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