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Vision and Story of Biology: How Life Works
Rethinking Biology
Rethinking the Textbook Through LaunchPad
Rethinking the Visual Program
Rethinking Assessment
Rethinking Activities
What’s New in the Second Edition?
Table of Contents
Praise for How Life Works
Chapter 1 Introduction
1.1 The Scientific Method
Observation allows us to draw tentative explanations called hypotheses.
A hypothesis makes predictions that can be tested by observation and experiments.
General explanations of natural phenomena supported by many experiments and observations are called theories.
1.2 Chemical and Physical Principles
The living and nonliving worlds follow the same chemical rules and obey the same physical laws.
The scientific method shows that living organisms come from other living organisms.
1.3 The Cell
Nucleic acids store and transmit information needed for growth, function, and reproduction.
Membranes define cells and spaces within cells.
Metabolism converts energy from the environment into a form that can be used by cells.
A virus is genetic material in need of a cell.
1.4 Evolution
Variation in populations provides the raw material for evolution.
Evolution predicts a nested pattern of relatedness among species, depicted as a tree.
Evolution can be studied by means of experiments.
1.5 Ecological Systems
Basic features of anatomy, physiology, and behavior shape ecological systems.
Ecological interactions play an important role in evolution.
1.6 The Human Footprint
Chapter 1 Summary
Case 1. The First Cell: Life’s Origins
Chapter 2 Introduction
2.1 Properties of Atoms
Atoms consist of protons, neutrons, and electrons.
Electrons occupy regions of space called orbitals.
Elements have recurring, or periodic, chemical properties.
2.2 Molecules and Chemical Bonds
A covalent bond results when two atoms share electrons.
A polar covalent bond is characterized by unequal sharing of electrons.
An ionic bond forms between oppositely charged ions.
A chemical reaction involves breaking and forming chemical bonds.
2.3 Water: The Medium of Life
Water is a polar molecule.
A hydrogen bond is an interaction between a hydrogen atom and an electronegative atom.
Hydrogen bonds give water many unusual properties.
pH is a measure of the concentration of protons in solution.
2.4 Carbon: Life’s Chemical Backbone
Carbon atoms form four covalent bonds.
Carbon-based molecules are structurally and functionally diverse.
2.5 Organic Molecules
Functional groups add chemical character to carbon chains.
Proteins are composed of amino acids.
Nucleic acids encode genetic information in their nucleotide sequence.
Complex carbohydrates are made up of simple sugars.
Lipids are hydrophobic molecules.
2.6 Case 1: How Did the Molecules of Life Form?
The building blocks of life can be generated in the laboratory.
Experiments show how life’s building blocks can form macromolecules.
Chapter 2 Summary
Chapter 3 Introduction
3.1 Major Biological Functions of DNA
DNA can transfer biological characteristics from one organism to another.
DNA molecules are copied in the process of replication.
Genetic information flows from DNA to RNA to protein.
3.2 Chemical Composition and Structure of DNA
A DNA strand consists of subunits called nucleotides.
DNA is a linear polymer of nucleotides linked by phosphodiester bonds.
Cellular DNA molecules take the form of a double helix.
The three-dimensional structure of DNA gave important clues about its functions.
Cellular DNA is coiled and packaged with proteins.
3.3 Retrieval of Genetic Information Stored in DNA: Transcription
Case 1: What was the first nucleic acid molecule, and how did it arise?
RNA is a polymer of nucleotides in which the 5-carbon sugar is ribose.
In transcription, DNA is used as a template to make complementary RNA.
Transcription starts at a promoter and ends at a terminator.
RNA polymerase adds successive nucleotides to the 3′ end of the transcript.
The RNA polymerase complex is a molecular machine that opens, transcribes, and closes duplex DNA.
3.4 Fate of the RNA Primary Transcript
Messenger RNA carries information for the synthesis of a specific protein.
Primary transcripts in eukaryotes undergo several types of chemical modification.
Some RNA transcripts are processed differently from protein-coding transcripts and have functions of their own.
Chapter 3 Summary
Chapter 4 Introduction
4.1 Molecular Structure of Proteins
Amino acids differ in their side chains.
Successive amino acids in proteins are connected by peptide bonds.
The sequence of amino acids dictates protein folding, which determines function.
Secondary structures result from hydrogen bonding in the polypeptide backbone.
Tertiary structures result from interactions between amino acid side chains.
Polypeptide subunits can come together to form quaternary structures.
Chaperones help some proteins fold properly.
4.2 Translation: How Proteins Are Synthesized
Translation uses many molecules found in all cells.
The genetic code shows the correspondence between codons and amino acids.
Translation consists of initiation, elongation, and termination.
Case 1: How did the genetic code originate?
4.3 Protein Evolution and the Origin of New Proteins
Most proteins are composed of modular folding domains.
Amino acid sequences evolve through mutation and selection.
Chapter 4 Summary
Chapter 5 Introduction
5.1 Structure of Cell Membranes
Cell membranes are composed of two layers of lipids.
Case 1: How did the first cell membranes form?
Cell membranes are dynamic.
Proteins associate with cell membranes in different ways.
5.2 The Plasma Membrane and Cell Wall
The plasma membrane maintains homeostasis.
Passive transport involves diffusion.
Primary active transport uses the energy of ATP.
Secondary active transport is driven by an electrochemical gradient.
Many cells maintain size and composition using active transport.
The cell wall provides another means of maintaining cell shape.
5.3 The Internal Organization of Cells
Eukaryotes and prokaryotes differ in internal organization.
Prokaryotic cells lack a nucleus and extensive internal compartmentalization.
Eukaryotic cells have a nucleus and specialized internal structures.
5.4 The Endomembrane System
The endomembrane system compartmentalizes the cell.
The nucleus houses the genome and is the site of RNA synthesis.
The endoplasmic reticulum is involved in protein and lipid synthesis.
The Golgi apparatus modifies and sorts proteins and lipids.
Lysosomes degrade macromolecules.
Protein sorting directs proteins to their proper location in or out of the cell.
5.5 Mitochondria and Chloroplasts
Mitochondria provide the eukaryotic cell with most of its usable energy.
Chloroplasts capture energy from sunlight.
Chapter 5 Summary
Chapter 6 Introduction
6.1 An Overview of Metabolism
Organisms can be classified according to their energy and carbon sources.
Metabolism is the set of chemical reactions that sustain life.
6.2 Kinetic and Potential Energy
Kinetic energy and potential energy are two forms of energy.
Chemical energy is a form of potential energy.
ATP is a readily accessible form of cellular energy.
6.3 The Laws of Thermodynamics
The first law of thermodynamics: Energy is conserved.
The second law of thermodynamics: Energy transformations always result in an increase in disorder in the universe.
6.4 Chemical Reactions
A chemical reaction occurs when molecules interact.
The laws of thermodynamics determine whether a chemical reaction requires or releases energy available to do work.
The hydrolysis of ATP is an exergonic reaction.
Non-spontaneous reactions are often coupled to spontaneous reactions.
6.5 Enzymes and the Rate of Chemical Reactions
Enzymes reduce the activation energy of a chemical reaction.
Enzymes form a complex with reactants and products.
Enzymes are highly specific.
Enzyme activity can be influenced by inhibitors and activators.
Allosteric enzymes regulate key metabolic pathways.
Case 1: What naturally occurring elements might have spurred the first reactions that led to life?
Chapter 6 Summary
Chapter 7 Introduction
7.1 An Overview of Cellular Respiration
Cellular respiration uses chemical energy stored in molecules such as carbohydrates and lipids to produce ATP.
ATP is generated by substrate-level phosphorylation and oxidative phosphorylation.
Redox reactions play a central role in cellular respiration.
Cellular respiration occurs in four stages.
7.2 Glycolysis: The Splitting of Sugar
Glycolysis is the partial breakdown of glucose.
7.3 Pyruvate Oxidation
The oxidation of pyruvate connects glycolysis to the citric acid cycle.
7.4 The Citric Acid Cycle
The citric acid cycle produces ATP and reduced electron carriers.
Case 1: What were the earliest energy-harnessing reactions?
7.5 The Electron Transport Chain and Oxidative Phosphorylation
The electron transport chain transfers electrons and pumps protons.
The proton gradient is a source of potential energy.
ATP synthase converts the energy of the proton gradient into the energy of ATP.
7.6 Anaerobic Metabolism and the Evolution of Cellular Respiration
Fermentation extracts energy from glucose in the absence of oxygen.
Case 1: How did early cells meet their energy requirements?
7.7 Metabolic Integration
Excess glucose is stored as glycogen in animals and starch in plants.
Sugars other than glucose contribute to glycolysis.
Fatty acids and proteins are useful sources of energy.
The intracellular level of ATP is a key regulator of cellular respiration.
Exercise requires several types of fuel molecules and the coordination of metabolic pathways.
Chapter 7 Summary
Chapter 8 Introduction
8.1 Photosynthesis: An Overview
Photosynthesis is widely distributed.
Photosynthesis is a redox reaction.
The photosynthetic electron transport chain takes place on specialized membranes.
8.2 The Calvin Cycle
The incorporation of CO2 is catalyzed by the enzyme rubisco.
NADPH is the reducing agent of the Calvin cycle.
The regeneration of RuBP requires ATP.
The steps of the Calvin cycle were determined using radioactive CO2.
Carbohydrates are stored in the form of starch.
8.3 Capturing Sunlight Into Chemical Forms
Chlorophyll is the major entry point for light energy in photosynthesis.
Photosystems use light energy to drive the photosynthetic electron transport chain.
The photosynthetic electron transport chain connects two photosystems.
The accumulation of protons in the thylakoid lumen drives the synthesis of ATP.
Cyclic electron transport increases the production of ATP.
8.4 Challenges to Photosynthetic Efficiency
Excess light energy can cause damage.
Photorespiration leads to a net loss of energy and carbon.
Photosynthesis captures just a small percentage of incoming solar energy.
8.5 The Evolution of Photosynthesis
Case 1: How did early cells use sunlight to meet their energy requirements?
The ability to use water as an electron donor in photosynthesis evolved in cyanobacteria.
Eukaryotic organisms are believed to have gained photosynthesis by endosymbiosis.
Chapter 8 Summary
Case 2. Cancer: When Good Cells Go Bad
Chapter 9 Introduction
9.1 Principles of Cell Communication
Cells communicate using chemical signals that bind to specific receptors.
Signaling involves receptor activation, signal transduction, response, and termination.
9.2 Cell Signaling Over Long and Short Distances
Endocrine signaling acts over long distances.
Signaling can occur over short distances.
Signaling can occur by direct cell–cell contact.
9.3 Cell-Surface and Intracellular Receptors
Receptors for polar signaling molecules are on the cell surface.
Receptors for nonpolar signaling molecules are in the interior of the cell.
Cell-surface receptors act like molecular switches.
9.4 G Protein-Coupled Receptors and Short-Term Responses
The first step in cell signaling is receptor activation.
Signals are often amplified in the cytosol.
Signals lead to a cellular response.
Signaling pathways are eventually terminated.
9.5 Receptor Kinases and Long-Term Responses
Receptor kinases phosphorylate each other, activate intracellular signaling pathways, lead to a response, and are terminated.
Case 2: How do cell signaling errors lead to cancer?
Signaling pathways are integrated to produce a response in a cell.
Chapter 9 Summary
Chapter 10 Introduction
10.1 Tissues and Organs
Tissues and organs are communities of cells.
The structure of skin relates to its function.
10.2 The Cytoskeleton
Microtubules and microfilaments are polymers of protein subunits.
Microtubules and microfilaments are dynamic structures.
Motor proteins associate with microtubules and microfilaments to cause movement.
Intermediate filaments are polymers of proteins that vary according to cell type.
The cytoskeleton is an ancient feature of cells.
10.3 Cell Junctions
Cell adhesion molecules allow cells to attach to other cells and to the extracellular matrix.
Anchoring junctions connect adjacent cells and are reinforced by the cytoskeleton.
Tight junctions prevent the movement of substances through the space between cells.
Communicating junctions allow the passage of molecules between cells.
10.4 The Extracellular Matrix
The extracellular matrix of plants is the cell wall.
The extracellular matrix is abundant in connective tissues of animals.
Case 2: How do cancer cells spread throughout the body?
Extracellular matrix proteins influence cell shape and gene expression.
Chapter 10 Summary
Chapter 11 Introduction
11.1 Cell Division
Prokaryotic cells reproduce by binary fission.
Eukaryotic cells reproduce by mitotic cell division.
The cell cycle describes the life cycle of a eukaryotic cell.
11.2 Mitotic Cell Division
The DNA of eukaryotic cells is organized as chromosomes.
Prophase: Chromosomes condense and become visible.
Prometaphase: Chromosomes attach to the mitotic spindle.
Metaphase: Chromosomes align as a result of dynamic changes in the mitotic spindle.
Anaphase: Sister chromatids fully separate.
Telophase: Nuclear envelopes re-form around newly segregated chromosomes.
The parent cell divides into two daughter cells by cytokinesis.
11.3 Meiotic Cell Division
Pairing of homologous chromosomes is unique to meiosis.
Crossing over between DNA molecules results in exchange of genetic material.
The first meiotic division brings about the reduction in chromosome number.
The second meiotic division resembles mitosis.
Division of the cytoplasm often differs between the sexes.
Meiosis is the basis of sexual reproduction.
11.4 Regulation of the Cell Cycle
Protein phosphorylation controls passage through the cell cycle.
Different cyclin–CDK complexes regulate each stage of the cell cycle.
Cell cycle progression requires successful passage through multiple checkpoints.
11.5 Case 2: What Genes Are Involded in Cancer?
Oncogenes promote cancer.
Proto-oncogenes are genes that when mutated may cause cancer.
Tumor suppressors block specific steps in the development of cancer.
Most cancers require the accumulation of multiple mutations.
Chapter 11 Summary
Case 3. You, from A to T: Your Personal Genome
Chapter 12 Introduction
12.1 DNA Replication
During DNA replication, the parental strands separate and new partners are made.
New DNA strands grow by the addition of nucleotides to the 3′ end.
In replicating DNA, one daughter strand is synthesized continuously and the other in a series of short pieces.
A small stretch of RNA is needed to begin synthesis of a new DNA strand.
Synthesis of the leading and lagging strands is coordinated.
DNA polymerase is self-correcting because of its proofreading function.
12.2 Replication of Chromosomes
Replication of DNA in chromosomes starts at many places almost simultaneously.
Telomerase restores tips of linear chromosomes shortened during DNA replication.
12.3 Isolation, Identification, and Sequencing of DNA Fragments
The polymerase chain reaction selectively amplifies regions of DNA.
Electrophoresis separates DNA fragments by size.
Restriction enzymes cleave DNA at particular short sequences.
DNA strands can be separated and brought back together again.
DNA sequencing makes use of the principles of DNA replication.
Case 3: What new technologies are being developed to sequence your personal genome?
12.4 Genetic Engineering
Recombinant DNA combines DNA molecules from two or more sources.
Recombinant DNA is the basis of genetically modified organisms.
DNA editing can be used to alter gene sequences almost at will.
Chapter 12 Summary
Chapter 13 Introduction
13.1 Genome Sequencing
Complete genome sequences are assembled from smaller pieces.
Sequences that are repeated complicate sequence assembly.
Case 3: Why sequence your personal genome?
13.2 Genome Annotation
Genome annotation identifies various types of sequence.
Genome annotation includes searching for sequence motifs.
Comparison of genomic DNA with messenger RNA reveals the intron–exon structure of genes.
An annotated genome summarizes knowledge, guides research, and reveals evolutionary relationships among organisms.
The HIV genome illustrates the utility of genome annotation and comparison.
13.3 Gene Number, Genome Size, and Organismal Complexity
Gene number is not a good predictor of biological complexity.
Viruses, bacteria, and archaeons have small, compact genomes.
Among eukaryotes, there is no relationship between genome size and organismal complexity.
About half of the human genome consists of transposable elements and other types of repetitive DNA.
13.4 Organization of Genomes
Bacterial cells package their DNA as a nucleoid composed of many loops.
Eukaryotic cells package their DNA as one molecule per chromosome.
The human genome consists of 22 pairs of chromosomes and two sex chromosomes.
Organelle DNA forms nucleoids that differ from those in bacteria.
13.5 Viruses and Viral Genomes
Viruses can be classified by their genomes.
The host range of a virus is determined by viral and host surface proteins.
Viruses have diverse sizes and shapes.
Viruses are capable of self-assembly.
Chapter 13 Summary
Chapter 14 Introduction
14.1 The Rate and Nature of Mutations
For individual nucleotides, mutation is a rare event.
Across the genome as a whole, mutation is common.
Only germ-line mutations are transmitted to progeny.
Case 3: What can your personal genome tell you about your genetic risk factors?
Mutations are random with regard to an organism’s needs.
14.2 Small-Scale Mutations
Point mutations are changes in a single nucleotide.
Small insertions and deletions involve several nucleotides.
Some mutations are due to the insertion of a transposable element.
14.3 Chromosomal Mutations
Duplications and deletions result in gain or loss of DNA.
Gene families arise from gene duplication and evolutionary divergence.
An inversion has a chromosomal region reversed in orientation.
A reciprocal translocation joins segments from nonhomologous chromosomes.
14.4 DNA Damage and Repair
DNA damage can affect both DNA backbone and bases.
Most DNA damage is corrected by specialized repair enzymes.
Chapter 14 Summary
Chapter 15 Introduction
15.1 Genotype and Phenotype
Genotype is the genetic makeup of a cell or organism; phenotype is its observed characteristics.
The effect of a genotype often depends on several factors.
Some genetic differences are major risk factors for disease.
Not all genetic differences are harmful.
A few genetic differences are beneficial.
15.2 Genetic Variation and Individual Uniqueness
Areas of the genome with variable numbers of tandem repeats are useful in DNA typing.
Some polymorphisms add or remove restriction sites in the DNA.
15.3 Genomewide Studies of Genetic Variation
Single-nucleotide polymorphisms (SNPs) are single-base changes in the genome.
Case 3: How can genetic risk factors be detected?
Copy-number variation constitutes a significant proportion of genetic variation.
15.4 Genetic Variation in Chromosomes
Nondisjunction in meiosis results in extra or missing chromosomes.
Some human disorders result from nondisjunction.
Extra or missing sex chromosomes have fewer effects than extra autosomes.
Nondisjunction is a major cause of spontaneous abortion.
Chapter 15 Summary
Chapter 16 Introduction
16.1 Early Theories of Inheritance
Early theories of heredity predicted the transmission of acquired characteristics.
Belief in blending inheritance discouraged studies of hereditary transmission.
16.2 The Foundations of Modern Transmission Genetics
Mendel’s experimental organism was the garden pea.
In crosses, one of the traits was dominant in the offspring.
16.3 Segregation: Mendel’s Key Discovery
Genes come in pairs that segregate in the formation of reproductive cells.
The principle of segregation was tested by predicting the outcome of crosses.
A testcross is a mating to an individual with the homozygous recessive genotype.
Segregation of alleles reflects the separation of chromosomes in meiosis.
Dominance is not universally observed.
The principles of transmission genetics are statistical and are stated in terms of probabilities.
Mendelian segregation preserves genetic variation.
16.4 Independent Assortment
Independent assortment is observed when genes segregate independently of one another.
Independent assortment reflects the random alignment of chromosomes in meiosis.
Phenotypic ratios can be modified by interactions between genes.
16.5 Patterns of Inheritance Observed in Family Histories
Dominant traits appear in every generation.
Recessive traits skip generations.
Many genes have multiple alleles.
Incomplete penetrance and variable expression can obscure inheritance patterns.
Case 3: How do genetic tests identify disease risk factors?
Chapter 16 Summary
Chapter 17 Introduction
17.1 The X and Y Sex Chromosomes
In many animals, sex is genetically determined and associated with chromosomal differences.
Segregation of the sex chromosomes predicts a 1:1 ratio of females to males.
17.2 Inheritance of Genes in the X Chromosome
X-linked inheritance was discovered through studies of male fruit flies with white eyes.
Genes in the X chromosome exhibit a “crisscross” inheritance pattern.
X-linkage provided the first experimental evidence that genes are in chromosomes.
Genes in the X chromosome show characteristic patterns in human pedigrees.
17.3 Genetic Linkage and Recombination
Nearby genes in the same chromosome show linkage.
The frequency of recombination is a measure of the genetic distance between linked genes.
Genetic mapping assigns a location to each gene along a chromosome.
Genetic risk factors for disease can be localized by genetic mapping.
17.4 Inheritance of Genes in the Y Chromosome
Y-linked genes are transmitted from father to son to grandson.
Case 3: How can the Y chromosome be used to trace ancestry?
17.5 Inheritance of Mitochondrial and Chloroplast DNA
Mitochondrial and chloroplast genomes often show uniparental inheritance.
Maternal inheritance is characteristic of mitochondrial diseases.
Case 3: How can mitochondrial DNA be used to trace ancestry?
Chapter 17 Summary
Chapter 18 Introduction
18.1 Heredity and Environment
Complex traits are affected by the environment.
Complex traits are affected by multiple genes.
The relative importance of genes and environment can be determined by differences among individuals.
Genetic and environmental effects can interact in unpredictable ways.
18.2 Resemblance Among Relatives
For complex traits, offspring resemble parents but show regression toward the mean.
Heritability is the proportion of the total variation due to genetic differences among individuals.
18.3 Twin Studies
Twin studies help separate the effects of genes and environment in differences among individuals.
18.4 Complex Traits in Health and Disease
Most common diseases and birth defects are affected by many genes that each have relatively small effects.
Human height is affected by hundreds of genes.
Case 3: Can personalized medicine lead to effective treatments of common diseases?
Chapter 18 Summary
Chapter 19 Introduction
19.1 Chromatin to Messenger RNA in Eukaryotes
Gene expression can be influenced by chemical modification of DNA or histones.
Gene expression can be regulated at the level of an entire chromosome.
Transcription is a key control point in gene expression.
RNA processing is also important in gene regulation.
19.2 Messenger RNA to Phenotype in Eukaryotes
Small regulatory RNAs inhibit translation or promote mRNA degradation.
Translational regulation controls the rate, timing, and location of protein synthesis.
Protein structure and chemical modification modulate protein effects on phenotype.
Case 3: How do lifestyle choices affect expression of your personal genome?
19.3 Transcriptional Regulation in Prokaryotes
Transcriptional regulation can be positive or negative.
Lactose utilization in E. coli is the pioneering example of transcriptional regulation.
The repressor protein binds with the operator and prevents transcription, but not in the presence of lactose.
The function of the lactose operon was revealed by genetic studies.
The lactose operon is also positively regulated by CRP–cAMP.
Transcriptional regulation determines the outcome of infection by a bacterial virus.
Chapter 19 Summary
Chapter 20 Introduction
20.1 Genetic Programs of Development
The fertilized egg is a totipotent cell.
Cellular differentiation increasingly restricts alternative fates.
Case 3: Can cells with your personal genome be reprogrammed for new therapies?
20.2 Hierarchical Control of Development
Drosophila development proceeds through egg, larval, and adult stages.
The egg is a highly polarized cell.
Development proceeds by progressive regionalization and specification.
Homeotic genes determine where different body parts develop in the organism.
20.3 Evolutionary Conservation of Key Transcription Factors in Development
Animals have evolved a wide variety of eyes.
Pax6 is a master regulator of eye development.
20.4 Combinatorial Control in Development
Floral differentiation is a model for plant development.
The identity of the floral organs is determined by combinatorial control.
20.5 Cell Signaling in Development
A signaling molecule can cause multiple responses in the cell.
Developmental signals are amplified and expanded.
Chapter 20 Summary
Case 4. Malaria: Coevolution of Humans and a Parasite
Chapter 21 Introduction
21.1 Genetic Variation
Population genetics is the study of patterns of genetic variation.
Mutation and recombination are the two sources of genetic variation.
21.2 Measuring Genetic Variation
To understand patterns of genetic variation, we require information about allele frequencies.
Early population geneticists relied on observable traits and gel electrophoresis to measure variation.
DNA sequencing is the gold standard for measuring genetic variation.
21.3 Evolution and the Hardy–Weinberg Equilibrium
Evolution is a change in allele or genotype frequency over time.
The Hardy–Weinberg equilibrium describes situations in which allele and genotype frequencies do not change.
The Hardy–Weinberg equilibrium relates allele frequencies and genotype frequencies.
The Hardy–Weinberg equilibrium is the starting point for population genetic analysis.
21.4 Natural Selection
Natural selection brings about adaptations.
The Modern Synthesis combines Mendelian genetics and Darwinian evolution.
Natural selection increases the frequency of advantageous mutations and decreases the frequency of deleterious mutations.
Case 4: What genetic differences have made some individuals more and some less susceptible to malaria?
Natural selection can be stabilizing, directional, or disruptive.
Sexual selection increases an individual’s reproductive success.
21.5 Migration, Mutation, Genetic Drift, and Non-Random Mating
Migration reduces genetic variation between populations.
Mutation increases genetic variation.
Genetic drift has a large effect in small populations.
Non-random mating alters genotype frequencies without affecting allele frequencies.
21.6 Molecular Evolution
The molecular clock relates the amount of sequence difference between species and the time since the species diverged.
The rate of the molecular clock varies.
Chapter 21 Summary
Chapter 22 Introduction
22.1 The Biological Species Concept
Species are reproductively isolated from other species.
The BSC is more useful in theory than in practice.
The BSC does not apply to asexual or extinct organisms.
Ring species and hybridization complicate the BSC.
Ecology and evolution can extend the BSC.
22.2 Reproductive Isolation
Pre-zygotic isolating factors occur before egg fertilization.
Post-zygotic isolating factors occur after egg fertilization.
22.3 Speciation
Speciation is a by-product of the genetic divergence of separated populations.
Allopatric speciation is speciation that results from the geographical separation of populations.
Dispersal and vicariance can isolate populations from each other.
Co-speciation is speciation that occurs in response to speciation in another species.
Case 4: How did malaria come to infect humans?
Sympatric populations—those not geographically separated—may undergo speciation.
Speciation can occur instantaneously.
22.4 Speciation and Selection
Speciation can occur with or without natural selection.
Natural selection can enhance reproductive isolation.
Chapter 22 Summary
Chapter 23 Introduction
23.1 Reading a Phylogenetic Tree
Phylogenetic trees provide hypotheses of evolutionary relationships.
The search for sister groups lies at the heart of phylogenetics.
A monophyletic group consists of a common ancestor and all its descendants.
Taxonomic classifications are information storage and retrieval systems.
23.2 Building a Phylogenetic Tree
Homology is similarity by common descent.
Shared derived characters enable biologists to reconstruct evolutionary history.
The simplest tree is often favored among multiple possible trees.
Molecular data complement comparative morphology in reconstructing phylogenetic history.
Phylogenetic trees can help solve practical problems.
23.3 The Fossil Record
Fossils provide unique information.
Fossils provide a selective record of past life.
Geological data indicate the age and environmental setting of fossils.
Fossils can contain unique combinations of characters.
Rare mass extinctions have altered the course of evolution.
23.4 Comparing Evolution’s Two Great Patterns
Phylogeny and fossils complement each other.
Agreement between phylogenies and the fossil record provides strong evidence of evolution.
Chapter 23 Summary
Chapter 24 Introduction
24.1 The Great Apes
Comparative anatomy shows that the human lineage branches off the great apes tree.
Molecular analysis reveals that the human lineage split from the chimpanzee lineage about 5–7 million years ago.
The fossil record gives us direct information about our evolutionary history.
24.2 African Origins
Studies of mitochondrial DNA reveal that modern humans evolved in Africa relatively recently.
Studies of the Y chromosome provide independent evidence for a recent origin of modern humans.
Neanderthals disappear from the fossil record as modern humans appear, but have contributed to the modern human gene pool.
24.3 Distinct Features of Our Species
Bipedalism was a key innovation.
Adult humans share many features with juvenile chimpanzees.
Humans have large brains relative to body size.
The human and chimpanzee genomes help us identify genes that make us human.
24.4 Human Genetic Variation
The prehistory of our species has had an impact on the distribution of genetic variation.
The recent spread of modern humans means that there are few genetic differences between groups.
Some human differences have likely arisen by natural selection.
Case 4: What human genes are under selection for resistance to malaria?
24.5 Culture, Language, and Consciousness
Culture changes rapidly.
Is culture uniquely human?
Is language uniquely human?
Is consciousness uniquely human?
Chapter 24 Summary
Chapter 25 Introduction
25.1 The Short-Term Carbon Cycle
Photosynthesis and respiration are key processes in short-term carbon cycling.
The regular oscillation of CO2 reflects the seasonality of photosynthesis in the Northern Hemisphere.
Human activities play an important role in the modern carbon cycle.
Carbon isotopes show that much of the CO2 added to air over the past half century comes from burning fossil fuels.
25.2 The Long-Term Carbon Cycle
Reservoirs and fluxes are key in long-term carbon cycling.
Physical processes add and remove CO2 from the atmosphere.
Records of atmospheric composition over 400,000 years show periodic shifts in CO2 content.
Variations in atmospheric CO2 over hundreds of millions of years reflect plate tectonics and evolution.
25.3 The Carbon Cycle: Ecology, Biodiversity, and Evolution
Food webs trace the cycling of carbon through communities and ecosystems.
Biological diversity reflects the many ways that organisms participate in the carbon cycle.
The carbon cycle weaves together biological evolution and environmental change through Earth history.
Chapter 25 Summary
Case 5. The Human Microbiome: Diversity Within
Chapter 26 Introduction
26.1 Two Prokaryotic Domains
The bacterial cell is small but powerful.
Diffusion limits cell size in bacteria.
Horizontal gene transfer promotes genetic diversity in bacteria.
Archaea form a second prokaryotic domain.
26.2 An Expanded Carbon Cycle
Many photosynthetic bacteria do not produce oxygen.
Many bacteria respire without oxygen.
Photoheterotrophs obtain energy from light but obtain carbon from preformed organic molecules.
Chemoautotrophy is a uniquely prokaryotic metabolism.
26.3 Other Biogeochemical Cycles
Bacteria and archaeons dominate Earth’s sulfur cycle.
The nitrogen cycle is also driven by bacteria and archaeons.
26.4 The Diversity of Bacteria
Bacterial phylogeny is a work in progress.
What, if anything, is a bacterial species?
Proteobacteria are the most diverse bacteria.
The gram-positive bacteria include organisms that cause and cure disease.
Photosynthesis is widely distributed on the bacterial tree.
26.5 The Diversity of Archaea
The archaeal tree has anaerobic, hyperthermophilic organisms near its base.
The Archaea include several groups of acid-loving microorganisms.
Only Archaea produce methane as a by-product of energy metabolism.
One group of the Euryarchaeota thrives in extremely salty environments.
Thaumarchaeota may be the most abundant cells in the deep ocean.
26.6 The Evolutionary History of Prokaryotes
Life originated early in our planet’s history.
Prokaryotes have coevolved with eukaryotes.
Case 5: How do intestinal bacteria influence human health?
Chapter 26 Summary
Chapter 27 Introduction
27.1 The Eukaryotic Cell: A Review
Internal protein scaffolding and dynamic membranes organize the eukaryotic cell.
In eukaryotic cells, energy metabolism is localized in mitochondria and chloroplasts.
The organization of the eukaryotic genome also helps explain eukaryotic diversity.
Sex promotes genetic diversity in eukaryotes and gives rise to distinctive life cycles.
27.2 Eukaryotic Origins
Case 5: What role did symbiosis play in the origin of chloroplasts?
Case 5: What role did symbiosis play in the origin of mitochondria?
Case 5: How did the eukaryotic cell originate?
In the oceans, many single-celled eukaryotes harbor symbiotic bacteria.
27.3 Eukaryotic Diversity
Our own group, the opisthokonts, is the most diverse eukaryotic superkingdom.
Amoebozoans include slime molds that produce multicellular structures.
Archaeplastids, which include land plants, are photosynthetic organisms.
Stramenopiles, alveolates, and rhizarians dominate eukaryotic diversity in the oceans.
Photosynthesis spread through eukaryotes by repeated endosymbioses involving eukaryotic algae.
27.4 The Fossil Record of Protists
Fossils show that eukaryotes existed at least 1800 million years ago.
Protists have continued to diversify during the age of animals.
Chapter 27 Summary
Chapter 28 Introduction
28.1 The Phylogenetic Distribution of Multicellular Organisms
Simple multicellularity is widespread among eukaryotes.
Complex multicellularity evolved several times.
28.2 Diffusion and Bulk Flow
Diffusion is effective only over short distances.
Animals achieve large size by circumventing limits imposed by diffusion.
Complex multicellular organisms have structures specialized for bulk flow.
28.3 How to Build a Multicellular Organism
Complex multicellularity requires adhesion between cells.
How did animal cell adhesion originate?
Complex multicellularity requires communication between cells.
Complex multicellularity requires a genetic program for coordinated growth and cell differentiation.
28.4 Variations On a Theme: Plants Versus Animals
Cell walls shape patterns of growth and development in plants.
Animal cells can move relative to one another.
28.5 The Evolution of Complex Multicellularity
Fossil evidence of complex multicellular organisms is first observed in rocks deposited 579–555 million years ago.
Oxygen is necessary for complex multicellular life.
Land plants evolved from green algae that could carry out photosynthesis on land.
Regulatory genes played an important role in the evolution of complex multicellular organisms.
Chapter 28 Summary
Case 6. Agriculture: Feeding a Growing Population
Chapter 29 Introduction
29.1 Plant Structure and Function: An Evolutionary Perspective
Land plants are a monophyletic group that includes vascular plants and bryophytes.
29.2 The Leaf: Acquiring CO2 While Avoiding Desiccation
CO2 uptake results in water loss.
The cuticle restricts water loss from leaves but inhibits the uptake of CO2.
Stomata allow leaves to regulate water loss and carbon gain.
CAM plants use nocturnal CO2 storage to avoid water loss during the day.
C4 plants suppress photorespiration by concentrating CO2 in bundle-sheath cells.
29.3 The Stem: Transport of Water Through Xylem
Xylem provides a low-resistance pathway for the movement of water.
Water is pulled through xylem by an evaporative pump.
Xylem transport is at risk of conduit collapse and cavitation.
29.4 The Stem: Transport of Carbohydrates Through Phloem
Phloem transports carbohydrates from sources to sinks.
Carbohydrates are pushed through phloem by an osmotic pump.
Phloem feeds both the plant and the rhizosphere.
29.5 The Root: Uptake of Water and Nutrients From the Soil
Plants obtain essential mineral nutrients from the soil.
Nutrient uptake by roots is highly selective.
Nutrient uptake requires energy.
Mycorrhizae enhance nutrient uptake.
Symbiotic nitrogen-fixing bacteria supply nitrogen to both plants and ecosystems.
Case 6: How has nitrogen availability influenced agricultural productivity?
Chapter 29 Summary
Chapter 30 Introduction
30.1 Alternation of Generations
The algal sister groups of land plants have one multicellular generation in their life cycle.
Bryophytes illustrate how the alternation of generations allows the dispersal of spores in the air.
Dispersal enhances reproductive fitness in several ways.
Spore-dispersing vascular plants have free-living gametophytes and sporophytes.
30.2 Seed Plants
The seed plant life cycle is distinguished by four major steps.
Pine trees illustrate how the transport of pollen in air allows fertilization to occur in the absence of external sources of water.
Seeds enhance the establishment of the next sporophyte generation.
30.3 Flowering Plants
Flowers are reproductive shoots specialized for the transfer and receipt of pollen.
The diversity of floral morphology is related to modes of pollination.
Angiosperms have mechanisms to increase outcrossing.
Angiosperms delay provisioning their ovules until after fertilization.
Fruits enhance the dispersal of seeds.
Case 6: How did scientists increase crop yields during the Green Revolution?
30.4 Asexual Reproduction
Asexually produced plants disperse with and without seeds.
Chapter 30 Summary
Chapter 31 Introduction
31.1 Shoot Growth and Development
Stems grow by adding new cells at their tips.
Stem elongation occurs just below the apical meristem.
The development of new apical meristems allows stems to branch.
The shoot apical meristem controls the production and arrangement of leaves.
Young leaves develop vascular connections to the stem.
Flower development terminates the growth of shoot meristems.
31.2 Plant Hormones
Hormones affect the growth and differentiation of plant cells.
Polar transport of auxin guides the placement of leaf primordia and the development of vascular connections with the stem.
Case 6: What is the developmental basis for the shorter stems of high-yielding rice and wheat?
Cytokinins, in combination with other hormones, control the outgrowth of axillary buds.
31.3 Secondary Growth
Shoots produce two types of lateral meristem.
The vascular cambium produces secondary xylem and phloem.
The cork cambium produces an outer protective layer.
Wood has both mechanical and transport functions.
31.4 Root Growth and Development
Roots grow by producing new cells at their tips.
Root elongation and vascular development are coordinated.
The formation of new root apical meristems allows roots to branch.
The structures and functions of root systems are diverse.
31.5 The Environmental Context of Growth and Development
Plants orient the growth of their stems and roots by light and gravity.
Seeds can delay germination if they detect the presence of plants overhead.
Plants grow taller and branch less when growing in the shade of other plants.
Roots elongate more and branch less when water is scarce.
Exposure to wind results in shorter and stronger stems.
31.6 Timing of Developmental Events
Flowering time is affected by day length.
Plants use their internal circadian clock and photoreceptors to determine day length.
Vernalization prevents plants from flowering until winter has passed.
Plants use day length as a cue to prepare for winter.
Chapter 31 Summary
Chapter 32 Introduction
32.1 Protection Against Pathogens
Plant pathogens infect and exploit host plants by a variety of mechanisms.
Plants are able to detect and respond to pathogens.
Plants respond to infections by isolating infected regions.
Mobile signals trigger defenses in uninfected tissues.
Plants defend against viral infections by producing siRNA.
A pathogenic bacterium provides a way to modify plant genomes.
32.2 Defense Against Herbivores
Plants use mechanical and chemical defenses to avoid being eaten.
Diverse chemical compounds deter herbivores.
Some plants provide food and shelter for ants, which actively defend them.
Grasses can regrow quickly following grazing by mammals.
32.3 Allocating Resources to Defense
Some defenses are always present, whereas others are turned on in response to a threat.
Plants can sense and respond to herbivores.
Plants produce volatile signals that attract insects that prey upon herbivores.
Nutrient-rich environments select for plants that allocate more resources to growth than to defense.
Exposure to multiple threats can lead to trade-offs.
32.4 Defense and Plant Diversity
The evolution of new defenses may allow plants to diversify.
Pathogens, herbivores, and seed predators can increase plant diversity.
Case 6: Can modifying plants genetically protect crops from herbivores and pathogens?
Chapter 32 Summary
Chapter 33 Introduction
33.1 Plant Diversity: An Evolutionary Overview
Four major transformations in life cycle and structure characterize the evolutionary history of plants.
Plant diversity has changed over time.
33.2 Bryophytes
Bryophytes are small, simple, and tough.
The small gametophytes and unbranched sporophytes of bryophytes are adaptations for reproducing on land.
Bryophytes exhibit several cases of convergent evolution with the vascular plants.
Sphagnum moss plays an important role in the global carbon cycle.
33.3 Spore-Dispersing Vascular Plants
Rhynie cherts provide a window into the early evolution of vascular plants.
Lycophytes are the sister group of all other vascular plants.
Ancient lycophytes included giant trees that dominated coal swamps about 320 million years ago.
Ferns and horsetails are morphologically and ecologically diverse.
Fern diversity has been strongly affected by the evolution of angiosperms.
An aquatic fern contributes to rice production.
33.4 Gymnosperms
Cycads and ginkgos are the earliest diverging groups of living gymnosperms.
Conifers are woody plants that thrive in dry and cold climates.
Gnetophytes are gymnosperms that have independently evolved xylem vessels and double fertilization.
33.5 Angiosperms
Angiosperms may have originated in the shady understory of tropical forests.
Angiosperm diversity results from flowers and xylem vessels, among other traits, as well as coevolutionary interactions with animals and other organisms.
Monocots are diverse in shape and size despite not forming a vascular cambium.
Eudicots are the most diverse group of angiosperms.
Case 6: What can be done to protect the genetic diversity of crop species?
Chapter 33 Summary
Chapter 34 Introduction
34.1 Growth and Nutrition
Hyphae permit fungi to explore their environment for food resources.
Fungi transport materials within their hyphae.
Not all fungi produce hyphae.
Fungi are principal decomposers of plant tissues.
Fungi are important plant and animal pathogens.
Many fungi form symbiotic associations with plants and animals.
Lichens are symbioses between a fungus and a green alga or a cyanobacterium.
34.2 Reproduction
Fungi proliferate and disperse using spores.
Multicellular fruiting bodies facilitate the dispersal of sexually produced spores.
The fungal life cycle often includes a stage in which haploid cells fuse, but nuclei do not.
Genetically distinct mating types promote outcrossing.
34.3 Diversity
Fungi are highly diverse.
Fungi evolved from aquatic, unicellular, and flagellated ancestors.
Zygomycetes produce hyphae undivided by septa.
Glomeromycetes form endomycorrhizae.
The Dikarya produce regular septa during mitosis.
Ascomycetes are the most diverse group of fungi.
Basidiomycetes include smuts, rusts, and mushrooms.
Case 6: How do fungi threaten global wheat production?
Chapter 34 Summary
Case 7. Predator–Prey: A Game of Life and Death
Chapter 35 Introduction
35.1 Nervous System Function and Evolution
Animal nervous systems have three types of nerve cell.
Nervous systems range from simple to complex.
Case 7: What body features arose as adaptations for successful predation?
35.2 Neuron Structure
Neurons share a common organization.
Neurons differ in size and shape.
Neurons are supported by other types of cell.
35.3 Neuron Function
The resting membrane potential is negative and results in part from the movement of potassium ions.
Neurons are excitable cells that transmit information by action potentials.
Neurons propagate action potentials along their axons by sequentially opening and closing adjacent Na+ and K+ ion channels.
Neurons communicate at synapses.
Signals between neurons can be excitatory or inhibitory.
35.4 Nervous System Organization
Nervous systems are organized into peripheral and central components.
Peripheral nervous systems have voluntary and involuntary components.
The nervous system helps to maintain homeostasis.
Simple reflex circuits provide rapid responses to stimuli.
Chapter 35 Summary
Chapter 36 Introduction
36.1 Animal Sensory Systems
Specialized sensory receptors detect diverse stimuli.
Chemoreceptors are universally present in animals.
Mechanoreceptors are a second general class of ancient sensory receptors.
Electromagnetic receptors sense light, thermoreceptors sense temperature, and nociceptors sense pain.
Stimuli are transmitted by changes in the firing rate of action potentials.
36.2 Smell and Taste
Smell and taste depend on chemoreception of molecules carried in the environment and in food.
36.3 Gravity, Movement, and Sound
Hair cells sense gravity and motion.
Hair cells detect the physical vibrations of sound.
Case 7: How have sensory systems evolved in predators and prey?
36.4 Vision
Animals see the world through different types of eyes.
The structure and function of the vertebrate eye underlie image processing.
Vertebrate photoreceptors are unusual because they hyperpolarize in response to light.
Color vision detects different wavelengths of light.
Local sensory processing of light determines basic features of shape and movement.
36.5 Brain Organization and Function
The brain processes and integrates information received from different sensory systems.
The brain is divided into lobes with specialized functions.
Information is topographically mapped into the vertebrate cerebral cortex.
36.6 Memory and Cognition
The brain serves an important role in memory and learning.
Cognition involves brain information processing and decision making.
Chapter 36 Summary
Chapter 37 Introduction
37.1 Muscles: Biological Motors That Generate Force and Produce Movement
Muscles use chemical energy to produce force and movement.
Muscles can be striated or smooth.
Skeletal and cardiac muscle fibers are organized into repeating contractile units called sarcomeres.
Muscles contract by the sliding of myosin and actin filaments.
Calcium regulates actin–myosin interaction through excitation–contraction coupling.
Calmodulin regulates Ca2+ activation and relaxation of smooth muscle.
37.2 Muscle Contractile Properties
Muscle length affects actin–myosin overlap and generation of force.
Muscle force and shortening velocity are inversely related.
Antagonist pairs of muscles produce reciprocal motions at a joint.
Muscle force is summed by an increase in stimulation frequency and the recruitment of motor units.
Skeletal muscles have slow-twitch and fast-twitch fibers.
Case 7: How do different types of muscle fiber affect the speed of predators and prey?
37.3 Animal Skeletons
Hydrostatic skeletons support animals by muscles that act on a fluid-filled cavity.
Exoskeletons provide hard external support and protection.
The rigid bones of vertebrate endoskeletons are jointed for motion and can be repaired if damaged.
37.4 Vertebrate Skeletons
Vertebrate bones form directly or by forming a cartilage model first.
Two main types of bone are compact and spongy bone.
Bones grow in length and width, and can be repaired.
Joint shape determines range of motion and skeletal muscle organization.
Muscles exert forces by skeletal levers to produce joint motion.
Chapter 37 Summary
Chapter 38 Introduction
38.1 An Overview of Endocrine Function
The endocrine system helps to regulate an organism’s response to its environment.
The endocrine system regulates growth and development.
The endocrine system underlies homeostasis.
38.2 Properties of Hormones
Hormones act specifically on cells that bind the hormone.
Two main classes of hormone are peptide and amines, and steroid hormones.
Hormonal signals are amplified to strengthen their effect.
Hormones are evolutionarily conserved molecules with diverse functions.
38.3 The Vertebrate Endocrine System
The pituitary gland integrates diverse bodily functions by secreting hormones in response to signals from the hypothalamus.
Many targets of pituitary hormones are endocrine tissues that also secrete hormones.
Other endocrine organs have diverse functions.
Case 7: How does the endocrine system influence predators and prey?
38.4 Other Forms of Chemical Communication
Local chemical signals regulate neighboring target cells.
Pheromones are chemical compounds released into the environment to signal physiological and behavioral changes in other species members.
Chapter 38 Summary
Chapter 39 Introduction
39.1 Delivery of Oxygen and Elimination of Carbon Dioxide
Diffusion governs gas exchange over short distances.
Bulk flow moves fluid over long distances.
39.2 Respiratory Gas Exchange
Many aquatic animals breathe through gills.
Insects breathe air through tracheae.
Most terrestrial vertebrates breathe by tidal ventilation of internal lungs.
Mammalian lungs are well adapted for gas exchange.
The structure of bird lungs allows unidirectional airflow for increased oxygen uptake.
Voluntary and involuntary mechanisms control breathing.
39.3 Oxygen Transport by Hemoglobin
Blood is composed of fluid and several types of cell.
Hemoglobin is an ancient molecule with diverse roles related to oxygen binding and transport.
Hemoglobin reversibly binds oxygen.
Myoglobin stores oxygen, enhancing delivery to muscle mitochondria.
Many factors affect hemoglobin–oxygen binding.
39.4 Circulatory Systems
Circulatory systems have vessels of different sizes to facilitate bulk flow and diffusion.
Arteries are muscular, elastic vessels that carry blood away from the heart under high pressure.
Veins are thin-walled vessels that return blood to the heart under low pressure.
Compounds and fluid move across capillary walls by diffusion, filtration, and osmosis.
Case 7: How do hormones and nerves provide homeostatic regulation of blood flow as well as allow an animal to respond to stress?
39.5 The Evolution, Structure, and Function of the Heart
Fish have two-chambered hearts and a single circulatory system.
Amphibians and reptiles have three-chambered hearts and partially divided circulations.
Mammals and birds have four-chambered hearts and fully divided pulmonary and systemic circulations.
Cardiac muscle cells are electrically connected to contract in synchrony.
Heart rate and cardiac output are regulated by the autonomic nervous system.
Chapter 39 Summary
Chapter 40 Introduction
40.1 Patterns of Animal Metabolism
Animals rely on anaerobic and aerobic metabolism.
Metabolic rate varies with activity level.
Case 7: Does body temperature limit activity level in predators and prey?
Metabolic rate is affected by body size.
Metabolic rate is linked to body temperature.
40.2 Animal Nutrition and Diet
Energy balance is a form of homeostasis.
An animal’s diet must supply nutrients that it cannot synthesize.
40.3 Adaptations for Feeding
Suspension filter feeding is common in many aquatic animals.
Large aquatic animals apprehend prey by suction feeding and active swimming.
Jaws and teeth provide specialized food capture and mechanical breakdown of food.
40.4 Digestion and Absorption of Food
The digestive tract has regional specializations.
Digestion begins in the mouth.
Further digestion and storage of nutrients take place in the stomach.
Final digestion and nutrient absorption take place in the small intestine.
The large intestine absorbs water and stores waste.
The lining of the digestive tract is composed of distinct layers.
Plant-eating animals have specialized digestive tracts that reflect their diets.
Chapter 40 Summary
Chapter 41 Introduction
41.1 Water and Electrolyte Balance
Osmosis governs the movement of water across cell membranes.
Osmoregulation is the control of osmotic pressure inside cells and organisms.
Osmoconformers match their internal solute concentration to that of the environment.
Osmoregulators have internal solute concentrations that differ from that of their environment.
Case 7: Can the loss of water and electrolytes in exercise be exploited as a strategy to hunt prey?
41.2 Excretion of Wastes
The excretion of nitrogenous wastes is linked to an animal’s habitat and evolutionary history.
Excretory organs work by filtration, reabsorption and secretion.
Animals have diverse excretory organs.
Vertebrates filter blood under pressure through paired kidneys.
41.3 Structure and Function of the Mammalian Kidney
The mammalian kidney has an outer cortex and inner medulla.
Glomerular filtration isolates wastes carried by the blood along with water and small solutes.
The proximal convoluted tubule reabsorbs solutes by active transport.
The loop of Henle acts as a countercurrent multiplier to create a concentration gradient from the cortex to the medulla.
The distal convoluted tubule secretes additional wastes.
The final concentration of urine is determined in the collecting ducts and is under hormonal control.
The kidneys help regulate blood pressure and blood volume.
Chapter 41 Summary
Chapter 42 Introduction
42.1 The Evolutionary History of Reproduction
Asexual reproduction produces clones.
Sexual reproduction involves the formation and fusion of gametes.
Many species reproduce both sexually and asexually.
Exclusive asexuality is often an evolutionary dead end.
42.2 Movement onto Land and Reproductive Adaptations
Fertilization can take place externally or internally.
r-strategists and K-strategists differ in number of offspring and parental care.
Animals either lay eggs or give birth to live young.
42.3 Human Reproductive Anatomy and Physiology
The male reproductive system is specialized for the production and delivery of sperm.
The female reproductive system produces eggs and supports the developing embryo.
Hormones regulate the human reproductive system.
42.4 Gamete Formation to Birth in Humans
Male and female gametogenesis have both shared and distinct features.
Fertilization occurs when a sperm fuses with an oocyte.
The first trimester includes cleavage, gastrulation, and organogenesis.
The second and third trimesters are characterized by fetal growth.
Childbirth is initiated by hormonal changes.
Chapter 42 Summary
Chapter 43 Introduction
43.1 An Overview of the Immune System
Pathogens cause disease.
The immune system distinguishes self from nonself.
The immune system consists of innate and adaptive immunity.
43.2 Innate Immunity
The skin and mucous membranes provide the first line of defense against infection.
White blood cells provide a second line of defense against pathogens.
Phagocytes recognize foreign molecules and send signals to other cells.
Inflammation is a coordinated response to tissue injury.
The complement system participates in the innate and adaptive immune systems.
43.3 Adaptive Immunity: B Cells and Antibodies
B cells produce antibodies.
Mammals produce five classes of antibody with different functions.
Clonal selection is the basis for antibody specificity.
Clonal selection also explains immunological memory.
Genomic rearrangement generates antibody diversity.
43.4 Adaptive Immunity: T Cells and Cell-Mediated Immunity
T cells include helper and cytotoxic cells.
T cells have T cell receptors on their surface that recognize an antigen in association with MHC proteins.
The ability to distinguish between self and nonself is acquired during T cell maturation.
43.5 Three Pathogens: A Virus, Bacterium, and Eukaryote
The flu virus evades the immune system by antigenic drift and shift.
Tuberculosis is caused by a slow-growing, intracellular bacterium.
The malaria parasite changes surface molecules by antigenic variation.
Chapter 43 Summary
Case 8. Biodiversity Hotspots: Rain Forests and Coral Reefs
Chapter 44 Introduction
44.1 A Tree of Life for More Than a Million Animal Species
Phylogenetic trees propose an evolutionary history of animals.
Morphology and development provide clues to animal phylogeny.
Molecular sequence comparisons have confirmed some relationships and raised new questions.
44.2 The Simplest Animals: Sponges, Cnidarians, Ctenophores, and Placozoans
Sponges are simple and widespread in the oceans.
Cnidarians are the architects of life’s largest constructions: coral reefs.
Ctenophores and placozoans represent the extremes of body organization among animals that branch from early nodes.
Branching relationships among early nodes on the animal tree remain uncertain.
The discovery of new animals with a unique body plan complicates phylogenetic hypotheses still further.
44.3 Bilaterian Animals
Lophotrochozoans make up nearly half of all animal phyla, including the diverse and ecologically important annelids and mollusks.
Ecdysozoans include nematodes, the most numerous animals, and arthropods, the most diverse.
Deuterostomes include humans and other chordates, and also acorn worms and sea stars.
Chordates include vertebrates, cephalochordates, and tunicates.
44.4 Vertebrate Diversity
Fish are the earliest-branching and most diverse vertebrate animals.
The common ancestor of tetrapods had four limbs.
Amniotes evolved terrestrial eggs.
44.5 The Evolutionary History of Animals
Fossils and phylogeny show that animal forms were initially simple but rapidly evolved complexity.
The animal body plans we see today emerged during the Cambrian Period.
Tabulations of described fossils show that animal diversity has been shaped by both radiation and mass extinction over the past 500 million years.
Animals began to colonize the land 420 million years ago.
Case 8: How have reefs changed through time?
Chapter 44 Summary
Chapter 45 Introduction
45.1 Tinbergen’s Questions
45.2 Dissecting Behavior
The fixed action pattern is a stereotyped behavior.
The nervous system processes stimuli and evokes behaviors.
Hormones can trigger certain behaviors.
Breeding experiments can help determine the degree to which a behavior is genetic.
Molecular techniques provide new ways of testing the role of genes in behavior.
45.3 Learning
Non-associative learning occurs without linking two events.
Associative learning occurs when two events are linked.
Learning is an adaptation.
45.4 Orientation, Navigation, and Biological Clocks
Orientation involves a directed response to a stimulus.
Navigation is demonstrated by the remarkable ability of homing in birds.
Biological clocks provide important time cues for many behaviors.
45.5 Communication
Communication is the transfer of information between a sender and receiver.
Some forms of communication are complex and learned during a sensitive period.
Other forms of communication convey specific information.
45.6 Social Behavior
Group selection is a weak explanation of altruistic behavior.
Reciprocal altruism is one way that altruism can evolve.
The concept of kin selection is based on the idea that it is possible to contribute genetically to future generations by helping close relatives.
Chapter 45 Summary
Chapter 46 Introduction
46.1 Populations and Their Properties
A population includes all the individuals of a species in a particular place.
Three key features of a population are its size, range, and density.
Ecologists estimate population size by sampling.
46.2 Population Growth and Decline
Population size is affected by birth, death, immigration, and emigration.
Exponential growth is characterized by a constant per capita growth rate.
Carrying capacity is the maximum number of individuals a habitat can support.
Logistic growth produces an S-shaped curve and describes the growth of many natural populations.
Factors that influence population growth can be dependent on or independent of its density.
46.3 Age-Structured Population Growth
Birth and death rates vary with age and environment.
Survivorship curves record changes in survival probability over an organism’s life-span.
Patterns of survivorship vary among organisms.
Reproductive patterns reflect the predictability of a species’ environment.
The life history of an organism shows trade-offs among physiological functions.
46.4 Metapopulation Dynamics
A metapopulation is a group of populations linked by immigrants.
Island biogeography explains species diversity on habitat islands.
Case 8: How do islands promote species diversification?
Chapter 46 Summary
Chapter 47 Introduction
47.1 The Niche
The niche is a species’ place in nature.
The realized niche of a species is more restricted than its fundamental niche.
Niches are shaped by evolutionary history.
47.2 Antagonistic Interactions Between Species
Limited resources foster competition.
Competitive exclusion can prevent two species from occupying the same niche at the same time.
Case 8: Can competition drive species diversification?
Species compete for resources other than food.
Predation, parasitism, and herbivory are interactions in which one species benefits at the expense of another.
Facilitation can occur when two species prey on a third species.
47.3 Mutualistic Interactions Between Species
Mutualisms are interactions between species that benefit both participants.
Mutualisms may evolve increasing interdependence.
Digestive symbioses recycle plant material.
Mutualisms may be obligate or facultative.
The costs and benefits of species interactions can change over time.
47.4 Ecological Communities
Species that live in the same place make up communities.
Case 8: How is biodiversity measured?
One species can have a great effect on all other members of the community.
Keystone species have disproportionate effects on communities.
Disturbance can modify community composition.
Succession describes the community response to new habitats or disturbance.
47.5 Ecosystems
Species interactions result in food webs that cycle carbon and other elements through ecosystems.
Species interactions form trophic pyramids that transfer energy through ecosystems.
Light, water, nutrients, and diversity all influence rates of primary production.
Chapter 47 Summary
Chapter 48 Introduction
48.1 The Physical Basis of Climate
The principal control on Earth’s surface temperature is the angle at which solar radiation strikes the surface.
Heat is transported toward the poles by wind and ocean currents.
Global circulation patterns determine patterns of rainfall, but topography also matters.
48.2 Biomes
Terrestrial biomes reflect the distribution of climate.
Aquatic biomes reflect climate, and also the availability of nutrients and oxygen and the depth to which sunlight penetrates through water.
48.3 Global Ecology: Cycling Bioessential Elements
The biological carbon cycle shapes ecological interactions and reflects evolution.
The nitrogen cycle also reflects the interplay between ecology and evolution.
Phosphorus cycles through ecosystems, supporting primary production.
Global patterns of primary production reflect variations in climate and nutrient availability.
48.4 Global Biodiversity
Case 8: Why does biodiversity decrease from the equator toward the poles?
Evolutionary and ecological history underpins diversity.
Chapter 48 Summary
Chapter 49 Introduction
49.1 The Anthropocene Period
Humans are a major force on the planet.
49.2 Human Influence On the Carbon Cycle
As atmospheric carbon dioxide levels have increased, so has mean surface temperature.
Changing environments affect species distribution and community composition.
Case 8: How has global environmental change affected coral reefs around the world?
What can be done?
49.3 Human Influence On the Nitrogen and Phosphorus Cycles
Nitrogen fertilizer transported to lakes and the sea causes eutrophication.
Phosphate fertilizer is also used in agriculture, but has finite sources.
What can be done?
49.4 Human Influence On Evolution
Human activities have reduced the quality and size of many habitats, decreasing the number of species they can support.
Overexploitation threatens species and disrupts ecological relationships within communities.
Humans play an important role in the dispersal of species.
Humans have altered the selective landscape for many pathogens.
Are amphibians ecology’s “canary in the coal mine”?
49.5 Conservation Biology
Case 8: What are our conservation priorities?
Conservation biologists have a diverse toolkit for confronting threats to biodiversity.
Global change provides new challenges for conservation biology in the 21st century.
Sustainable development provides a strategy for conserving biodiversity while meeting the needs of the human population.
49.6 Scientists and Citizens in the 21st Century
Chapter 49 Summary
Quick Check Answers
Glossary
Index