! Rate of evolution

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Rates of evolution - How do we measure the rate of evolution?

The rate of evolution

The rate of evolution is a measurement of the change in an evolutionary lineage over time.

The method for measuring the rate of evolution can be illustrated by work done by MacFadden on horse teeth: horse teeth are classic materials in the study of evolution.

The rate of evolution is measured as follows:

Suppose that a character has been measured at two times, t1 and t2 ; t1 and t2 are expressed as times before the present in millions of years.

The time interval between the two samples can be written as:Dt = t1 - t2,

which is 1 million years if t1 = 15.2 and t2 =14.2 The average value of the character is defined as x1 in the earlier sample and x2 in the later sample; we then take natural logarithms of x1 and x2 (the natural logarithm is the log to base e where e = 2.718, and it is symbolized by ln ).

The evolutionary rate (r) then is

r = (ln(x2) - ln(x1)) / Dt

The rate of evolution is measured in 'darwins'.

Haldane (pictured opposite) defined a 'darwin' as a unit to measure evolutionary rates; one darwin is a change in the character by a factor of e in one million years.

The formula above for r gives the rate in darwins provided that the time interval is in millions of years.

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20. Evolutionary Developmental Biology: (Tutorial) Sample Chapter

    • Changes In Development, And The Genes Controlling Development, Underlie Morphological Evolution

    • The Theory Of Recapitulation Is A Classic Idea (Largely Discredited) About The Relation Between Development And Evolution

    • Humans May Have Evolved From Ancestral Apes By Changes In Regulatory Genes

    • Many Genes That Regulate Development Have Been Identified Recently

    • Modern Developmental Genetic Discoveries Have Challenged And Clarified The Meaning On Homology

    • The Hox Gene Complex Has Expanded At Two Points In The Evolution Of Animals

    • Changes In The Embryonic Expression Of Genes Are Associated With Evolutionary Changes In Morphology

    • Evolution Of Genetic Switches Enables Evolutionary Innovation, Making The System More "Evolvable"

    • Conclusion

Summary

Further Reading

Study And Review Questions

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21. Rates Of Evolution: (Tutorial)

    • Rates Of Evolution Can Be Expressed In "Darwins," As Illustrated By A Study Of Horse Evolution

    • Why Do Evolutionary Rates Vary?

    • The Theory Of Punctuated Equilibrium Applies The Theory Of Allopatric Speciation To Predict The Pattern Of Change In The Fossil Record

    • What Is The Evidence For Punctuated Equilibrium And For Phyletic Gradualism?

    • Evolutionary Rates Can Be Measured For Non-Continuous Character Changes, As Illustrated By A Study Of "Living Fossil" Lungfish

    • Taxonomic Data Can Be Used To Describe The Rate Of Evolution Of Higher Taxonomic Groups

    • Conclusion

Summary

Further Reading

Study And Review Questions

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22. Coevolution: (Tutorial)

    • Coevolution Can Give Rise To Coadaptations Between Species

    • Coadaptation Suggests, But Is Not Conclusive Evidence Of, Coevolution

    • Insect-Plant Coevolution

    • Coevolutionary Relations Will Often Be Diffuse

    • Parasite-Host Coevolution

    • Coevolution Can Proceed In An "Arms Race"

    • The Probability That A Species Will Go Extinct Is Approximately Independent Of How Long It Has Existed

    • Antagonistic Coevolution Can Have Various Forms, Including The Red Queen Mode

    • Both Biological And Physical Hypotheses Should Be Tested On Macroevolutionary Observations

Summary

Further Reading

Study And Review Questions

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23. Extinction And Radiation: (Tutorial)

    • The Number Of Species In A Taxon Increases Durings Phases Of Adaptive Radiation

    • Causes And Consequences Of Extinctions Can Be Studied In The Fossil Record

    • Mass Extinctions

    • Distributions Of Extinction Rates May Fit A Power Law

    • Changes In The Quality Of The Sedimentary Record Through Time Are Associated With Changes In The Observed Extinction Rate

    • Species Selection

    • One Higher Taxon May Replace Another, Because Of Chance, Environmental Change, Or Competitive Replacement

    • Species Diversity May Have Increased Logistically Or Exponentially Since The Cambrian, Or It May Have Increased Little At All

    • Conclusion: Biologists And Paleontologists Have Held A Range Of Views About The Importance Of Mass Extinctions In The History Of Life

Summary

Further Reading

Study And Review Questions

Glossary

Answers To Study And Review Questions

References

Index

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4. Natural Selection And Variation: (Tutorial) Sample Chapter

    • In Nature, There Is A Struggle For Existence

    • Natural Selection Operates If Some Conditions Are Met

    • Natural Selection Explains Both Evolution And Adaptation

    • Natural Selection Can Be Directional, Stabilizing, Or Disruptive

    • Variation In Natural Populations Is Widespread

    • Organisms In A Population Vary In Reproductive Success

    • New Variation Is Generated By Mutation And Recombination

    • New Variation Created By Recombination And Mutation Is Random With Respect To The Direction Of Adaptation

Summary

Further Reading

Study And Review Questions

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Part II: Evolutionary Genetics:

5. The Theory Of Natural Selection: (Tutorial 1|Tutorial 2)

    • Population Genetics Is Concerned With Genotype And Gene Frequencies

    • An Elementary Population Genetic Model Has Four Main Steps

    • Genotype Frequencies In The Absence Of Selection Go To The Hardy-Weinberg Equilibrium

    • We Can Test, By Simple Observation, Whether Genotypes In A Population Are At The Hardy-Weinberg Equilibrium

    • The Hardy-Weinberg Theorem Is Important Conceptually, Historically, In Practical >Research, And In The Workings Of Theoretical Models

    • The Simplest Model Of Selection Is For One Favored Allele At One Locus

    • The Model Of Selection Can Be Applied To The Peppered Moth

    • Pesticide Resistance In Insects Is An Example Of Natural Selection

    • Fitnesses Are Important Numbers In Evolutionary Theory And Can Be Estimated By Three Main Methods

    • Natural Selection Operating On A Favored Allele At A Single Locus Is Not Meant To Be A General Model Of Evolution

    • A Recurrent Disadvantageous Mutation Will Evolve To A Calculable Equilibrial Frequency

    • Heterozygous Advantage

    • The Fitness Of A Genotype May Depend On Its Frequency

    • Subdivided Populations Require Special Population Genetic Principles

Summary

Further Reading

Study And Review Questions

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6. Random Events In Population Genetics: (Tutorial)

    • The Frequency Of Alleles Can Change At Random Through Time In A Process Called Genetic Drift

    • A Small Founder Population May Have A Non-Representative Sample Of The Ancestral Population's Genes

    • One Gene Can Be Substituted For Another By Random Drift

    • Hardy-Weinberg "Equilibrium" Assumes The Absence Of Genetic Drift

    • Neutral Drift Over Time Produces A March To Homozygosity

    • A Calculable Amount Of Polymorphism Will Exist In A Population Because Of Neutral Mutation

    • Population Size And Effective Population Size

Summary

Further Reading

Study And Review Questionss

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7. Natural Selection And Random Drift In Molecular Evolution: (Tutorial)

    • Random Drift And Natural Selection Can Both Hypothetically Explain Molecular Evolution

    • Rates Of Molecular Evolution And Amounts Of Genetic Variation Can Be Measured

    • Rates Of Molecular Evolution Are Arguably Too Constant For A Process Controlled By Natural Selection

    • The Molecular Clock Shows A Generation Time Effect

    • The Nearly Neutral Theory

    • Evolutionary Rate And Functional Constraint

    • Conclusion And Comment: The Neutralist Paradigm Shift

    • Genomic Sequences Have Led To New Ways Of Studying Molecular Evolution

    • Conclusion: 35 Years Of Research On Molecular Evolution

Summary

Further Reading

Study And Review Questions

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8. Two-Locus And Multilocus Population Genetics: (Tutorial)

    • Mimicry In Papilio Is Controlled By More Than One Genetic Locus

    • Genotypes At Different Loci In Papilio Memnon Are Coadapted

    • Mimicry In Heliconius Is Controlled By More Than One Gene, But They Are Not Tightly Linked

    • Two-Locus Genetics Is Concerned With Haplotype Frequencies

    • Frequencies Of Haplotypes May Or May Not Be In Linkage Equilibrium

    • Human HLA Genes Are A Multilocus Gene System

    • Linkage Disequilibrium Can Exist For Several Reasons

    • Two-Locus Models Of Natural Selection Can Be Built

    • Hitch-Hiking Occurs In Two-Locus Selection Models

    • Selective Sweeps Can Provide Evidence Of Selection In DNA Sequences

    • Linkage Disequilibrium Can Be Advantageous, Neutral, Or Disadvantageous

    • Wright Invented The Influential Concept Of An Adaptive Topography

    • The Shifting Balance Theory Of Evolution

Summary

Further Reading

Study And Review Questions

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9. Quantitative Genetics: (Tutorial)

    • Climatic Changes Have Driven The Evolution Of Beak Size In One Of Darwin's Finches

    • Quantitative Genetics Is Concerned With Characters Controlled By Large Numbers Of Genes

    • Variation Is First Divided Into Genetic And Environmental Effects

    • Variance Of A Character Is Divided Into Genetic And Environmental Effects

    • Relatives Have Similar Genotypes, Producing The Correlation Between Relatives

    • Heritability Is The Proportion Of Phenotypic Variance That Is Additive

    • A Character's Heritability Determines Its Response To Artificial Selection

    • Strength Of Selection Has Been Estimated In Many Studies Of Natural Populations

    • Relations Between Genotype And Phenotype May Be Non-Linear, Producing Remarkable Responses To Selection

    • Stabilizing Selection Reduces The Genetic Variability Of A Character

    • Characters In Natural Populations Subject To Stabilizing Selection Show Genetic Variation

    • Levels Of Genetic Variation In Natural Populations Are Imperfectly Understood

    • Conclusion

Summary

Further Reading

Study And Review Questions

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Part III: Adaptation And Natural Selection:

10. Adaptive Explanation: (Tutorial)

    • Natural Selection Is The Only Known Explanation For Adaptation

    • Pluralism Is Appropriate In The Study Of Evolution, Not Of Adaptation

    • Natural Selection Can In Principle Explain All Known Adaptations

    • New Adaptations Evolve In Continuous Stages From Pre Existing Adaptations, But The Continuity Takes Various Forms

    • Genetics Of Adaptation

    • Three Main Methods Are Used To Study Adaptation

    • Adaptations In Nature Are Not Perfect

    • How Can We Recognize Adaptations?

Summary

Further Reading

Study And Review Questions

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11. The Units Of Selection: (Tutorial)

    • What Entities Benefit From The Adaptations Produced By Selection?

    • Natural Selection Has Produced Adaptations That Benefit Various Levels Of Organization

    • Another Sense Of "Unit Of Selection" Is The Entity Whose Frequency Is Adjusted Directly By Natural Selection

    • The Two Senses Of "Unit Of Selection" Are Compatible; One Specifies The Entity That Generally Shows Phenotypic Adaptations, The Other The Entity Whose Frequency Is Generally Adjusted By Natural Selection

Summary

Further Reading

Study And Review Questions

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12. Adaptations In Sexual Reproduction: (Tutorial)

    • The Existence Of Sex Is An Outstanding, Unsolved Problem In Evolutionary Biology

    • There Are Two Main Theories In Which Sex May Have A Short-Term Advantage

    • Conclusion: It Is Uncertain How Sex Is Adaptive

    • The Theory Of Sexual Selection Explains Many Differences Between Males And Females

    • The Sex Ratio Is A Well Understood Adaptation

    • Different Adaptations Are Understood In Different Levels Of Detail

Summary

Further Reading

Study And Review Questions

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Part IV: Evolution And Diversity:

13. Species Concepts And Intraspecific Variation: (Tutorial) Sample Chapter

    • In Practice Species Are Recognized And Defined By Phenetic Characters

    • Several Closely Related Species Concepts Exist

    • Isolating Barriers

    • Geographic Variation Within A Species Can Be Understood In Terms Of Population Genetic And Ecological Processes

    • "Population Thinking" And "Typological Thinking" Are Two Ways Of Thinking About Biological Diversity

    • Ecological Influences On The Form Of A Species Are Shown By The Phenomenon Of >Character Displacement

    • Some Controversial Issues Exist Between The Phenetic, Biological, And Ecological >Species Concepts

    • Taxonomic Concepts May Be Nominalist Or Realist

    • Conclusion

Summary

Further Reading

Study And Review Questions

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14. Speciation: (Tutorial)

    • How Can One Species Split Into Two Reproductively Isolated Groups Of Organisms?

    • A Newly Evolving Species Could Theoretically Have An Allopatric, Parapatric, Or Sympatric Geographic Relation With Its Ancestor

    • Reproductive Isolation Can Evolve As A By-Product Of Divergence In Allopatric Populations

    • The Dobzhansky-Muller Theory Of Postzygotic Isolation

    • An Interim Conclusion: Two Solid Generalizations About Speciation

    • Reinforcement

    • Some Plant Species Have Originated By Hybridization

    • Speciation May Occur In Non-Allopatric Populations, Either Parapatrically Or Sympatrically

    • Parapatric Speciation

    • Sympatric Speciation

    • The Influence Of Sexual Selection In Speciation Is One Current Trend In Research

    • Identification Of Genes That Cause Reproductive Isolation Is Another Current Trend In Research

    • Conclusion

Summary

Further Reading

Study And Review Questions

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15. The Reconstruction Of Phylogeny: (Tutorial)

    • Phylogenies Express The Ancestral Relations Between Species

    • Phyogenies Are Inferred From Morphological Characters Using Cladistic Techniques

    • Homologies Provide Reliable Evidence For Phylogenetic Inference, And Homoplasies Provide Unreliable Evidence

    • Homologies Can Be Distinguished From Homoplasies By Several Criteria

    • Derived Homologies Are More Reliable Indicators Of Phylogenetic Relations Than Are Ancestral Homologies

    • The Polarity Of Character States Can Be Inferred By Several Techniques

    • Some Character Conflict May Remain After Cladistic Character Analysis Is Complete

    • Molecular Sequences Are Becoming Increasingly Important In Phylogenetic Inference, And They Have Distinct Properties

    • Several Statistical Techniques Exist To Infer Phylogenies From Molecular Sequences

    • Molecular Phylogenetics In Action

    • Several Problems Have Been Encountered In Molecular Phylogenetics

    • Paralogous Genes Can Be Used To Root Unrooted Trees

    • Molecular Evidence Successfully Challenged Paleontological Evidence In The Analysis Of Human Phylogenetic Relations

    • Unrooted Trees Can Be Inferred From Other Kinds Of Evidence, Such As Chromosomal Inversions In Hawaiian Fruitflies

    • Conclusion

Summary

Further Reading

Study And Review Questions

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16. Classification And Evolution: (Tutorial)

    • Biologists Classify Species Into A Hierarchy Of Groups

    • There Are Phenetic And Phylogenetic Principles Of Classification

    • There Are Phenetic, Cladistic, And Evolutionary Schools Of Classification

    • A Method Is Needed To Judge The Merit Of A School Of Classification

    • Phenetic Classification Uses Distance Measures And Cluster Statistics

    • Phylogenetic Classification Uses Inferred Phylogenetic Relations

    • Evolutionary Classification Is A Synthesis Of Phenetic And Phylogenetic Principles

    • The Principle Of Divergence Explains Why Phylogeny Is Hierarchical

    • Conclusion

Summary

Further Reading

Study And Review Questions

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17. Evolutionary Biogeography: (Tutorial)

    • Species Have Defined Geographic Distributions

    • Ecological Characteristics Of A Species Limit Its Geographic Distribution

    • Geographic Distributions Are Influenced By Dispersal

    • Geographic Distributions Are Influenced By Climate, Such As In The Ice Ages

    • Local Adaptive Radiations Occur On Island Archipelagos

    • Species Of Large Geographic Areas Tend To Be More Closely Related To Other Local Species Than To Ecologically Similar Species Elsewhere In The Globe

    • Geographic Distributions Are Influenced By Vicariance Events, Some Of Which Are Caused By Plate Tectonic Movement

    • The Great American Interchange

    • Conclusion

Summary

Further Reading

Study And Review Questions

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Part V: Macroevolution:

18. The History Of Life: (Tutorial)

    • Fossils Are Remains Of Organisms From The Past And Are Preserved In Sedimentary >Rocks

    • Geological Time Is Divided Into A Series Of Eras, Periods, And Epochs

    • The Cambrian Explosion

    • Evolution Of Land Plants

    • Vertebrate Evolution

    • Human Evolution

    • Macroevolution May Or May Not Be An Extrapolated Form Of Microevolution

Summary

Further Reading

Study And Review Questions

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19. Evolutionary Genomics: (Tutorial)

    • Our Expanding Knowledge Of Genome Sequences Is Making It Possible To Ask, And Answer, Questions About The Evolution Of Genomes

    • The Human Genome Documents The History Of The Human Gene Set Since Early Life

    • The History Of Duplications Can Be Inferred In A Genomic Sequence

    • Genome Size Can Shrink By Gene Loss

    • Symbiotic Mergers, And Horizontal Gene Transfer, Between Species Influence Genome Evolution

    • The X/Y Sex Chromosomes Provide An Example Of Evolutionary Genomic Research At The Chromosomal Level

    • Genome Sequences Can Be Used To Study The History Of Non-Coding DNA

    • Conclusion

Summary

Further Reading

Study And Review Questions

http://www.blackwellpublishing.com/ridley/toc.asp

Table of Contents

Preface.

Acknowledgments.

Part I: Introduction:

1. The Rise Of Evolutionary Biology: (Tutorial)

    • Evolution Means Change In Living Things By Descent With Modification

    • Living Things Show Adaptations

    • A Short History Of Evolutionary Biology

Summary

Further Reading

Study And Review Questions

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2. Molecular And Mendelian Genetics: (Tutorial)

    • Inheritance Is Caused By DNA Molecules, Which Are Physically Passed From Parent To Offspring

    • DNA Structurally Encodes Information Used To Build The Body's Proteins

    • Information In DNA Is Decoded By Transcription And Translation

    • Large Amounts Of Non-Coding DNA Exist In Some Species

    • Mutational Errors May Occur During DNA Replication

    • Rates Of Mutation Can Be Measured

    • Diploid Organisms Inherit A Double Set Of Genes

    • Genes Are Inherited In Characteristic Mendelian Ratios

    • Darwin's Theory Would Probably Not Work If There Was A Non-Mendelian Blending

    • Mechanism Of Heredity

Summary

Further Reading

Study And Review Questions

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3. The Evidence For Evolution (Tutorial)

    • We Distinguish Three Possible Theories Of The History Of Life

    • On A Small Scale, Evolution Can Be Observed In Action

    • Evolution Can Also Be Produced Experimentally

    • Interbreeding And Phenotypic Similarity Provide Two Concepts Of Species

    • Ring "Species" Show That The Variation Within A Species Can Be Extensive Enough To Produce A New Species

    • New, Reproductively Distinct Species Can Be Produced Experimentally

    • Small-Scale Observations Can Be Extrapolated Over The Long Term

    • Groups Of Living Things Have Homologous Similarities

    • Different Homologies Are Correlated, And Can Be Hierarchically Classified

    • Fossil Evidence Exists For The Transformation Of Species

    • The Order Of The Main Groups In The Fossil Record Suggests They Have Evolutionary Relationships

    • Summary Of The Evidence For Evolution

    • Creationism Offers No Explanation Of Adaptation

    • Modern "Scientific Creationism" Is Scientifically Untenable

Summary

Further Reading

Study And Review Questions