NAME
DATE
CTASS
STUDY
GUIDE
GeologicTime
Use words in the box to fiII in the blanks.
EARTH'S
PAST
22=1The GeologicTimeScale
eras
Earth
epochs
columns
changes
Mesozoic
periods
Cenozoic
Data from geologic
ci<.lr^vwn5
Paleozoic
subdivide
geologists
has enabled
e)lt" tc-
sequenceof events in Earth's history on the
C,L.nrcre>
the
largest
e4e-l'-3
-T--
l1e-sozorc-*6"o
in life formshavebeenusedto
subdivision,
Far'l-l-,
chronologic
Precambrian
geologic time scale
g".ul,i.Je
are divided into
the time ..u1".
that
Most life forms have evolved in the
(middle life), and the
-l
:c(rlq-
Ce*to'z>ic
are furbher
P".l."z.,i-
Encr'S
divided
into
(ancient life), the
(recent life) Eras. The time from
formed about 4.5 biilion years ago to the paleozoic Era is know as
NAME
DATE
CLASS
EARLY
EARTH
HISTORY
22:4 Precambrian
Time
rapid.
oldest
shields
million
igneous
glaciation
Pc*o"o',La.i*r',
beginning
landmasses
Precambrian
microfossils
stromatolites
cyanobacteria
time began about 4.b billion years ago at Earth,s
and lasted to
. t!
about 600
n-,lliorr
years ago. The metamorphic o,
.Lvncltige-b
f{P d,
during the Precambri... Cl..'*L.r{*\l"e
l''n,'"-nr*rgri lt
nuclei of continents,
known rocks on Earth,s surface. tuturry.-uti
existed.,plate movements were more
or q\qc.ad'o
g\qcrd'dhn
fn"""
tlJot*
tlJuSl-
are the
the
,, are
called
igne**rs
, and there were periods
the oldestfossilsyet discovered.
, found.in Australia, have beenpreserv"a6
Si-r"ru-r.i*-l',L>
22:5 The PaleozoicEra
land
hard
fish
lung
water
fluids
scales
species
reptile
Permian
Devonian
reproduce
Paieozoic
Laurasia
amphibians
trilobites
ectotherms
brachiopods
Ordovician
extinctions
cold blooded
environment
temperatures
Pennsylvanian
Ar
ah"
tdleczs'ic-
Era began about 570 M.y.B.p. with the evolution of
parts. Characteristic fossils of the era are *.,l"L;L.
ri:["
in the sea by the b4vc,'rlh"'r
first appeared during the
kebpfrom losinguoav tl*il:
and to
variety of amphibian had evolved. into a
'r."tLczs
and do not need to return to
tou" .'t l bl*.le.I , areau *L*L-*t
of the gorvJroi:r,reerit
0trcry {tn
Itf.qnf
.tb"
i*a.
la*"L
I
ilVaohq
time. one
. Reptiles have a skin composedof hard
"*A-
. Fish, amphibians, and reptiles, referred
sincetheir Uoay -l<*tfunLrctchange
with that
once more joined Gondwana by the end of the
*J,',e"*r*rna
. The accompanying changes in environment caused
land and sea animals by the end of the Paleozoic.
and is considered
but return to water to
,By
(Y+:le-
, now extinct, and
andbecamedominant
. One type of fish deveioped,
to be the ancestorog orr',.rpt,itfar"q . Amphibians live o'
wiih
-.r,
of both
NAME
CLASS
MIDDLE
ANDRECENT
EARTH
HISTORY
22:6 The MesozoicEra
seeds
birds
extinct
reptiles
species
Gondwana
endotherms
Iandmasses
Mesozoic
changing
rzolc-
The
Jwassic
dinosaurs
Cretaceous
endothermic
angiosperms
Era began about 200 M.Y.B.F. when Laurasia and.
becameseparated.By the SaruisrL
rePf.leS
the best known reptiles were the climcsgt+f+
. One of the largest <arr niyor^orr5
that ever lived was lVrarrne,taqflJEDinosaurs
E"Arr*L*-r,
agam
were the dominant life form. probably
I
k"A'
envrronment
warm blooded
temperature
carnivorous
Tyrannosaurus
may have been an
ancestorof the
have a constant may *er-p,.r*Lre
Thesepiants had s€rxlq
. that could survive
the Mesozoic,major changesin the
*--i"rr"**occurred
land animals
and are said to be
environments. By the end of
uJt^rl. lnJ-rr*o'^
up into smaller units. The dinosaurs and about 1b percent of all animal
begantobreak
that existed
up to that point became €'l+;nd|
22:7 The CenozoicEra
clam
65
young
reptiles
mammals
y6.
Cer*-z.oic
mountain
Cenozoic
starfish
Northern
isolation
Era began about
cc;ntt-ir.;ta,causedmajo"
continents
glaciation
Quarternary
Pieistocene
marsupials
65
, snail,
during
and
e'nvita''r*tet;Is
, or
of the
ofspecies.Thisseems
became dominant in Austraiia.
migrated from North America into South America.
c-hrn
groups became the
the Cenozoic. Mammals
expanded into
. Early protection of their
different
iSrrl+horr
many life forms. H ur*upt\l<
while more ad.vanced lrnar/?itt\
SL"{i.l-
M.Y.B.P. Colliding plates, as weII as separathg
rrl', buitaingrnd
r-ror,ti.r-f..rl,r
to havechangedtn" Jetrdof-t'-tof
Homo sapiens
development
environments
invertebrates
dominant
marine
areas vacated by extinct
enabied mammals to survive in many
A very important, highiy
adaptable mammal,
tJorz:rt
al
humans, appeared in
the
(lu+Laf'te'rr)4r
CJ.4atf'fen f)r;.l,)/v
Hemisphere occurred in the
Period. Continental