topic 3 – age of the earth and life
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TOPIC 3 – AGE OF THE EARTH AND LIFE. 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 - PowerPoint PPT PresentationTRANSCRIPT
BIO 1130 Topic 3 — Slide 1
TOPIC 3 – AGE OF THE EARTH AND LIFE
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.
BIO 1130 Topic 3 — Slide 3
Ediacaran fauna: - 570 mya ancestors of modern post-Cambrian forms ? an extinct line ? controversy not yet settled.
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!!
BIO 1130 Topic 3 — Slide 5
Extinct Burgess shale Phyla
BIO 1130 Topic 3 — Slide 6
Extinct Burgess shale Phyla
BIO 1130 Topic 3 — Slide 7
Some survived
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)
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.
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
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
BIO 1130 Topic 3 — Slide 12
MASS EXTINCTIONS
Ordovician: 444 Mya Permian: 250 Mya end-Cretaceous: 135
Mya to 65 Mya
BIO 1130 Topic 3 — Slide 13
Evidence for life in rocks 3.8 Gyr old
#10How much 13C?