10-31 Lecture Notes
Transcript of 10-31 Lecture Notes
-
7/30/2019 10-31 Lecture Notes
1/14
s oryo
e
easege ou no es rom as mewe n s e
slideson
sympatric
speciation
Todays
questions:
. owcanwes u yevo u on s rea es s
.W y
scorro orat ng
ev ence
rom
n epen ent
sourcesofdataimportant?
-
7/30/2019 10-31 Lecture Notes
2/14
Thebasicformofthetetrapod limb:
Hypot es s:t etetrapo m evo ve rom
Four legged, for land mammals.
the lobes of the lobe
finned fish.
-
7/30/2019 10-31 Lecture Notes
3/14
Fossillimbsfromlobefinned
fishandearlytetrapods
Whichhave
the
basic
tetrapod
limbpattern?
W c ave g ts owmany
Whichswam?Crawled?
Walked?
-
7/30/2019 10-31 Lecture Notes
4/14
Phylogenyof
early
tetrapods,basedon
.
Dothesedatasupport
thehypothesis?
Whyor
why
not?
-
7/30/2019 10-31 Lecture Notes
5/14
-
7/30/2019 10-31 Lecture Notes
6/14
Specieswithlobedfinsarefoundinolderstrata(rockbeds)
thanspecieswithlimbs.Dothesedatasupportorconflict
withthefinstolimbshypothesis?Explain.Support because you expect the fins to show up first and be older since
it's an ancestral (basal) trait.
-
7/30/2019 10-31 Lecture Notes
7/14
2.Radiometric
dating
established
the
absolute
ages
of
the
fossilbearingrocks
1. Ratioof
parent
to
daughter
isotope
when
rock
formed
(e.g.initially,volcanicrockshavenoargon40;itisagas
thatbubblesoutofmagma)
2.Decayrate(e.g.rateatwhichpotassium40decaysto
argon40)measuredinhalflives
3.Currentratioofparenttodaughterisotope(e.g.
-
7/30/2019 10-31 Lecture Notes
8/14
onakeyassumption.What
isit?
Specieswithlobedfinsarefoundinrockswitholder
absoluteagesthanspecieswithlimbs.Dothesedata
That the isotopes behaviorsdoesn't change over time?
The data is relative.
-
7/30/2019 10-31 Lecture Notes
9/14
3.Associated
fossils
and
the
nature
of
the
host
rock
supportthehypothesisofanaquatictosemiaquaticto
Rockslaiddowninaquaticenvironmentsaredifferent
t anroc s ai owninterrestria environments;
Findfossils
of
a uatic
versus
terrestrial
or anisms
(algae,landplants)
-
7/30/2019 10-31 Lecture Notes
10/14
4.Comparative
morphology
supports
the
hypothesis
of
homologyinlimbelements
. v v
Studygenesandallelesinvolvedintheoriginofkey
synapomorphies morphologicalinnovations
-
7/30/2019 10-31 Lecture Notes
11/14
The phylogeny in your notes was estimated from skull characters, not
fin or limb characters, why is this important?
-Otherwise the argument it's circular.
-We use skull to have another independent source to help support our
thinking.
-
7/30/2019 10-31 Lecture Notes
12/14
7.Comparisons
with
extant
taxa:
Modernlobefinnedfish(coelacanths)donotusetheir
finsto
crawl.
But
when
they
swim,
they
move
their
fins
inthesamepatternastetrapods movetheirlimbs
whenwalking.
Modernlungfish
can
breathe
air
and
use
their
fins
to
crawlacrossdryingpondsurfaces
Dothesedatasu ortorconflictwiththefinstolimbs
hypothesis?Explain
your
reasoning.
If the lobe-finned fish were able to have a walking motion, it might suggest
that they are able to develop traits. The fins could be used in a walking
motion, so that means they could have been on land and selected for limbs
more fit for walking.
-
7/30/2019 10-31 Lecture Notes
13/14
Whichof
these
seven
sources
of
evidence
do
you
find
mostconvincing,andwhy?
Wh
doscientists
stress
the
im ortance
of
data
that
are
independentandcorroborating?
There is no one piece of evidence that is the most convincing, it's the
entire body of evidence that's convincing.
So it's more reliable. It helps prevent circular reasoning.
-
7/30/2019 10-31 Lecture Notes
14/14