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D1 Origin of life on Earth

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  1. D1 Origin of life on Earth

  2. D.1.1 Describe four processes needed for the spontaneous origin of life on Earth. • Abiotic synthesis of small organic molecules (ex: amino acids & nucleotides) • Joining of monomers into polymers • Origin of self-replicating molecules that made inheritance possible • Packaging of molecules into membranes with an internal chemistry different than their surroundings (protobionts)

  3. D.1.2 Outline the experiments of Miller and Urey into the origin of organic compounds. • Simulated ‘pre-biotic’ Earth • Atmosphere made of H2O, H2, CH4, and NH3(like hypothesized for early Earth) • Successfully created major biomolecules

  4. Electrodes discharge sparks (lightning simulation) Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") Origin of Organic Molecules CH4 • Abiotic synthesis • 1920Oparin & Haldane propose reducing atmosphere hypothesis • 1953Miller & Urey test hypothesis • formed organic compounds • amino acids • adenine H2 NH3

  5. Stanley Miller University of Chicago Produced: -amino acids -hydrocarbons -nitrogen bases -other organics

  6. D.1.3 State that comets may have delivered organic compounds to Earth. • Comets can carry organic compounds • Earth was bombarded with comets and asteroids 4 bya • Impact could delivered both organic compounds & water to the early earth

  7. D.1.4 Discuss possible locations where conditions would have allowed the synthesis of organic compounds. • In space: • Scientists recreated environment that mimics space (low-pressure and low-temp) and synthesized amino acids • Support hypothesis that molecules needed for life could have originated in space (Panspermia)

  8. 2. In alternating wet/dry conditions: • Seashore or flood plains of a river • Drying of clay particles could have catalyzed reactions to form early organic molecules • Evidence: Stromatolites (among oldest known fossils)

  9. 3. Near Volcanoes: • Eruptions spit out water vapor, gases, and minerals which could form organic matter • Those raw materials plus the heat from volcano could have provided conditions to form amino acids and sugars

  10. 4. In Deep Oceans: • Near thermal vents, hot water rises and picks up minerals along the way

  11. D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life. • RNA can self-replicate (w/o enzymes) • RNA can act as a catalyst (ribozyme) helping reactions

  12. D.1.6 State that living cells may have been preceded by protobionts, with an internal chemical environment different from their surroundings. • Protobionts are the evolutionary precursors of prokaryotic cells. • Protobionts may be originated as an array of microspheres or coacervates • coacervates : tiny spherical droplet of assorted organic molecules (specifically, lipid molecules) which is held together by hydrophobic forces from a surrounding liquid. • microspheres: Microscopic, firm spherules which form on the cooling of hot saturated solutions

  13. Bubbles…Tiny bubbles… Origin of Cells (Protobionts) • Bubbles  separate inside from outside  metabolism & reproduction microsphere

  14. D.1.7 Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere • About 3.5 bya, some bacteria developed the ability to photosynthesize • Helped convert iron dissolved in ocean water, into precipitates of iron oxide = rust-colored layers of rock • Waste production of photosynthesis is oxygen • Photosynthetic bacteria proliferated and produced more and more oxygen

  15. D.1.8 Discuss the endosymbiotic theory for the origin of eukaryotes.

  16. D.1.8 Discuss theendosymbiotictheory for the origin of eukaryotes Evidence in support: Mitochondria and Chloroplasts have their own DNA that is more like bacterial DNA than what is found in the nucleus The structure and biochemistry of chloroplasts is similar to cyanobacteria New organelles are made by a process that resembles binary fission Both organelles have a double membrane which resembles the structure of prokaryotic cells Their ribosomes resemble those of bacteria (70S) DNA analysis suggests that some DNA in plant nuclei was previously in the chloroplast Some proteins coded for in the nucleus are transported to the organelles. The organelles have lost the DNA to make it themselves. Endosymbiosis is the theory that chloroplasts and mitochondria were once free-living prokaryotes that were engulfed by larger prokaryotes and survived to evolve into the modern organelles

  17. Lynn Margulis Theory of Endosymbiosis • Evidence (another way to look at evidence) • structural • mitochondria & chloroplasts resemble bacterial structure • both have double membranes • genetic • mitochondria & chloroplasts have their own circular DNA, like bacteria • Mitochondria and chloroplasts have bacteria-like RNA and ribosomes (70S as opposed to 80S in eukaryote cytoplasms) that enable them to make their own proteins and divide independently of the host cell • functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell

  18. Species and Speciation D.2.1 – D.2.11 Chapter 15

  19. D.2.1: Define allele frequency and gene pool • Gene pool: all of the genetic information present in the reproducing members of a population • Large gene pool = lots of variety in traits • Small gene pool = little variation (ex: inbreeding)

  20. D.2.1: Define allele frequency and gene pool • Allele frequency: a measure of the proportion of a specific variation of a gene in a population (proportion or percent) • Allele b is present in 25% of chromosomes in a population = • ¼ of loci for a gene have that allele • ¾ of loci do not • 25% of chromosomes in a population have the allele (NOT 25% of members have the allele)

  21. D.2.2 • State that evolution involves a change in allele frequency in a population’s gene pool over a number of generations • No change in allele frequency = no evolution • Big change in allele frequency = evolution • What causes changes in allele frequencies? • Immigration, emigration, mutations, natural selection

  22. D.2.3: Discuss the definition of the term species • A species consists of organisms which: • Have similar physiological and morphological characteristics • Have the ability to interbreed and produce fertile offspring • Are genetically distinct from other species • Have a common phylogeny

  23. D.2.3: Discuss the definition of the term species • Xref 5.1.1 definition of species: • A group of organisms that can interbreed and produce fertile offspring. • Members of the same species have a common gene pool (genetic background)

  24. D.2.3: Discuss the definition of the term species • Challenges to the definition of species: • Sometimes similar species can reproduce and successfully produce offspring (but wouldn’t do so naturally) • Ex: horse & zebra or donkey & zebra

  25. D.2.3: Discuss the definition of the term species • Challenges to the definition of species: • Two populations which could interbreed but are separated by a long distance • Populations that don’t interbreed because they reproduce asexually • Infertile individuals

  26. D.2.4: Describe three examples of barriers between gene pools • Geographical isolation: physical barriers (land and water) prevent males and females from finding each other (making interbreeding impossible) • Temporal isolation: different breeding times • One population of same species is hibernating while the other population is ready to mate

  27. D.2.4: Describe three examples of barriers between gene pools • Behavioral isolation: unique mating rituals which are “attractive” to different populations of the same species • Hybrid infertility: the majority of animal and plant hybrids are infertile which creates a genetic barrier between species • donkey + horse = mule • lion + tiger = liger

  28. D.2.5: Explain how polyploidy can contribute to speciation • Polyploidy = cells contain 3 or more sets of chromosomes (3n, 4n, 5n) • Can be caused by errors in cell division when chromosome copies don’t completely separate (nondisjunction) • More common in plants than animals • In plants, extra chromosomes result in plants with bigger fruits or food storage organs

  29. D.2.5: Explain how polyploidy can contribute to speciation • Having extra sets of chromosomes results in more replication errors • 3n population and another 4n population, each population’s evolution will be different • The two populations could become so dissimilar that they no longer belong to the same species

  30. D.2.6: Compare allopatric speciation and sympatric speciation • Speciation: the formation of a new species by splitting of an existing species • Sympatric speciation: in the same geographical area • Ex: temporal or behavioral isolation • polyploidy • Allopatric speciation: in different geographical areas • Ex: a rise in sea level separates land-dwelling species from one another and they evolve separately



  33. D.2.7: Outline the process of adaptive radiation • Adaptive radiation: similar but distinct species evolve relatively rapidly from a single species or form a small number of species • Variation in a species results in some members of the population exploiting a different niche more successfully • Ex: finches in the Galapagos Islands • Ex: silversword plants on Hawaiian islands

  34. D.2.8: Compare convergent evolution and divergent evolution • Both refer to organisms’ features and how they use certain molecules • Both are a process of natural selection that allowed organisms to adapt to their environment

  35. D.2.8: Compare convergent evolution and divergent evolution • Convergent evolution: species which become more similar over time (similar features “selected for” due to similar environment • Ex: euphorbias vs. cacti • Ex: sugar glider vs. flying squirrel

  36. D.2.8: Compare convergent evolution and divergent evolution • Divergent evolution: species which become less and less similar over time • Ex: bird w/long, thin beak vs. bird w/short, fat beak

  37. D.2.9 Discuss ideas on the pace of evolution including gradualism and punctuated equilibrium • Gradualism is the slow change from one form to another

  38. D.2.9 Discuss ideas on the pace of evolution including gradualism and punctuated equilibrium • Punctuated equilibrium implies long periods without appreciable change and short periods of rapid evolution (based on fossil record) • Ex: volcanic eruptions & meteorite impacts affecting evolution on Earth • Species of mammals taking over habitats abandoned by dinosaurs 65 mya

  39. D.2.10: Describe one example of transient polymorphism • Polymorphism is when two or more forms of a phenotype are represented in high enough frequencies to be readily noticeable.

  40. D.2.10: Describe one example of transient polymorphism • Transient polymorphism is one that is changing in frequency over time. • Ex: Industrial melanism: factory pollution changing the population of peppered moths • Temporary increase in a certain allele

  41. change occurred in a number of moth species populations in the late 1800’s in industrialized areas of England and the United States. • Prior to this period, moth populations were primarily composed of light colored mottled moths with occasional mutant dark colored (melanic) moths. • During this period, over a number of generations, the populations changed such that the majority of moths were dark colored. • This could be explained by a change in the bark of trees in the woods surrounding the industrial areas. • The bark had gone from being whitish in color to a soot-covered black. Moths rest on bark during the day. • Light colored moths were now conspicuous to birds whereas dark moths were not. • Dark colored moths therefore had higher fitness and left more offspring for the next generation.

  42. D.2.11: Describe sickle-cell anemia (SCA) as an example of balanced polymorphism • Balanced polymorphism: frequencies of characteristics remain fairly constant over time. • Sickle-cell anemia is an example of balanced polymorphism where heterozygotes have an advantage in malarial regions because they are fitter than either homozygote • Allows for an increase in the allele because it is favored in heterozygotes

  43. D3 Human evolution

  44. D.3.2 Define half-life. • Half life is the amount of time it takes for half of a sample (50%) of a certain substance to decay.

  45. D.3.1 Outline the method for dating rocks and fossils using radioisotopes, with reference to 14C and 40K. • Fossils contain isotopes of elements that accumulated in the living organisms. • If the isotopes are unstable, they will lose protons and break down over time. • Since each radioactive isotope has a fixed half-life it can be used to date fossils based on the relative concentrations of the reactant and product of the decay. • Carbon-14 has a half life of 5730 years; useful for dating fossils less than 62,000 years old. • Potassium-40 has a half-life of 1.25 billions years so useful for long-term dating. Error of less than 10%.

  46. D.3.3 Deduce the approximate age of materials based on a simple decay curve for a radioisotope.