Table of Contents

1  Evolution, the Themes of Biology, and Scientific Inquiry
Inquiring About Life
CONCEPT 1.1 The study of life reveals common themes 
CONCEPT 1.2 The Core Theme: Evolution accounts for the unity and diversity of life 
CONCEPT 1.3 In studying nature, scientists make observations and form and test hypotheses 
CONCEPT 1.4 Science benefits from a cooperative approach and diverse viewpoints 
UNIT 1  THE CHEMISTRY OF LIFE 
2  The Chemical Context of Life
A Chemical Connection to Biology
CONCEPT 2.1 Matter consists of chemical elements in pure form and in combinations called compounds 
CONCEPT 2.2 An element’s properties depend on the structure of its atoms 
CONCEPT 2.3 The formation and function of molecules depend on chemical bonding between atoms 
CONCEPT 2.4 Chemical reactions make and break chemical bonds 
3  Water and Life
The Molecule That Supports All of Life
CONCEPT 3.1 Polar covalent bonds in water molecules result in hydrogen bonding 
CONCEPT 3.2 Four emergent properties of water contribute to Earth’s suitability for life 
CONCEPT 3.3 Acidic and basic conditions affect living organisms 
4  Carbon and the Molecular Diversity of Life 
Carbon: The Backbone of Life
CONCEPT 4.1 Organic chemistry is the study of carbon compounds 
CONCEPT 4.2 Carbon atoms can form diverse molecules by bonding to four other atoms 
CONCEPT 4.3 A few chemical groups are key to molecular function 
5  The Structure and Function of Large Biological Molecules
The Molecules of Life
CONCEPT 5.1 Macromolecules are polymers, built from monomers 
CONCEPT 5.2 Carbohydrates serve as fuel and building material 
CONCEPT 5.3 Lipids are a diverse group of hydrophobic molecules 
CONCEPT 5.4 Proteins include a diversity of structures, resulting in a wide range of functions 
CONCEPT 5.5 Nucleic acids store, transmit, and help express hereditary information 
CONCEPT 5.6 Genomics and proteomics have transformed biological inquiry and applications 
UNIT 2  THE CELL 
6  A Tour of the Cell
The Fundamental Units of Life
CONCEPT 6.1 Biologists use microscopes and biochemistry to study cells 
CONCEPT 6.2 Eukaryotic cells have internal membranes that compartmentalize their functions 
CONCEPT 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes 
CONCEPT 6.4 The endomembrane system regulates protein traffic and performs metabolic functions 
CONCEPT 6.5 Mitochondria and chloroplasts change energy from one form to another 
CONCEPT 6.6 The cytoskeleton is a network of fibers that organizes structures and activities in the cell 
CONCEPT 6.7 Extracellular components and connections between cells help coordinate cellular activities 
CONCEPT 6.8 A cell is greater than the sum of its parts
7  Membrane Structure and Function
Life at the Edge
CONCEPT 7.1 Cellular membranes are fluid mosaics of lipids and proteins 
CONCEPT 7.2 Membrane structure results in selective permeability 
CONCEPT 7.3 Passive transport is diffusion of a substance across a membrane with no energy investment 
CONCEPT 7.4 Active transport uses energy to move solutes against their gradients 
CONCEPT 7.5 Bulk transport across the plasma membrane occurs by exocytosis and endocytosis 
8  An Introduction to Metabolism
The Energy of Life
CONCEPT 8.1 An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics 
CONCEPT 8.2 The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously 
CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions 
CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers 
CONCEPT 8.5 Regulation of enzyme activity helps control metabolism 
9  Cellular Respiration and Fermentation
Life Is Work
CONCEPT 9.1 Catabolic pathways yield energy by oxidizing organic fuels 
CONCEPT 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate 
CONCEPT 9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules 
CONCEPT 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 
CONCEPT 9.5 Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen 
CONCEPT 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways 
10  Photosynthesis
The Process That Feeds the Biosphere
CONCEPT 10.1 Photosynthesis converts light energy to the chemical energy of food 
CONCEPT 10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH 
CONCEPT 10.3 The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO₂ to sugar 
CONCEPT 10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates
CONCEPT 10.5Life depends on photosynthesis  
11  Cell Communication
Cellular Messaging
CONCEPT 11.1 External signals are converted to responses within the cell 
CONCEPT 11.2 Reception: A signaling molecule binds to a receptor protein, causing it to change shape 
CONCEPT 11.3 Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell 
CONCEPT 11.4 Response: Cell signaling leads to regulation of transcription or cytoplasmic activities 
CONCEPT 11.5 Apoptosis integrates multiple cell-signaling pathways 
12  The Cell Cycle
The Key Roles of Cell Division
CONCEPT 12.1 Most cell division results in genetically identical daughter cells 
CONCEPT 12.2 The mitotic phase alternates with interphase in the cell cycle 
CONCEPT 12.3 The eukaryotic cell cycle is regulated by a molecular control system 
UNIT 3  GENETICS 
13  Meiosis and Sexual Life Cycles
Variations on a Theme
CONCEPT 13.1 Offspring acquire genes from parents by inheriting chromosomes 
CONCEPT 13.2 Fertilization and meiosis alternate in sexual life cycles 
CONCEPT 13.3 Meiosis reduces the number of chromosome sets from diploid to haploid 
CONCEPT 13.4 Genetic variation produced in sexual life cycles contributes to evolution 
14  Mendel and the Gene Idea
Drawing from the Deck of Genes
CONCEPT 14.1 Mendel used the scientific approach to identify two laws of inheritance 
CONCEPT 14.2 Probability laws govern Mendelian inheritance 
CONCEPT 14.3 Inheritance patterns are often more complex than predicted by simple Mendelian genetics 
CONCEPT 14.4 Many human traits follow Mendelian patterns of inheritance 
15 The Chromosomal Basis of Inheritance
Locating Genes Along Chromosomes
CONCEPT 15.1 Morgan showed that Mendelian inheritance has its physical basis in the behavior of chromosomes: scientific inquiry 
CONCEPT 15.2 Sex-linked genes exhibit unique patterns of inheritance 
CONCEPT 15.3 Linked genes tend to be inherited together because they are located near each other on the same chromosome 
CONCEPT 15.4 Alterations of chromosome number or structure cause some genetic disorders 
CONCEPT 15.5 Some inheritance patterns are exceptions to standard Mendelian inheritance 
16  The Molecular Basis of Inheritance
Life’s Operating Instructions
CONCEPT 16.1 DNA is the genetic material 
CONCEPT 16.2 Many proteins work together in DNA replication and repair 
CONCEPT 16.3 A chromosome consists of a DNA molecule packed together with proteins 
17  Gene Expression: From Gene to Protein
The Flow of Genetic Information
CONCEPT 17.1 Genes specify proteins via transcription and translation 
CONCEPT 17.2 Transcription is the DNA-directed synthesis of RNA: a closer look 
CONCEPT 17.3 Eukaryotic cells modify RNA after transcription 
CONCEPT 17.4 Translation is the RNA-directed synthesis of a polypeptide: a closer look 
CONCEPT 17.5 Mutations of one or a few nucleotides can affect protein structure and function 
18  Regulation of Gene Expression
Beauty in the Eye of the Beholder
CONCEPT 18.1 Bacteria often respond to environmental change by regulating transcription 
CONCEPT 18.2 Eukaryotic gene expression is regulated at many stages 
CONCEPT 18.3 Noncoding RNAs play multiple roles in controlling gene expression 
CONCEPT 18.4 A program of differential gene expression leads to the different cell types in a multicellular organism 
CONCEPT 18.5 Cancer results from genetic changes that affect cell cycle control 
19  Viruses
A Borrowed Life
CONCEPT 19.1 A virus consists of a nucleic acid surrounded by a protein coat 
CONCEPT 19.2 Viruses replicate only in host cells 
CONCEPT 19.3 Viruses and prions are formidable pathogens in animals and plants 
20  DNA Tools and Biotechnology
The DNA Toolbox
CONCEPT 20.1 DNA sequencing and DNA cloning are valuable tools for genetic engineering and biological inquiry 
CONCEPT 20.2 Biologists use DNA technology to study gene expression and function 
CONCEPT 20.3 Cloned organisms and stem cells are useful for basic research and other applications 
CONCEPT 20.4 The practical applications of DNA-based biotechnology affect our lives in many ways 
21  Genomes and Their Evolution
Reading the Leaves from the Tree of Life
CONCEPT 21.1 The Human Genome Project fostered development of faster, less expensive sequencing techniques 
CONCEPT 21.2 Scientists use bioinformatics to analyze genomes and their functions 
CONCEPT 21.3 Genomes vary in size, number of genes, and gene density 
CONCEPT 21.4 Multicellular eukaryotes have a lot of noncoding DNA and many multigene families 
CONCEPT 21.5 Duplication, rearrangement, and mutation of DNA contribute to genome evolution 
CONCEPT 21.6 Comparing genome sequences provides clues to evolution and development 
UNIT 4  MECHANISMS OF EVOLUTION 
22  Descent with Modification: A Darwinian View of Life
Endless Forms Most Beautiful
CONCEPT 22.1 The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species
CONCEPT 22.2 Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life 
CONCEPT 22.3 Evolution is supported by an overwhelming amount of scientific evidence 
23  The Evolution of Populations
The Smallest Unit of Evolution
CONCEPT 23.1 Genetic variation makes evolution possible
CONCEPT 23.2 The Hardy-Weinberg equation can be used to test whether a population is evolving 
CONCEPT 23.3 Natural selection, genetic drift, and gene flow can alter allele frequencies in a population 
CONCEPT 23.4 Natural selection is the only mechanism that consistently causes adaptive evolution 
24  The Origin of Species
That “Mystery of Mysteries”
CONCEPT 24.1 The biological species concept emphasizes reproductive isolation 
CONCEPT 24.2 Speciation can take place with or without geographic separation 
CONCEPT 24.3 Hybrid zones reveal factors that cause reproductive isolation 
CONCEPT 24.4 Speciation can occur rapidly or slowly and can result from changes in few or many genes 
25  The History of Life on Earth
A Surprise in the Desert 
CONCEPT 25.1 Conditions on early Earth made the origin of life possible 
CONCEPT 25.2 The fossil record documents the history of life 
CONCEPT 25.3 Key events in life’s history include the origins of unicellular and multicellular organisms and the colonization of land 
CONCEPT 25.4 The rise and fall of groups of organisms reflect differences in speciation and extinction rates 
CONCEPT 25.5 Major changes in body form can result from changes in the sequences and regulation of developmental genes 
CONCEPT 25.6 Evolution is not goal oriented 
UNIT 5  THE EVOLUTIONARY HISTORY OF BIOLOGICAL DIVERSITY 
26  Phylogeny and the Tree of Life
Investigating the Tree of Life
CONCEPT 26.1 Phylogenies show evolutionary relationships 
CONCEPT 26.2 Phylogenies are inferred from morphological and molecular data
CONCEPT 26.3 Shared characters are used to construct phylogenetic trees 
CONCEPT 26.4 An organism’s evolutionary history is documented in its genome 
CONCEPT 26.5 Molecular clocks help track evolutionary time 
CONCEPT 26.6 Our understanding of the tree of life continues to change based on new data 
27  Bacteria and Archaea
Masters of Adaptation
CONCEPT 27.1 Structural and functional adaptations contribute to prokaryotic success 
CONCEPT 27.2 Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes 
CONCEPT 27.3 Diverse nutritional and metabolic adaptations have evolved in prokaryotes 
CONCEPT 27.4 Prokaryotes have radiated into a diverse set of lineages 
CONCEPT 27.5 Prokaryotes play crucial roles in the biosphere 
CONCEPT 27.6 Prokaryotes have both beneficial and harmful impacts on humans 
28  Protists
Living Small
CONCEPT 28.1 Most eukaryotes are single-celled organisms 
CONCEPT 28.2 Excavates include protists with modified mitochondria and protists with unique flagella 
CONCEPT 28.3 SAR is a highly diverse group of protists defined by DNA similarities 
CONCEPT 28.4 Red algae and green algae are the closest relatives of land plants 
CONCEPT 28.5 Unikonts include protists that are closely related to fungi and animals 
CONCEPT 28.6 Protists play key roles in ecological communities 
29  Plant Diversity I: How Plants Colonized Land
The Greening of Earth
CONCEPT 29.1 Plants evolved from green algae 
CONCEPT 29.2 Mosses and other nonvascular plants have life cycles dominated by gametophytes 
CONCEPT 29.3 Ferns and other seedless vascular plants were the first plants to grow tall 
30  Plant Diversity II: The Evolution of Seed Plants
Transforming the World
CONCEPT 30.1 Seeds and pollen grains are key adaptations for life on land 
CONCEPT 30.2 Gymnosperms bear “naked” seeds, typically on cones 
CONCEPT 30.3 The reproductive adaptations of angiosperms include flowers and fruits 
CONCEPT 30.4 Human welfare depends on seed plants 
31  Fungi
Mighty Mushrooms
CONCEPT 31.1 Fungi are heterotrophs that feed by absorption 
CONCEPT 31.2 Fungi produce spores through sexual or asexual life cycles 
CONCEPT 31.3 The ancestor of fungi was an aquatic, single-celled, flagellated protist 
CONCEPT 31.4 Fungi have radiated into a diverse set of lineages 
CONCEPT 31.5 Fungi play key roles in nutrient cycling, ecological interactions, and human welfare 
32  An Overview of Animal Diversity
A Kingdom of Consumers
CONCEPT 32.1 Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers 
CONCEPT 32.2 The history of animals spans more than half a billion years 
CONCEPT 32.3 Animals can be characterized by “body plans” 
CONCEPT 32.4 Views of animal phylogeny continue to be shaped by new molecular and morphological data
33  An Introduction to Invertebrates
A Dragon Without a Backbone
CONCEPT 33.1 Sponges are basal animals that lack tissues 
CONCEPT 33.2 Cnidarians are an ancient phylum of eumetazoans 
CONCEPT 33.3 Lophotrochozoans, a clade identified by molecular data, have the widest range of animal body forms 
CONCEPT 33.4 Ecdysozoans are the most species-rich animal group
CONCEPT 33.5 Echinoderms and chordates are deuterostomes 
34  The Origin and Evolution of Vertebrates
Half a Billion Years of Backbones
CONCEPT 34.1 Chordates have a notochord and a dorsal, hollow nerve cord 
CONCEPT 34.2 Vertebrates are chordates that have a backbone 
CONCEPT 34.3 Gnathostomes are vertebrates that have jaws 
CONCEPT 34.4 Tetrapods are gnathostomes that have limbs 
CONCEPT 34.5 Amniotes are tetrapods that have a terrestrially adapted egg 
CONCEPT 34.6 Mammals are amniotes that have hair and produce milk 
CONCEPT 34.7 Humans are mammals that have a large brain and bipedal locomotion 
UNIT 6  PLANT FORM AND FUNCTION 
35  Vascular Plant Structure, Growth, and Development
Are Plants Computers?
CONCEPT 35.1 Plants have a hierarchical organization consisting of organs, tissues, and cells 
CONCEPT 35.2 Different meristems generate new cells for primary and secondary growth 
CONCEPT 35.3 Primary growth lengthens roots and shoots 
CONCEPT 35.4 Secondary growth increases the diameter of stems and roots in woody plants 
CONCEPT 35.5 Growth, morphogenesis, and cell differentiation produce the plant body 
36  Resource Acquisition and Transport in Vascular Plants
A Whole Lot of Shaking Going On
CONCEPT 36.1 Adaptations for acquiring resources were key steps in the evolution of vascular plants 
CONCEPT 36.2 Different mechanisms transport substances over short or long distances 
CONCEPT 36.3 Transpiration drives the transport of water and minerals from roots to shoots via the xylem 
CONCEPT 36.4 The rate of transpiration is regulated by stomata 
CONCEPT 36.5 Sugars are transported from sources to sinks via the phloem 
CONCEPT 36.6 The symplast is highly dynamic 
37  Soil and Plant Nutrition
The Corkscrew Carnivore
CONCEPT 37.1 Soil contains a living, complex ecosystem
CONCEPT 37.2 Plant roots absorb essential elements from the soil
CONCEPT 37.3 Plant nutrition often involves relationships with other organisms 
38  Angiosperm Reproduction and Biotechnology
Flowers of Deceit
CONCEPT 38.1 Flowers, double fertilization, and fruits are key features of the angiosperm life cycle 
CONCEPT 38.2 Flowering plants reproduce sexually, asexually, or both 
CONCEPT 38.3 People modify crops by breeding and genetic engineering 
39  Plant Responses to Internal and External Signals
Stimuli and a Stationary Life
CONCEPT 39.1 Signal transduction pathways link signal reception to response 
CONCEPT 39.2 Plant hormones help coordinate growth, development, and responses to stimuli 
CONCEPT 39.3 Responses to light are critical for plant success 
CONCEPT 39.4 Plants respond to a wide variety of stimuli other than light
CONCEPT 39.5 Plants respond to attacks by pathogens and herbivores 
UNIT 7  ANIMAL FORM AND FUNCTION 
40  Basic Principles of Animal Form and Function
Diverse Forms, Common Challenges
CONCEPT 40.1 Animal form and function are correlated at all levels of organization 
CONCEPT 40.2 Feedback control maintains the internal environment in many animals 
CONCEPT 40.3 Homeostatic processes for thermoregulation involve form, function, and behavior 
CONCEPT 40.4 Energy requirements are related to animal size, activity, and environment 
41  Animal Nutrition
The Need to Feed
CONCEPT 41.1 An animal’s diet must supply chemical energy, organic building blocks, and essential nutrients 
CONCEPT 41.2 Food processing involves ingestion, digestion, absorption, and elimination 
CONCEPT 41.3 Organs specialized for sequential stages of food processing form the mammalian digestive system 
CONCEPT 41.4 Evolutionary adaptations of vertebrate digestive systems correlate with diet 
CONCEPT 41.5 Feedback circuits regulate digestion, energy storage, and appetite 
42  Circulation and Gas Exchange
Trading Places
CONCEPT 42.1 Circulatory systems link exchange surfaces with cells throughout the body 
CONCEPT 42.2 Coordinated cycles of heart contraction drive double circulation in mammals 
CONCEPT 42.3 Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels 
CONCEPT 42.4 Blood components function in exchange, transport, and defense 
CONCEPT 42.5 Gas exchange occurs across specialized respiratory surfaces 
CONCEPT 42.6 Breathing ventilates the lungs 
CONCEPT 42.7 Adaptations for gas exchange include pigments that bind and transport gases 
43  The Immune System
Recognition and Response
CONCEPT 43.1 In innate immunity, recognition and response rely on traits common to groups of pathogens 
CONCEPT 43.2 In adaptive immunity, receptors provide pathogen-specific recognition 
CONCEPT 43.3 Adaptive immunity defends against infection of body fluids and body cells 
CONCEPT 43.4 Disruptions in immune system function can elicit or exacerbate disease 
44  Osmoregulation and Excretion
A Balancing Act
CONCEPT 44.1 Osmoregulation balances the uptake and loss of water and solutes 
CONCEPT 44.2 An animal’s nitrogenous wastes reflect its phylogeny and habitat 
CONCEPT 44.3 Diverse excretory systems are variations on a tubular theme 
CONCEPT 44.4 The nephron is organized for stepwise processing of blood filtrate 
CONCEPT 44.5 Hormonal circuits link kidney function, water balance, and blood pressure 
45  Hormones and the Endocrine System
The Body’s Long-Distance Regulators 
CONCEPT 45.1 Hormones and other signaling molecules bind to target receptors, triggering specific response pathways 
CONCEPT 45.2 Feedback regulation and coordination with the nervous system are common in hormone pathways 
CONCEPT 45.3 Endocrine glands respond to diverse stimuli in regulating homeostasis, development, and behavior 
46  Animal Reproduction
Let Me Count the Ways
CONCEPT 46.1 Both asexual and sexual reproduction occur in the animal kingdom 
CONCEPT 46.2 Fertilization depends on mechanisms that bring together sperm and eggs of the same species 
CONCEPT 46.3 Reproductive organs produce and transport gametes 
CONCEPT 46.4 The interplay of tropic and sex hormones regulates mammalian reproduction 
CONCEPT 46.5 In placental mammals, an embryo develops fully within the mother’s uterus 
47  Animal Development
A Body-Building Plan
CONCEPT 47.1 Fertilization and cleavage initiate embryonic development 
CONCEPT 47.2 Morphogenesis in animals involves specific changes in cell shape, position, and survival 
CONCEPT 47.3 Cytoplasmic determinants and inductive signals regulate cell fate
48  Neurons, Synapses, and Signaling
Lines of Communication
CONCEPT 48.1 Neuron structure and organization reflect function in information transfer 
CONCEPT 48.2 Ion pumps and ion channels establish the resting potential of a neuron 
CONCEPT 48.3 Action potentials are the signals conducted by axons 
CONCEPT 48.4 Neurons communicate with other cells at synapses 
49  Nervous Systems
Command and Control Center
CONCEPT 49.1 Nervous systems consist of circuits of neurons and supporting cells 
CONCEPT 49.2 The vertebrate brain is regionally specialized 
CONCEPT 49.3 The cerebral cortex controls voluntary movement and cognitive functions 
CONCEPT 49.4 Changes in synaptic connections underlie memory and learning 
CONCEPT 49.5 Many nervous system disorders can be explained in molecular terms 
50  Sensory and Motor Mechanisms
Sense and Sensibility
CONCEPT 50.1 Sensory receptors transduce stimulus energy and transmit signals to the central nervous system 
CONCEPT 50.2 In hearing and equilibrium, mechanoreceptors detect moving fluid or settling particles 
CONCEPT 50.3 The diverse visual receptors of animals depend on light-absorbing pigments
CONCEPT 50.4 The senses of taste and smell rely on similar sets of sensory receptors 
CONCEPT 50.5 The physical interaction of protein filaments is required for muscle function
CONCEPT 50.6 Skeletal systems transform muscle contraction into locomotion 
51  Animal Behavior
The How and Why of Animal Activity
CONCEPT 51.1 Discrete sensory inputs can stimulate both simple and complex behaviors 
CONCEPT 51.2 Learning establishes specific links between experience and behavior 
CONCEPT 51.3 Selection for individual survival and reproductive success can explain diverse behaviors 
CONCEPT 51.4 Genetic analyses and the concept of inclusive fitness provide a basis for studying the evolution of behavior 
UNIT 8  ECOLOGY 
52  An Introduction to Ecology and the Biosphere
Discovering Ecology
CONCEPT 52.1 Earth’s climate varies by latitude and season and is changing rapidly 
CONCEPT 52.2 The distribution of terrestrial biomes is controlled by climate and disturbance 
CONCEPT 52.3 Aquatic biomes are diverse and dynamic systems that cover most of Earth
CONCEPT 52.4 Interactions between organisms and the environment limit the distribution of species 
CONCEPT 52.5Ecological change and evolution affect one another over long and short periods of time
53  Population Ecology
Turtle Tracks
CONCEPT 53.1 Biotic and abiotic factors affectpopulation density, dispersion, and demographics 
CONCEPT 53.2 The exponential model describes population growth in an idealized, unlimited environment 
CONCEPT 53.3 The logistic model describes how a population grows more slowly as it nears its carrying capacity 
CONCEPT 53.4 Life history traits are products of natural selection 
CONCEPT 53.5 Density-dependent factors regulate population growth
CONCEPT 53.6 The human population is no longer growing exponentially but is still increasing rapidly 
54  Community Ecology
Communities in Motion
CONCEPT 54.1 Community interactions are classified by whether they help, harm, or have no effect on the species involved 
CONCEPT 54.2 Diversity and trophic structure characterize biological communities 
CONCEPT 54.3 Disturbance influences species diversity and composition 
CONCEPT 54.4 Biogeographic factors affect community diversity 
CONCEPT 54.5 Pathogens alter community structure locally and globally 
55  Ecosystems and Restoration Ecology
Transformed to Tundra
CONCEPT 55.1 Physical laws govern energy flow and chemical cycling in ecosystems 
CONCEPT 55.2 Energy and other limiting factors control primary production in ecosystems 
CONCEPT 55.3 Energy transfer between trophic levels is typically only 10% efficient 
CONCEPT 55.4 Biological and geochemical processes cycle nutrients and water in ecosystems 
CONCEPT 55.5 Restoration ecologists return degraded ecosystems to a more natural state 
56  Conservation Biology and Global Change
Psychedelic Treasure
CONCEPT 56.1 Human activities threaten Earth’s biodiversity 
CONCEPT 56.2 Population conservation focuses on population size, genetic diversity, and critical habitat 
CONCEPT 56.3 Landscape and regional conservation help sustain biodiversity 
CONCEPT 56.4 Earth is changing rapidly as a result of human actions
CONCEPT 56.5 Sustainable development can improve human lives while conserving biodiversity