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  • 1. Option D: Evolution IB Biology HL

2. Outline of Option D D.1 Origin of Life on Earth Physical conditions Miller and Ureys experiments Role of RNA Origin of prokaryotes Origin of eukaryotes (endosymbiosis) D.2 Origin of Species Lamarck and acquired characters Darwin-Wallace theory and natural selection Other theories and evidence D.3 Evidence for Evolution Geographical distribution Fossils and dating Biochemical evidence Homologous structures D.4 Human Evolution Classification Physical features of primates Fossil evidence Ecological pressures Bipedalism and brain size Genetic vs. cultural evolution D.5 Neo-Darwinism Mutations and examples Recombination Adaptations Speciation and isolation Gradualism Punctuated equilibrium D.6 The Hardy-Weinberg Principle Calculation of allele, genotype, and phenotype frequencies Conditions of HW equilibrium 3. D.1 Origin of Life on Earth 4. D.1.1 Outline the conditions of pre-biotic Earth, including high temperature, lightning, UV light penetration and a reducing atmosphere The Earth formed about 4.6 bya Collisions of material (comets and meteorites) led to the formation of the planet As the mass increased, gravity and radioactive decay caused the formation of the dense metal core surrounded by the liquid mantle and topped with the solid crust Cooling of the crust led to the formation of a very hot, dense, reducing atmosphere Pre-biotic Earth Reducing atmosphere No oxygen (O2) Reducing (hydrogen-containing) agents present hydrogen, water vapor, methane, ammonia, nitrogen, and hydrogen sulfide High temperatures High UV light levels Frequent lightning storms 5. D.1.2 Outline the experiments of Miller and Urey into the origin of organic compounds. Miller and Urey (1953) Simulated conditions of early Earth in order to determine whether chemical evolution could occur in primeval soup Sealed water, methane, ammonia, and hydrogen in sterile glass flasks connected by tubing One flask contained water and another contained a set of electrodes The water was heated to produce vapor and sparks were produced with the electrodes to simulate lightning The mixture was allowed to cool and condense and drip back into the first flask to simulate processes likely to have occurred on Earth This continued for one week, then M & U analyzed the contents to find: 13 amino acids present (of the 20 that occur naturally) High concentration of adenine 6. D.1.3 Discuss the hypothesis that the first catalysts responsible for polymerization reactions were clay minerals and RNA Miller and Ureys experiments provide a hypothesis for the origin of amino acids and nucleotides Subsequent experiments produced all 20 amino acids, nucleic acids, sugars, lipids, and nucleoside triphosphates from inorganic compounds How did the compounds combine to form larger polymers? RNA can act as both a form of genetic material and an enzyme Rybozymes are short sequences of RNA that can act as enzymes and are capable of Polymerizing nucleotides using ATP (and are thus capable of replication) Cleaving chemical bonds, including peptide bonds Ribosomes (composed of rRNA) are rybozymes Clay minerals RNA and other organic compounds adhered to clay particles Clay exists in very close layers, concentrating amino acids and other monomers in a small area Metal ions in the clay may have acted as catalysts for dehydration reactions Clays provide stable environments for polymerization D.1.4 Discuss the possible role of RNA as the first molecule capable of replicating 7. D.1.5 Discuss a possible origin of membranes and prokaryotic cells Origin of Membranes All cells are surrounded by membranes, and formation of these was critical in the development of the first cells Closed membrane vesicles can form spontaneously from lipids Due to structure and hydrophobic properties (think about a phospholipid) The first prokaryotes required a genetic mechanism and a membrane enclosure Origin of Prokaryotic Cells Coacervates are like little bundles of organic material surrounded by a hydrophobic layer Protobionts are groups of abiotically produced molecules Probably preceded by coacervates Surrounded by a protein membrane (can form bilayer in the presence of lipids) Maintain fairly constant internal environment Probably the predecessors for the first prokaryotes With RNA, these molecules could replicate and pass on their characteristics 8. D.1.6 Discuss the endosymbiotic theory for the origin of eukaryotes Anaerobic prokaryotes eventually developed chlorophyll and a simple form of photosynthesis, leading to the accumulation of oxygen in the atmosphere and aerobic life Reviewdifferences between prokaryotes and eukaryotes? Endosymbiotic theory: chloroplasts and mitochondria are derived from free-living prokaryotes that were engulfed by larger prokaryotes but survived inside the cytoplasm Mitochondria probably evolved from proteobacteria Chloroplasts probably evolved from cyanobacteria Evidence for endosymbiotic theory Both mitochondria and chloroplasts contain DNA that is different from nuclear DNA and similar to bacterial DNA Both are surrounded by double-membranes similar to prokaryotic membranes New organelles are formed by a process similar to binary fission Internal structure of chloroplasts similar to structure of cyanobacteria Analysis of nuclear DNA in plants suggests that some genes were incorporated from DNA of the chloroplast Ribosomes are found within mitochondria and chloroplasts and resemble bacterial ribosomes 9. Endosymbiosis 10. D.2 Origin of Species 11. D.2.1 Outline Lamarcks theory of evolution by the inheritance of acquired characteristics D.2.2 Discuss the mechanism of, and lack of evidence for, the inheritance of acquired characteristics Lamarck (1809) proposed a theory based on the inheritance of acquired characteristics Acquired characters are those that are acquired during an organisms lifetime For example, if muscles are used, they grow stronger Giraffe example: The ancestors of modern giraffes had short necks. According to Lamarks theory, the giraffes had to stretch up to the trees to reach their food, so their necks lengthened slightly. The next generation inherited the lengthened necks and stretched more. After many generations, long-necked giraffes came into existence. No significant cases of acquired characters have been found, and Lamarcks theory does not fit in with the principles of inheritanceno mechanism exists for the acquired character to cause a mutation in the gene controlling the trait 12. D.2.3 Explain the Darwin-Wallace theory of evolution by natural selection Darwin and Wallace proposed the theory of evolution by natural selection in 1858 Evolution is the accumulation of changes in the heritable characteristics of a population A series of observations and deductions led to the development of this theory Observation Deduction Populations tend to increase exponentially, but the number of individuals in a population remains nearly constant More offspring are produced than the environment can support; there is a struggle for existence in which some individuals survive and others die Living organisms vary; some individuals have characteristics that make them better adapted to their environment than others The better-adapted individuals tend to survive and reproduce more than less well-adapted individuals (this is natural selection) Much variation is heritable Better-adapted individuals pass on their characteristics to more offspring than less well-adapted individuals, causing the results of natural selection to accumulate. Over generations, the characteristics of the species gradually change (this is evolution) 13. D.2.4 Discuss other theories for the origin of species including special creation and panspermia D.2.5 Discuss the evidence for all these theories and the applicability of the scientific method for further investigation Other theories for the origin of species exist Spontaneous Generation Life arises from non-life Pasteurs experiments disproved theory Special creation God created life Panspermia Organic material arrived on Earth from space This theory has not been scientifically excluded In a 2001 study, experiments simulated interstellar dust clouds containing ammonia, CO2, and methanol mixed with ice crystals at low temperatures and high levels of UV Organic compounds were formed The scientific method cannot be used to test these Modern experiments will never determine with certainty what happened billions of years ago Experiments (such as Miller & Ureys) determine what is possible in conditions known to have existed 14. D.3 Evidence for Evolution 15. Types of Evidence There are three basic types of evidence for a common ancestor: Geographic Similar organisms exist in areas of the world known to have been connected by land at some point in the Earths history Biochemical Comparisons of DNA and amino acid sequences reveal similarities among all organisms Paleontological The fossil record provides information about organisms that lived in the pastsome of which are similar to modern organisms When all available evidence is compiled, phylogenies can be constructed. 16. D.3.1 Describe the evidence for evolution as shown by the geographical distribution of living organisms, including the distribution of placental, marsupial and monotreme mammals. 17. Evolution of monotremes, marsupials, and placental mammals The groups of mammals Monotremes Egg-laying mammals Examples: platypus and some anteaters Marsupials Young carried in pouch until fully developed Examples: kangaroo, koala Placental mammals Young carried in uterus until fully developed and nourished by placenta Examples: humans, dogs, horses Looking at the way in which continents have drifted over time and examining the fossils in them we can map out the de