Page 108 - Science Course 3 (Book 1)

Mo3-L1b: What is the Evidence for Evolution?

Lava Flow
450 m.y

Granite 480 m.y

Age of shale between Shale known by
fossils to be
450 and 480 m.y Ordovician, now
(Ordovician known to be 450-480
index fossils) m.y. old by correction
to Section A.

If the age of the igneous layers is known, it is
possible to estimate the age of the sedimentary
layers—and the fossils they contain—between them.

Relative Absolute-age
age Dating
440 mya
Younger 480 mya Extinction
520 mya
Extinction occurs when the last individual organism
545 mya of a species dies.

A mass extinction occurs when many species
become extinct within a few million years or less.
Older
Extinctions can occur when environments change.
Fossils over Time

The geologic time Era Period
scale is a chart
that divides Earth’s Quanternary (1.8 mya- present)
history into different Cenozoic
time units. Tertiary (65-1.8 mya)
Cretaceous (146-65 mya)
Earth’s history is
divided into four Mesozoic Jurassic (200-146 mya)
eons—the longest Triassic (251-200 mya)
time units in the
geologic time scale. Permian (299-251 mya)

Carboniferous (359-299 mya)
Devonian (416-359 mya)
Paleozoic
Silurian (488-416 mya)
Ordovician (488-444 mya)
Cambrian (542-488 mya)
Precambrian (4750-542 mya)

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