1. BIO 1130 Topic 3 — Slide 1 TOPIC 3 – AGE OF THE EARTH AND LIFE

2. 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.

3. BIO 1130 Topic 3 — Slide 3 Ediacaran fauna: - 570 mya  ancestors of modern post-Cambrian forms ?  an extinct line ?  controversy not yet settled.

4. 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!!

5. BIO 1130 Topic 3 — Slide 5 Extinct Burgess shale Phyla

6. BIO 1130 Topic 3 — Slide 6 Extinct Burgess shale Phyla

7. BIO 1130 Topic 3 — Slide 7 Some survived

8. 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)

9. 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.

10. BIO 1130 Topic 3 — Slide 10 TABLE 3-1: PARENT AND DAUGHTER ISOTOPES USED IN RADIOMETRIC DATING MethodParent Isotope Daughter isotope Half-lifeEffective dating range Rubidium Strontium Rb-87Sr-8747 Gyr*10 Myr** to 4.6 Gyr Potassium Argon K-40Ar-401.3 Gyr100,000-4.6 Gyr Uranium Lead U-238Pb-2064.5 Gyr10 Myr – 4.6 Gyr Uranium Lead U-235Pb-20771.3 Myr10 Myr – 4.6 Gyr Thorium Lead Th-232Pb-20814.1 Gyr10 Myr – 4.6 Gyr Carbon-14 Nitrogen-14 C-14N-145,730 years100 – 100,000 years *Gyr = gigayears or billions of years **Myr = millions of years #13

11. 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 Gyr Precambrian 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 Mya Cambrian Period: 540 Mya to 488 Mya - Burgess forms and Tommotian fauna - virtually all extant phyla represented Ordovician Period: 488 Mya to 444 Mya Permian Period: 300 Mya to 251 Mya Mesozoic Era: 250 Mya to 65 Mya Cretaceous: 135 Mya to 65 Mya Cenozoic Era: 65 Mya to present SOME IMPORTANT TIMES

12. BIO 1130 Topic 3 — Slide 12 MASS EXTINCTIONS  Ordovician: 444 Mya  Permian: 250 Mya  end-Cretaceous: 135 Mya to 65 Mya

13. BIO 1130 Topic 3 — Slide 13 Evidence for life in rocks 3.8 Gyr old #10 How much 13 C?