2. AP Biology 2007-2008 Origin of Life “…sparked by just the right combination of physical events & chemical processes…”

3. AP Biology BacteriaArchae- bacteria AnimaliaFungiProtistaPlantae 4500 4000 3500 3000 2500 2000 500 1500 0 1000 Formation of earth Molten-hot surface of earth becomes cooler Oldest definite fossils of prokaryotes Appearance of oxygen in atmosphere Oldest definite fossils of eukaryotes First multicellular organisms Appearance of animals and land plants Colonization of land by animals Paleozoic Mesozoic Cenozoic Millions of years ago ARCHEAN PRECAMBRIAN PROTEROZOIC The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story… The evolutionary tree of life can be documented with evidence. The Origin of Life on Earth is another story…

4. AP Biology What is Life?  First we have to define LIFE…  organized as _________  ___________to stimuli  ___________internal processes  __________________  use ________to ______  metabolism  ___________  change & mature within lifetime  ___________  ___________  DNA / RNA  adaptation & evolution

5. AP Biology The Origin of Life is ____________  Special Creation  Was life created by a supernatural or divine force?  __________________  Extraterrestrial Origin  Was the original source of organic (carbon) materials comets & meteorites striking early Earth?  __________________  Spontaneous Abiotic Origin  Did life evolve spontaneously from inorganic molecules?  __________________

6. AP Biology Conditions on early Earth  ________________________  water vapor (H 2 O), CO 2, N 2, NO x, H 2, NH 3, CH 4, H 2 S  lots of available H & its electron  __________________  Energy source  lightning, UV radiation, volcanic low O 2 = organic molecules do not breakdown as quickly What’s missing from that atmosphere?

7. AP Biology Conditions on early Earth made the origin of life possible Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages: 1._________________________________________ 2._________________________________________ 3._________________________________________ 4._________________________________________

8. AP Biology Water vapor Condensed liquid with complex, organic molecules Condenser Mixture of gases ("primitive atmosphere") Heated water ("ocean") Electrodes discharge sparks (lightning simulation) Water Origin of Organic Molecules  Abiotic synthesis  1920 Oparin & Haldane propose reducing atmosphere hypothesis  1953 Miller & Urey test hypothesis  formed organic compounds  amino acids  adenine CH 4 NH 3 H2H2

9. AP Biology Stanley Miller University of Chicago produced -amino acids -hydrocarbons -nitrogen bases -other organics It ’ s ALIVE!

10. AP Biology Bubbles … Tiny bubbles … Origin of Cells (Protobionts)  Bubbles  separate inside from outside  metabolism & reproduction

11. AP Biology Origin of Genetics  RNA is likely first genetic material  multi-functional  codes information  self-replicating molecule  makes inheritance possible  natural selection & evolution  enzyme functions  _________________  replication  regulatory molecule  transport molecule  ________ & ________ Dawn of natural selection

12. AP Biology The fossil record documents the history of life The fossil record reveals changes in the history of life on earth Sedimentary rocks are deposited into layers called strata and are the richest source of fossils The fossil record is biased in favor of species that – __________________________

13. AP Biology Fig. 25-4 Present Dimetrodon Coccosteus cuspidatus Fossilized stromatolite Stromatolites Tappania, a unicellular eukaryote Dickinsonia costata Hallucigenia Casts of ammonites Rhomaleosaurus victor, a plesiosaur 100 million years ago 200 175 300 270 400 375 500 525 565 600 3,500 1,500 2.5 cm 4.5 cm 1 cm

14. AP Biology How Rocks and Fossils Are Dated Sedimentary strata reveal the ____________ ages of fossils The absolute ages of fossils can be determined by __________________ A “parent” isotope decays to a “daughter” isotope at a constant rate Each isotope has a known ___________, the time required for half the parent isotope to decay

15. AP Biology Problem Your measurements indicate that a fossilized skull you unearthed has a carbon-14/carbon-12 ratio about 1/16 that of the skulls of present-day animals. What is the approximate age of the fossilized skull?

16. AP Biology Radiocarbon dating can be used to date fossils up to 75,000 years old For older fossils, some isotopes can be used to date sedimentary rock layers above and below the fossil The magnetism of rocks can also provide dating information Reversals of the magnetic poles leave their record on rocks throughout the world

17. AP Biology Key Events in Origin of Life  Key events in evolutionary history of life on Earth  life originated 3.5–4.0 bya

18. AP Biology Prokaryotes  Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteria modern bacteria chains of one-celled cyanobacteria

19. AP Biology Stromatolites Fossilized mats of prokaryotes resemble modern microbial colonies Lynn Margulis

20. AP Biology Oxygen atmosphere  Oxygen begins to accumulate 2.7 bya  reducing  ______________atmosphere  evidence in banded iron in rocks = rusting  makes aerobic respiration possible  photosynthetic bacteria (blue-green algae)

21. AP Biology First Eukaryotes  Development of internal membranes  create internal micro-environments  advantage: specialization = increase efficiency  natural selection! infolding of the plasma membrane DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell ____________ nuclear envelope ________ plasma membrane ~2 bya

22. AP Biology Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion internal membrane system aerobic bacterium _______________ Endosymbiosis  Evolution of eukaryotes  origin of __________________  engulfed aerobic bacteria, but did not digest them  mutually beneficial relationship  natural selection!

23. AP Biology mitochondrion chloroplast Eukaryotic cell with chloroplast & mitochondrion Endosymbiosis photosynthetic bacterium Endosymbiosis  Evolution of eukaryotes  origin of _____________________  engulfed photosynthetic bacteria, but did not digest them  mutually beneficial relationship  natural selection! Eukaryotic cell with mitochondrion

24. AP Biology  Evidence  structural  mitochondria & chloroplasts resemble bacterial structure  genetic  mitochondria & chloroplasts have their own circular DNA, like bacteria  functional  mitochondria & chloroplasts move freely within the cell  mitochondria & chloroplasts reproduce independently from the cell Theory of Endosymbiosis Lynn Margulis

25. AP Biology Cambrian explosion  Diversification of Animals  within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya

26. AP Biology

28. Diversity of life & periods of mass extinction Cambrian explosion

29. AP Biology The Chicxulub impact crater in the Caribbean Sea near the Yucatan Peninsula of Mexico indicates an asteroid or comet struck the earth and changed conditions 65 million years ago Cretaceous extinction

30. AP Biology Early mammal evolution  125 mya mammals began to radiate out & fill niches

31. AP Biology Fig. 25-18 Close North American relative, the tarweed Carlquistia muirii Argyroxiphium sandwicense Dubautia linearis Dubautia scabra Dubautia waialealae Dubautia laxa HAWAII 0.4 million years OAHU 3.7 million years KAUAI 5.1 million years 1.3 million years MOLOKAI MAUI LANAI

32. AP Biology You should now be able to: 1. Define radiometric dating, serial endosymbiosis, Pangaea, snowball Earth, exaptation, heterochrony, and paedomorphosis 2. Describe the contributions made by Oparin, Haldane, Miller, and Urey toward understanding the origin of organic molecules 3. Explain why RNA, not DNA, was likely the first genetic material

33. AP Biology 4. Describe and suggest evidence for the major events in the history of life on Earth from Earth’s origin to 2 billion years ago 5. Briefly describe the Cambrian explosion 6. Explain how continental drift led to Australia’s unique flora and fauna 7. Describe the mass extinctions that ended the Permian and Cretaceous periods 8. Explain the function of Hox genes