Topic Coverage and Order

From a cursory glance, the organization of Biology: How Life Works is similar to other textbooks—we move from molecules, to cells, to genetics, to evolution, to organisms, and close with ecology.

On closer look, there are significant differences that aim to help biology teachers incorporate the outlooks and research of biology today. Scroll down to view the Table of Contents, with video annotations from the authors that highlight these differences and explain the reasons behind them.

Table of Contents
with video annotationsLook for this icon

We invite you to explore the Biology: How Life Works Table of Contents.
• To view the section-level details for each chapter, click the plus sign icon to the left of the chapter title.
• Wherever you see a play icon click to watch the video annotation where the authors talk about content coverage decisions and the reasons behind them.

Click here to see all video annotations.

Click here to see all visual synthesis figures.


Chapter 1: Life

Chemical, Cellular, and Evolutionary Foundations.1-1

1.1The Scientific Method1-2

  • Observation allows us to draw tentative explanations called hypotheses.1-2
  • A hypothesis makes predictions that can be tested by observation and experiments.1-3
  • How Do We Know? What caused the extinction of the dinosaurs? 1-4
  • General explanations of natural phenomena supported by many experiments and observations are called theories.1-5

1.2Chemical and Physical Principles1-5

  • The living and nonliving worlds share the same chemical foundations and obey the same physical laws.1-6
  • The scientific method shows that living organisms come from other living organisms.1-7
  • How Do We Know? Can living organisms arise from nonliving matter?1-8
  • How Do We Know? Can microscopic life arise from nonliving matter? 1-8

1.3The Cell1-8

  • Nucleic acids store and transmit information needed for growth, function, and reproduction.1-10
  • Membranes define cells and spaces within cells.1-11
  • Metabolism converts energy from the environment into a form that can be used by cells.1-12
  • A virus is genetic material in need of a cell.1-12


  • Variation in populations provides the raw material for evolution, change over time.1-12
  • Evolution predicts a nested pattern of relatedness among species, depicted as a tree. 1-13
  • Evolution can be studied by means of experiments.1-15
  • How Do We Know?Can evolution be demonstrated in the laboratory?1-15

1.5Ecological Systems1-16

  • Basic features of anatomy, physiology, and behavior shape ecological systems.1-16
  • Ecological interactions play an important role in evolution.1-17

1.6The Human Footprint1-18

Case 1:The First Cell: Life's Origins


Chapter 2:The Molecules of Life James Morris on the organization of The Molecular Chapters

James Morris on the organization of The Molecular Chapters 2-8

Click here to see all video annotations.

2.1Properties of Atoms2-1

  • Atoms consist of protons, neutrons, and electrons.2-1
  • Electrons occupy regions of space called orbitals.2-1
  • Elements have recurring, or periodic, chemical properties.2-3

2.2Molecules and Chemical Bonds2-4

  • A covalent bond results when two atoms share electrons.2-4
  • A polar covalent bond is characterized by unequal sharing of electrons.2-5
  • A hydrogen bond is an interaction of a hydrogen atom and an electronegative atom.2-5
  • An ionic bond forms between oppositely charged ions.2-6
  • A chemical reaction involves breaking and forming chemical bonds.2-6

2.3Water: The Medium of Life2-7

  • Water is a polar molecule.2-7
  • pH is a measure of the concentration of protons in solution.2-7
  • Hydrogen bonds give water many unusual properties.2-8

2.4Carbon: Life’s Chemical Backbone2-9

  • Carbon atoms form four covalent bonds.2-9
  • Carbon-based molecules are structurally and functionally diverse.2-9

2.5Organic Molecules2-11

  • Proteins are composed of amino acids.2-11
  • Nucleic acids encode genetic information in their nucleotide sequence. 2-12
  • Complex carbohydrates are made up of simple sugars.2-13
  • Lipids are hydrophobic molecules.2-15

2.6How Did the Molecules of Life Form2-17

  • How Do We Know?Could the building blocks of organic molecules have been generated on the early Earth?2-18
  • The building blocks of life can be generated in the laboratory.2-18
  • Experiments show how life’s building blocks can form macromolecules.2-18

Chapter 3:Nucleic Acids and the Encoding of Biological InformationJames Morris on Structure and Function

James Morris on Structure and Function

Click here to see all video annotations.

3.1Major Biological Functions of DNA3-2

  • DNA can transfer biological characteristics from one organism to another.3-2
  • How Do We Know?What is the nature of the genetic material?3-2
  • DNA molecules are copied in the process of replication.3-3
  • Genetic information flows from DNA to RNA to protein.3-3
  • How Do We Know?What is the nature of the genetic material?3-3

3.2Chemical Composition and Structure of DNA3-4

  • A DNA strand consists of subunits called nucleotides.3-4
  • DNA is a linear polymer of nucleotides linked by phosphodiester bonds.3-6
  • Cellular DNA molecules take the form of a double helix.3-6
  • The three-dimensional structure of DNA gave important clues about its functions.3-8
  • Cellular DNA is coiled and packaged with proteins.3-9

3.3Retrieval of Genetic Information Stored in DNA: Transcription3-10

  • What was the first nucleic acid molecule, and how did it arise? 3-10
  • In transcription, DNA is used as a template to make complementary RNA.3-11
  • Transcription starts at a promoter and ends at a terminator.3-12
  • RNA polymerase adds successive nucleotides to the 3´ end of the transcript.3-13
  • The RNA polymerase complex is a molecular machine that opens, transcribes, and closes duplex DNA. 3-14

3.4Fate of the RNA Primary Transcript3-15

  • Messenger RNA carries information for the synthesis of a specific protein.3-15
  • Primary transcripts in eukaryotes undergo several types of chemical modification.3-16
  • Some RNA transcripts are processed differently from protein-coding transcripts and have functions of their own.3-18

Chapter 4:Translation and Protein StructureVISUAL SYNTHESIS: Gene Expression


4.1Molecular Structure of Proteins4-1

  • Amino acids differ in their side chains.4-2
  • Successive amino acids in proteins are connected by peptide bonds.4-3
  • The sequence of amino acids dictates protein folding, which determines function.4-4
  • Secondary structures result from hydrogen bonding in the polypeptide backbone.4-5
  • How Do We Know?What are the shapes of proteins?4-5
  • Tertiary structures result from interactions between amino acid side chains.4-6
  • Polypeptide subunits can come together to form quaternary structures.4-7
  • Chaperones help some proteins fold properly.4-8

4.2Translation: How Proteins Are Synthesized4-8

  • Translation uses many molecules found in all cells.4-8
  • The genetic code shows the correspondence between codons and amino acids.4-10
  • How Do We Know?How was the genetic code deciphered?4-11
  • Translation consists of initiation, elongation,and termination.4-12
  • How did the genetic code originate?4-14

4.3Protein Evolution and the Origin of New Proteins4-15

Chapter 5:Organizing Principles

Lipids, Membranes, and Cell Compartments5-1
cell membrane

5.1Structure of Cell Membranes5-1

  • Cell membranes are composed of two layers of lipids.5-2
  • How did the first cell membranes form?5-3
  • Cell membranes are dynamic.5-3
  • Proteins associate with cell membranes in different ways.5-5

5.2The Plasma Membrane and Cell Wall5-6

  • How Do We Know?Do proteins move in the plane of the membrane?5-7
  • The plasma membrane maintains homeostasis.5-8
  • Passive transport involves diffusion.5-8
  • Primary active transport uses the energy of ATP.5-9
  • Secondary active transport is driven by an electrochemical gradient.5-10
  • Many cells maintain size and composition using active transport.5-11
  • The cell wall provides another means of maintaining cell shape.5-12

5.3The Internal Organization of Cells5-12

  • Eukaryotes and prokaryotes differ in internal organization.5-13
  • Prokaryotic cells lack a nucleus and extensive internal compartmentalization.5-13
  • Eukaryotic cells have a nucleus and specialized internal structures.5-13

5.4The Endomembrane System5-15

  • The endomembrane system compartmentalizes the cell.5-16
  • The nucleus houses the genome and is the site of RNA synthesis.5-17
  • The endoplasmic reticulum is involved in protein and lipid synthesis.5-17
  • The Golgi apparatus modifies and sorts proteins and lipids.5-18
  • Lysosomes degrade macromolecules. 5-195-19
  • Protein sorting directs proteins to their proper location in or out of the cell.5-20

5.5Mitochondria and Chloroplasts5-22

  • Mitochondria provide the eukaryotic cell with most of its useable energy.5-22
  • Chloroplasts capture energy from sunlight.5-23

Chapter 6:Making Life Work

Capturing and Using Energy6-1

6.1An Overview of Metabolism6-1

  • Organisms can be classified according to their energy and carbon sources. 6-2
  • Metabolism is the set of chemical reactions that sustain life. 6-3


  • Kinetic and potential energy are two forms of energy.6-3
  • Chemical energy is a form of potential energy.6-4
  • ATP is the cell’s energy currency.6-4

6.3The Laws of Thermodynamics6-5

  • The first law of thermodynamics: Energy is conserved.6-5
  • The second law of thermodynamics: Disorder tends to increase.6-5

6.4Chemical Reactions 6-6

  • A chemical reaction occurs when molecules interact.6-6
  • Chemical reactions are subject to the laws of thermodynamics.6-7
  • The hydrolysis of ATP releases energy. 6-8
  • Non-spontaneous reactions are often coupled to spontaneous reactions. 6-9

6.5Enzymes and the Rate of Chemical Reactions6-10

  • Enzymes reduce the activation energy of a chemical reaction.6-10
  • Enzymes form a complex with reactants and products. 6-11
  • Enzymes are highly specific. 6-12
  • How Do We Know?Do enzymes form complexes with substrates?6-12
  • How Do We Know?Do enzymes form complexes with substrates?6-13
  • Enzyme activity can be influenced by inhibitors and activators.6-13
  • Allosteric enzymes in the cell are regulated by activators and inhibitors.6-14
  • What naturally occurring elements might have spurred the first reactions that led to life?6-15

Chapter 7:Cellular Respiration

Harvesting Energy from Carbohydrates and Other Fuel Molecules7-1

7.1An Overview of Cellular Respiration 7-1

  • Cellular respiration occurs in four stages.7-2
  • Cellular respiration involves a series of redox reactions.7-2
  • Chemical energy is stored in reduced molecules such as carbohydrates and lipids.7-4
  • Electron carriers transport high-energy electrons.7-4
  • ATP is generated by substrate-level phosphorylation and oxidative phosphorylation.7-4

7.2Glycolysis: The Splitting of Sugar 7-5

  • Glycolysis is the partial breakdown of glucose.7-7

7.3Acetyl-CoA Synthesis 7-7

  • The oxidation of pyruvate connects glycolysis to the citric acid cycle.7-7

7.4The Citric Acid Cycle 7-8

  • The citric acid cycle produces ATP and electron carriers.7-8
  • What were the earliest energy-harnessing reactions? 7-10

7.5The Electron Transport Chain and Oxidative Phosphorylation7-10

  • The electron transport chain transfers electrons and pumps protons.7-10
  • The proton gradient is a source of potential energy.7-12
  • ATP synthase converts the energy of the proton gradient into the energy of ATP.7-12
  • How Do We Know?Can a proton gradient drive the synthesis of ATP?7-13

7.6Anaerobic Metabolism and the Evolution of Cellular Respiration7-14

  • Fermentation extracts energy from glucose in the absence of oxygen.7-15
  • How did early cells meet their energy requirements?7-16

7.7Metabolic Integration7-17

  • Excess glucose is stored as glycogen in animals and starch in plants.7-17
  • Sugars other than glucose contribute to glycolysis.7-17
  • Fatty acids and proteins are useful sources of energy.7-18
  • The intracellular level of ATP is a key regulator of cellular respiration.7-19
  • Exercise requires several types of fuel molecules and the coordination of metabolic pathways.7-20

Chapter 8:PhotosynthesisMissy Holbrook on The Calvin Cycle and the Light Reactions of PhotosynthesisVISUAL SYNTHESIS: Harnessing Energy: Photosynthesis and Cellular RespirationMissy Holbrook on C4 and CAM coverage

Using Sunlight to Build Carbohydrates 8-1
Missy Holbrook on the Calvin Cycle and the Light Reactions of Photosynthesis

Click here to see all video annotations.

See also Missy Holbrook on C4 and CAM coverage (CH: 29).

8.1The Natural History of Photosynthesis 8-1

  • Photosynthesis is a redox reaction 8-1
  • How Do We Know? Does the oxygen released by photosynthesis come from H2O or CO2?8-2
  • Photosynthesis is widely distributed.8-3
  • The evolutionary history of photosynthesis includes both horizontal gene transfer and endosymbiosis.8-4
  • The photosynthetic electron transport chain takes place on specialized membranes.8-5

8.2The Calvin Cycle 8-6

  • The incorporation of CO2 is catalyzed by the enzyme rubisco.8-6
  • NADPH is the reducing agent of the Calvin cycle.8-6
  • The regeneration of RuBP requires ATP.8-7
  • The steps of the Calvin cycle were determined using radioactive CO2.8-7
  • Carbohydrates are stored in the form of starch. 8-78-7
  • How Do We Know?How is CO2 used to synthesize carbohydrates?8-8

8.3Capturing Sunlight into Chemical Forms8-9

  • Photosystems use light energy to set the photosynthetic electron transport chain in motion.8-9
  • How Do We Know?Do chlorophyll molecules operate on their own or in groups?8-11
  • The photosynthetic electron transport chain connects two photosystems.8-12
  • The accumulation of protons in the thylakoid lumen drives the synthesis of ATP.8-14
  • Cyclic electron transport increases the production of ATP.8-14
  • The spatial organization of the thylakoid membrane contributes to its functioning.8-15
  • How did early cells meet their energy requirements?8-15

8.4Challenges to Photosynthetic Efficiency8-16

Case 2:Cancer: When Good Cells Go Bad


Chapter 9:Cell Communication

cell communication

9.1Principles of Cell Communication9-1

  • Cells communicate using chemical signals that bind to specific receptors.9-2
  • Signaling involves receptor activation, signal transduction, response, and termination.9-2

9.2Types of Cell Signaling 9-3

  • Endocrine signaling acts over long distances.9-3
  • Paracrine and autocrine signaling act over short distances.9-4
  • How Do We Know? Where do growth factors come from?9-4
  • Juxtacrine signaling depends on direct cell–cell contact.9-5

9.3Receptors and Receptor Activation9-6

  • Receptors can be on the cell surface or in the interior of the cell.9-6
  • There are three major types of cell-surface receptor, which act like molecular switches.9-7

9.4Signal Transduction, Response, and Termination9-8

  • Signals transmitted by G protein-coupled receptors are amplified and regulated at several steps.9-8
  • Receptor kinases phosphorylate each other and activate intracellular signaling pathways.9-11
  • Ligand-gated ion channels alter the movement of ions across the plasma membrane.9-13
  • How do cell signaling errors lead to cancer?9-15
  • Signaling pathways can intersect with one another in a cell.9-15

Chapter 10:Cell Form and Function

Cytoskeleton, Cellular Junctions, and Extracellular Matrix 10-1

10.1Tissues and Organs10-1

  • Tissues and organs are communities of cells.10-2
  • The structure of skin relates to its function.10-2

10.2The Cytoskeleton10-3

  • Microtubules are hollow, tubelike polymers of tubulin dimers.10-4
  • Microfilaments are helical polymers of actin.10-4
  • Intermediate filaments are polymers of proteins that vary according to cell type.10-4
  • How can doctors test for the spread of cancer?10-5
  • Microtubules and microfilaments are dynamic structures.10-6
  • The cytoskeleton is an ancient feature of cells.10-7

10.3Cellular Movement10-8

  • Motor proteins associate with microtubules and microfilaments to cause movement.10-8
  • Organelles with special arrangements of microtubules propel cells through the environment.10-10
  • Actin polymerization moves cells forward.10-10

10.4Cell Adhesion10-11

  • Cell adhesion molecules allow cells to attach to other cells and to the extracellular matrix.10-11
  • Adherens junctions and desmosomes connect adjacent animal cells and are anchored to the cytoskeleton.10-12
  • Tight junctions prevent the movement of substances through the space between animal cells.10-13
  • Gap junctions and plasmodesmata allow the passage of substances from one cell to another.10-15

10.5The Extracellular Matrix10-15

  • The extracellular matrix of plants is the cell wall.10-15
  • The extracellular matrix is abundant in connective tissues of animals.10-17
  • The basal lamina is a special form of extracellular matrix.10-18
  • How do cancer cells spread throughout the body?10-18
  • Extracellular matrix proteins influence cell shape and gene expression.10-18
  • How Do We Know? Can extracellular matrix proteins influence gene expression?10-20

Chapter 11:Cell DivisionVISUAL SYNTHESIS: Cellular Communities

Variations, Regulation, and Cancer 11-1

11.1Cell Division11-2

  • Prokaryotic cells reproduce by binary fission.11-2
  • Eukaryotic cells reproduce by mitotic cell division.11-3
  • The cell cycle describes the life cycle of a eukaryotic cell.11-3

11.2Mitotic Cell Division11-4

  • The DNA of eukaryotic cells is organized as chromosomes.11-4
  • Prophase: Chromosomes condense and become visible.11-5
  • Prometaphase: Chromosomes attach to the mitotic spindle.11-6
  • Metaphase: Chromosomes align as a result of dynamic changes in the mitotic spindle.11-6
  • Anaphase: Sister chromatids fully separate.11-6
  • Telophase: Nuclear envelopes re-form around newly segregated chromosomes.11-6
  • The parent cell divides into two daughter cells by cytokinesis.11-7

11.3Meiotic Cell Division11-7

  • Pairing of homologous chromosomes is unique to meiosis.11-8
  • Crossing over between DNA molecules results in exchange of genetic material.11-8
  • The first meiotic division brings about the reduction in chromosome number.11-9
  • The second meiotic division resembles mitosis.11-10
  • Division of the cytoplasm often differs between the sexes.11-11
  • Meiosis is the basis of sexual reproduction.11-13

11.4Regulation of the Cell Cycle11-14

  • Protein phosphorylation controls passage through the cell cycle.11-14
  • How Do We Know? How is progression through the cell cycle controlled?11-15
  • Different cyclin–CDK complexes regulate each stage of the cell cycle.11-16
  • Cell cycle progression requires successful passage through multiple checkpoints.11-16

11.5What Genes Are Involved In Cancer?11-17

  • Oncogenes promote cancer.11-17
  • How Do We Know? Can a virus cause cancer?11-18
  • Proto-oncogenes are genes that when mutated may cause cancer.11-19
  • Tumor suppressors block specific steps in the development of cancer.11-19
  • Most cancers require the accumulation of multiple mutations.11-19
  • VISUAL SYNTHESIS: Cellular Communities11-22

Case 3:You, From A to T: Your Personal GenomeDan Hartl on Your Personal Genome

Dan Hartl on Your Personal Genome

Click here to see all video annotations.

Chapter 12:DNA Replication and ManipulationDan Hartl on the Organization of the Genetics Section

Dan Hartl on the Organization of the Genetics Section

Click here to see all video annotations.

12.1DNA Replication 12-1

  • During DNA replication, the parental strands separate and new partners are made.12-2
  • How Do We Know?How is DNA replicated? 12-2
  • New DNA strands grow by the addition of nucleotides to the 3' end.12-4
  • In replicating DNA, one daughter strand is synthesized continuously and the other in a series of short pieces.12-4
  • A small stretch of RNA is needed to begin synthesis of a new DNA strand.12-5
  • DNA polymerase is self-correcting because of its proofreading function.12-6
  • Many proteins participate in DNA replication.12-7

12.2Replication of Chromosomes12-8

  • Replication of DNA in chromosomes starts at many places almost simultaneously.12-8
  • Telomerase restores tips of linear chromosomes shortened during DNA replication.12-8

12.3Isolation, Identification, and Sequencing of DNA Fragments 12-10

  • The polymerase chain reaction selectively amplifies regions of DNA.12-10
  • Electrophoresis separates DNA fragments by size.12-11
  • Restriction enzymes cleave DNA at particular short sequences.12-13
  • DNA strands can be separated and brought back together again.12-14
  • DNA sequencing makes use of the principles of DNA replication.12-15
  • What new technologies will be required to sequence your personal genome?12-16

12.4Recombinant DNA and Genetically Modified Organisms12-17

  • Recombinant DNA combines DNA molecules from two sources.12-18
  • Recombinant DNA is the basis of genetically modified organisms.12-19

Chapter 13:Genomes

DNA Sequencing

13.1Genome Sequencing13-1

  • Complete genome sequences are assembled from smaller pieces.13-2
  • How Do We Know?How are whole genomes sequenced?13-2
  • Sequences that are repeated complicate sequence assembly13-2
  • Why sequence your personal genome?13-4

13.2Genome Annotation13-4

  • Genome annotation identifies various types of sequence.13-4
  • Genome annotation includes searching for sequence motifs.13-5
  • Comparison of genomic DNA with messenger RNA reveals the intron–exon structure of genes.13-6
  • An annotated genome summarizes knowledge, guides research, and reveals evolutionary relationships among organisms.13-6
  • The HIV genome illustrates the utility of genome annotation and comparison.13-6

13.3Gene Number, Genome Size, and Organismal Complexity13-7

  • Gene number is not a good predictor of biological complexity.13-7
  • Viruses, bacteria, and archaeons have small, compact genomes.13-8
  • Among eukaryotes, there is no relationship between genome size and organismal complexity.13-9
  • About half of the human genome consists of repetitive DNA and transposable elements.13-10

13.4Organization of Genomes13-11

  • Bacterial cells package their DNA as a nucleoid composed of many loops.13-11
  • Eukaryotic cells package their DNA as one molecule per chromosome.13-13
  • The human genome consists of 22 pairs of chromosomes and two sex chromosomes.13-13
  • Organelle DNA forms nucleoids that differ from those in bacteria.13-14

Chapter 14:Mutation and DNA Repair


14.1The Rate and Nature of Mutations14-1

  • For individual nucleotides, mutation is a rare event.14-1
  • Across the genome as a whole, mutation is common.14-2
  • Only germ-line mutations are transmitted to progeny.14-3
  • What can your personal genome tell you about your genetic risk factors?14-4
  • Mutations are random with regard to an organism’s needs.14-5

14.2Small-Scale Mutations14-5

  • Point mutations are changes in a single nucleotide.14-5
  • How Do We Know?Do mutations occur randomly, or are they directed by the environment?14-6
  • Small insertions and deletions involve several nucleotides.14-8
  • How Do We Know?What causes sectoring in corn kernels?14-10
  • Some mutations are due to the insertion of a transposable element.14-10

14.3Chromosomal Mutations14-11

  • Duplications and deletions result in gain or loss of DNA.14-11
  • Gene families arise from gene duplication and evolutionary divergence.14-12
  • An inversion has a chromosomal region reversed in orientation. 14-12
  • A reciprocal translocation joins segments from nonhomologous chromosomes.14-13

14.4DNA Damage and Repair14-13

  • DNA damage can affect both DNA backbone and bases.14-13
  • Most DNA damage is corrected by specialized repair enzymes.14-14

Chapter 15:Genetic Variation


15.1Genotype and Phenotype15-1

  • Genotype is the genetic makeup of a cell or organism; phenotype is its observed characteristics.15-1
  • The effect of a genotype often depends on several factors. 15-2
  • Some genetic differences are major risk factors for disease. 15-3
  • Not all genetic differences are harmful. 15-3
  • A few genetic differences are beneficial. 15-5

15.2Genetic Variation and Individual Uniqueness15-6

  • Areas of the genome with variable numbers of tandem repeats are useful in DNA typing. 15-6
  • Some polymorphisms add or remove restriction sites in the DNA. 15-7

15.3Genomewide Studies of Genetic Variation15-8

  • Single-nucleotide polymorphisms (SNPs) are single base changes in the genome. 15-8
  • How can genetic risk factors be detected? 15-9
  • SNPs can be detected by DNA microarrays. 15-9
  • Copy-number variation constitutes a significant proportion of genetic variation. 15-10

15.4Genetic Variation in Chromosomes15-11

  • Nondisjunction in meiosis results in extra or missing chromosomes. 15-11
  • Some human disorders result from nondisjunction. 15-12
  • How Do We Know?What is the genetic basis of Down syndrome? 15-13
  • Extra sex chromosomes have fewer effects than extra autosomes. 15-14
  • Nondisjunction is a major cause of spontaneous abortion. 15-15

Chapter 16:DNA Replication and Manipulation


16.1Early Theories of Inheritance16-1

  • Early theories of heredity predicted the transmission of acquired characteristics. 16-1
  • Belief in blending inheritance discouraged studies of hereditary transmission. 16-2

16.2The Foundations of Modern Transmission Genetics16-3

  • Mendel’s experimental organism was the garden pea. 16-3
  • In crosses, one of the traits was dominant in the offspring. 16-4

16.3Segregation: Mendel’s Key Discovery16-5

  • Genes come in pairs that segregate in the formation of reproductive cells. 16-6
  • The principle of segregation was tested by predicting the outcome of crosses. 16-7
  • A testcross is a mating to an individual with the homozygous recessive genotype. 16-7
  • Segregation of alleles reflects the separation of chromosomes in meiosis. 16-8
  • Dominance is not universally observed. 16-8
  • The principles of transmission genetics are statistical and stated in terms of probabilities. 16-9
  • Mendelian segregation preserves genetic variation. 16-10

16.4Independent Assortment16-10

  • Independent assortment is observed when genes segregate independently of one another. 16-11
  • Independent assortment reflects the random alignment of chromosomes in meiosis. 16-12
  • How Do We Know?How are simple traits inherited? 16-12
  • Phenotypic ratios can be modified by interactions between genes. 16-14

16.5Patterns of Inheritance Observed in Family Histories16-14

  • Dominant traits appear in every generation. 16-15
  • Recessive traits skip generations. 16-16
  • Many genes have multiple alleles. 16-16
  • Incomplete penetrance and variable expression can obscure inheritance patterns. 16-17
  • How do genetic tests identify disease risk factors? 16-17

Chapter 17:Beyond Mendel

Sex Chromosomes, Linkage, and Organelles17-1
color test

17.1The X and Y Sex Chromosomes17-1

  • In many animals, sex is genetically determined and associated with chromosomal differences. 17-2
  • Segregation of the sex chromosomes predicts a 1:1 ratio of females to males. 17-2

17.2Inheritance of Genes in the X Chromosome17-3

  • X-linked inheritance was discovered through studies of male fruit flies with white eyes. 17-3
  • Genes in the X chromosome exhibit a “crisscross” inheritance pattern. 17-4
  • X-linkage provided the first experimental evidence that genes are in chromosomes. 17-6
  • Genes in the X chromosome show characteristic patterns in human pedigrees. 17-7

17.3Genetic Linkage and Recombination17-10

  • Nearby genes in the same chromosome show linkage. 17-8
  • Recombination frequency is a measure of the distance between linked genes. 17-8
  • Genetic mapping assigns a location to each gene along a chromosome. 17-11
  • Genetic risk factors for disease can be localized by genetic mapping. 17-11
  • How Do We Know?Can recombination be used to construct a genetic map of a chromosome? 17-12

17.4Inheritance of Genes in the Y Chromosome17-13

  • Y-linked genes are transmitted from father to son to grandson. 17-13
  • How can the Y chromosome be used to trace ancestry? 17-14

17.5Inheritance of Mitochondrial and Chloroplast DNA17-15

  • Mitochondrial and chloroplast genomes often show uniparental inheritance. 17-15
  • Maternal inheritance is characteristic of mitochondrial diseases. 17-15
  • How can mitochondrial DNA be used to trace ancestry? 17-16

Chapter 18:The Genetic and Environmental Basis of Complex Traits


18.1Heredity and Environment18-2

  • Complex traits are affected by the environment. 18-2
  • Complex traits are affected by multiple genes. 18-3
  • The relative importance of genes and environment can be determined by differences among individuals. 18-4
  • Genetic and environmental effects can interact in unpredictable ways. 18-5

18.2Resemblance Among Relatives18-6

  • For complex traits, offspring resemble parents but show regression toward the mean. 18-6
  • Heritability is the proportion of the total variation due to genetic differences among individuals. 18-7

18.3Twin Studies18-8

  • Identical twins share the same genotype. 18-8
  • Twin studies help separate the effects of genes and environment in differences among individuals. 18-9
  • How Do We Know?What is the relative importance of genes and the environment for complex traits? 18-10

18.4Complex Traits in Health and Disease18-10

  • Most common diseases and birth defects are affected by many genes that each have relatively small effects. 18-11
  • Human height is affected by hundreds of genes. 18-12
  • Can personalized medicine lead to effective treatments of common diseases? 18-12

Chapter 19:Genetic and Epigenetic Regulation


19.1Chromatin to Messenger RNA in Eukaryotes19-2

  • Gene expression can be influenced by chemical modification of DNA or histones. 19-2
  • Gene expression can be regulated at the level of an entire chromosome. 19-3
  • Transcription is a key control point in gene expression. 19-5
  • RNA processing is also important in gene regulation. 19-6

19.2 Messenger RNA to Phenotype in Eukaryotes19-8

  • Small regulatory RNAs inhibit translation or promote RNA degradation. 19-8
  • Translational regulation controls the rate, timing, and location of protein synthesis. 19-9
  • Protein structure and chemical modification modulate protein effects on phenotype. 19-10
  • How do lifestyle choices affect expression of your personal genome? 19-10

19.3Transcriptional Regulation in Prokaryotes19-10

  • Transcriptional regulation can be positive or negative. 19-11
  • Lactose utilization in E. coli is the pioneering example of transcriptional regulation. 19-12
  • How Do We Know?How does lactose lead to the production of active ß-galactosidase enzyme? 19-12
  • The repressor protein binds with the operator and prevents transcription, but not in the presence of lactose. 19-13
  • The function of the lactose operon was revealed by genetic studies. 19-14
  • The lactose operon is also positively regulated by CRP–cAMP. 19-14
  • Transcriptional regulation determines the outcome of infection by a bacterial virus. 19-15

Chapter 20:Genes and DevelopmentVISUAL SYNTHESIS: Genetic Variation and Inheritance


20.1Genetic Programs of Development20-1

  • The fertilized egg is a totipotent cell. 20-2
  • Cellular differentiation increasingly restricts alternative fates. 20-2
  • How Do We Know?How do stem cells lose their ability to differentiate into any cell type? 20-3
  • Can cells with your personal genome be reprogrammed for new therapies? 20-5

20.2Hierarchical Control of Development20-5

  • Drosophila development proceeds through egg, larval, and adult stages. 20-5
  • The egg is a highly polarized cell. 20-6
  • Development proceeds by progressive regionalization and specification. 20-8
  • Homeotic genes determine where different body parts develop in the organism. 20-9

20.3Evolutionary Conservation of Key Transcription20-10

  • Factors in Development 20-11
  • Animals have evolved a wide variety of eyes. 20-11
  • Pax6 is a master regulator of eye development. 20-12

20.4Combinatorial Control in Development20-13

  • Floral differentiation is a model for plant development. 20-13
  • The identity of the floral organs is determined by combinatorial control. 20-14
  • 20.5 Cell Signaling in Development 20-15
  • A signaling molecule can cause multiple responses in the cell. 20-16
  • Developmental signals are amplified and expanded. 20-16
  • VISUAL SYNTHESIS: Genetic Variation and Inheritance20-18

Case 4:Malaria: Coevolution of Humans and a Parasite


Chapter 21:EvolutionAndrew Berry on Human Evolution

How Genotypes and Phenotypes Change over Time21-1
Andrew Berry on Human Evolution

Click here to see all video annotations.

21.1Genetic Variation21-1

  • Population genetics is the study of patterns of genetic variation. 21-1
  • Mutation and recombination are the two sources of genetic variation. 21-2
  • Mutations can be harmful, neutral, or beneficial. 21-2

21.2Measuring Genetic Variation21-3

  • To understand patterns of genetic variation, we require information about allele frequencies. 21-3
  • Early population geneticists relied on observable traits to measure variation. 21-4
  • Gel electrophoresis facilitates the detection of genetic variation. 21-4
  • DNA sequencing is the gold standard for measuring genetic variation. 21-4
  • How Do We Know?How is genetic variation measured? 21-5

21.3Evolution and the Hardy–Weinberg Equilibriumn21-6

  • Evolution is a change in allele or genotype frequency over time. 21-6
  • The Hardy–Weinberg equilibrium describes situations in which allele and genotype frequencies do not change. 21-6
  • The Hardy–Weinberg equilibrium translates allele frequencies into genotype frequencies. 21-7
  • The Hardy–Weinberg equilibrium is the starting point for population genetic analysis. 21-8

21.4Natural Selection21-8

  • Natural selection brings about adaptations. 21-8
  • The Modern Synthesis is a marriage between Mendelian genetics and Darwinian evolution.21-9
  • Natural selection increases the frequency of advantageous mutations and decreases the frequency of deleterious mutations. 21-10
  • What genetic differences have made some individuals more and some less susceptible to malaria? 21-10
  • Natural selection can be stabilizing, directional, or disruptive. 21-10
  • How Do We Know?How far can artificial selection be taken? 21-12
  • Sexual selection increases an individual’s reproductive success. 21-13

21.5Migration, Mutation, and Genetic Drift21-13

  • Migration reduces genetic variation between populations. 21-13
  • Mutation increases genetic variation. 21-13
  • Genetic drift is particularly important in small populations. 21-13

21.621.6 Molecular Evolution21-14

  • The extent of sequence difference between species is a function of the time since the species diverged. 21-15
  • The rate of the molecular clock varies. 21-15

Chapter 22:Species and SpeciationVISUAL SYNTHESIS: Speciation


22.1The Biological Species Concept22-1

  • The species is the fundamental evolutionary unit. 22-1
  • Reproductive isolation is the key to the Biological Species Concept (BSC). 22-2
  • The BSC is more useful in theory than in practice. 22-2
  • The BSC does not apply to asexual or extinct organisms. 22-3
  • Ring species and hybridization complicate the BSC. 22-4
  • Ecology and evolution can extend the BSC. 22-4

22.2Reproductive Isolation22-5

  • Pre-zygotic isolating factors occur before egg fertilization. 22-5
  • Post-zygotic isolating factors occur after egg fertilization. 22-6


  • Speciation is a by-product of the genetic divergence of separated populations. 22-6
  • Allopatric speciation is speciation that results from the geographical separation of populations. 22-6
  • How Do We Know? Can a vicariance event cause speciation? 22-8
  • Co-speciation is speciation that occurs in response to speciation in another species. 22-11
  • How did malaria come to infect humans? 22-11
  • Can sympatric populations—those not geographically separated—undergo speciation? 22-12
  • Speciation can occur instantaneously. 22-13

22.4Speciation and Selection22-15

  • Speciation can occur with or without natural selection. 22-15
  • Natural selection can enhance reproductive isolation. 22-15
  • VISUAL SYNTHESIS: Speciation 22-16

Chapter 23:Evolutionary Patterns

Phylogeny and Fossils23-1

23.1Reading a Phylogenetic Tree23-1

  • Phylogenetic trees provide hypotheses of evolutionary relationships. 23-2
  • The search for sister groups lies at the heart of phylogenetics. 23-3
  • A monophyletic group consists of a common ancestor and all its descendants. 23-4
  • Taxonomic classifications are information storage and retrieval systems. 23-4

23.2Building a Phylogenetic Tree23-3

  • Homology is similarity by common descent. 23-5
  • Shared derived characteristics enable biologists to reconstruct evolutionary history. 23-6
  • The simplest tree is often favored among multiple possible trees. 23-6
  • Molecular data complement comparative morphology in reconstructing phylogenetic history. 23-8
  • How Do We Know? Did an HIV-positive dentist spread the AIDS virus to his patients? 23-10
  • Phylogenetic trees can help solve practical problems. 23-10

23.3The Fossil Record23-11

  • Fossils provide unique information. 23-11
  • Fossils provide a selective record of past life. 23-12
  • Geological data indicate the age and environmental setting of fossils. 23-14
  • Fossils can contain unique combinations of characters. 23-16
  • How Do We Know? Can fossils bridge the evolutionary gap between fish and tetrapod vertebrates? 23-18
  • Rare mass extinctions have altered the course of evolution. 23-18

23.4Comparing Evolution’s Two Great Patterns23-19

  • Phylogeny and fossils complement each other. 23-19
  • Agreement between phylogenies and the fossil record provides strong evidence of evolution.23-19

Chapter 24:Human Origins and Evolution


24.1The Great Apes24-1

  • Comparative anatomy shows that the human lineage branches off the great apes tree. 24-1
  • Molecular analysis reveals that our lineage split from the chimpanzee lineage about 5-7 million years ago. 24-3
  • How Do We Know? How closely related are humans and chimpanzees? 24-3
  • The fossil record gives us direct information about our evolutionary history. 24-4

24.2African Origins24-6

  • Studies of mitochondrial DNA reveal that modern humans evolved in Africa. 24-6
  • How Do We Know? When and where did the most recent common ancestor of all living humans live? 24-6
  • Neanderthals disappear from the fossil record as modern humans appear but have contributed to the modern human gene pool. 24-8

24.3Distinct Features of Our Species24-9

  • Bipedalism was a key innovation. 24-9
  • Adult humans share many features with juvenile chimpanzees. 24-10
  • Humans have large brains relative to body size. 24-11
  • The human and chimpanzee genomes help us identify genes that make us human. 24-12

24.4Human Genetic Variation24-12

  • The prehistory of our species has had an impact on the distribution of genetic variation. 24-13
  • The recent spread of modern humans means that there are few genetic differences between groups. 24-14
  • Some human differences have likely arisen by natural selection. 24-14
  • What human genes are under selection for resistance to malaria? 24-15

24.5Culture, Language, and Consciousness24-15

  • Culture changes rapidly. 24-15
  • Is culture uniquely human? 24-16
  • Is language uniquely human? 24-17
  • Is consciousness uniquely human? 24-18

Part Two: From Organisms to the Environment

Chapter 25:Cycling CarbonAndrew Knoll on The Prominent Position of the Carbon Cycle

Andrew Knoll on The Prominent Position of the Carbon Cycle

Click here to see all video annotations.

25.1The Short-Term Carbon Cycle25-1

  • Photosynthesis and respiration are key processes in short-term carbon cycling. 25-2
  • The regular oscillation of CO2 reflects the seasonality of photosynthesis in the Northern Hemisphere. 25-2
  • Human activities play an important role in the modern carbon cycle. 25-3
  • How Do We Know? How much CO2 was in the atmosphere 1000 years ago? 25-3
  • Carbon isotopes show that much of the CO2 added to air over the past half century comes from burning fossil fuels. 25-4
  • How Do We Know? What is the major source of the carbon dioxide that has accumulated in Earth’s atmosphere over the last two centuries? 25-4

25.2The Long-Term Carbon Cycle25-3

  • Reservoirs and fluxes are key in long-term carbon cycling. 25-6
  • Physical processes add and remove CO2 from the atmosphere. 25-7
  • Records of atmospheric composition over 400,000 years show periodic shifts in CO2 content. 25-9
  • Variations in atmospheric CO2 over hundreds of millions of years reflect plate tectonics and evolution. 25-11

25.3The Carbon Cycle, Ecology, and Evolution25-12

  • Food webs trace the movement of carbon through communities. 25-12
  • Trophic pyramids trace the flow of energy through communities. 25-13
  • The diversity of photosynthetic organisms reflects adaptation to a wide range of environments. 25-13
  • The diversity of respiring organisms reflects many sources of food. 25-14
  • The carbon cycle provides a framework for understanding life’s evolutionary history. 25-14
  • The Human Microbiome: Diversity Within C5-2

Case 5:The Human Microbiome: Diversity Within


Chapter 26:Bacteria and Archaea


26.1Two Prokaryotic Domains26-1

  • The bacterial cell is small but powerful. 26-1
  • Diffusion limits cell size in bacteria. 26-2
  • Horizontal gene transfer promotes genetic diversity in bacteria. 26-4
  • The Archaea form a second prokaryotic domain. 26-5

26.2An Expanded Carbon Cycle26-6

  • Many photosynthetic bacteria do not produce oxygen. 26-7
  • Many bacteria respire without oxygen. 26-8
  • Photoheterotrophs obtain energy from light but obtain carbon from preformed organic molecules. 26-8
  • Chemoautotrophy is a uniquely prokaryotic metabolism. 26-9

26.3Other Biogeochemical Cycles26-10

  • Bacteria and archaeons dominate Earth’s sulfur cycle. 26-10
  • The nitrogen cycle is also driven by bacteria and archaeons. 26-10

26.4The Diversity of Bacteria26-12

  • Bacterial phylogeny is a work in progress. 26-12
  • How Do We Know? How many kinds of bacterium live in the oceans? 26-13
  • What, if anything, is a bacterial species? 26-14
  • Proteobacteria are the most diverse bacteria. 26-15
  • The gram-positive bacteria include organisms that cause and cure disease. 26-15
  • Photosynthesis is widely distributed on the bacterial tree. 26-15

26.5The Diversity of Archaea26-16

  • The archaeal tree has anaerobic, hyperthermophilic organisms near its base. 26-17
  • The Crenarchaeota and and Euryarchaeota both include acid-loving microorganisms. 26-18
  • Euryarchaeote archaeons include heat-loving, methane-producing, and salt-loving microorganisms. 26-18
  • Thaumarchaeota may be the most abundant cells in the oceans. 26-18
  • How Do We Know? How abundant are archaeons in the oceans? 26-19

26.6The Evolutionary History of Prokaryotes26-20

  • Life originated early in our planet’s history. 26-20
  • Prokaryotes have coevolved with eukaryotes. 26-21
  • How do intestinal bacteria influence human health? 26-22

Chapter 27:Eukaryotic Cells

Origins and Diversity27-1
Multicellular Animals

27.1The Eukaryotic Cell: A Review27-1

  • Internal protein scaffolding and dynamic membranes organize the eukaryotic cell. 27-1
  • In eukaryotic cells, energy metabolism is localized in mitochondria and chloroplasts. 27-2
  • The organization of the eukaryotic genome also helps explain eukaryotic diversity. 27-2
  • Sex promotes genetic diversity in eukaryotes and gives rise to distinctive life cycles. 27-3

27.2Eukaryotic Origins27-4

  • What role did symbiosis play in the origin of chloroplasts? 27-4
  • How Do We Know? What is the evolutionary origin of chloroplasts? 27-5
  • What role did symbiosis play in the origin of mitochondria? 27-6
  • How did the eukaryotic cell originate? 27-7
  • In the oceans, many single-celled eukaryotes harbor symbiotic bacteria. 27-9

27.3Eukaryotic Diversity27-9

  • Our own group, the opisthokonts, is the most diverse eukaryotic superkingdom. 27-10
  • Amoebozoans include slime molds that produce multicellular structures. 27-12
  • Archaeplastids are photosynthetic organisms, including land plants. 27-13
  • Other photosynthetic organisms occur in the stramenopiles and alveolates. 27-15
  • Photosynthesis spread through eukaryotes by repeated endosymbioses involving eukaryotic algae. 27-16
  • How Do We Know? How did photosynthesis spread through the Eukarya? 27-18
  • The first branch of the eukaryotic tree may separate animals and slime molds from plants and diatoms. 27-19

27.4The Fossil Record of Protists27-20

  • Fossils show that eukaryotes existed at least 1800 million years ago. 27-20
  • Protists have continued to diversify during the age of animals. 27-21

Chapter 28:Being Multicellular

Multicellular Animals

28.1 The Phylogenetic Distribution of Multicellular Organisms 28-1

  • Simple multicellularity is widespread among eukaryotes. 28-1
  • Complex multicellularity evolved several times. 28-3

28.2 Diffusion vs. Bulk Transport 28-4

  • Diffusion is effective only over short distances. 28-4
  • Animals achieve large size by circumventing limits imposed by diffusion. 28-4
  • Complex multicellular organisms have structures specialized for bulk transport. 28-5

28.3 How to Build a Multicellular Organism 28-6

  • Complex multicellularity requires adhesion between cells. 28-6
  • How Do We Know? How do bacteria influence the life cycles of choanoflagellates? 28-6
  • How did animal cell adhesion originate? 28-7
  • Complex multicellularity requires communication between cells. 28-7
  • Complex multicellularity requires a genetic program for coordinated growth and cell differentiation. 28-8

28.4 Variations on a Theme: Plants vs. Animals 28-10

  • Cell walls shape patterns of growth and development in plants. 28-10
  • Animal cells can move relative to one another. 28-11

28.5 The Evolution of Complex Multicellularity 28-12

  • Complex multicellularity appeared in the oceans 575 to 555 million years ago. 28-12
  • Oxygen is necessary for complex multicellular life. 28-13
  • Land plants evolved from green algae that could carry out photosynthesis on land. 28-14
  • Regulatory genes have played an important role in the evolution of complex multicellular organisms. 28-15
  • How Do We Know? What controls color pattern in butterfly wings? 28-15

Case 6:Agriculture: Feeding a Growing Population


Chapter 29:Plant Structure and Function Missy Holbrook on the Plant Chapters

Moving Photosynthesis onto Land Missy Holbrook on CAM and C4 coverage29-1
Missy Holbrook on the Plant Chapters

Click here to see all video annotations.

29.1Plant Structure and Function: An Evolutionary Perspective29-1

29.2 The Leaf: Acquiring CO2 While Avoiding Dessication 29-2

  • CO2 uptake results in water loss. 29-3
  • The cuticle restricts water loss from leaves but inhibits the uptake of CO2. 29-4
  • Stomata allow leaves to regulate water loss and carbon gain. 29-5
  • CAM plants use nocturnal CO2 storage to avoid water loss during the day. 29-6
  • C4 plants suppress photorespiration. 29-7
  • How Do We Know? How do we know that C4 photosynthesis suppresses photorespiration? 29-8

29.3 The Stem: Transport of Water Through Xylem 29-8

  • Xylem provides a low-resistance pathway for the movement of water. 29-9
  • Water is pulled through xylem by an evaporative pump. 29-10
  • How Do We Know? How large are the forces that allow leaves to pull water from the soil? 29-10
  • The structure of xylem conduits reduces the risks of collapse and cavitation. 29-11

29.4 The Stem: Transport of Carbohydrates Through Phloem 29-12

  • Carbohydrates are pushed through phloem by an osmotic pump. 29-13
  • Phloem feeds both the plant and the rhizosphere. 29-14

29.5 The Root: Uptake of Water and Nutrients from the Soil 29-15

  • Nutrient uptake by roots is highly selective. 29-15
  • Nutrient uptake requires energy. 29-16
  • Mycorrhizae enhance the uptake of phosphorus. 29-17
  • Symbiotic nitrogen-fixing bacteria supply nitrogen to both plants and ecosystems. 29-17
  • How has nitrogen availability influenced agricultural productivity? 29-18

Missy Holbrook on CAM and C4 coverage

Click here to see all video annotations.

Chapter 30:Plant Reproduction

Finding Mates and Dispersing Young30-1

30.1 The Plant Life Cycle and Evolution of Pollen and Seeds 30-1

  • The algal sister groups of land plants have one multicellular generation in their life cycle. 30-2
  • Bryophytes illustrate how the alternation of generations allows the dispersal of spores in the air. 30-2
  • Vascular plants evolved a large photosynthetic sporophyte generation. 30-4
  • In seed plants, the transport of pollen in air allows fertilization to occur in the absence of external sources of water. 30-6
  • Seeds enhance dispersal and establishment of the next sporophyte generation. 30-8

30.2 Flowering Plants 30-9

  • Flowers are reproductive shoots specialized for the production, transfer, and receipt of pollen. 30-9
  • The diversity of floral morphology is related to modes of pollination. 30-10
  • Angiosperms have mechanisms to increase outcrossing. 30-12
  • How Do We Know? Can pollinator shifts enhance rates of species formation? 30-13
  • Angiosperms delay provisioning their ovules until after fertilization. 30-15
  • Fruits enhance the dispersal of seeds. 30-15

30.3 Timing of Reproductive Events 30-17

  • Flowering time is affected by day length. 30-17
  • Photoreceptors enable plants to measure day length. 30-17
  • Vernalization prevents plants from flowering until winter has passed. 30-18
  • Dormant seeds can delay germination if they detect the presence of plants overhead. 30-18
  • How Do We Know? How do plants measure day length? 30-19
  • How Do We Know? How do seeds detect the presence of plants growing overhead? 30-20
  • What is the basis for the spectacular increases in the yield of cereal grains during the Green Revolution? 30-21

30.4 Vegetative Reproduction 30-22

Chapter 31:Plant Growth and Development

Building the Plant Body31-1
Tree Rings

31.1 Shoot Growth and Development 31-2

  • Shoots grow by adding new cells at their tips. 31-2
  • Stem elongation occurs primarily in a zone just below the apical meristem where new cells elongate. 31-3
  • The shoot apical meristem controls the production and arrangement of leaves. 31-4
  • The development of new apical meristems allows stems to branch. 31-5
  • Flowers grow from and consume shoot meristems. 31-6

31.2 Plant Hormones 31-6

  • Hormones affect the growth and differentiation of plant cells. 31-7
  • Auxin transport guides the development of vascular connections between leaves and stems. 31-8
  • What is the developmental basis for the shorter stems of high-yielding rice and wheat? 31-9
  • Branching is affected by multiple hormones. 31-10

31.3 Secondary Growth 31-10

  • Shoots produce two types of lateral meristem. 31-10
  • The vascular cambium produces secondary xylem and phloem. 31-11
  • The cork cambium produces an outer protective layer. 31-12
  • Wood has both mechanical and transport functions. 31-12

31.4 Root Growth and Development 31-13

  • Roots grow by producing new cells at their tips. 31-14
  • The formation of new root apical meristems allows roots to branch. 31-15
  • The structures and functions of root systems are diverse. 31-15

31.5 The Environmental Context of Growth and Development 31-16

  • Plants orient the growth of their stems and roots by light and gravity. 31-17
  • How Do We Know? How do plants grow toward light? 31-17
  • Plants grow taller and branch less when light levels are low. 31-19
  • Roots elongate more and branch less when water is scarce. 31-19
  • Exposure to wind results in shorter and stronger stems. 31-20
  • Plants use day length as a cue to prepare for winter. 31-20

Chapter 32:Plant Defense

Keeping the World Green32-1

32.1 Protection Against Pathogens 32-1

  • Plant pathogens infect and exploit host plants by a variety of mechanisms. 32-2
  • An innate immune system allows plants to detect and respond to pathogens. 32-3
  • Plants respond to infections by isolating infected regions. 32-4
  • Mobile signals trigger defenses in uninfected tissues. 32-5
  • How Do We Know? Can plants develop immunity to specific pathogens? 32-6
  • Plants defend against viral infections by producing siRNA. 32-6
  • A pathogenic bacterium provides a way to modify plant genomes. 32-7

32.2 Defense Against Herbivores 32-8

  • Plants use mechanical and chemical defenses to avoid being eaten. 32-8
  • Diverse chemical compounds deter herbivores. 32-9
  • Some plants provide food and shelter for ants, which actively defend them. 32-11
  • Grasses can regrow quickly following grazing by mammals. 32-12

32.3 Allocating Resources to Defense 32-13

  • Plants can sense and respond to herbivores. 32-13
  • Plants produce volatile signals that attract insects that prey upon herbivores. 32-14
  • Nutrient-rich environments select for plants that allocate more resources to growth than to defense. 32-14
  • How Do We Know? Can plants communicate? 32-14
  • Exposure to multiple threats can lead to trade-offs. 32-16

32.4 Defense and Plant Diversity 32-16

  • Pathogens, herbivores, and seed predators can increase plant biodiversity. 32-16
  • The evolution of new defenses may allow plants to diversify. 32-17
  • Can modifying plants genetically protect crops from herbivores and pathogens? 32-17

Chapter 33:Plant DiversityAndrew Knoll on Plant and Animal Diversity Following Physiology

VISUAL SYNTHESIS: Angiosperms: Reproduction, Growth, and Photosynthesis33-1
Andrew Knoll on Plant and Animal Diversity Following Physiology

Click here to see all video annotations.

33.1 Plant Diversity: An Evolutionary Overview33-1

33.2 Bryophytes 33-2

  • Bryophytes are small, simple, and tough. 33-3
  • Bryophytes exhibit several cases of convergent evolution with the vascular plants. 33-4
  • Sphagnum moss plays an important role in the global carbon cycle. 33-5

33.3 Spore-Dispersing Vascular Plants 33-5

  • Rhynie cherts provide a window into the early evolution of vascular plants. 33-5
  • Lycophytes are the sister group of all other vascular plants. 33-6
  • Ancient lycophytes included giant trees that dominated coal swamps about 320 million years ago. 33-7
  • How Do We Know? Did woody plants evolve more than once? 33-8
  • Ferns and horsetails are morphologically and ecologically diverse. 33-9
  • An aquatic fern contributes to rice production. 33-10

33.4 Gymnosperms 33-11

  • Cycads and ginkgos are the earliest diverging groups of living gymnosperms. 33-11
  • Conifers are forest giants that thrive in dry and cold climates. 33-13
  • Gnetophytes are gymnosperms that have independently evolved xylem vessels and double fertilization. 33-14

33.5 Angiosperms 33-14

  • Angiosperm diversity remains a puzzle. 33-15
  • Early diverging angiosperms have low diversity. 33-15
  • Monocots develop according to a novel body plan. 33-16
  • How Do We Know? When did grasslands expand over the land surface? 33-18
  • Eudicots are the most diverse group of angiosperms. 33-19
  • What can be done to protect the genetic diversity of crop species? 33-20
  • VISUAL SYNTHESIS: Angiosperms: Reproduction, Growth, and Photosynthesis 33-22

Chapter 34:Fungi

Structure, Function, and Diversity 34-1

34.1 Growth and Nutrition 34-1

  • Hyphae permit fungi to explore their environment for food resources. 34-2
  • Fungi transport materials within their hyphae. 34-2
  • Not all fungi produce hyphae. 34-2
  • Fungi are principal decomposers of plant tissues.34-3
  • Fungi are important plant and animal pathogens. 34-4
  • Many fungi form symbiotic associations with plants and animals. 34-5
  • Lichens are symbioses between a fungus and a green alga or a cyanobacterium. 34-6

34.2 Reproduction 34-7

  • Fungi proliferate and disperse using spores. 34-7
  • Multicellular fruiting bodies facilitate the dispersal of sexually produced spores. 34-8
  • How Do We Know? What determines the shape of fungal spores that are ejected into the air? 34-9
  • The fungal life cycle often includes a stage in which haploid cells fuse, but nuclei do not. 34-10
  • Genetically distinct mating types promote outcrossing. 34-11
  • Fungi that lack sexual reproduction have other means of generating genetic diversity. 34-11

34.3 Diversity 34.12

  • Fungi are highly diverse. 34-12
  • Fungi evolved from aquatic, unicellular, and flagellated ancestors. 34-12
  • Zygomycetes produce hyphae undivided by septa. 34-13
  • Glomeromycetes form endomycorrhizae. 34-14
  • The Dikarya produce regular septa during mitosis. 34-14
  • Ascomycetes are the most diverse group of fungi. 34-14
  • How Do We Know? Can a fungus influence the behavior of an ant? 34-16
  • Basidiomycetes include smuts, rusts, and mushrooms. 34-17
  • How do fungi threaten global wheat production?

Case 7:Predator–Prey: A Game of Life and Death


Chapter 35:Animal Nervous Systems James Morris on The Animal Physiology Chapters

James Morris on The Animal Physiology Chapters

Click here to see all video annotations.

35.1 Nervous System Function and Evolution 35-1

  • Animal nervous systems have three types of nerve cell. 35-2
  • Nervous systems range from simple to complex. 35-2
  • What body features arose as adaptations for successful predation? 35-4

35.2 Neuron Structure 35-4

  • Neurons share a common organization. 35-5
  • Neurons differ in size and shape. 35-5
  • Neurons are supported by other types of cell. 35-6

35.3 Neuron Function 35-6

  • The resting membrane potential is negative and results from the movement of potassium ions. 35-6
  • Neurons are excitable cells that transmit information by action potentials. 35-8
  • Neurons propagate action potentials along their axons by sequentially opening and closing adjacent Na+ and K+ ion channels. 35-8
  • How Do We Know? What is the resting membrane potential and what changes in electrical activity occur during an action potential? 35-11
  • Nerve cells communicate at synapses. 35-12
  • Signals between neurons can be excitatory or inhibitory. 35-13

35.4 Nervous System Organization 35-15

  • Nervous systems are organized into peripheral and central components. 35-15
  • Nervous systems have voluntary and involuntary components. 35-16
  • The nervous system helps to maintain homeostasis. 35-17
  • Simple reflex circuits provide rapid responses to stimuli. 35-18

Chapter 36:Animal Sensory Systems and Brain Function

A Brain

36.1 Animal Sensory Systems 36-1

  • Specialized sensory receptors evolved to sample features of the environment. 36-2
  • Stimuli are sensed by changes in membrane potential and signaled by changes in the firing rate of action potentials. 36-4

36.2 Smell and Taste 36-5

  • Smell and taste depend on chemoreception of molecules carried in the environment and in food. 36-5

36.3 Sensing Gravity, Movement, and Sound 36-6

  • Hair cells sense gravity and motion. 36-7
  • Hair cells detect the physical vibrations of sound. 36-8
  • How have sensory systems evolved in predators and prey? 36-10

36.4 Vision 36-10

  • All animals use a similar photosensitive protein called opsin to detect light. 36-11
  • Animals see the world through different types of eyes. 36-11
  • The structure and function of the vertebrate eye underlie image processing. 36-13
  • Color vision detects different wavelengths of light. 36-14
  • Local sensory processing of light determines basic features of shape and movement. 36-15
  • How Do We Know? How does the retina process visual information? 36-16

36.5 Brain Organization and Function 36-17

  • The brain processes and integrates information received from different sensory systems. 36-17
  • The brain is divided into lobes with specialized functions. 36-18

36.6 Memory and Cognition 36-20

  • The brain serves an important role in memory and learning. 36-20
  • Cognition involves brain information processing and decision making. 36-21

Chapter 37:Animal Movement

Muscles and Skeletons37-1

37.1 Muscles: Biological Motors That Generate Force and Produce Movement 37-1

  • Muscles can be striated or smooth. 37-1
  • Skeletal muscle fibers are organized into repeating contractile units called sarcomeres. 37-2
  • Muscles contract by the sliding of myosin and actin filaments. 37-4
  • Calcium regulates actin–myosin interaction through excitation–contraction coupling. 37-6
  • Calmodulin regulates Ca2+ activation and relaxation of smooth muscle. 37-7

37.2 Muscle Contractile Properties 37-8

  • Muscle length affects actin–myosin overlap and generation of force. 37-8
  • How Do We Know? How does filament overlap affect force generation in muscles? 37-8
  • Muscle force and shortening velocity are inversely related. 37-9
  • Antagonist pairs of muscles produce reciprocal motions at a joint. 37-10
  • Muscle force is summed by an increase in stimulation frequency and the recruitment of motor units. 37-10
  • Skeletal muscles have slow-twitch and fast-twitch fibers. 37-11
  • How do different types of muscle fiber affect the speed of predators and prey? 37-12

37.3 Animal Skeletons 37-13

  • Hydrostatic skeletons support animals by muscles that act on a fluid-filled cavity. 37-13
  • Exoskeletons provide hard external support and protection. 37-14
  • The rigid bones of vertebrate endoskeletons are jointed for motion and can be repaired if damaged. 37-15

37.4 Vertebrate Skeletons 37-16

  • Vertebrate bones form by intramembranous and endochondral ossification. 37-16
  • Joint shape determines range of motion and skeletal muscle organization. 37-17
  • Muscles exert forces by skeletal levers to produce joint motion. 37-18

Chapter 38:Animal Endocrine Systems

Endocrine System

38.1An Overview of Endocrine Function38-1

  • The endocrine system helps to regulate an organism’s response to its environment. 38-1
  • The endocrine system is involved in growth and development. 38-2
  • How Do We Know? How are growth and development controlled in insects? 38-3
  • The endocrine system underlies homeostasis. 38-5

38.2 Properties of Hormones 38-7

  • Three main classes of hormone are peptide, amine, and steroid hormones. 38-7
  • Hormonal signals are typically amplified. 38-8
  • Hormones act specifically on cells with receptors that bind the hormone. 38-11
  • Hormones are evolutionarily conserved molecules with diverse functions. 38-11

38.3 The Vertebrate Endocrine System 38-12

  • The pituitary gland integrates diverse bodily functions by secreting hormones in response to signals from the hypothalamus. 38-13
  • Many targets of pituitary hormones are endocrine tissues that also release hormones. 38-14
  • Other endocrine organs have diverse functions. 38-15
  • How does the endocrine system influence predators and prey? 38-15

38.4 Other Forms of Chemical Communication 38-16

  • Local chemical signals regulate neighboring target cells. 38-16
  • Pheromones are chemical compounds released into the environment to signal behavioral cues to other species members. 38-17

Chapter 39:Animal Cardiovascular and Respiratory Systems

Oxygen Delivery

39.1 Delivery of Oxygen and Elimination of Carbon Dioxide 39-1

  • Diffusion governs gas exchange over short distances. 39-2
  • Bulk flow moves fluid over long distances. 39-2

39.2 Respiratory Gas Exchange 39-3

  • Many aquatic animals breathe through gills. 39-4
  • Insects breathe air through tracheae. 39-5
  • Terrestrial vertebrates breathe by tidal ventilation of internal lungs. 39-6
  • Mammalian lungs are well adapted for gas exchange. 39-7
  • The structure of bird lungs allows unidirectional airflow for increased oxygen uptake. 39-8
  • Voluntary and involuntary mechanisms control breathing. 39-9

39.3 Oxygen Transport by Hemoglobin 39-10

  • Hemoglobin is an ancient molecule with diverse roles related to oxygen binding and transport. 39-10
  • How Do We Know? What is the molecular structure of hemoglobin and myoglobin? 39-10
  • Hemoglobin reversibly binds oxygen. 39-11
  • Myoglobin stores oxygen, enhancing delivery to muscle mitochondria. 39-12
  • Many factors affect hemoglobin-oxygen binding. 39-12

39.4 Circulatory Systems 39-13

  • Circulatory systems have vessels of different sizes to facilitate bulk flow and diffusion. 39-15
  • Arteries are muscular, elastic vessels that carry blood away from the heart under high pressure. 39-15
  • Veins are thin-walled vessels that return blood to the heart under low pressure. 39-16
  • Compounds and fluid move across capillary walls by diffusion, filtration, and osmosis. 39-16
  • How do hormones and nerves provide homeostatic regulation of blood flow as well as allow an animal to respond to stress? 39-17

39.5 The Evolution, Structure, and Function of the Heart 39-17

  • Fish have two-chambered hearts and a single circulatory system. 39-18
  • Amphibians and reptiles have more three-chambered hearts and partially divided circulations. 39-18
  • Mammals and birds have four-chambered hearts and fully divided pulmonary and systemic circulations. 39-19
  • Cardiac muscle cells are electrically connected to contract in synchrony. 39-20
  • Cardiac output is regulated by the autonomic nervous system. 39-21

Chapter 40:Animal Metabolism, Nutrition, and DigestionVISUAL SYNTHESIS: Homeostasis and Thermoregulation


40.1Patterns of Animal Metabolism40-x

  • Animals rely on anaerobic and aerobic metabolism. 40-x
  • Metabolic rate varies with activity level.40-2
  • Does body temperature limit activity level in predators and prey?40-x
  • Metabolic rate is affected by body size.40-x
  • Metabolic rate is linked to body temperature.40-x
  • How Do We Know? How is metabolic rate affected by running speed and body size?40-x
  • VISUAL SYNTHESIS: Homeostasis and Thermoregulation40-x

40.2Animal Nutrition and Diet40-x

  • Energy balance is a form of homeostasis.40-x
  • An animal’s diet must supply nutrients that it cannot synthesize.40-x

40.3Adaptations for Feeding40-x

  • Suspension filter feeding is common in many aquatic animals.40-x
  • Large aquatic animals apprehend prey by suction feeding and active swimming.40-x
  • Jaws and teeth provide specialized food capture and mechanical breakdown of food.40-x

40.4Digestion and Absorption of Food40-x

  • The digestive tract has regional specializations.40-x
  • Digestion begins in the mouth.40-13
  • The stomach is an initial storage and digestive chamber.40-x
  • The small intestine is specialized for nutrient absorption.40-x
  • The large intestine reabsorbs water and stores waste.40-x
  • The lining of the digestive tract is composed of distinct layers.40-x
  • Plant-eating animals have specialized digestive tracts that reflect their diets.40-x

Chapter 41:Animal Renal Systems

Water and Waste41-1
Elephants drinking water

41.1Water and Electrolyte Balance41-1

  • Osmosis governs the movement of water across cell membranes41-x
  • Osmoregulation is the control of osmotic pressure inside cells and organisms.41-x
  • Osmoconformers match their internal solute concentration to that of the environment.41-x
  • Osmoregulators have internal solute concentrations that differ from that of their environment.41-x
  • Can the loss of water and electrolytes in exercise be exploited as a strategy to hunt prey? 41-x

41.2Excretion of Wastes in Relation to Electrolyte Balance40-x

  • The excretion of nitrogenous wastes is linked to an animal’s habitat and evolutionary history.40-x
  • Excretory organs work by filtration, reabsorption, and secretion.40-x
  • Animals have diverse excretory organs.40-7
  • Vertebrates filter blood under pressure through paired kidneys.40-x

41.3Structure and Function of the Mammalian Kidney 40-x

  • The mammalian kidney has an outer cortex and inner medulla.40-x
  • Glomerular filtration isolates wastes carried by the blood along with water and small solutes.40-x
  • The proximal convoluted tubule reabsorbs solutes by active transport.40-x
  • The loop of Henle acts as a countercurrent multiplier to create a concentration gradient from the cortex to the medulla.40-x
  • How Do We Know? How does the mammalian kidney produce concentrated urine?40-x
  • The distal convoluted tubule secretes additional wastes.40-x
  • The final concentration of urine is determined in the collecting ducts and is under hormonal control.40-x
  • The kidneys help regulate blood pressure and blood volume.40-x

Chapter 42:Animal Reproductions and DevelopmentVISUAL SYNTHESIS: Reproduction and Development


42.1The Evolutionary History of Reproduction42-1

  • Asexual reproduction produces clones.42-2
  • Sexual reproduction involves the formation and fusion of gametes.42-3
  • Many species reproduce both sexually and asexually.42-4
  • Exclusive asexuality is often an evolutionary dead end.42-4
  • How Do We Know? Do bdelloid rotifers only reproduce asexually?42-6

42.2Movement onto Land and Reproductive Adaptations42-7

  • Fertilization can take place externally or internally.42-7
  • r-strategists and K-strategists differ in number of offspring and parental care.42-8
  • Oviparous animals lay eggs, and viviparous animals give birth to live young.42-8

42.3Human Reproductive Anatomy and Physiology42-9

  • The male reproductive system is specialized for the production and delivery of sperm.42-9
  • The female reproductive system produces eggs and supports the developing embryo.42-12
  • Hormones regulate the human reproductive system.42-13

42.4Gamete Formation to Birth in Humans42-15

  • Male and female gametogenesis have shared and distinct features.42-15
  • Fertilization occurs when a sperm fuses with an oocyte.42-16
  • The first trimester includes cleavage, gastrulation, and organogenesis.42-17
  • The second and third trimesters are characterized by fetal growth.42-19
  • VISUAL SYNTHESIS: Reproduction and Development42-20
  • Childbirth is initiated by hormonal changes.42-22

Chapter 43:Animal Immune Systems

Virus near blood

43.1Innate Immunity43-1

  • The skin and mucous membranes provide the first line of defense against infection.43-x
  • Some cells act broadly against a diverse array of pathogens.43-x
  • Phagocytes recognize foreign molecules and send signals to other cells.43-x
  • Inflammation is a coordinated response to tissue injury.43-x
  • The complement system participates in the innate and adaptive immune systems.43-x

43.2Adaptive Immunity: B cells, Antibodies, and Humoral Immunity43-x

  • B cells produce antibodies.43-x
  • Mammals produce five classes of antibody with different biological functions.43-x
  • Clonal selection is the basis for antibody specificity.43-x
  • Clonal selection also explains immunological memory.43-x
  • Genomic rearrangement creates antibody diversity.43-x
  • How Do We Know? How is antibody diversity generated?43-x

43.3Adaptive Immunity: T cells and Cell-Mediated Immunity43-x

  • T cells include helper and cytotoxic cells.43-x
  • T cells have T cell receptors on their surface.43-x
  • T cell activation requires the presence of antigen in association with MHC proteins.43-x
  • The ability to distinguish between self and non-self is acquired during T cell maturation.43-x

43.4Three Infections: By a Virus, a Bacterium, and a Eukaryote43-x

  • The flu virus evades the immune system through antigenic drift and shift.43-x
  • Tuberculosis is caused by a slow-growing, intracellular bacterium.43-x
  • The malaria parasite uses antigenic variation to change surface molecules.43-x
  • The ability to distinguish between self and non-self is acquired during T cell maturation.43-x

Case 8:Biodiversity Hotspots: Rain Forests and Reefs


Chapter 44:Animal DiversityAndrew Knoll on Plant and Animal Diversity Following Physiology

VISUAL SYNTHESIS: Diversity through Time44-1

44.1A Tree of Life for More than a Million Animal Species44-1

  • Phylogenetic trees propose an evolutionary history of animals.44-x
  • Nineteenth-century biologists grouped animals by anatomical and embryological features.44-x
  • Molecular sequence comparisons have confirmed some relationships and raised new questions.44-x

44.2The Simplest Animals: Sponges, Cnidarians, Ctenophores, and Placozoans44-x

  • Sponges are simple and widespread in the oceans.44-x
  • Cnidarians are the architects of life’s largest constructions: coral reefs.44-x
  • Ctenophores and placozoans represent the extremes of body organization among early-branching animals.44-x

44.3Bilaterian Animals44-x

  • Lophotrozochoans make up nearly half of all animal phyla, including the diverse and ecologically important annelids and mollusks.44-x
  • Ecdysozoans include arthropods, the most diverse animals.44-x
  • How Do We Know? How did the diverse feeding appendages of arthropods arise?44-x
  • Deuterostomes include humans and other chordates, but also acorn worms and sea stars.44-x
  • Chordates include vertebrates, cephalochordates, and tunicates.44-x

44.4Vertebrate Diversity44-x

  • Fish are the earliest branching and most diverse vertebrate animals.44-x
  • The common ancestor of tetrapods had four limbs.44-x
  • Amniotes evolved terrestrial eggs.44-x

44.5The Evolutionary History of Animals44-x

  • Fossils and phylogeny show that animal forms were initially simple but rapidly evolved complexity.44-x
  • The animal body plans we see today emerged during the Cambrian Period.44-x
  • Animals began to colonize the land 420 million years ago.44-x
  • How have coral reefs changed through time?
  • VISUAL SYNTHESIS: Diversity through Time44-x

Chapter 45:Animal Behavior


45.1Tinbergen’s Questions45-1

45.2Genes and Behavior45-x

  • The fixed action pattern is a stereotyped behavior.45-x
  • The nervous system processes stimuli and evokes behaviors.45-x
  • Hormones can trigger certain behaviors.45-x
  • Breeding experiments can help determine the degree to which a behavior is genetic.45-x
  • Molecular techniques provide new ways of testing the role of genes in behavior.45-x
  • How Do We Know? Can genes influence behavior?45-x


  • Non-associative learning occurs without linking two events.45-x
  • Associative learning occurs when two events are linked.45-x
  • Learning takes many forms.45-x
  • How Do We Know? To what extent are insects capable of learning?45-x

45.4Orientation, Navigation, and Biological Clocks45-x

  • Orientation involves a directed response to a stimulus.45-x
  • Navigation is illustrated by the remarkable ability of homing in birds.45-x
  • Biological clocks provide important time cues for many behaviors.45-x
  • How Do We Know? Does a biological clock play a role in birds’ ability to orient?45-x


  • Communication is the transfer of information between a sender and receiver.45-x
  • Some forms of communication are complex and learned during a sensitive period.45-x
  • Other forms of communication convey specific information.45-x

45.6Social Behavior45-x

  • Group selection is a weak explanation of altruistic behavior.45-x
  • Reciprocal altruism is one way that altruism can evolve.45-x
  • Kin selection is based on the idea that it is possible to contribute genetically to future generations by helping close relatives.45-x

45.7Sexual Selection and Behavior45-x

  • Patterns of sexual selection are governed by differences between the sexes in their investment in offspring.45-x
  • Sexual selection can be intrasexual or intersexual.45-x

Chapter 46:Population Ecology

Birds in Flight

46.1Populations and Their Properties46-1

  • Three key features of a population are its size, range, and density.46-x
  • Population size can increase or decrease over time.46-x
  • Carrying capacity is the maximum number of individuals a habitat can support.46-x
  • Factors that influence population growth can be dependent on or independent of its density.46-x
  • Ecologists estimate population size and density by sampling.46-x
  • How Do We Know? How many butterflies are there in a given population?46-x

46.2Age-Structured Population Growth46-x

  • Birth and death rates vary with age and environment.46-x
  • Survivorship curves record changes in survival probability over an organism’s life-span.46-x
  • Patterns of survivorship vary among organisms.46-x
  • Reproductive patterns reflect the predictability of a species’ environment.46-x
  • The life history of an organism shows trade-offs among physiological functions.46-x

46.3Metapopulation Dynamics46-x

  • A metapopulation is a group of populations linked by immigrants.46-x
  • Island biogeography explains species diversity on habitat islands.46-x
  • How do islands promote species diversification?46-x
  • Species coexistence depends on habitat diversity.46-x
  • How Do We Know? Can predators and prey coexist stably in certain environments?46-x

Chapter 47:Species Interactions, Communities, and Ecosystems


47.1The Niche47-1

  • The niche is the ecological role played by a species in its community.47-x
  • The realized niche of a species is more restricted than its fundamental niche.47-x

47.2Antagonistic Interactions Between Species47-x

  • Limited resources foster competition.47-x
  • Competition promotes niche divergence.47-x
  • Species compete for resources other than food.47-x
  • Predators and parasites can limit prey population size, minimizing competition.47-x

47.3Mutualistic Interactions Between Species47-x

  • Mutualisms are interactions between species that benefit both participants.47-x
  • Mutualisms may evolve increasing interdependence.47-x
  • How Do We Know? Have aphids and their symbiotic bacteria coevolved?47-x
  • Mutualisms may be obligate or facultative.47-x
  • The costs and benefits of species interactions can change over time.47-x

47.4Ecological Communities47-x

  • Species that live in the same place make up communities.47-x
  • A single herbivore species can affect other herbivores and their predators.47-x
  • Keystone species have disproportionate effects on communities.47-x
  • Disturbance can modify community composition.47-x
  • Succession describes the community response to new habitats or disturbance.47-x


  • Species interactions result in food webs that cycle carbon and other elements through ecosystems.47-x
  • Species interactions form trophic pyramids that transfer energy through ecosystems.47-x
  • Light, water, nutrients, and diversity all influence rates of primary production.47-x
  • How Do We Know? Does species diversity promote primary productivity?47-x

47.6Biomes and Diversity Gradients47-x

  • Biomes reflect the interaction of Earth and life.47-x
  • Tropical biomes usually have more species than temperate habitats.47-x
  • Why are tropical species so diverse?47-x
  • Evolutionary and ecological history underpins diversity.47-x

Chapter 48:The AnthropoceneVISUAL SYNTHESIS: Ecology in Microcosm

Humans as a Planetary Force48-1

48.1The Anthropocene Period48-1

  • Humans are a major force on the planet.48-x

48.2Human Influence on the Carbon Cycle48-x

  • As atmospheric carbon dioxide levels have increased, so has mean surface temperature.48-x
  • Changing environments affect species distribution and community composition.48-x
  • How has climate change affected coral reefs around the world?48-x
  • How Do We Know? What is the effect of increased atmospheric CO2 and reduced ocean pH on skeleton formation in marine algae?48-x
  • What can be done?48-x

48.3Human Influence on the Nitrogen and Phosphorus Cycles48-x

  • Nitrogen fertilizer transported to lakes and the sea causes eutrophication.48-x
  • Phosphate fertilizer is also used in agriculture, but has finite sources.48-x
  • What can be done?48-x

48.4Human Influence on Evolution48-x

  • How has human activity affected biological diversity?48-x
  • Humans play an important role in the dispersal of species.48-x
  • Humans have altered the selective landscape for many pathogens.48-x
  • Are amphibians ecology’s “canary in the coal mine”?48-x

48.5Scientists and Citizens in the 21st Century48-x