Earth part 3


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Earth part 3

  1. 1. Earth Part III: Extremophiles
  2. 2. What is Life? <ul><li>“ Life is what dies when you stomp on it” -Dave Barry </li></ul><ul><li>Simple definitions all fail </li></ul><ul><ul><li>Moves? Grows? Feeds? Reproduces? </li></ul></ul><ul><li>Best definitions focus on: </li></ul><ul><ul><li>Self-organizing, complexity, adaptation </li></ul></ul><ul><ul><li>Information coding </li></ul></ul><ul><ul><li>Feedback (homeostasis) </li></ul></ul>
  3. 3. Life Would you know it if you saw it?
  4. 4. A virus? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>Ebola virus
  5. 5. The potato that’s been in the cupboard for 3 weeks? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>
  6. 6. A human ovum (egg cell)? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>
  7. 7. Blood? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>
  8. 8. A embryo frozen at a fertility clinic? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
  9. 9. An apple seed? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>
  10. 10. Your fingernails? <ul><li>Yes </li></ul><ul><li>No </li></ul><ul><li>I don’t know? </li></ul>
  11. 11. Brief History of Life on Earth <ul><li>4.4 billion years - early oceans form </li></ul><ul><li>3.5 billion years - cyanobacteria start releasing oxygen. </li></ul><ul><li>2.0 billion years - oxygen begins building up in atmosphere </li></ul><ul><li>540-500 million years - Cambrian Explosion </li></ul><ul><li>225-65 million years - dinosaurs and small mammals (dinosaurs ruled) </li></ul><ul><li>Few million years - earliest hominids </li></ul>
  12. 12. Necessities for Life <ul><li>Nutrient source: The elements necessary for life: </li></ul><ul><ul><li>98%: C , H, N, O, P, S </li></ul></ul><ul><ul><li>2%: Na, Cl, K, F, Ca, Mg, B, Al, Si, Cr, Mg, Cu, Zn, Se, Sr, Mo, Ag, Sn, I, Pb, Ni, Br, Va </li></ul></ul><ul><li>Energy Source (sunlight, chemical reactions, internal heat) </li></ul><ul><ul><ul><li>Photosynthesis – 98% of energy </li></ul></ul></ul><ul><ul><ul><li>Chemolithotrophic – chemical redox reactions </li></ul></ul></ul><ul><ul><ul><li>Heterotrophic – other organisms </li></ul></ul></ul>
  13. 13. Necessities for Life <ul><li>Liquid water (or possibly some other liquid) </li></ul><ul><li>Some sort of liquid is necessary </li></ul><ul><ul><li>Solid – no mixing </li></ul></ul><ul><ul><li>Gas – too light </li></ul></ul><ul><li>Water is special </li></ul><ul><ul><li>High heat capacity – stable temperatures </li></ul></ul><ul><ul><li>Expansion on freezing – keeps ice floating so it can eventually melt </li></ul></ul><ul><ul><li>High dielectric constant – keeps charged groups separate </li></ul></ul><ul><ul><li>Universal solvent – makes lots of reactions work </li></ul></ul><ul><li>Stable environment for life to form (e.g. not devastated by volcanoes or impacts every 5 minutes) </li></ul>Hardest to find on other planets
  14. 14. THE GOLDILOCKS THEORY Too Hot Too Cold Just Right G O Giant Stars M Dwarf Stars 273K 373K Liquid H2O We are lucky enough to be living in just the right place for life to exist, in what is called in astronomy a habitable zones. Terrforming
  15. 15. Earth’s Alternative Biology <ul><li>Extremophiles: organisms that thrive under extreme temperature, pressure, or chemical conditions </li></ul><ul><li>Many of Earth’s simplest organisms are extremophiles </li></ul><ul><li>Extremophile domain is a bigger target </li></ul><ul><ul><li>We’re more likely to find planets inhabitable by extremophiles than planets suitable for humans </li></ul></ul>
  16. 16. Tolerance Ranges
  17. 17. Life in Unexpected Places (Extremophiles) <ul><li>Extreme cold </li></ul><ul><li>Extreme heat </li></ul><ul><li>Extreme pressure </li></ul><ul><li>No sunlight </li></ul><ul><li>Low water content </li></ul>Poison tolerant Salt tolerant Acid tolerant Alkali tolerant Radiation tolerant Lives in minerals No sunlight No oxygen
  18. 18. Types of Extremophiles Types of Extremophiles
  19. 19. More Types of Extremophiles <ul><li>Barophiles -survive under high pressure levels, especially in deep sea vents </li></ul><ul><li>Osmophiles –survive in high sugar environments </li></ul><ul><li>Xerophiles -survive in hot deserts where water is scarce </li></ul><ul><li>Anaerobes -survive in habitats lacking oxygen </li></ul><ul><li>Microaerophiles -thrive under low-oxygen conditions </li></ul><ul><li>Endoliths –dwell in rocks and caves </li></ul><ul><li>Toxitolerants -organisms able to withstand high levels of damaging agents. For example, living in water saturated with benzene, or in the water-core of a nuclear reactor </li></ul>
  20. 20. EXTREME PROKARYOTES Sample Hyperthermophiles Thermus aquaticus 1  m Pyrococcus abyssi 1  m Frequent habitats include volcanic vents and hot springs, as in the image to the left
  21. 21. 1. Hyperthermophiles <ul><li>Possibly the earliest organisms </li></ul><ul><li>Early earth was excessively hot, organisms would have to been able to survive intense heat. </li></ul><ul><li>These organisms contain heat stable proteins that prevent unfolding or denature at higher temperatures </li></ul><ul><li>They can live without sunlight or organic carbon as food. Living instead on sulfur, hydrogen, and other materials that other organisms cannot metabolize. </li></ul>The red on these rocks is produced by Sulfolobus solfataricus, near Naples, Italy
  22. 22. <ul><li>Deep-sea floor and hydrothermal vents involve the following conditions: </li></ul><ul><ul><li>2. Psychrophiles are present at low temperatures (2-3º C). </li></ul></ul><ul><ul><li>3. Oligotrophs are present at low nutrient levels. </li></ul></ul><ul><ul><li>4. Barotolerant (at 1000-4000 meters) </li></ul></ul><ul><ul><li>5. Barophilic (at greater then 4000 meters) can withstand great pressures. </li></ul></ul>Deep-sea floor A black smoker, i.e. a submarine hot spring, which can reach 518- 716°F (270-380°C)
  23. 23. 2. Psychrophiles Some microorganisms thrive in temperatures below the freezing point of water (this location in Antarctica) Some people believe that psychrophiles live in conditions mirroring those found on Mars – but is this true?
  24. 24. <ul><li>Proteins rich in  -helices and polar groups </li></ul><ul><ul><li>allow for greater flexibility </li></ul></ul><ul><li>“ Antifreeze proteins” </li></ul><ul><ul><li>maintain liquid intracellular conditions by lowering freezing points of other biomolecules </li></ul></ul><ul><li>Membranes that are more fluid </li></ul><ul><ul><li>contain unsaturated cis- fatty acids which help to prevent freezing </li></ul></ul><ul><li>active transport at lower temperatures </li></ul>Characteristics of Psychrophiles
  25. 25. 3. Oligotrophs <ul><li>Organisms that can live in an environment that offers very low levels of nutrients. </li></ul><ul><li>Characterized by slow growth, low rates of metabolism, and generally low population density. </li></ul><ul><li>Their environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils. . </li></ul>
  26. 26. 4. Barophiles <ul><li>Survive under levels of pressure that are lethal to most organisms </li></ul><ul><li>Found deep in the Earth, in deep sea, hydrothermal vents, etc. </li></ul>A sample of barophilic bacteria from the earth’s interior 1  m
  27. 27. 6. Halophiles <ul><li>Survive high salt concentrations by </li></ul><ul><ul><li>interacting more strongly with water such as using more negatively charged amino acids in key structures </li></ul></ul><ul><ul><li>accumulating high levels of salt in the cell in order to outweigh the salt outside </li></ul></ul>Deinococcus
  28. 28. 7. Xerophiles <ul><li>Extremophiles which live in water-scarce habitats , such as deserts </li></ul><ul><li>Produce desert varnish as seen in the image to the left </li></ul><ul><ul><li>a thin coating of Mn, Fe, and clay on the surface of desert rocks, formed by colonies of bacteria living on the rock surface for thousands of years </li></ul></ul>
  29. 29. Pace of Evolution <ul><li>Extremophiles, especially hyperthermophiles, possess slow “evolutionary clocks” </li></ul><ul><ul><li>They have not evolved much from their ancestors as compared to other organisms </li></ul></ul><ul><ul><li>Hyperthermophiles today are similar to hyperthermophiles of over 3 billion years ago </li></ul></ul><ul><li>Slower evolution may be the direct result of living in extreme habitats and little competition </li></ul><ul><li>Other extremophiles, such as extreme halophiles and psychrophiles, appear to have undergone faster modes of evolution since they live in more specialized habitats that are not representative of early earth conditions </li></ul>
  30. 30. What do we know? <ul><li>We don’t know exactly what life is. </li></ul><ul><li>We don’t know exactly how life began. </li></ul><ul><li>What do we know? </li></ul><ul><ul><li>Where does life live? Almost everywhere on Earth. </li></ul></ul><ul><ul><li>What are the requirements for life to exist and thrive? </li></ul></ul><ul><li>This isn’t too bad. After all, to find life, we first need to know where to look. </li></ul><ul><li>Step 1: Decide what life needs and identify the places that meet these requirements so we know where to look. </li></ul>
  31. 31. What is needed for life? <ul><li>The presence of liquid water </li></ul><ul><li>The elements needed for metabolism and reproduction (biogenic elements) </li></ul><ul><li>A biologically useful source of energy </li></ul><ul><li>Suitable environmental conditions </li></ul><ul><li> </li></ul>
  32. 32. Limiting factor <ul><li>Biogenic elements (CHONSP…) are all over the Solar System (even in asteroids and meteorites) </li></ul><ul><li>Sources of energy: </li></ul><ul><ul><li>Sunlight (photosynthesis) </li></ul></ul><ul><ul><li>Many chemical reactions generated by heat </li></ul></ul><ul><ul><li>Others? </li></ul></ul><ul><li>Liquid water requires temperatures of 273-373 K (0-100 C). </li></ul><ul><li>Environment </li></ul><ul><ul><li>Mainly, no harmful UV rays </li></ul></ul><ul><li>Bottom Line: Follow the water </li></ul><ul><li> </li></ul>
  33. 33. Follow the Water <ul><li>What planetary bodies have liquid water? </li></ul><ul><li>Water needs warmth (273-373 K), so heat is necessary. </li></ul><ul><li>Where does heat come from in the Solar System? </li></ul><ul><ul><li>Internal heat </li></ul></ul><ul><ul><li>Solar heat </li></ul></ul><ul><ul><li>Tidal heat </li></ul></ul><ul><li>That lead us to… </li></ul><ul><ul><li>Earth (duh) </li></ul></ul><ul><ul><li>Mars </li></ul></ul><ul><ul><li>Europa </li></ul></ul><ul><li> </li></ul>