Origin of Life Where did Life come from?

1. Origin of Life Where did Life come from? “…sparked by just the right combination of physical events & chemical processes…”

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

3. What is Life? • First we have to define LIFE… • organized as cells • respond to stimuli • regulateinternal processes • homeostasis • use energy to grow • metabolism • develop • change & mature within lifetime • reproduce • heredity • DNA / RNA • adaptation & evolution

4. The Origin of Life is Hypothesis • Special Creation • Was life created by a supernatural or divine force? • not testable • Extraterrestrial Origin • Was the original source of organic (carbon) materials comets & meteorites striking early Earth? • testable • Spontaneous Abiotic Origin • Did life evolve spontaneously from inorganic molecules? • testable

5. Conditions on early Earth: Immediately after “Big Bang” (H and He form in minutes!) • Reducing atmosphere • water vapor (H2O), CO2, N2, NOx, H2,NH3, CH4, H2S • lots of available H & its electron • no free oxygen – How would this have changed things, had it been present? • Energy source….lightening…sun

6. Electrodes discharge sparks (lightning simulation) Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") What is the…Origin of Organic Molecules?? Current hypothesis: Life evolves via: Abiotic synthesis • 1920Oparin & Haldane propose that a.a. and other building blocks of life can be generated from early inorganic compounds. • 1953Miller & Ureytest hypothesis • Put gases thought to be in early atmosphere in rx chamber + zap with electricity CH4 H2 NH3

7. University of Chicago Stanley Miller Less than one week after setting the experiment up: it produced -amino acids -hydrocarbons -nitrogen bases -other organics

8. But…how did actual CELLS emerge? WE don’t really know, but we can investigate how various steps or parts evolved!

9. Ex: Formation of proteins: Clay-template hypothesis The first proteins assembled on clay-rich, tidal flats. Sunlight provided energy for a.a. to form proteins! Some research supports this! • Why clay? Clay has a slightly negative charge and could potentially attract positively charged amino acids. • Clay forms sheets where molecules could react, build and be held • Then, with low tide, exposure to air and sun would dry it out compounds and condense them.

10. Example: Origin of cell membrane • Early cells are referred to a ‘protocells’ • Hypothesis: these cells were surrounded by a mb. that captured energy, materials, engaged in metabolism and replicated itself. • Spontaneous formations of saclike structures in lab show how these cells might have formed

11. Origin of Genetic material (and the dawn of natural selection) Evidence of an ‘RNA World” RNA is likely the first genetic material Has many functions! self-replicating molecule makes inheritance possible enzyme functions regulatory molecule transport molecule: tRNA & mRNA (see pg 321 in text)

12. Key Events in Origin of Life • Key events in evolutionary history of life on Earth • life originated 3.5–4.0 bya

13. 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-celledcyanobacteria

14. Lynn Margulis Stromatolites Fossilized mats of prokaryotes resemble modern microbial colonies

15. Oxygen atmosphere • Oxygen begins to accumulate 2.7 bya • reducing oxidizing atmosphere • evidence in banded iron in rocks = rusting • makes aerobic respiration possible • photosynthetic bacteria (blue-green algae)

16. ~2 bya First Eukaryotes • Development of internal membranes • create internal micro-environments • advantage: specialization = increase efficiency • natural selection! nuclear envelope endoplasmicreticulum (ER) plasma membrane infolding of theplasma membrane nucleus DNA cell wall plasma membrane Prokaryotic cell Prokaryotic ancestor of eukaryotic cells Eukaryotic cell

17. Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell

18. Eukaryotic cell with mitochondrion Endosymbiosis • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

19. Lynn Margulis Theory of Endosymbiosis • 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

20. Cambrian explosion - Diversification of Animals • within 10–20 million years most of the major phyla of animals appear in fossil record; this type of explosion of diversity has never happened again!! 543 mya

21. This slide Correlates movement of plates with evolution of the species

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

23. Cretaceous extinction 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

24. Early mammal evolution • 125 mya mammals began to radiateout & fill niches

25. Classifying Life • Molecular datachallenges 5 Kingdoms • Monera was too diverse • 2 distinct lineages of prokaryotes • Protists are still too diverse • not yet sorted out

26. 3 Domain system • Domains = “Super” Kingdoms • Bacteria • Archaea • extremophiles = live in extreme environments • methanogens • halogens • thermophiles • Eukarya • eukaryotes • protists • fungi • plants • animals

27. KingdomBacteria KingdomArchaebacteria KingdomProtista KingdomFungi KingdomPlantae KingdomAnimalia

28. Quad: Chp 20 1. The Big Bang Model proposes that the universe began in an instant; all matter and energy was suddenly distributed outward from a single point. • What evidence is used to support the idea of energy/matter moving out from a single point? • How did they estimate the time of the birth of the Universe? • What were the two elements formed within minutes? • How did they condense into stars • What evidence is used to prove this?

29. 2. Examine fig. 20.3 on page 319. Relate this picture to the formation of our own galaxy (Explain). • How did earth form? • What evidence do we have to support the belief that oxygen was not one of the earth’s early elements? • How would the evolution of life on earth as we know it have been altered if free oxygen was around? • How were the early seas formed?

30. Is there life elsewhere? Does it look like life on Earth? Any Questions??