1. Evolution
In biology,evolutionisthe change inthe characteristicsof a speciesoverseveral generationsand
reliesonthe processof natural selection.
• The theoryof evolutionisbasedonthe ideathatall species?are relatedandgradually
change overtime.
• Evolutionreliesonthere beinggeneticvariation?inapopulationwhichaffectsthe physical
characteristics(phenotype) of anorganism.
• Some of these characteristicsmaygive the individual anadvantage overotherindividuals
whichthey can thenpasson to theiroffspring.
Evolution of man
Human evolutionisthe lengthyprocessof change bywhichpeopleoriginatedfromapelike
ancestors.Scientificevidenceshowsthatthe physical andbehavioural traitssharedbyall people
originatedfromapelike ancestorsandevolvedoveraperiodof approximatelysix millionyears.
Humansare primates.Physical andgeneticsimilaritiesshow thatthe modernhumanspecies,Homo
sapiens,hasa veryclose relationshiptoanothergroupof primate species, the apes.Humansandthe
great apes(large apes) of Africa -- chimpanzees(includingbonobos,orsocalled“pygmy
chimpanzees”)andgorillas -- share acommonancestorthat livedbetween8and6 millionyearsago.
HumansfirstevolvedinAfrica,andmuchof human evolutionoccurredonthatcontinent.The fossils
of earlyhumanswholivedbetween6and 2 millionyearsagocome entirelyfromAfrica.
Palaeoanthropology
Palaeoanthropologyisthe scientificstudyof humanevolution.Palaeoanthropologyisasubfieldof
anthropology,the studyof humanculture,society,andbiology.The fieldinvolvesanunderstanding
of the similaritiesanddifferencesbetweenhumansandotherspeciesintheirgenes,bodyform,
physiology,andbehaviour.Paleoanthropologistssearchforthe rootsof humanphysical traitsand
behaviour.
Early humanfossilsandarchaeological remainsofferthe mostimportantcluesaboutthisancient
past.These remainsinclude bones,toolsandanyotherevidence (suchasfootprints,evidence of
hearths,or butcherymarkson animal bones) leftbyearlierpeople.Usually,the remainswere buried
and preservednaturally.Theyare thenfoundeitheronthe surface (exposedbyrain,rivers,and
winderosion) orbydigginginthe ground.By studyingfossilizedbones,scientistslearnaboutthe
physical appearance of earlierhumansandhow itchanged.Bone size,shape,andmarkingsleftby
musclestell ushowthose predecessorsmovedaround,heldtools,andhow the size of theirbrains
changedovera longtime.Archaeological evidencereferstothe thingsearlier
THEORIES AND CONCEPTS OF EVOLUTION
1) Lamarckism
theoryisbasedon the inheritance of acquiredcharacterswhichare definedasthe
changes(variations) developedinthe bodyof anorganismfromnormal characters,
inresponse tothe changesin environment,orinthe functioning(useanddisuse)of
organs,in theirownlife time,tofulfill theirnew needs.
2. 2) Darwinism
CharlesDarwin’stheoryof evolutionstatesthatevolutionhappensbynatural
selection.
Individualsinaspeciesshow variationinphysicalcharacteristics.Thisvariationis
because of differencesintheir genes?
.
Individualswithcharacteristicsbestsuitedtotheirenvironmentare more likelyto
survive,findingfood,avoidingpredatorsandresistingdisease.These individualsare
more likelytoreproduce andpasstheirgenesontotheirchildren.
3) Mutation
Hugo de Vriesbelievedthatmutationcausesevolutionandnotthe minorheritable
variationswhichwasmentionedbyDarwin.Mutationsare randomanddirectionless
while Darwin’svariationsare small anddirectional.AccordingtoDarwinevolutionis
gradual while Hugode Vriesbelievedthatmutationcausedspeciesformationand
hence knownassaltation(single steplarge mutation).
Darwinism
Darwin'sTheoryof Evolution - Natural Selection WhileDarwin'sTheoryof Evolutionisarelatively
youngarchetype,the evolutionaryworldview itself isasoldasantiquity.AncientGreekphilosophers
such as Anaximanderpostulatedthe developmentof lifefromnon-lifeandthe evolutionarydescent
of manfrom animal.CharlesDarwinsimplybroughtsomethingnew tothe oldphilosophy -- a
plausible mechanismcalled"natural selection."Natural selectionactstopreserve andaccumulate
minoradvantageousgeneticmutations.Suppose amemberof aspeciesdeveloped afunctional
advantage (itgrewwingsandlearnedtofly).Itsoffspringwouldinheritthatadvantage andpassit on
to their
offspring.The inferior(disadvantaged) membersof the same specieswouldgraduallydie out,
leavingonlythe superior(advantaged) membersof the species.Natural selectionisthe preservation
of a functional advantage thatenablesaspeciestocompete betterinthe wild.Natural selectionis
the naturalisticequivalenttodomesticbreeding.Overthe centuries,humanbreedershave
produceddramaticchangesindomesticanimal populationsbyselectingindividualstobreed.
Breederseliminateundesirable traitsgraduallyovertime.Similarly,natural selectioneliminates
inferiorspeciesgraduallyovertime.
Summaryof Darwin'sTheoryof Evolution
• A speciesisapopulationof organismsthatinterbreedsandhasfertile offspring.
• Livingorganismshave descendedwithmodificationsfromspeciesthatlivedbefore them.
3. • Natural selectionexplainshowthisevolutionhashappened:
— More organismsare producedthancan survive because of limitedresources.
— Organismsstruggle forthe necessitiesof life;thereiscompetitionforresources.
— Individualswithinapopulationvaryintheirtraits;some of these traitsare heritable -- passedon
to offspring.
— Some variantsare betteradaptedto survive andreproduce underlocal conditionsthanothers.
— Better-adaptedindividuals(the"fitenough") are more likelytosurvive andreproduce,thereby
passingoncopiesof theirgenestothe nextgeneration.
— Specieswhose individualsare bestadaptedsurvive;othersbecomeextinct.
Difference between ancestry and speciation
Commondescentdescribeshow,inevolutionarybiology,agroupof organismsshare a most recent
commonancestor.Commonancestrybetweenorganismsof differentspeciesarisesduring
speciation,inwhichnewspeciesare establishedfromasingle ancestral population.Organisms
whichshare a more-recentcommonancestorare more closely related.The mostrecentcommon
ancestorof all currentlylivingorganismsisthe lastuniversalancestor,[1] whichlivedabout3.9
billionyearsago.
Speciation
Speciation,the formationof newanddistinctspeciesinthe course of evolution.Speciationinvolves
the splittingof asingle evolutionarylineage intotwoormore geneticallyindependentlineages.
