speciation 1 shahril

7/24/2019 Speciation 1 SHAHRIL

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SpeciationBy: Mohamad Shahril B.

Mohamad Salim


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In Darwins words, speciation is the multiplication of species.


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SpeciationThe process through which new species

form.

Speciation is a lineage-splitting eventthat produces two or more separatespecies.

A species is a group of organisms able

to interbreed and produce fertileospring.


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Species

Barrierseographic

!re "ygotic

!ost "ygotic

#eproductive$solation

ene%ow

Speciation Slow&ast


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eographical Barriers 'eep populations physically isolated

from each other. Thus( the organisms

from the populations are unable tointerbreed with each other.

)*amples include:

#ivers( mountains( oceans


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Biological Barriers 'eep species reproductively isolated

from each other.

#eproductive barriers fall into twobroad categories:

+. !re-"ygotic barriers

,. !ost-"ygotic barriers


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!re-"ygotic Barriers !re-fertili"ation barriers( either impede mating

between species or prevent fertili"ation of theegg if individuals from dierent species attemptto mate.

Types of pre-"ygotic barriers include: Behavioural isolation e*. ierent mating calls /abitat isolation e*. 0ccupying dierent parts of a

region Temporal isolation e*. ierent mating seasons Mechanical isolation e*. Anatomical dierences-

snails ametic isolation e*. )gg and sperm not compatible


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Behavioral $solation -Song in)astern and 1esternMeadowlar2s


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&our species of leopard frogs: dier in their mating calls./ybrids are inviable.


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!ost-"ygotic barriers !ost-fertili"ation barriers( prevent hybrid

"ygotes from developing into normal( fertile

ospring.

Types of post-"ygotic barriers include: /ybrid inviability hybrid dies.

/ybrid sterility hybrid is unable to reproduce. /ybrid brea2down complication3problem and

dies.


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The hybrid ospring is eitherwea2er than the parent species(or totally inviable 4meaning itcannot stay alive5. This could be

caused by minor or ma6or geneticdefects( and even slightlyreduced viability can cause bigdecreases in reproduction.


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Hybrid Breakdown:This is similar to hybridinviability or sterility(but s2ipping ageneration. 1e getsuccessful mating withviable( fertile ospring(but when the ospringtry to have ospring(things go wrong. Thesecond generation canbe either inviable(infertile( or showreduced 7tness. )itherway it8s 6ust notwor2ing out.


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Notaden

bennetti

i

Litoria

rubell

a


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Modes of Speciation


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Modes of SpeciationAllopatric speciation

)tymology: 9allo-patric ; 9dierent-

country reproductive isolation occurs in complete

geographic isolation. ene pools isolated via geographic

separation. !revalent mechanism of speciation in

animals.


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Allopatric Speciation:eographic $solation


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A. harrisii A. leucurus


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Allopatric speciation.

A population forms a

new species while

geographically isolated

from its parent population.

Sympatric speciation.

A subset of a population

forms a new species

without geographic

separation.


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Sympatric Speciation )tymology: 9sym-patric ; 9same-

country.

ene pools isolated via process otherthan geographic separation.

via polyploidy( particularly in plants via behavior( ecology and to a lesser

e*tent polyploidy in animals. ?@ of species via

sympatric speciation5.


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Summary Sympatric speciation is an important

evolutionary process that can separate

a species into two new ones. Thedivergence of the two species willgenerally ta2e place over a long periodof time( and it can be the eect of

dierences in things such as diet(behavior( and mate selection.

speciation 1 shahril

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