ET Life 15. Requirements of Life &Evolu6on of Life Next Week: Habitability & Mars

Transcription

1 ET Life 15 Requirements of Life &Evolu6on of Life Next Week: Habitability & Mars

2 Paper Proposals A bit short on references 4-5 modern scien6fic references (journals, high- level books) No websites or TV shows. Don t rely on one work, or only work from the 60 s I have started puwng some valuable references on D2L, so check there Europa, HZ, panspermia, hydrothermal vents These would be good star6ng points to find more references and solid background informa6on. Depth many topics were very broad Try to zoom in to the level of current research. Hand them in AGAIN March 15 th. Easy points AND a chance to have more help on the topic/references YOU MUST INCLUDE 5 references (in a readable format, Mar6n et al Nature 123, p 456) Paper copies this 6me (unless we arrange otherwise)! Drafs are due April 5

3 Bill Bohke Fiske Thurs & Friday 7:30 $7 adults Free, $5 students 10 pts for 1 page summary

4 Solar Eclipse May 20

5 Solar Eclipse hhp://eclipse.gsfc.nasa.gov/eclipse.html

6 Annular

7 Total Eclipse Aug 21, 2017 is the next in North America

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9 How we built our first cells. 1. Organic soup was available - Organics also deliverable or made in vents. 2. Complex organics developed (mineral templates?). 3. Pre- cells enclosed complex organics. 4. Natural selec6on increased RNA complexity. 5. DNA developed within some successful cell(s). A reasonable scenario, though many details are missing!

10 1. Key ingredients to build our first cell 2.

11 Key ingredients to build our first cell 1. A liquid solvent Water is essen6al for life on Earth. 2.

12 Key ingredients to build our first cell 1. A liquid solvent Water is essen6al for life on Earth. 2. Carbon based: C, H, O, N are 96% of all life Carbon is the hub for all the organic molecules

13 Why water? Why carbon? Carbon can link to 4 atoms at a 6me, forming long complex structures At the heart of all complex organic molecules Abundant, light, small, 4 valence electrons Liquid water Heat regula6on Dense accumula6on of material Mobility carries waste/food

14 Also, common elements are useful Li, Be, B are all rare in nucleosynthesis It is best to start with something there is a lot of

15 Water Water is the most likely vola6le from nucleosynthesis H, C, O are among the most commen elements Remains stable over wide range of temperature Other compounds with this property are liquid at low T Chemical reac6ons get slower at low T lifes processes slow down Organic compounds (food) dissolve poorly at low T Melt Boil ΔT (C) H 2 O NH 3 (ammonia) CH 4 (methane) C 2 H 6 (ethane)

16 Special proper6es of Water High freezing point - > Large ΔT High heat of vaporiza6on Amount of heat needed to turn it into gas Basis for cooling system for plants/animals H 2 O evapora6ng uses up heat High specific heat Amount of heat needed to raise 1 g by 1 deg C Cell are buffered against environmental Temp changes High cohesion (s6cking together) Polar bonds High tensile strength (hard to pull apart) Lower density upon freezing Important for habitability

17 Polar Molecule Water is bent Electrons spend more 6me orbi6ng its O, than its H s This causes a charge separa6on Hydrogen bond Ahrac6ve force between the H of our electronega6ve atom and an electronega6ve atom in another moldecule Bonds are 5-10% as strong as covalent Hydrogen bonds in water Each H 2 O molecule can bond with 4 others High boiling point is due to large number of H- bonds and low molecular weight

18 Silicon based life Tracing one column from the periodic table (4 valence electrons) Can combine with 4 other atoms Allows for complex molecules DNA is the most complex with 100,000 s of atoms C is accesible due to CO 2 Silicon is 2 nd most abundant element in Earth s crust Largest naturally occuring Si molecule has 6 silicon atoms

19 Other basis for life Problem with Silicon Forms rocks when combined with O and isn t mobile Hard to get the energy to break that Si- O bond Si- H bonds are less stable than C- H bonds SiO 2 is solid at temperatures where water is liquid Silcon life would have to eat rocks and shit bricks Other elements in the same column Ge (Germanium) very rare 1 ppm Sn - 2 ppm

20 Key ingredients to build our first cell 1. A liquid solvent Water is essen6al for life on Earth. 2. Carbon based: C, H, O, N are 96% of all life Carbon is the hub for all the organic molecules

21 How to build beher cells 1. Organic soup was available - Organics also deliverable or made in vents. 2. Complex organics developed (mineral templates?). 3. Pre- cells enclosed complex organics. 4. Natural selec6on increased RNA complexity. 5. DNA developed within some successful cell(s). 6. Evolve over 3.8 Gyr A reasonable scenario, though many details are missing!

22 Evolu6on Evolu6on is any change across successive genera6ons in the heritable characteris6cs of biological popula6ons. Evolu6onary processes give rise to diversity at every level of biological organisa6on, including species, individual organisms and molecules such as DNA and proteins.

23 More Evolu6on Basics Evolu6on by natural selec6on is a process based on three facts about popula6ons: 1) overproduc6on of offspring (can t all survive) 2) traits vary among individuals, leading to differen6al rates of survival and reproduc6on 3) trait differences are heritable When members of a popula6on die they are replaced by the progeny of parents that were beher adapted to survive and reproduce in the environment in which natural selec6on took place. This process creates and preserves traits that are seemingly fihed for the func6onal roles they perform. Natural selec6on is the only known cause of adapta6on, but not the only known cause of evolu6on. Muta6on biased muta6on: preference for specific muta6on Gene6c drif random walk of gene frequencies

24 Varia6on within a popula6on allows evolu6on Textbook case are the peppered moths. Peppered moths feed on lichen on light- colored trees Industrial revolu6on starts, lichen dies, and trees are stained black. 1848, only 2% are black 1895, 95% are black

25 Muta6on Changes in the DNA sequence of a genome No effect Alter a gene s product Or prevent the gene from func6oning Drosophila studies show us that the chance changing of a protein produced by the gene Typically harmful (70%) The rest are neutral or weakly benefical New genes can be generated A duplicate copy of an ancestral gene mutates and acquires a new func6on. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new func6on while the other copy con6nues to perform its original func6on.

26 Preda6on!!!! Co- evolu6on in predator prey situa6ons. The evolu6on of one species causes adapta6ons in a second species Which then causes more evolu6ons. Rough- skinned Newt Tetrodotoxin Common Garter Snake Now resistant to tetrodotoxin

27 Process of one species diverging into two Barriers to reproduc6on are required for them to become new species Bad defini6on for prokaryotes Allopatric geographic isola6on Peripatric small popula6ons get separatered founder effect Parapatric small popula6on enters new habitat (no physical sep) Sympatric tough, species diverge, depends on non- random ma6ng for the isola6on Specia6on

28 Punctuated equilibrium Theory sta6ng that most species exhibit lihle net change stasis Major change is rare and fast cladogenesis. One species quickly spliwng into two, rather than gradually transforming. Sound familiar from our jaunt through Earth s fossil history?

29 Punctuated equilibrium Theory sta6ng that most species exhibit lihle net change stasis Major change is rare and fast cladogenesis. One species quickly spliwng into two, rather than gradually transforming. Sound familiar from our jaunt through Earth s fossil history?

30 Punctuated equilibrium Theory sta6ng that most species exhibit lihle net change stasis Major change is rare and fast cladogenesis. One species quickly spliwng into two, rather than gradually transforming. Sound familiar from our jaunt through Earth s fossil history?

31 Tree of Life Evolu6onary branches determined by DNA comparisons. Bacteria seem most ancient; archaea closer to eukarya. OK. We built this. What about the rest?

32 Eukaryotes vs. Prokaryotes? All Archaea and Bacteria are Prokaryotes because they lack a dis6nct nucleus with a membranous compartment (some excep6ons). All Eukarya are related on the phylogene6c tree. They are big and complicated. How then did they emerge? Thought ques6ons: If there WAS invasive Alien life on Earth, would we expect it to fit on our Phylogene6c Tree?

33 Evolu6on of Eukaryotes Prokaryote membrane infoldings may have compartmentalized cell func6ons. DNA isolated within membrane: nucleus.

34 Evolu6on of Eukaryotes Specialized prokaryotes may have developed symbio6c rela6onships with host cells. Mitochondria & chloroplasts do have bacteria- like DNA!

35 Mul6cellularity Exists in both prokaryotes (rare, temporary) and eukaryotes First appears Gyr ago in cyanobacteria Origin (wild guesses) Symbio6c - Func6on- specific cells become dependent (DNA?) Primi6ve cells having nucleus division, with a membrane then separa6ng the two (some things s6ll do this slime molds) Failed division, followed by specializa6on. Must solve the problem of reproduc6on Germ cells Thus thought to have been precipitated and predated by the rise of sexual reproduc6on in unicellular organisms.

36 Mul6cellularity Advantages: Get bigger and more compe66ve Get more complicated, by allowing the numerous cellular lineages within an organism Appearance? Around 1 billion years ago (hard to nail down) Thus preceded by 2.8 billion years of unicellular life and evolu6on

37 Coloniza6on of the Land For macroscopic life, protec6ve ozone (O 3 ) layer was vital step to inhabi6ng land: Shields the surface from dangerous ultraviolet sunlight. Life generated O 2 (through photosynthesis), which forms O 3, which protects life!

38 Coloniza6on of Land:Obstacles Gravity aqua6c life buoyed by water Need some sort of suppor6ng 6ssues Dessica6on Air is dryer than water Need some kind of skin Respira6on- valuable O and CO2 are no longer found dissolved in water Reproduc6on Can t simply release eggs/sperm into the water anymore.. Locomo6on swimming in out Senses Most senses need to evolve to new environment

39 Coloniza6on of Land: History Silurian Period ( Myr ago) Primi6ve plants came first, ahracted by the plen6ful real estate and good views The came types of land- liking arthopods Bugs etc. ea6ng the plants and each other At this 6me our ancestors and the the dinosaurs ancestors were s6ll aqua6c Devonian ( Myr ago) Fish con6nue to diversify Lungfish develop in freshwater areas that use lungs to gulp air once their small pond is depleted Lobefish develop bones in their fins for strength to deal with other freshwater issues Others could start to move from pool to pool to hunt, or find other resources By the end of the Devonian: bony limbs, wrists, ankles and digits.

40 Coloniza6on of Land: History Carboniferous Period ( ) Early tetrapods necks develop beher hun6ng Amnio6c Egg evolves Shell to prevent dessica6on Self- contained nutrients Tissue to handle waster and gas exchange At this point they are no longer bound to water for egg- laying.

41 Coloniza6on of Land: History Permian ( ) Evolve Synapsids mammal- like rep6les Types of predators Slow- moving herbivores Specialized carnivores/omnivores End of Permian comes with the greatest ex6nc6on of life (95% of species Permo- Triassic Ex6nc6on) Siberian Traps???

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43 Timeline of Geology & Life on Earth Eons: Eras: Hadean: hellish Paleozoic: old life Archaean: ancient Mesozoic: middle life Proterozoic: earlier life Cenozoic: recent life Phanerozoic: visible life

44 How we built our first cells. 1. Organic soup was available - Organics also deliverable or made in vents Complex organics developed (mineral templates?). Pre- cells enclosed complex organics. Natural selec6on increased RNA complexity. DNA developed within some successful cell(s). A reasonable scenario, though many details are missing!

45 Bill Bohke Fiske Thurs & Friday 7:30 $7 adults Free, $5 students 10 pts for 1 page summary