition, predation,
parasitism, and mutualism (and the broader topic of facilitation). This format, however, did not
provide a general framework for viewing the role of population interactions in the process of evolution by natural selection that is common to all species interactions—the process of coevolution.
New Species Interactions Introductory Chapter
To meet this need, we now open Part Four (Species Interactions) with a new chapter entitled Species Interactions, Population Dynamics, and Natural Selection. The objective of this
new chapter is to introduce the variety of species interactions that occur among populations,
and to explore how these interactions influence the respective populations (species) involved
xv
at two timescales: (1) the influence of species interactions on the processes of mortality and
reproduction, which directly influence population dynamics, and (2) the role of species interaction as agents of natural selection by influencing the relative fitness of individuals within the
population(s). The chapter provides a common framework for exploring the specific species interactions that are introduced in the chapters of Part Four that follow.
Expanded Coverage of Key Ecological Topics
Although the majority of this new edition retains the general structure of the seventh edition,
we have added additional and expanded coverage of a wide variety of topics throughout the text
including coevolution, metacommunities, landscape connectivity, sources of organic carbon in
aquatic ecosystems, and the evolution of life history characteristics.
Updated Research Results: Part Eight
A historical feature of the Elements of Ecology text is our focus on applying the science of ecology to current environmental issues, providing students with a first-hand understanding of the
importance of ecology in the relationship between the human population and the natural environment. Since publication of the seventh edition, advances have been made in our understanding
of the issues that are presented in Part Eight: Human Ecology (Chapter 28: Population Growth,
Resource Use, and Sustainability; Chapter 29: Habitat Loss, Biodiversity, and Conservation; and
Chapter 30: Global Climate Change). In response, we have updated many of the research results
presented in these chapters to reflect the most current understanding of these issues.
Expanded Quantitative Features
Ecology is a science rich in concepts, yet as with all science, it is quantitative. As such, a major
objective of any science course should be the development of basic skills relating to the analysis
and interpretation of empirical data. As with the seventh edition, the Quantifying Ecology feature
in this new edition functions to provide students with an understanding of how concepts introduced in the chapters are quantified. In many chapters, the Quantifying Ecology boxes focus on
assisting the reader with the interpretation of graphs, mathematical models, or quantitative methods that we have introduced within the main body of the text. In the seventh edition, however, we
added an additional feature, Interpreting Ecological Data, to assist students in the development of
quantitative skills. We have retained and expanded this feature in the eighth edition. Interpreting
Ecological Data is associated directly with various figures and tables in the text. The feature consists of two or more questions relating directly to the interpretation of data and analyses presented
in the associated figure or table. It has become a common practice in many new textbooks to embellish figures and tables with annotations that function to provide the reader with an interpretation of the graph or data. Although we also use this technique for a number of complex graphics,
our annotations are meant only as an extension of the figure or table captions. Rather, we believe
that it is better to ask specific questions that will both encourage and assist the reader in the interpretation and understanding of the data and analyses that are presented. In doing so we hope
to assist the reader in building the basic skills that are necessary to move beyond the examples
presented in the text and begin to explore the wealth of ecological studies published in the books
and journals that are referenced throughout the text. It is our belief that the development of these
basic quantitative and interpretative skills are as important as understanding the body of concepts
presented in the text that form the framework of the science of ecology. The answers to the questions presented in the Interpreting Ecological Data features are provided at the associated website.
Structure and Content
The structure and content of the text is guided by our basic belief that: (1) the fundamental unit
in the study of ecology is the individual organism, and (2) the concept of adaptation through
natural selection provides the framework for unifying the study of ecology at higher levels of
organization: populations, communities, and ecosystems. A central theme of the text is the concept of trade-offs—that the set of adaptations (characteristics) that enable an organism to survive,
grow, and reproduce under one set of environmental conditions inevitably impose constraints on
its ability to function (survive, grow, and reproduce) equally well under different environmental
conditions. These environmental conditions include both the physical environment as well as
xvi
the variety of organisms (both the same and different species) that occupy the same habitat. This
basic framework provides a basis for understanding the dynamics of populations at both an evolutionary and demographic scale.
The text begins with an introduction to the science of ecology in Chapter 1 (The Nature of
Ecology). The remainder of the text is divided into eight parts. Part One examines the constraints
imposed on living organisms by the physical environment, both aquatic and terrestrial. Part Two
begins by examining how these constraints imposed by the environment function as agents of
change through the process of natural selection, the process through which adaptations evolve.
The remainder of Part Two explores specific adaptations of organisms to the physical environment,
considering both organisms that derive their energy from the sun (autrotrophs) and those that derive their energy from the consumption and break-down of plant and animal tissues (heterotrophs).
Part Three examines the properties of populations, with an emphasis on how characteristics
expressed at the level of the individual organisms ultimately determine the collective dynamics of
the population. As such, population dynamics are viewed are a function of life history characteristics that are a product of evolution by natural selection. Part Four extends our discussion from
interactions among individuals of the same species to interactions among populations of different
species (interspecific interactions). In these chapters we expand our view of adaptations to the
environment from one dominated by the physical environment, to the role of species interactions
in the process of natural selection and on the dynamics of populations.
Part Five explores the topic of ecological communities. This discussion draws upon topics
covered in Parts Two through Four to examine the factors that influence the distribution and
abundance of species across environmental gradients, both spatial and temporal.
Part Six combines the discussions of ecological communities (Part Five) and the physical
environment (Part One) to develop the concept of the ecosystem. Here the focus is on the flow of
energy and matter through natural systems. Part Seven continues the discussion of communities
and ecosystems in the context of biogeography, examining the broad-scale distribution of terrestrial and aquatic ecosystems, as well as regional and global patterns of biological diversity.
Part Eight focuses on the interactions between humans and ecological systems. It is here that
we examine the important current environmental issues relating to population growth, sustainable
resource use, declining biological diversity, and global climate change. The objective of these
chapters is to explore the role of the science of ecology in both understanding and addressing
these critical environmental issues.
Throughout the text we explore this range of topics by drawing upon current research in
the various fields of ecology, providing examples that enable the reader to develop an understanding of species natural history, the ecology of place (specific ecosystems), and the basic
process of science.
Associated Materials
• Instructor’s Resource DVD (0-321-74290-7)
• Instructor Guide (0-321-74288-5)
• Computerized Test Bank (0-321-74289-3)
• Ecology Place Companion Website (www.ecologyplace.com)
• Course Management Options (All CourseCompass and Blackboard courses offer preloaded
content including tests, quizzes, and more.)
Acknowledgments
No textbook is a product of the authors alone. The material this book covers represents the work
of hundreds of ecological researchers who have spent lifetimes in the field and the laboratory.
Their published experimental results, observations, and conceptual thinking provide the raw
material out of which the textbook is fashioned. We particularly acknowledge and thank the
fourteen ecologists that are featured in the Field Studies boxes. Their cooperation in providing
artwork and photographs is greatly appreciated.
xvii
Revision of a textbook depends heavily on the input of users who point out mistakes and
opportunities. We took these suggestions seriously and incorporated most of them. We are
deeply grateful to the following reviewers for their helpful comments and suggestions on how
to improve this edition:
Judith Bramble, DePaul University
William Brown, SUNY Fredonia
Steve Blumenshine, Fresno State University
Mike Farabee, Estrella Mountain Community College
Sue Hum-Musser, Western Illinois University
Gerlinde Hoebel, University of Wisconsin, Milwaukee
Jacob Kerby, University of South Dakota
Ned J. Knight, Linfield College
David Pindel, Corning Community College
B.K Robertson, Alabama State University
Erik P. Scully, Towson University
Daniela Shebitz, Kean University
Neal J. Voelz, St. Cloud State University
Reviewers of Previous Editions:
Peter Alpert, University of Massachusetts
John Anderson, College of the Atlantic
Morgan Barrows, Saddleback College
Paul Bartell, Texas A&M University
Christopher Beck, Emory University
Nancy Broshot, Linfield College
Chris Brown, Tennessee Tech University
Evert Brown, Casper College
David Bybee, Brigham Young University, Hawaii
Dan Capuano, Hudson Valley Community College
Brian Chabot, Cornell University
Mitchell Cruzan, Portland State University
Robert Curry, Villanova University
Richard Deslippe, Texas Tech University
Darren Divine, Community College of Southern Nevada
Curt Elderkin, The College of New Jersey
Lauchlan Fraser, University of Akron
Sandi Gardner, Triton College
E. O. Garton, University of Idaho
Frank Gilliam, Marshall University
xviii
Brett Goodwin, University of North Dakota
James Gould, Princeton University
Mark C. Grover, Southern Utah University
Mark Gustafson, Texas Lutheran University
Greg Haenel, Elon University
William Hallahan, Nazareth College
Douglas Hallett, Northern Arizona University
Gregg Hartvigsen, State University of New York at Geneseo
Floyd Hayes, Pacific Union College
Michael Heithaus, Florida International University
Jessica Hellman, Notre Dame University
Jason Hoeksema, University of California at Santa Cruz
John Jaenike, University of Rochester
John Jahoda, Bridgewater State University
Stephen Johnson, William Penn University
Doug Keran, Central Lakes Community College
Jeff Klahn, University of Iowa
Jamie Kneitel, California State University, Sacramento
Frank Kuserk, Moravian College
Kate Lajtha, Oregon State University
Vic Landrum, Washburn University
James Lewis, Fordham University
Richard Lutz, Rutgers University
Richard MacMillen, University of California at Irvine
Ken R. Marion, University of Alabama, Birmingham
Deborah Marr, Indiana University at South Bend
Chris Migliaccio, Miami Dade Community College
Don Miles, Ohio University
L. Maynard Moe, California State University, Bakersfield
Sherri Morris, Bradley University
Steve O’Kane, University of Northern Iowa
Matthew Parris, University of Memphis
James Refenes, Concordia University
Seith Reice, University of North Carolina
Ryan Rehmeir, Simpson College
Rick Relyea, University of Pittsburgh
Carol Rhodes, College of San Mateo
Eric Ribbens, Western Illinois University
xix
Robin Richardson, Winona State University
Thomas Rosburg, Drake University
Tatiana Roth, Coppin State College
Irene Rossell, University of North Carolina, Asheville
Rowan Sage, University of Toronto
Nathan Sanders, University of Tennessee
Thomas Sarro, Mount Saint Mary College
Maynard Schaus, Virginia Wesleyan College
Wendy Sera, University of Maryland
Mark Smith, Chaffey College
Paul Snelgrove, Memorial University of Newfoundland
Amy Sprinkle, Jefferson Community College Southwest
Barbara Shoplock, Florida State University
Alan Stam, Capital University
Christopher Swan, University of Maryland
Alessandro Tagliabue, Stanford University
Charles Trick, University of Western Ontario
Peter Turchin, University of Connecticut
Joe von Fischer, Colorado State University
Mitch Wagener, Western Connecticut State University
David Webster, University of North Carolina at Wilmington
Jake Weltzin, University of Tennessee
The publication of a modern textbook requires the work of many editors to handle the
specialized tasks of development, photography, graphic design, illustration, copy editing,
and production, to name only a few. We’d like to thank acquisitions editor Star MacKenzie
for her editorial guidance. Her ideas and efforts have help to shape this edition. We’d
also like to thank the rest of the editorial team—Leata Holloway, Project Editor; Lee Ann
Doctor, Media Producer; and Frances Sink, Assistant Editor. We also appreciate the efforts of Production Project Manager Shannon Tozier and Debbie Meyer at Integra-Chicago,
for keeping the book on schedule. Finally, we are indebted to Brian Morris at Scientific
Illustrators, for all his efforts on the art program.
Through it all our families, especially our spouses Nancy and Alice, had to endure the throes
of book production. Their love, understanding, and support provide the balanced environment
that makes our work possible.
Thomas M. Smith
Robert Leo Smith
xx
CHAPTER
The Nature of Ecology
1.1
Ecology Is the Study of
the Relationship between
Organisms and Their
Environment
1.2
Organisms Interact with the
Environment in the Context
of the Ecosystem
1.3
Ecological Systems Form a
Hierarchy
1.4
Ecologists Study Pattern and
Process at Many Levels
1.5
Ecologists Investigate Nature
Using the Scientific Method
1.6
Models Provide a Basis for
Predictions
1.7
Uncertainty Is an Inherent
Feature of Science
1.8
Ecology Has Strong Ties to
Other Disciplines
1.9
The Individual Is the Basic Unit
of Ecology
1
As part of an ongoing research project, wildlife biologists in Alaska fit a Barren-ground
Caribou (Rangifer tarandus groenlandicus) with a radio collar to track the animal and
map its patterns of movement and habitat use.
1
2
CHAPTER 1 • THE NATURE OF ECOLOGY
T
he color photograph of Earthrise, taken by Apollo 8
astronaut William A. Anders on December 24, 1968, is a
powerful and eloquent image (Figure 1.1). One leading
environmentalist has rightfully described it as “the most influential environmental photograph ever taken.” Inspired by the
photograph, economist Kenneth E. Boulding summed up the
finite nature of our planet as viewed in the context of the vast
expanse of space in his metaphor “spaceship Earth.” What had
been perceived throughout human history as a limitless frontier
had suddenly become a tiny sphere: limited in its resources,
crowded by an ever-expanding human population, and threatened by our use of the atmosphere and the oceans as repositories for our consumptive wastes.
A little more than a year later, on April 22, 1970, as many
as 20 million Americans participated in environmental rallies,
demonstrations, and other activities as part of the first Earth
Day. The New York Times commented on the astonishing rise
in environmental awareness, stating that “Rising concern about
the environmental crisis is sweeping the nation’s campuses
with an intensity that may be on its way to eclipsing student
discontent over the war in Vietnam.” At the core of this social
movement was a belief in the need to redefine our relationship
with nature, and the particular field of study called upon to provide the road map for this new course of action was ecology.
1.1 Ecology Is the Study of the
Relationship between Organisms
and Their Environment
With the growing environmental movement of the late 1960s
and early 1970s, ecology—until then familiar only to a relatively
small number of academic and applied biologists—was suddenly thrust into the limelight (see Ecological Issues: Ecology
Has Complex Roots). Hailed as a framework for understanding
the relationship of humans to their environment, ecology became
a household word that appeared in newspapers, magazines, and
books—although the term was often misused. Even now, people
confuse it with terms such as environment and environmentalism.
Ecology is neither. Environmentalism is activism with a stated
aim of protecting the natural environment, particularly from the
Figure 1.1 Photograph of Earthrise taken by Apollo 8 astronaut
William A. Anders on December 24, 1968.
negative impacts of human activities. This activism often takes
the form of public education programs, advocacy, legislation,
and treaties.
So what is ecology? Ecology is a science. According to
one accepted definition, ecology is the scientific study of the
relationships between organisms and their environment. That
definition is satisfactory so long as one considers relationships and environment in their fullest meanings. Environment
includes the physical and chemical conditions as well as the
biological or living components of an organism’s surroundings.
Relationships include interactions with the physical world as
well as with members of the same and other species.
The term ecology comes from the Greek words oikos,
meaning “the family household,” and logy, meaning “the study
of.” It has the same root word as economics, meaning “management of the household.” In fact, the German zoologist Ernst
Haeckel, who originally coined the term ecology in 1866, made
explicit reference to this link when he wrote:
By ecology we mean the body of knowledge concerning the economy of nature—the investigation of the
total relations of the animal both to its inorganic and to
its organic; including above all, its friendly and inimical relations with those animals and plants with which
it comes directly or indirectly into contact—in a word,
ecology is the study of all those complex interrelationships referred to by Darwin as the conditions of the
struggle for existence.
Haeckel’s emphasis on the relation of ecology to the new
and revolutionary ideas put forth in Charles Darwin’s The
Origin of Species (1859) is important. Darwin’s theory of natural selection (Haeckel called it “the struggle for existence”) is a
cornerstone of the science of ecology. It is a mechanism allowing the study of ecology to go beyond descriptions of natural
history and examine the processes that control the distribution
and abundance of organisms.
1.2 Organisms Interact with the
Environment in the Context of
the Ecosystem
Organisms interact with their environment at many levels. The
physical and chemical conditions surrounding an organism—
such as ambient temperature, moisture, concentrations of oxygen and carbon dioxide, and light intensity—all influence basic
physiological processes crucial to survival and growth. An organism must acquire essential resources from the surrounding
environment and in doing so must protect itself from becoming
food for other organisms. It must recognize friend from foe,
differentiating between potential mates and possible predators.
All of this effort is an attempt to succeed at the ultimate goal
of all living organisms: to pass their genes on to successive
generations.
The environment in which each organism carries out this
“struggle for existence” is a place—a physical location in time
and space. It can be as large and stable as an ocean or as small
and transient as a puddle on the soil surface after a spring rain.
CHAPTER 1 • THE NATURE OF ECOLOGY
ECOLOG IC AL IS S U ES
T
Ecology Has Complex Roots
he genealogy of most sciences is direct. Tracing the roots of
chemistry and physics is relatively easy. The science of ecology is different: its roots are complex.
You can argue that ecology goes back to the ancient Greek
scholar Theophrastus, a friend of Aristotle, who wrote about the
relations between organisms and the environment. On the other
hand, ecology as we know it today has vital roots in plant geography and natural history.
In the 1800s, botanists began exploring and mapping the
world’s vegetation. One of the early plant geographers was Carl
Ludwig Willdenow (1765–1812). He pointed out that similar climates supported vegetation similar in form, even though the species were different. Another was Friedrich Heinrich Alexander
von Humboldt (1769–1859), for whom the Humboldt Current is
named. He spent five years exploring Latin America, including
the Orinoco and Amazon rivers. Humboldt correlated vegetation with environmental characteristics and coined the term plant
association.
Among a second generation of plant geographers was Johannes
Warming (1841–1924) at the University of Copenhagen, who studied the tropical vegetation of Brazil. He wrote the first text on plant
ecology, Plantesamfund. In this book Warming integrated plant
morphology, physiology, taxonomy, and biogeography into a coherent whole. This book had a tremendous influence on the development of ecology.
Early plant ecologists were concerned mostly with terrestrial
vegetation. Another group of European biologists was interested
in the relationship between aquatic plants and animals and their
environment. They advanced the ideas of organic nutrient cycling and feeding levels, using the terms producers and consumers. Their work influenced a young limnologist at the University
of Minnesota, R. A. Lindeman. He traced “energy-available”
relationships within a lake community. His 1942 paper, “The
Trophic-Dynamic Aspects of Ecology,” marked the beginning of
ecosystem ecology, the study of whole living systems.
Lindeman’s theory stimulated further pioneering work in
the area of energy flow and nutrient cycling by G. E. Hutchinson
of Yale University and E. P. and H. T. Odum of the University of
Georgia. Their work became a foundation of ecosystem ecology.
The use of radioactive tracers, a product of the atomic age, to
measure the movements of energy and nutrients through ecosystems and the use of computers to analyze large amounts of data
stimulated the development of systems ecology, the application
of general system theory and methods to ecology.
Activities in other areas of natural history also assumed important roles. One was the voyage of Charles Darwin (1809–1882)
on the Beagle. Working for years on notes and collections from
this trip, Darwin compared similarities and dissimilarities among
organisms within and among continents. He attributed differences
to geological barriers. He noted how successive groups of plants
and animals, distinct yet obviously related, replaced one another.
Developing his theory of evolution and the origin of species, Darwin came across the writings of Thomas Malthus
(1766–1834). An economist, Malthus advanced the principle that
populations grow in a geometric fashion, doubling at regular intervals until they outstrip the food supply. Ultimately, a “strong,
constantly operating force such as sickness and premature death”
would restrain the population. From this concept Darwin developed the idea of “the survival of the fittest” as a mechanism of
natural selection and evolution.
Meanwhile, unknown to Darwin, an Austrian monk,
Gregor Mendel (1822–1884), was studying the transmission of
characteristics from one generation of pea plants to another in
his garden. Mendel’s work on inheritance and Darwin’s work
on natural selection provided the foundation for the study of
evolution and adaptation, the field of population genetics.
Interest in Malthusian theory stimulated the study of population in two directions. One, population ecology, is concerned
with population growth (including birthrates and death rates),
regulation and intraspecific and interspecific competition, mutualism, and predation. The other, a combination of population
genetics and population ecology is evolutionary ecology that
deals with the role of natural selection in physical and behavioural adaptations and speciation. Focusing on adaptations,
physiological ecology is concerned with the responses of individual organisms to temperature, moisture, light, and other
environmental conditions. Closely associated with population
and evolutionary ecology is community ecology, which deals
with the physical and biological structure of communities and
community development. Associated with community ecology
is landscape ecology, the study of causes behind landscape
patterns and the ecological consequences of spatial patterns on
the landscape.
Natural history observations led to studies of animal reactions to their living and nonliving environment. It began with
19th-century behavioral studies including those of ants by
William Wheeler and of South American monkeys by Charles
Carpenter. Later, the pioneering studies of Konrad Lorenz and
Niko Tinbergen on the role of imprinting and instinct in the
social life of animals, particularly birds and fish, gave rise to
ethology. It spawned an offshoot behavioral ecology, exemplified early by L. E. Howard’s study on territoriality in birds.
Behavioral ecology is concerned with intraspecific and interspecific relationships such as mating, foraging, and defense and
how behavior is influenced by natural selection, all tying into
evolutionary ecology.
Other observations led to investigations of chemical substances in the natural world. Scientists began to explore the use
and nature of chemicals in animal recognition, trail-making, and
courtship, and in plant and animal defense. Such studies make up
the specialized field of chemical ecology.
Ecology has so many roots that it probably will always remain many-faceted—as the ecological historian Robert McIntosh
calls it, “a polymorphic discipline.” Insights from these many
specialized areas of ecology will continue to enrich the science
as it moves forward into the 21st century.
3
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