Organic Evolution Organic Evolution & Natural Selection& Natural Selection

Organic EvolutionOrganic Evolution

►changes in life through timechanges in life through time

►development of complex life formsdevelopment of complex life forms

►development of a variety of life development of a variety of life formsforms

Natural SelectionNatural Selection

►mechanism responsible for mechanism responsible for evolutionevolution

►through mutation and selectionthrough mutation and selection►survival of thesurvival of the

fittest (for a niche)fittest (for a niche) luckiestluckiest combinationcombination

Scientific ExplanationsScientific Explanations

►must be naturalmust be natural►must be supported by available datamust be supported by available data►must be testable & falsifiablemust be testable & falsifiable►subject to revision or refinement or subject to revision or refinement or

negationnegation►should be predictiveshould be predictive

►OE and NS meet all of these requirementsOE and NS meet all of these requirements

Theory & HypothesisTheory & Hypothesis

►HypothesisHypothesis a working explanation or “educated guess”a working explanation or “educated guess” competing hypotheses are often competing hypotheses are often

investigated simultaneouslyinvestigated simultaneously

►TheoryTheory the best explanation supported by a the best explanation supported by a

preponderance of the evidencepreponderance of the evidence the best a scientist can hope forthe best a scientist can hope for

TerminologyTerminology

►speciesspecies reproductively isolated group of reproductively isolated group of

living organismsliving organisms

►populationpopulation group of organisms consisting of all group of organisms consisting of all

the members of a species living in an the members of a species living in an areaarea

Organic evolution: Organic evolution: observationsobservations

►sedimentary rockssedimentary rocks deposited in layersdeposited in layers oldest layers are on the bottomoldest layers are on the bottom layers may be correlated with layers layers may be correlated with layers

in other areasin other areas►conclusionsconclusions

relative time scalerelative time scale the Earth is very oldthe Earth is very old confirmed with absolute datingconfirmed with absolute dating

Organic evolution: Organic evolution: observationsobservations

►fossil recordfossil record oldest rocks have only simple fossilsoldest rocks have only simple fossils

younger rocks have more organisms younger rocks have more organisms similar to those living today (at levels similar to those living today (at levels from species to kingdom)from species to kingdom)

fossils record includes appearances fossils record includes appearances and extinctions of many speciesand extinctions of many species

Organic evolution: Organic evolution: observationsobservations

►geographic distribution of organismsgeographic distribution of organisms many organisms are similar but uniquemany organisms are similar but unique they are confined to specific areas they are confined to specific areas

(islands, continents, water bodies)(islands, continents, water bodies) includes modern includes modern and fossiland fossil organisms organisms distribution has changed through timedistribution has changed through time

Organic evolution: Organic evolution: observationsobservations

►anatomyanatomy cell structurecell structure is similar in all living is similar in all living

organismsorganisms embryologyembryology - embryos of mammals, - embryos of mammals,

birds, and reptiles are very similarbirds, and reptiles are very similar homologus organshomologus organs - similar organs, - similar organs,

different functionsdifferent functions vestigal organsvestigal organs - no purpose in one, - no purpose in one,

purpose in anotherpurpose in another

Organic evolution: Organic evolution: observationsobservations

►geneticsgenetics structure of DNA and RNA is the structure of DNA and RNA is the

same in all living organismssame in all living organisms similarity in genetic code varies similarity in genetic code varies

between organisms (some organisms between organisms (some organisms are more similar than others)are more similar than others)

mitochondrial and plasmid DNAmitochondrial and plasmid DNA►separate from nuclear DNAseparate from nuclear DNA►similar to some bacteriasimilar to some bacteria

Organic evolution: Organic evolution: observationsobservations

►cladistic analysescladistic analyses statistical examination usingstatistical examination using

►anatomyanatomy►DNADNA►behaviorbehavior

indicates strength of affinity between indicates strength of affinity between speciesspecies

Organic evolution: Organic evolution: observationsobservations

► combining datacombining data cladistic analyses of fossils and living cladistic analyses of fossils and living

speciesspecies time data (relative & absolute)time data (relative & absolute) spatial relationshipsspatial relationships

(where fossils and living populations (where fossils and living populations are found)are found)

► reveals phylogenyreveals phylogeny(“tree of life through time”)(“tree of life through time”)

Organic evolution: Organic evolution: conclusionsconclusions

►the characteristics of populations of the characteristics of populations of living organisms have changed living organisms have changed through timethrough time life has become more complexlife has become more complex life has become more diverselife has become more diverse all life is relatedall life is related

►this is accepted as a factual this is accepted as a factual observationobservation

Evolutionary TrendsEvolutionary Trends

►divergence & speciationdivergence & speciation►extinctionextinction►convergenceconvergence

►phyletic gradualismphyletic gradualism►punctuated equilibriumpunctuated equilibrium

Organic evolution:Organic evolution:Missing links!!!Missing links!!!

► the “link” between two fossil species OR the “link” between two fossil species OR between a fossil species and a living between a fossil species and a living speciesspecies

► PRESERVATION AS A FOSSIL IS RARE!PRESERVATION AS A FOSSIL IS RARE!

► many “links” found many “links” found (it’s just a matter of time and (it’s just a matter of time and effort)effort)

► however:however: each “gap” filled creates two each “gap” filled creates two new “gaps”new “gaps”

QuestionQuestion

►What is the mechanism that What is the mechanism that resulted in the evolution of life?resulted in the evolution of life?

Natural selection: Natural selection: observationsobservations

►populationspopulations of organisms display of organisms display a variety of characteristicsa variety of characteristics characteristics may be useful, not characteristics may be useful, not

useful, or detrimentaluseful, or detrimental the variety is reflected in an the variety is reflected in an

organisms genesorganisms genes

Natural selection: Natural selection: observationsobservations

►new genes provided bynew genes provided by mutationmutation duplicationduplication exchangeexchange

►passed to offspring during passed to offspring during reproductionreproduction

Natural selection: Natural selection: observationsobservations

►SymbiosisSymbiosis Living organisms in close proximity, Living organisms in close proximity,

at least one of the symbionts cannot at least one of the symbionts cannot live without the other live without the other

►Symbiotic relationships can result Symbiotic relationships can result in new characteristicsin new characteristics

Natural selection: Natural selection: observationsobservations

► artificial selectionartificial selection domesticated plants and animals can be domesticated plants and animals can be

bred to favor certain characteristicsbred to favor certain characteristics

ONLY ONLY individuals with desired individuals with desired characteristics are allowed to breedcharacteristics are allowed to breed

descendant descendant populationspopulations of plants and of plants and animals are dominated by characteristics animals are dominated by characteristics that are desired by breeders…that are desired by breeders…

……and thus favored their survivaland thus favored their survival

Natural selection: Natural selection: observationsobservations

►The natural environment acts as a The natural environment acts as a selective breederselective breeder

contains opportunities and stresses contains opportunities and stresses for living organismsfor living organisms

selection is enhanced byselection is enhanced by►stress on an existing nichestress on an existing niche►a new nichea new niche

Natural selection: Natural selection: observationsobservations

►PopulationsPopulations of a species may of a species may become isolated by geography or become isolated by geography or behaviorbehavior

►IsolationIsolation provides new opportunities and provides new opportunities and

stressesstresses isolates the population from the isolates the population from the

larger gene poollarger gene pool

ConclusionConclusion

The variety of conditions in The variety of conditions in the natural environment the natural environment results in results in natural selectionnatural selection of of populations which, in turn, is populations which, in turn, is responsible for responsible for biological biological evolutionevolution..

Natural selection: detailsNatural selection: details

► organisms with favorable characteristics organisms with favorable characteristics for their niche are more likely to thrive for their niche are more likely to thrive and reproduce while organisms with and reproduce while organisms with unfavorable characteristics are less unfavorable characteristics are less likely to thrive and reproducelikely to thrive and reproduce

► over time, favorable characteristics can over time, favorable characteristics can accumulate in a accumulate in a populationpopulation until the until the members of the members of the populationpopulation can no longer can no longer reproduce with the reproduce with the populationpopulation from from which they became isolatedwhich they became isolated

Natural selection: detailsNatural selection: details

►genetic changesgenetic changes favorablefavorable: more likely to be passed : more likely to be passed

on to offspringon to offspring neutral: likely to be passed on to neutral: likely to be passed on to

offspringoffspring unfavorableunfavorable: less likely to be passed : less likely to be passed

on to offspringon to offspring

►natural selection is not randomnatural selection is not random

Evolutionary trendsEvolutionary trends

►divergence, speciation, & divergence, speciation, & extinctionextinction

►convergenceconvergence►homology & vestigal organshomology & vestigal organs►coevolution & symbiogenesiscoevolution & symbiogenesis►phyletic gradualism & punctuated phyletic gradualism & punctuated

equilibriumequilibrium

Divergence & SpeciationDivergence & Speciation► a a populationpopulation has a gene pool has a gene pool► members of the members of the populationpopulation interbreed interbreed► the the populationpopulation may become isolated may become isolated

from others of a speciesfrom others of a species development of niches & resource development of niches & resource

partitioningpartitioning migrationmigration development of physical barriersdevelopment of physical barriers

► populationspopulations may be selected may be selected by stressby stress by opportunityby opportunity

► isolation may result in genetic isolation may result in genetic divergence & speciationdivergence & speciation

ExtinctionExtinction

►stress on limiting factors destroy stress on limiting factors destroy a populationa population

►““divergent” evolution into divergent” evolution into subsequent species (pseudo-subsequent species (pseudo-extinction)extinction)

ConvergenceConvergence

► Characteristics of a habitat favor Characteristics of a habitat favor certain styles of adaptationcertain styles of adaptation e.g. streamlined shape, tooth shapee.g. streamlined shape, tooth shape

► Natural selection results in organisms Natural selection results in organisms in similar niches having similar formsin similar niches having similar forms

► Similar forms resulting from Similar forms resulting from convergence usually do not have convergence usually do not have similar underlying structuressimilar underlying structures

Homology & Vestigial Homology & Vestigial OrgansOrgans

► a slightly modified organ or organ a slightly modified organ or organ system my provide advantage in a system my provide advantage in a nicheniche

► when the modification results in when the modification results in selection generation after generation, selection generation after generation, the modification may become enhancedthe modification may become enhanced

► when compared with closely related when compared with closely related species, the organ or organ system will species, the organ or organ system will have the same parts used for different have the same parts used for different functions (homology) and some parts functions (homology) and some parts may no longer be in use (vestigial)may no longer be in use (vestigial)

Coevolution & Coevolution & SymbiogenisisSymbiogenisis

► A niche may be associated with another A niche may be associated with another organismorganism

► The characteristics that favor interdependence The characteristics that favor interdependence may be subject to continued selection may be subject to continued selection (coevolution)(coevolution)

► Selection that favors an “organic” niche may Selection that favors an “organic” niche may result in dependence or interdependence result in dependence or interdependence (symbiosis)(symbiosis)

► Symbiotic relationships may become permanent Symbiotic relationships may become permanent due to genetic exchange and/or incorporation due to genetic exchange and/or incorporation (symbiogenesis)(symbiogenesis)

PhylogenyPhylogeny

►relationships between organisms relationships between organisms can be determined usingcan be determined using geneticsgenetics anatomy & physiology anatomy & physiology fossilsfossils

Phyletic Gradualism &Phyletic Gradualism &Punctuated EquilibriumPunctuated Equilibrium

►gradualismgradualism slow, steady changeslow, steady change

►equilibrium & punctuationequilibrium & punctuation long periods with little changelong periods with little change short bursts of rapid changeshort bursts of rapid change

How did it start?How did it start?

► Chemical evolutionChemical evolution needs energy, but no oxygenneeds energy, but no oxygen

simple compounds form(CO2, NH3)simple compounds form(CO2, NH3) organic compounds form (amino acids, nucleic acids)organic compounds form (amino acids, nucleic acids) organic compounds assemble (microspherules, organic compounds assemble (microspherules,

bubbles, clay particles, ice crystals)bubbles, clay particles, ice crystals)

► First life: simple, wall-less, fermenting bacteriaFirst life: simple, wall-less, fermenting bacteria

► Where?Where? deep ocean vents, tidal pools, ice sheet, clay deep ocean vents, tidal pools, ice sheet, clay

sedimentsediment

RandomnessRandomness

►mutations mutations are randomare random►evolution is evolution is not randomnot random►natural selection is natural selection is not randomnot random

►favorable mutations survive favorable mutations survive through reproductionthrough reproduction

End pointEnd point

►Evolution has no endEvolution has no end