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EvolutionMacroevolution/Speciation


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Macroevolution

Macroevolutionis the occurrence oflarge-scale changes in the characteristics(traits) of life -- in effect, the evolution ofspecies and higher taxa.

It is distinct from microevolution, hich isthe se!uence of changes that occur ithina single population.


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According to Charles Darwin and alsothe modern synthesis, this distinctionis relative and purely a matter of

scale.The modern evolutionary synthesis

(often referred to simply as the modernsynthesis), rings together Charles

Darwin!s theory of the evolution ofspecies y natural selection with thetheory of genetics as the asis foriological inheritance.


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Proposed Mechanisms for

Macroevolution

Extrapolation of microevolutionary

processes......Gradualism.

The second way in which macroevolution is

believed to occur is through sudden and rapidchanges......Punctuated Equilibrium.


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Based on the fact that thereare critical genes in all livingorganisms, and a small changein them could cause drasticchanges in the organism,resulting in a new species

Tiny microevolutions, oversucient time, add up andaccumulate in isolatedpopulations andeventually result in new


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Too long of a time scale!

Whilst speciation events have been demonstrated in the laboratoryand observed in the field really dramatic differences between speciesdo not usually occur in directly observable timescales it occurs too"uic#ly for the process to be shown in the fossil record.$

%t is argued that since macroevolution can not be confirmed by acontrolled experiment it cannot be considered to be part of ascientific theory.

&owever evolutionists counter that astronomy geology archaeologyand the other historical sciences li#e macroevolution have to chec#

hypotheses through natural experiments.

They confirm hypotheses by finding out if they conform or fit with thephysical or observational evidence and can ma#e valid predictions. %nthis way macroevolution is testable and falsifiable.


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&ow is it studied then'

(lassical evidence of macroevolutionary

processes

) fossils extinction and radiation$

) biogeography global taxa distribution$

) comparative biology

Phenetics and cladistics* tree+building

Molecular evolution and molecular

phylogenetics


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We need to inferthe shape of the tree evolutionaryrelationships$ from leaves extanttaxa$ andbranches extinctor fossil taxa$ and from #nowledge

of geological events ...,. What waspresent where' -ossils$

. What happened when' /eology palaeoclimatology$

0. What ispresent where' 1iogeography$

The tree of life* stems and leaves

extant sppextant spp

extinct sppextinct spp

biogeographic/

geological events


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2etermining evolutionary

relationships

3nderstanding structure similarities and

differences

) &omologous structures from a commonancestor based on descent

) 4nalagous structures with similar functionality

but not dervied from common ancestor) (onvergent and divergent evolution

2erived characters vs. 4ncestral


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&ow is it studied then'

(lassical evidence of macroevolutionary(lassical evidence of macroevolutionary

processesprocesses

) fossils extinction and radiation$fossils extinction and radiation$

) biogeography global taxa distribution$biogeography global taxa distribution$

) comparative biologycomparative biology

Phenetics and cladistics* tree+buildingPhenetics and cladistics* tree+building

Molecular evolution and molecular

phylogenetics


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(omparative 1iochemistry

Many genes are found in all living thingsbecause we all use similar metabolism.

/enes can also be described as homologousand analogous.

(onsidering homologous genes the genes of

closely related species are or similar than genesfrom more distantly related species. %ncreasingtime since the divergence of two species givesincreasing numbers of random mutations.


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(ytochrome ( is part of the electron transport system in the mitochondria. %tis found in all eu#aryotes and some aerobic pro#aryotes as well. Thenumber of amino acid differences between the cytochrome c found indifferent species is proportional to the time since they diverged.


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Speciation

Speciationrefers to the appearance of a ne speciesoflife on earth.

Species occur hen a parent species (also referred to as acommon ancestor) splits into to (or more)reproductivel"-isolated populations# each of hich then accumulates changes from sexual

reproduction and/or random mutation (in addition to an" othervarious contri$utors to genetic change)..........

until the populations are no longer capa$le ofinter$reeding.
http://en.wikipedia.org/wiki/Specieshttp://en.wikipedia.org/wiki/Species


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Macroevolution% Speciation

&rocess here$" ne species arise 'enerall" one of to conditions

re!uired%

# 'eographic $arriers# eproductive isolation

umulative process of drift and

selection acting over man" generations


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eproductive Isolation Mechanisms(&re-*"gotic ($efore mating) vs. post-*"gotic (after mating)

&re-*"gotic

# different $reeding seasons (either "earl"or time of da")

# different signals% sight, sound, smell,$ehavior

# mechanical pro$lems+genitalia dont fittogether

# gametic isolation% sperm dont detect theegg or cant fertili*e it

&ost-*"gotic# h"$rid invia$ilit"% h"$rids dont survive

to $irth or adulthood# h"$rid sterilit"% as ith the mule, a

sterile h"$rid.

Even having h"$rids that aresignificantl" less fit (a$le to survive andreproduce) than pure$reds is anisolating mechanism, a a" to preventthe to populations from fusing into

one population.

horsehorse

(fert.)(fert.)

donkdonk

eyey

(fert.)(fert.)

mulemule

(sterile(sterile

))


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llopatric Speciation% he 'reat ivide

0r, the $arrier develops slol" as conditions change% the gradual

formation of the 'rand an"on split a population into 1 isolatedgroups, that have diverged into separate species, the 2ai$a$ andl$ert s!uirrels.

he simplest and most common form of speciation

# 1 groups of one species are isolated geographicall" (mountains,oceans, rivers).....

# and diverge into separate species.


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S"mpatric Speciation

S"mpatric speciation means

speciation that occurs ithinthe same geographical location.

n example% cichlid fish in3a4e 5armo$i M$o inameroon, frica+an isolated

volcanic la4e.# 6ine species, all more closel"

related to each other ($" 6evidence) than to similar fishin other la4es.

# 3a4e has no distinctgeographical *ones, and thefish can easil" sim an"here

in it.# he" feed in differentlocations, $ut all $reed in thesame location, close to the

$ottom.# he mechanism is not clear.


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5ates and results of speciation

%solation low dispersal strong sexual selection

and reductions in population si6e all favor

speciation

7peciation gives rise to adaptive diversity

4ccording to the theory of punctuated e"uilibriaspeciation has been the ma8or source of adaptive

change as opposed to phyletic gradualism

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