bio 1130 topic 3 — slide 1 topic 3 – age of the earth and life
TRANSCRIPT
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BIO 1130 Topic 3 — Slide 1
TOPIC 3 – AGE OF THE EARTH AND LIFE
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BIO 1130 Topic 3 — Slide 2
Three Distinct Cambrian Fauna
All major extant phyla are present at the start of the Cambrian??
They must have been present and evolving during the pre-Cambrian
Therefore, they did not arise suddenly at the start of the Cambrian
The roots of extant Phyla go back into the Precambrian.
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BIO 1130 Topic 3 — Slide 3
Ediacaran fauna: - 570 mya ancestors of modern post-Cambrian forms ? an extinct line ? controversy not yet settled.
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BIO 1130 Topic 3 — Slide 4
Burgess forms
Burgess shale (500 to 600 Mya) some clearly related to animals that survived and
diversified later e.g. , snails, clams, and some types of worms. compare with Ediacaran and Tommotian fauna
Diverse with many that went extinct very early (see next four slides)
One very big surprise!!
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BIO 1130 Topic 3 — Slide 5
Extinct Burgess shale Phyla
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BIO 1130 Topic 3 — Slide 6
Extinct Burgess shale Phyla
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BIO 1130 Topic 3 — Slide 7
Some survived
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BIO 1130 Topic 3 — Slide 8
The Earliest Recorded Chordate Myotomes Notochord Why do humans exist? Because Pikaia gracilins survived
the Burgess decimation. The survival of Pikaia was a
contingency of just history. We are indeed an accident.
Amphioxsus (Subphylum: Cephalochordata)
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BIO 1130 Topic 3 — Slide 9
Tommotian fauna
dating from the very beginning of the Cambrian (570 Mya)
hard body parts which fossilized easily many but not all are clear relatives and precursors of
modern forms.
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BIO 1130 Topic 3 — Slide 10
TABLE 3-1: PARENT AND DAUGHTER ISOTOPESUSED IN RADIOMETRIC DATING
Method ParentIsotope
Daughterisotope
Half-life Effective datingrange
RubidiumStrontium
Rb-87 Sr-87 47 Gyr* 10 Myr** to 4.6 Gyr
PotassiumArgon
K-40 Ar-40 1.3 Gyr 100,000-4.6 Gyr
UraniumLead
U-238 Pb-206 4.5 Gyr 10 Myr – 4.6 Gyr
UraniumLead
U-235 Pb-207 71.3 Myr 10 Myr – 4.6 Gyr
ThoriumLead
Th-232 Pb-208 14.1 Gyr 10 Myr – 4.6 Gyr
Carbon-14Nitrogen-14
C-14 N-14 5,730 years 100 – 100,000 years
*Gyr = gigayears or billions of years**Myr = millions of years #13
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BIO 1130 Topic 3 — Slide 11
Big Bang (Origin of the Universe) - 14 Gyr (gigayears) or Bya (billions of years ago)Formation of our solar system - 5 GyrPrecambrian Eon- 4.6 Byr to 540 Mya
Archean: 4.6 Byr to 2.5 Byr, origin of life, Ediacaran fauna Phanerozoic (Eon): 540 Mya to present – we are in this Eon now
Paleozoic Era: 540 Mya to 250 MyaCambrian Period: 540 Mya to 488 Mya - Burgess forms andTommotian fauna - virtually all extant phyla representedOrdovician Period: 488 Mya to 444 MyaPermian Period: 300 Mya to 251 Mya
Mesozoic Era: 250 Mya to 65 MyaCretaceous: 135 Mya to 65 Mya
Cenozoic Era: 65 Mya to present
SOME IMPORTANT TIMES
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BIO 1130 Topic 3 — Slide 12
MASS EXTINCTIONS
Ordovician: 444 Mya Permian: 250 Mya end-Cretaceous: 135
Mya to 65 Mya
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BIO 1130 Topic 3 — Slide 13
Evidence for life in rocks 3.8 Gyr old
#10How much 13C?