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Ch. 14 Evolution

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Ch. 14 Evolution

  1. 1. Mutation<br />
  2. 2. Types of mutation<br />Point mutations<br />Change in a single DNA nucleotide<br />Substitution<br />Insertion<br />Deletion<br />Block mutation<br />Changes to a segment of a chromosome<br />Deletion<br />Duplication<br />Inversion<br />Translocation<br />Aneuploidy<br />Changes in number of chromosomes<br />2<br />
  3. 3. Point mutations - substitution<br />A change in a single base can have dramatic phenotypic effects<br />eg. Sickle Cell Anaemia<br />A change in a base will alter the codon transcribed<br />So an entirely different amino acid could be added to a protein chain<br />AAA = Lysine<br />AAU = Asparagine<br />Alternatively, seeing as multiple codons code for a single amino acid, it could have no effect at all<br />AAG = Lysine<br />3<br />
  4. 4. Point mutations – insertion / deletion<br />Can have far more dramatic effects than a substitution<br />A new nucleotide is inserted in to or deleted from an existing gene sequence<br />AUG CCU GGA GUA<br />met pro glyval<br />AUG CAC UGGAGU A<br />met his trp ser<br />This is called “a shift in the reading frame”<br />4<br />
  5. 5. Block mutations<br />The rearrangement of entire blocks of code in a gene<br />Normal<br />Deletion<br />Segment lost<br />Duplication<br />Inversion<br />Translocation<br />5<br />
  6. 6. Aneuploidy<br />Please examine the following karyotype, chromosomes are in numerical order<br />This individual has 3 copies of chromosome 21.<br />A condition known as Trisomy 21 or “Down Syndrome”<br />6<br />
  7. 7. Evolution<br />changes over time<br />
  8. 8. Evolution<br />There are currently ~30 million species on the planet and many times more than this that have existed at some time in the past<br /> Evolution is only a “theory” in the same sense as atomic theory or the theory of general relativity<br />It is based on the same solid scientific data as any other established truths (ie. gravity)<br />
  9. 9. Development of evolutionary theory<br />Erasmus Darwin<br />Father of Charles Darwin<br />Believed that all living things were derived from a single common ancestor<br />...but could not suggest a mechanism for how this could have ocured<br />
  10. 10. Development of evolutionary theory<br />John Baptiste Lamarck<br />Believed that acquired characteristics could be inherited by the next generation<br />Through the use or disuse of structures, an organism’s appearance could change over time<br />
  11. 11. Development of evolutionary theory<br />Charles Darwin & <br />Alfred Russel Wallace<br />Developed the current accepted theory of evolution via natural selection<br />Could not describe a mechanism of inheritance, even though their work was preceded by that of Gregor Mendel<br />
  12. 12. How old is the Earth?<br />According to James Ussher’s biblical calculations the earth is approx. 6000 years old (created on the evening of 23 October 4004 BC)<br />Clair Patterson’s accurate and reliable dating of an iron meteorite places the age of the Earth closer to 4500 million years old.<br />
  13. 13. The relative age of rocks<br />The age of rocks can be expressed in relative or absolute terms<br />The rule of superposition states that the relative age of a stratigraphic layer of rock can be determined by being aware of the order in which these layers were deposited<br />
  14. 14. The relative age of rocks<br />The rule of correlation states that the relative age of rocks can be determined by the presence of indicator fossils<br />These are of short-lived species of which existed at a known period in the earth’s pre-history<br />
  15. 15. The absolute age of rocks<br />Radiometric dating is based on the decomposition of particular unstable elements found in the rock layers.<br />
  16. 16. The absolute age of rocks<br />Each element has a known “half-life”, ie the time taken for 50% of the mass of the unstable parent element to decompose to a stable daughter element.<br />
  17. 17. The absolute age of rocks<br />As the daughter element is usually a gas, one cannot determine the original mass of the parent element from the remaining mass.<br />The unstable element exists in set ratios with its stable isotope. ie 0.012% of Potassium found in feldspar is P-40, so the original amount of potassium can be determined by the mass of the stable P-39.<br />Specific dating method are useful only for rocks containing the particular unstable element, and only if the half-life is of appropriate length.<br />Eg. Carbon-14 dating, with a half life of 5730 years is not usesul for material older than 60,000 years.<br />
  18. 18. The absolute age of rocks<br />Electron spin resonance is useful for organic material 50,000 – 500,000 years old<br />When materials are buried, they accumulate high energy electrons at a particular rate.<br />These electrons are returned to a ground state by exposure to fire or sunlight.<br />So we are able to determine how long it has been since the electrons in the material were in a ground state, and therefore how long they have been buried.<br />
  19. 19. Evidence of evolution<br />The fossil record<br />Transition fossils<br />Comparative biochemistry<br />Comparative anatomy<br />Bio-geographic distribution<br />
  20. 20. The fossil record<br />A very small percentage of individual organisms are fossilised, the conditions have to be perfect.<br />Burial needs to be very rapid in alkaline or oxygen poor water or soil.<br />Fossilised bone, teeth, shells, etc, are considered direct evidence.<br />Footprints, teeth marks, coprolites (fossilised dung), etc are considered indirect evidence.<br />
  21. 21.
  22. 22. The fossil record<br />The fossil record details the evolution of horses over time.<br />All its ancestors have since ceased to exist, but members of the genus Equus persist.<br />This includes numerous species of horses, donkeys and zebras<br />
  23. 23. Transitional fossils<br />Every current species evolved from an extinct but previously successful ancestor, so it is logical that there must have been transitional species in between.<br />A prime example is the transitional fossil between birds and dinosaurs<br />Archaeopteryx<br />
  24. 24. Comparative anatomy<br />Fossils bearing homologous structures as their origin can be traced to a common ancestor.<br />The same cannot be done with analogous structures (independently developed for a similar purpose (eg. bat’s wing and fly’s wing)<br />Mammalian <br />forelimb<br />
  25. 25. Knee<br />Ankle<br />Toe<br />Toenail<br />Homologous structures in locomotion<br />
  26. 26.
  27. 27. Comparative anatomy<br />Vestigial structures will also give clues to an animals origin. A disused structure will take a long to to completely dissappear (eg. nestigial hind limbs in whales)<br />Homeotic genes may prevent the development of disused structures in adults but evidence of these structures can still be found in embryos (eg. Non-functional gill slits in terrestrial vertibrates (some reptiles, birds and mammals – comparative embryology.<br />
  28. 28. Comparative biochemistry and genetics<br />Evolution predicts that the more similar two species are, the more biochemical and genetic similarities there will be.<br />It is already curious that all species share the same amino acid building blocks for proteins<br />As well as the same sucleotide building blocks for DNA<br />
  29. 29. The protein, haemoglobin<br />Fish<br />Goose<br />Human<br />Worm<br />Pig<br />
  30. 30. Molecular studies<br />
  31. 31. Amino acid sequence studies<br />The tables below represent the number of differences in amino acid subunits in a) the β chain of haemoglobin and b)cytochrome C<br />a)<br />b)<br />
  32. 32. DNA Hybridisation<br />DNA from two species is mixed and cut by restriction enzymes to a length of ~500 bp<br />Heat is applied to separate the strands<br />Solution is cooled to allow single strands from each species to hybridise to each other.<br />Heat is again gradually applied, hybrid strands with a higher degree of complementarity will have a higher melting (separation) point than strands with a lower degree of complementarity.<br />
  33. 33. DNA hybridisation<br />Data obtained for primates using DNA hybridisation<br />Data can be calibrated using the fossil record and used to create a phylogenic tree of inferred evolutionary relationships.<br />
  34. 34. Other techniques<br />Comparison of DNA sequences<br />Greater understanding from comparing entire genome instead of single genes<br />Comparison of chromosomes<br />Can compare with regard to number and banding pattern<br />Carried out via karyotype analysis<br />Led to the discovery that chimpanzee chromosomes #12 and #13 fused to form the human chromosome #2,<br />
  35. 35. Biogeographic distributions<br />Evolutionary perspective<br />If all the Earth’s creatures were ‘created’ then why aren’t similar species found in similar environments around the world?<br />Australian desert dwelling animals should display greater similarity with African desert dwelling animals rather than Australian rainforest dwellers, yet it is the other way around!<br />
  36. 36. Biogeographic distributions – the expectations<br />1. native species in different isolated regions will be distinctive, having evolved from different ancestral species<br />This can be seen in any island including Australia.<br />Species display distinct features, often found only in that particular location<br />
  37. 37. Biogeographic distributions – the expectations<br />2. modern species native to a given region will be more similar to species that lived in that region in the geological past than to modern species living in a distant region with similar environmental conditions<br />This can be seen in the fossil record<br />There are far greater similarities found between current and prehistoric Australian fauna than with animals found in other countries<br />
  38. 38. Biogeographic distributions – the expectations<br />3. the same ecological niche in different isolated regions will be occupied by different species (that are descended from different ancestral species that once lived in that region).<br />A distinct ecological niche is that of ant eating mammals.<br />They exist around the world but bear greater similarity to their geographical ancestors than to each other<br />
  39. 39. Echidna (Australia)<br />Giant anteater (South America)<br />Aardvark (Africa)<br />Pangolin (South-East Asia)<br />
  40. 40. The Molecular Clock<br />
  41. 41. The molecular clock<br />Used to calculate evolutionary distance between two current species<br />This evolutionary distance represents the time (in millions of years) since they diverged from a common ancestor.<br />A protein is selected and the number of differences in the amino acid sequence between two species is recorded<br />
  42. 42. Table of amino acid differences in the haemoglobin protein (by percentage)<br />
  43. 43. The molecular clock<br />Changes in AA sequences have been discovered to change at a steady rate<br />If accurate data on the time of emergence for one or two species exists in the fossil record, the clack can be ‘calibrated’<br />The calibrated clock converts relative data in to absolute data<br />
  44. 44. The data<br />Time scale of clock must be adjusted as large % differences are an underestimate due to amino acids being changed, and then changed again.<br />
  45. 45. The molecular clock<br />Caution is advised when using data as it is not without its problems<br />The rate of change with regard to amino acid sequences has been found to be different for different species.<br />Also the rate of change (per amino acid) is not the same for all proteins<br />
  46. 46. Patterns of evolution<br />Divergent evolution<br />Convergent evolution<br />Parallel evolution<br />Co-evolution<br />
  47. 47. Divergent evolution<br />An ancestral species can give rise to multiple new species (from different founder populations)<br />These new species will adapt to the individual environments in which they live and may eventually look quite different to each other<br />The ancestral species is gradually replaced in all locations by its more competitive evolutionary product<br />
  48. 48. American hares<br />These two species evolved from a more generalised hare, but to two very different environments<br />Snowshoe hare<br />Lepusamericanus<br />Alpine regions<br />Black-tailed jack rabbit<br />Lepuscalifornicus<br />Desert regions<br />
  49. 49. Adaptive radiation<br />Adaptive radiation will occur when an ancestral species will give rise to multiple evolutionary products, all evolving to suit a different environment<br />Eg. Darwin’s Galapagos finches<br />
  50. 50. Convergent evolution<br />The result of unrelated organisms developing similar features due to similar environmental conditions.<br />The resulting structures will serve similar purposes but will have had completely separate evolutionary origins.<br />Eg both Arctic and Antarctic fish (unrelated) have developed glycoproteins that act as a natural ‘anti-freeze’. These are produced by totally different genes.<br />
  51. 51. Example #1 – the opposable digit<br />The primate thumb was formed by one of the 5 digits in the forelimb migrating down towards the wrist.<br />This evolutionary development is shared by all monkeys, apes and humans (due to it being present in a common ancestor)<br />
  52. 52. In a completely separate evolutionary incident, koala’s had two of their five digits migrate down towards the wrist<br />The original 5 forward-facing digits were present in the common ancestor of virtually all mammals<br />
  53. 53. The panda started with the original 5 digits and then a 6th digit developed from the radial sesamoidbone in the list enlarging.<br />This phenomenon of similar environmentally induced requirements resulting in simillar morphological developments is called ‘convergent evolution’<br />
  54. 54. Well developed sagittal crest<br />An African mammal of Order Carnivora<br />Spotted Hyena<br />An Australian mammal of Order Dasyuromorphia<br />Tasmanian devil<br />
  55. 55. Well developed sagittal crest<br />An African mammal of Order Carnivora<br />Spotted Hyena<br />An Australian mammal of Order Dasyuromorphia<br />Tasmanian devil<br />
  56. 56. Parallel evolution / Co-evolution<br />Occurs when two species have such a close interaction that they steer each other’s evolution in a particular direction.<br />A good example is flowers and insects, their physical forms are uniquely adapted to maximise their benefit from thei interaction with each other.<br />eg. flowers produce pheromones to attract insects<br />eg. insect mouth parts adapt to the shape of flowers<br />
  57. 57.
  58. 58. Speciation<br />The result of time and the necessity to adapt to changing environmental conditions<br />Phyletic evolution – 1 species evolving in to a new form<br />Branching evolution – 1 species gives rise to two or more unique forms<br />Allopatric speciation – The result of members of the original population becoming geographically isolated<br />
  59. 59. Evolution: gradual or intermittent<br />Darwin’s theory states that evolution is the result of gradual changes accumulating over time.<br />Gould & Eldridge proposed the theory of Punk Ekk(Punctuated Equilibrium)<br />Long periods will pass with no changes occurring<br />When the appropriate conditions arise, change occurs at a rapid pace<br />The adapted species quickly replace those less suited to the new environment<br />The fossil record appears to lend some support to this theory<br />
  60. 60. Extinction<br />Can occur as a result of:<br />Loss of habitat / food<br />Competition / predation<br />Can be as the result of a catastrophic event. The asteroid that is believed to have hit Mexico’s Yukutan Peninsula 65 mya wiped out 70% of the species that nhabited the earth at that time<br />The asteroid would have been 10-20km in diameter, causing a crater 180km wide<br />
  61. 61. The death toll<br />Humans have been responsible for the vast majority of the world’s recent extinctions<br />In the last 200 years, Australian species account for 50% of the world’s extinctions<br />What do these names mean to you?<br />
  62. 62. The last 10 large animals we lost<br />
  63. 63. Comparitive genomics<br />Advancing technology now gives is the ability to sequence and compare the entire genomes of organisms rather than individual genes.<br />Computers are required to compare these vast quantities of genetic code<br />This graph displays various species % of alignment with the human genome<br />

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