EvolutionEvolution

IntroductionIntroduction Historical context of evolutionHistorical context of evolution Processes and mechanisms of Processes and mechanisms of

evolutionevolution Origin and evolution of lifeOrigin and evolution of life Specific topics for discussionSpecific topics for discussion

Take-Home MessagesTake-Home Messages

Darwin: Darwin: Voyage of the BeagleVoyage of the Beagle and the and the Origin of Origin of SpeciesSpecies: the epitomy of the scientific method: the epitomy of the scientific method

Mechanism: natural selection operates on genetic Mechanism: natural selection operates on genetic variation at the level of populations and over time variation at the level of populations and over time gradually changes the gene pool, leading to gradually changes the gene pool, leading to microevolution (populations) and/or macroevolution microevolution (populations) and/or macroevolution (species)(species)

““As you sleep”, evolution is in action: GMO’s, pesticide As you sleep”, evolution is in action: GMO’s, pesticide resistance in plants and animals, and antibiotic resistance in plants and animals, and antibiotic resistance in microbesresistance in microbes

Theory of evolution extraordinarily provides the Theory of evolution extraordinarily provides the mechanism to explain two sides of the same coin: mechanism to explain two sides of the same coin: diversity and similarity of living systemsdiversity and similarity of living systems

Theory of evolution is a gift of monumental importance Theory of evolution is a gift of monumental importance in the life sciences, and its importance has only grown in the life sciences, and its importance has only grown since Darwin’s seminal publication in 1859 (since Darwin’s seminal publication in 1859 (Origin of Origin of SpeciesSpecies))

IntroductionIntroduction Two sides of the same coin: diversity and Two sides of the same coin: diversity and

similaritysimilarity Theory of evolutionTheory of evolution

Define theory of evolutionDefine theory of evolution Species evolve gradually from ancestral Species evolve gradually from ancestral

speciesspecies Mechanism is natural selectionMechanism is natural selection

Gift to biologyGift to biology Unifying theory to explain diversity and Unifying theory to explain diversity and

similarity of all living systemssimilarity of all living systems Impressive and substantial underpinning to the Impressive and substantial underpinning to the

life sciences (ecology, environmental sciences, life sciences (ecology, environmental sciences, genetic engineering, astrobiology, etc.)genetic engineering, astrobiology, etc.)

Historical Context: Historical Context: DarwinDarwin

Voyage of the BeagleVoyage of the Beagle on the on the HMS Beagle (1831)HMS Beagle (1831) Age 22 as naturalist to Age 22 as naturalist to

catalogue plants and catalogue plants and animalsanimals

Convention at the time: Convention at the time: static view (pre-ordained)static view (pre-ordained)

Frame of reference for Frame of reference for Darwin: UK landscape and Darwin: UK landscape and biodiversity as bland as UK biodiversity as bland as UK foodfood

Notable Observations by Notable Observations by DarwinDarwin

South American diversity of South American diversity of landscapes and biotalandscapes and biota Brazilian rainforestBrazilian rainforest Savannas of ArgentinaSavannas of Argentina Dry deserts of Terra del FuegoDry deserts of Terra del Fuego Towering mountains of the Towering mountains of the

AndesAndes Flora and fauna distinct Flora and fauna distinct

from Europefrom Europe Plethora of structures with Plethora of structures with

intuitive value in the intuitive value in the environment (adaptations)environment (adaptations)

Seeding of idea:Seeding of idea: living living systems are not static but systems are not static but vary as a function of the vary as a function of the environmentenvironment

Observations Observations (Galapagos)(Galapagos)

Galapagos Islands Galapagos Islands (seminal event)(seminal event) Volcanic islands off Volcanic islands off

Ecuador and PeruEcuador and Peru Fauna (birds, tortoises, Fauna (birds, tortoises,

plants, etc.)plants, etc.) Distinct lineage to species Distinct lineage to species

on S. American mainlandon S. American mainland FinchesFinches TortoiseTortoise

Seeding of idea:Seeding of idea: fauna arrived from fauna arrived from

mainland, then mainland, then Fauna diversified in new Fauna diversified in new

environmentenvironment

Darwin back to the UK Darwin back to the UK (1836)(1836)

Two seminal ideas in 1830’sTwo seminal ideas in 1830’s MalthusMalthus: population growth exceeds available : population growth exceeds available

resourcesresources CompetitionCompetition for limited resources (food, water, for limited resources (food, water,

light, mates) limits number of offspring light, mates) limits number of offspring maple tree produces 1000’s of seed of which ~ 10 maple tree produces 1000’s of seed of which ~ 10

germinate and grow – 0.0001%)germinate and grow – 0.0001%) Hypothesis:Hypothesis:

Environment drives the origin of species Environment drives the origin of species viavia the gradual accumulation of traits that the gradual accumulation of traits that incrementally improve survival over time incrementally improve survival over time (centuries to millennia)(centuries to millennia)

Darwin and Natural Darwin and Natural Selection (1840)Selection (1840)

Idea No. 1: Organisms differ in their Idea No. 1: Organisms differ in their success in reproduction and therefore success in reproduction and therefore contribute differently to future contribute differently to future generationsgenerations

Idea No. 2: Driving force for this Idea No. 2: Driving force for this differentialdifferential success is natural selection success is natural selection acting on the variability among acting on the variability among individualsindividuals

Product: Evolution of Product: Evolution of adaptationsadaptations that that enhance success (enhance success (fitnessfitness))

Darwin: Darwin: Origin of SpeciesOrigin of Species (1859)(1859)

Two principal tenetsTwo principal tenets Species Species evolveevolve gradually from ancestral gradually from ancestral

speciesspecies Mechanism is Mechanism is natural selectionnatural selection

Theory of Evolution as a gift to Theory of Evolution as a gift to biologybiology Origin of diversityOrigin of diversity Origin of similarityOrigin of similarity

Heads: DiversityHeads: Diversity

Tails: SimilarityTails: Similarity

Molecular Similarity/Dis-Molecular Similarity/Dis-similartitysimilartity

Human beta chain 0

Gorilla 1

Gibbon 2

Rhesus monkey 8

Dog 15

Horse, cow 25

Mouse 27

Gray kangaroo 38

Chicken 45

Frog 67

Lamprey 125

Sea slug (a mollusk) 127

Number of amino acid differences among animals in reference to humans in the protein hemoglobin

Processes and Processes and MechanismsMechanisms

Populations and species evolve (hierarchy)Populations and species evolve (hierarchy) KingdomKingdom

FamilyFamily SpeciesSpecies

PopulationsPopulations

IndividualsIndividuals Evolution at the population level is called Evolution at the population level is called

microevolutionmicroevolution Evolution at the species level is called Evolution at the species level is called

macroevolutionmacroevolution

Concept of FitnessConcept of Fitness

FitnessFitness = relative contribution of an = relative contribution of an individual to the individual to the next generationnext generation Positive fitnessPositive fitness Negative fitnessNegative fitness

Contrast fitness to “survival of the Contrast fitness to “survival of the fittest” and “struggle for survival”fittest” and “struggle for survival”

Variation in Fitness Variation in Fitness

Organisms vary in their morphology, Organisms vary in their morphology, physiology and biochemistryphysiology and biochemistry

Source of variation is genetics (yet Source of variation is genetics (yet to be discovered)to be discovered) Inheritance of traits by Mendel (1Inheritance of traits by Mendel (18860’s)60’s) DNA structure by Watson and Crick DNA structure by Watson and Crick

((1950’s1950’s)) Gene sequences (Gene sequences (1970’s1970’s)) Genetic engineering (2000’s)Genetic engineering (2000’s)

Summary of Mechanism Summary of Mechanism (1940’s)(1940’s)

Two cardinal tenetsTwo cardinal tenets Natural selectionNatural selection (Darwin) (Darwin) Individuals Individuals differdiffer genetically genetically

(Mendel)(Mendel) Result: Result:

gene pool of the next generation is gene pool of the next generation is a consequence of the action of a consequence of the action of natural selection on inherited natural selection on inherited variation at the level of populationsvariation at the level of populations

First GenerationGene Pool

Second Generation Gene Pool

N>100 Generations Gene Pool

N>1000 Generations Gene Pool

Selection

Fitness

Gene Pool

Microevolution

Macroevolution

Large-Scale Changes: Large-Scale Changes: Global Selective AgentsGlobal Selective Agents

Progressive Progressive physical/chemical physical/chemical changeschanges Carbon dioxide in the Carbon dioxide in the

atmosphereatmosphere Oxygen in the atmosphereOxygen in the atmosphere Breakup of PangeaeBreakup of Pangeae

Catastrophic climate Catastrophic climate changechange Asteroid impacts (dinosaurs Asteroid impacts (dinosaurs

followed by mammals)followed by mammals) Instantaneous biological Instantaneous biological

changeschanges Evolution of enzymesEvolution of enzymes

Origin and Evolution of Life Origin and Evolution of Life on Earthon Earth

Origin of Life in the Origin of Life in the Universe: AstrobiologyUniverse: Astrobiology

Chemicals of lifeChemicals of life Information brokers: nucleic acids and Information brokers: nucleic acids and

nucleotidesnucleotides Carbohydrates (carbon skeletons for Carbohydrates (carbon skeletons for

polymers)polymers) Lipids (e.g., membranes)Lipids (e.g., membranes) Proteins (e.g., enzymes)Proteins (e.g., enzymes)

Medium for life is water (HMedium for life is water (H22O)O) Elements for life are common in the UniverseElements for life are common in the Universe Probability: Probability: extremelyextremely high probability that life high probability that life

has originated and evolved elsewhere in the has originated and evolved elsewhere in the Universe at multiple timesUniverse at multiple times

PanspermiaPanspermia: hypothesis that life on Earth : hypothesis that life on Earth originated elsewhere in the Universeoriginated elsewhere in the Universe

PanspermiaPanspermia

Origin and Evolution of Life: Origin and Evolution of Life: ClassificationClassification

Domain Domain Domain Domain DomainDomain

Bacteria Archaea Bacteria Archaea EukaryaEukarya

Common Ancestor Common Ancestor (4 - 4.5 Billion Years Ago)(4 - 4.5 Billion Years Ago)

Classification of Life on Classification of Life on EarthEarth

Illustration of a Virus

24-519Figure 24.28

Virus

HIV

Influenza

Ebola virus

Smallpox

Some forms of cancer

Colds

Polio

Some Common Viruses

Influenza virus

HIV

Evolution of Humans

Evolution in Action “As You Evolution in Action “As You Sleep”Sleep”

Antibiotic resistance in Antibiotic resistance in microbesmicrobes 100+ antibiotics since 100+ antibiotics since

1940’s (penicillium)1940’s (penicillium) Efficacy of antibioticsEfficacy of antibiotics

Resistance to Resistance to insecticides in insecticides in cockroachescockroaches ““Godzilla the Godzilla the

Cockroach”Cockroach”

Evolution While You Evolution While You SleepSleep

Industrial Industrial melanism in the melanism in the peppered moth in peppered moth in UKUK

pollution as pollution as stress followed stress followed by selection by selection predation by predation by birdsbirds

Peppered Moth

Melanic Peppered Moth

Evolution As You SleepEvolution As You Sleep

Genetically Modified Organisms (GMO’s)

Cotton plants engineered for frost resistance with DNA insert (Bt gene) from a bacterium