! 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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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