Evoltuion - Types of Selection Notes

7/26/2019 Evoltuion - Types of Selection Notes

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Evoltuion - types of selection

Monday, November 9, 2015

2:58 M

rocess of natural selection -

! main in"rediants from natural selection

#ariation of traits in population

$ %eedin" out process

&ome t'in"s selected for and some t'in"s selected a"ainst

(o ma)e t'at selection - 'as to be some basis

*i+erences amon" individuals amon" population

&ome sort of stru""le for survivle

(ypical in natural %orld

$ll sorts of problems or"anisms encounter

(emperature and so on

esult of t'is stru""le

Not all individuals survive

('ird component

'at %e come to )no% as survival of t'e .ttest

/oo) at t'e individuals t'at survive and compare t'em to indiduals %'o didntsurvive posses traits

itter individuals %'o survive - .tter individuals

(raits - individual traits to survive - "enetic basis

ass t'em o+ to o+sprin" - o+sprin" also e'ibit t'ose traits



3dentify t'ose )ey in"rediants

#ariation - in t'is mot' population

4onsists of blac) peppered form

#ery important t'in" to point out

re-eistin" variation

Eits in population if anyt'in" else is "oin" on or not

$t time polution occurred some blac) forms of mot' but most 'ad peppered

&tru""le for survile

('is case - birds tryin" to eat mot's

Not noticed by birds and arent eaten

/o%er ri"'t - tree trun) after polution 'as occurred

*ar) form - pretty %ell camo6o"ued but peppered form stands out

7irds see peppered form and consume it

7lac) form better to .ttest

eppered form removed



4oloration pattern determined by sin"le "ene ma)essome blac) some ppered

+sprin" carryin" "ene for dar) form

(al)in" about selection for blac) form of "ene or peppered form

ocusin" on sin"le trait

&election acts on individuals - all its "enes

&ome 'ave "ood some 'ave bad

Not sin"le trait determines 'o% .t you are

n avera"e individuals %'o 'ave "reater number of "ood alleles do beter t'anindivuduals %'o 'ave less

3ndividuals %'o 'ave "reater - put "ood alleles into "ene pool

More "ood alleles "et into "eneration t'an bad alleles

More "ood alleles t'an previous "eneration

ound t'at population 'ave lar"er number more .t and better to cope and muc'better adapted t'an ot'er individuals

irst in"rediant - variation

#ariation amon" individuals %it'in population

'at is responsible for variation

#ary a%are of %'at it is

/oo) at people %e )no%

Not same as us

*i+erent c'aracteristics

#ariation acted upon by natural selection

'at is responsible

'y arent individuals more similar

Main source - in t'e process of "ametes and seual reproductions



&'uin" of "enetic matirial

ecombination

or eample

3ndividual ma)es "ametes by meiosis

;ametes made by individual

None are t'e same

'y are t'ey di+erent

'en meiosis occurs - independent assortment of c'romosome

'en you ma)e "ametes

;ametes 'ave 'alf number of c'romosomes

<no% %'en you ma)e t'em

ne representative from eac' 'omolo"ous pair of c'romosomes

7ut eac' one you ta)e is random

/ots of combinations in "ametes

4ross over %it' eac' ot'er

&'arin" e'an"e of "enetic information

urt'er s'ues "enetic material

Made "ametes very di+erent 0 matin" partner also ma)in" "ametes di+erent

(o ma)e individual combine "ametes

4'ances you loo) li)e brot'er or sister are slim

Made by parents eac' di+erent possible of combinin" very di+erent as %ell

/ots of opportunities for recombination

3mportant source

=ltimate source



Mutation

>o% c'an"es 'appen to "enes

Mutations c'an"e dna messa"e in some %ay

Most are bad

&ome are neutural - doesnt c'an"e function

4ases %'ere c'an"es are "ood

;rabs and puts t'em up to 'i"'er fre?uency

(ypes of variation t'at eist in population

Natural selection acts on t'em - outcome dependent on type involved

@ualitative

(raits - consist of eit'er 2 states

>ave trait or dont

*etermined by sin"le "ene

Earlobe attac'ment

Not'in" in bet%een

ne t'in" or t'e ot'er

(ypes of variation called ?uantitative or continuous variation

4onsists of all de"redations in bet%een



Many traits or"anisms 'ave fall under t'is cate"ory

(raits 'umans 'ave

&in"le "ene and come in one state or ot'er

>o% tall

'at i?

&)in color

Many "enes

4ontinuous variation

Not tall or s'ort - everyt'in" in bet%een

Not Aust 'i"' or lo% - a lot in bet%een

Muc' colors from dar) to li"'t

Number of t'in"s not Aust t'ree "enes

4ontribution on "enes

Eac' produces a little bit of melonin

&um of contribution of all contributes to 'o% dar) your s)in is



$lleles eit'er open or dar) circle

*ar) circle - melonin production

/oo) at "rap' - all di+erent )inds of variation in t'is population

3ndividuals on left - li"'t s)in

3ndividuals on ri"'t - all dar) type - dar)est s)in

an"e of t'in"s inbet%een

4ontinous variation and traits determined by many "enes

B types t'at can occur %it' some variation

=pper picture

ri"inal startin" population

n y ais fre?uency

n ais - bunc' of mice- li"'t colored to dar)er colored

opulation - li"'t in color some dar) in color

>ump in middle

Most individuals are some%'ere in t'e middle



opulation li)e t'is

/oo) at mice

&ome dar)er some li"'ter

'at if natural selection %ere to opperate on t'is population

3ndividuals dar)er - did better t'an li"'ter in color

'at %e 'ave t'en - type of selection - direction selection

/o%er left 'and panel - %'at result %ould be

*otted blue line - ori"inal population

&election for dar)er colored individuals - be more li)ely to leave o+sprin" - t'eir

o+sprin" "iven dar) alleles from parents "o out many "enerations - see populationcurve s'ifted to one side

3ndividuals on avera"e muc' dar)er t'an ori"inal population

1 direction selection - mean of population moves in particular direction

Mice eample moves from medium dar) to even dar)er fur

'ats 'appenin" - c'an"e in value of trait over time

&een before peppered mot'

*irection selection - peppered to primarily blac) colored mot's

(%o di+erent )ids of variation

@ualitative - t'in"s can be in one state or ot'er or continus variation

@ualitative - direction selection -

;oin" to eliminate bad allele and . on best allele

eppered mot' story - allele t'at determined blac) and one t'at determined pepper

$s peppered mot's dies o+

4'an"e to potentially all alleles %ill be of blac) form - etreme possibility - cant "oany fart'er



*irectional selection on ?uanitative traits

3ts possible after many "enerations - avera"e value eceed anyt'in" present inpopulation

@uantitative traits - many "enes

$lleles of all t'ose "enes

Many "enerations of selection

More and more of t'ose "enes 'ave "ood allele

(a)es time for t'at to 'appen

;et to a point %'ere all "enes 'ave "ood alleles ori"inal population 'ad all "oodallele

Eample 'avin" to do for bristle number on drosop'ila

fruit 6ies

ri"inal population - re"ular old population - count number of bristles - .nd is t'aton avera"e individuals 'ave !0 bristles

&ome t'at 'ave as fe% as B0 some as many as 50

urple s'ape - re?uency of t'ose %it' di+erent bristle numbers

*o a selection eperiment



$ lot of bristles - pull aside and let t'em mate

7lue ."ure on ri"'t - %'at you %ould "et after certain number of "eneration

Mean around 90 bristles

n avera"e in ori"inal about !0

No% %e are up to 90

Every individual 'as more bristles t'an 'i"'est in ori"nal population

3n t'is eperiment selected individuals %it' fe%est bristles

Number of "enerations c'oose ones %it' fe%est bristles

/o% selected population

$vera"e little above 10

$nd even one %it' 'i"est number is lo%er t'an t'e B0 from ori"inal population

&election on traits determined by many "enes selection ta)e population fart'er t'anyou %ould epect

/imits to natural selection

&elections actin" on "eneration after "eneration

Eliminate all bad alleles - and selection %ould stop

'y 'avent t'at 'appened

>uman population - lot of bad alleles 6oatin" around

4ystic .brosis sic)le cell anemia

'y 'asnt selection eliminated t'em

ecessive alleles - bad allleles

(%o copies in individual - 'ave disease

Not "ood as individual %'o doesnt

&election 'as a problem in "ettin" at bad alleles and eliminatin" t'em



>eteroCy"ote - dont s'o% recessive allele

nly s'o% dominant allele

$lt'ou"' t'ey carry bad allele

&election - loo) li)e dominant individual

ecessive 'ide in 'eteroCy"ote

3mpossible to "et all bad alleles out

$lleles seem to be bad in one contet "ood in anot'er contet

opulation of united states

7lac)s in us 'ave 'i"'er rate t'an %'ites do

e need to loo) at africa %'ere blac)s in t'e united states come from

3nterestin" pattern

;rey s'ado%ed area

'ere t'e maleria parasite very common

Malaria - millions people die every year

3n places %'ere malaria common

>i"' fre?uency of sic)le cell allele



$t .rst "lance- very odd

(urns out t'at malaria paracite attac)s red blood cell

&ic)le cell also a+ects red blood cell

>eteroCy"ous for sic)le cell allele

esist maleria t'an t'ose %'o dont 'ave t'is allele

>i"' incedent of sic)le cell "ives you resistance of alllele

&laves in nort' america

&ic)le cell alllele

Nort' america no maleria for advanta"e

&ee over time t'is allele slo%ly eliminated

>i"'er in blac) t'an %'ite

/o%er panel on ri"'t

3lustrates stabeliCin" selection

Eliminate bot' etremes

3n t'is case

3ndividuals li"'ter and dar)er dont survive as %ell



Eliminatin" dar)est and li"'test ones and population stabeliCed on inbet%eenp'enotype

;ood eample %it' re"ard to 'uman birt' %ei"'t

#ery small very lar"e babies

&mall babies - diDculty survivin"

/ar"e - more problems t'an babies in t'e middle on avera"e

n avera"e babies -8 pounds

Fello% tells you somet'in" about %'at types of birt' %ei"'ts you .nd

F ais - percent of population

n avera"e babies -8 pounds

#ery small - lo%er

&ome babies 9 10 11 pounds

'ite - percent mortality %it' babies of di+erent birt' rate

-8 do%n - mortality increases

-8 to 9, 10, 11 mortality also increases

7ot' lo%est and 'i"'est %ei"'t - tend to be eliminated from population

&tabeliCe about -8 pounds



7ot' etremes are selected but t'in"s in middle selected a"ainst

#ery rare

/i"'test colored do %ell

*ar)est do %ell

3n bet%een dont do %ell

*isruptive

us'es population to eit'er side



7lac) bellied seed crac)ers

May not be obvious to you

7ut bidr on left

7illbee) not as %ide as t'e bee) on t'e ri"'t

/oo) at population .nd t'at rat'er bein" ran"e of bill siCes from small to lar"e

('ey actually Aust 2 classes

&mall billed and ar"er billed

/oo) at %'at t'ey are eatin"

&ome smaller softer seeds and also some bi""er 'arder seeds

&mall bills - smaller seeds

/ar"e bills - lar"er seeds

Medium bill - doesnt 'elp you %it' eit'er

&peciation

&in"le species to 'ave 2 di+erent species of or"anisms

ossible %ays speciation can come about



('rou"' disruptive selection

;eneral idea

it'in population

ne etreme and ot'er etreme

Many "enerations - smaller billed becomes one species

$nd lar"er becomes di+erent species

ont say more no%

(ac)le amon" speciation

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Evoltuion - Types of Selection Notes

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