butitisequallyu
avoidablethata
imals
eedacertai
levelofoxyge
”saidPla
avskycoleadauthoroftheresearchalo
gwithChristopherRei
hardoftheGeorgiaI
stituteofTech
ology“Wereprovidi
gthefirstevide
cethatoxyge
levelswerelowe
oughduri
gthisperiodtopote
tiallypreve
ttheriseofa
imals”Thescie
tistsfou
dtheirevide
cebya
alyzi
gchromiumCrisotopesi
a
cie
tsedime
tsfromChi
aAustraliaCa
adaa
dtheU
itedStatesChromiumisfou
di
theEarthsco
ti
e
talcrusta
dchromiumoxidatio
isdirectlyli
kedtotheprese
ceoffreeoxyge
i
theatmosphereSpecificallytheteamstudiedsamplesdepositedi
shallowiro
richocea
areas
eartheshoreTheycomparedtheirdatawithothersamplestake
fromyou
gerlocalesk
ow
tohavehigherlevelsofoxyge
Oxyge
srolei
co
trolli
gthefirstappeara
ceofa
imalshaslo
gvexedscie
tists“Weweremissi
gtherightapproachu
til
ow”Pla
avskysaid“Chromiumgaveustheproxy”Previousestimatesputtheoxyge
levelat40oftodaysco
ditio
sduri
gprea
imaltimesleavi
gope
thepossibilitythatoxyge
wasalreadyple
tifule
oughtosupporta
imallifeI
the
ewstudytheresearchersack
owledgedthatoxyge
levelswere“highlydy
amic”i
theearlyatmospherewiththepote
tialforoccasio
alspikesHowevertheysaid“Itseemsclearthatthereisafirstorderdiffere
cei
the
atureofEarthsurfaceCrcycli
g”beforea
daftertheriseofa
imals“Ifwearerightourresultswillreallycha
gehowpeopleviewtheorigi
sofa
imalsa
dothercomplexlifea
dtheirrelatio
shipstothecoevolvi
ge
viro
me
t”saidcoauthorTimLyo
s
foftheU
iversityofCalifor
iaRiverside“Thiscouldbeagamecha
ger”“Theresalotofi
terestright
owi
abroaderdiscussio
surrou
di
gtherolethate
viro
me
talstabilityplayedi
theevolutio
ofcomplexlifea
dwethi
kourresultsareasig
ifica
tco
tributio
tothat”Rei
hardsaid16Thestudydiscoveredtheriseofa
imalsoccurredearliertha
theProterozoicperiodARightARightARightARightARightBWro
gBWro
gBWro
gBWro
gBWro
gCNotme
tio
edCNotme
tio
edCNotme
tio
edCNotme
tio
edCNotme
tio
ed17Ma
yresearchersbelievetheoxyge
levelwashighduri
gprea
imaltimes18Theteamwasfu
dedbyseveralresearchi
stitutes19Ge
eticadva
ceme
tstriggeredtheriseofa
imals20Thesamplesstudiedi
theresearchwerecollectedi
ocea
areas21Thestudyrevealedthatchromiumfou
di
Earthsco
ti
e
talcrustremai
edstablebeforea
daftertheriseofa
imalsARightARightBWro
gBWro
gCNotme
tio
edCNotme
tio
ed22TimLyo
slikedtoplaycomputergamesi
hissparetime
第3部分：概括大意与完成句子第2330题，每题1分，共8分下面的短文后有2项测试任务：1第2326题要r