11-02 Lecture Notes

7/30/2019 11-02 Lecture Notes

1/13

a a onsan

x nc ons

o ay sques ons:

I. W y oa apt vera at onsoccur

II. Whydomassextinctionsoccur?


2/13

I. Whydoadaptiveradiationsoccur?

Adaptiveradiation

=the

rapid diversificationofa

singlelineageintoanarray of

speciesthat

fill

awide

variety

=

orresourcesusedbya

species(awayofmakinga Time

living)


3/13

700 species?60 species?

30 species

Dothese

qualify

as

adaptive

radiations?


4/13

Twoclassicalexplanations:

A.Ecologicalopportunity(resourceavailability;empty

niches)1. Competitorswipedout

. o on zeanewreg on

No competitors to compete with for resources.

New resources available,selection pressure for traits that will take

advantage of those resources.

Lots of resources available, "nobody else" using resource.


5/13

.

v

=

makesit

possible

to

exploit

resources

in

anew

way

or

occupynewhabitats(newniches)


6/13

Issue:

these

hypotheses

can

be

difficult

to

testCorrelation?Causation?

e.g.Cam rianexp osion:

.

2. Newgenes,newbodieshypothesis

Most major animal groups appear for the 1st time in about 40 million year.

Allows aerobic respiration and more growth.

Testing of rock found correlation in oxygen increase and speciation.

Polyploidy and genetic information go up.

Mutation go up so genetic variation will go up and selection can act on

these.

Variables may be correlated but have no cause-effect relationship.


7/13

Hypothesis:theadaptiveradiationofblackbirdswas

triggeredbyamorphologicalinnovation:anextended

processus retroarticulatus thatmade

gaping

possible.


8/13

Phylogenyof

blackbirds:

Note:therearestatisticaltechniquesforestimatingthestateof

particulartraits

at

each

on

the

tree.

(Go

Dawgs!)

Whatpredictiondoesthe

morphologicalinnovation(gaping)

hypothesismake?


9/13

II.Whydomassextinctionsoccur?

ac groun ex nc on=norma ex nc onra es, ue o

normalrates

of

environmental

change

(environment

Massextinction

=at

least

60%

of

species

present

go

extinctinlessthan1millionyears;duetoextremerates

ofenvironmentalchange

Massextinctionsfunctionlikeaspecieslevelbottleneck

event.(Anotherreasonevolutionisnotprogressive.)


10/13

AtthePermianTriassicevent250millionyearsago,over

90%ofexistingspecieswerewipedout.

environmentalchangesthatextinguishedmostspecies.

Killingmechanisms:-Dust, soot, ash-blocks sunlight, plants wouldn't really able to grow.

Those species will die, then the ones that rely on those species will also

die.

-Increasing CO2, acidification of ocean.

-Initial impact will wipe stuff out at the site. Heat generates lots of

lots wildfire.


11/13

WorldWenttoHellHypothesis

1.global

warming

high

CO2,highCH4

2.anoxicconditionsintheoceanandatmosphere

Keyobservation:Siberiantrapsdateto250mya

Killingmechanisms:


12/13

Impacthypothesismakespredictions:

WWTH:

Weknow

that

anoxia

and

high

CO2 occurred,

but

what

causedthechangesinatmosphericandoceanicchemistry?


13/13

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11-02 Lecture Notes