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Evolution

Evolution. A Change through time. Evolution defined for our purposes. The theory that life arose by natural processes at an early stage of the earth’s history and that complex organisms developed from simple organisms by a process of gradual change.

erin-osborn
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Evolution

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  1. Evolution A Change through time

  2. Evolution defined for our purposes The theory that life arose by natural processes at an early stage of the earth’s history and that complex organisms developed from simple organisms by a process of gradual change.

  3. Lamarckism The first scientific explanation of evolution Jean Baptiste de Lamarck was the first to publish the idea that fossils were the remains of extinct animals (1809)

  4. Lamarckism The first scientific explanation of evolution His theory was that organisms strived to adapt to their environment, acquired adaptations and pass them on to their offspring.

  5. Lamarckism The first scientific explanation of evolution • The giraffe got a long neck from stretching for food • The snake lost its legs because they got in the way in dense vegetation

  6. Lamarckism The first scientific explanation of evolution • A man who exercised a lot would pass his strength on to his sons. Unsurprisingly this has been disproved by geneticists as there is no genetic evidence to support the theory.

  7. Fossils • The use of fossils as evidence was still accepted and is now considered the strongest evidence for evolution. • A fossil is the remains of or an imprint of past life uncovered from the crust of the Earth. • Biased because of selective preservation.

  8. Fossils – Methods of fossilization 1. Preservation in Amber • Amber is a sticky gum-like resin from trees that hardens into a transparent yellow material. • Organisms can be trapped and embedded in the resin before it hardens.

  9. Fossils – Methods of fossilization 2. Preservation in ice • In Arctic regions, organisms could be preserved for thousands of years from the last ice age. • The 25000 year old wooly mammoth was found with skin and hair intact.

  10. Fossils – Methods of fossilization 3. Preserved hard parts • After the soft tissues are decomposed by oxidation, bacterial action and fungi, the hard materials were easily buried under water borne sediments or tar and preserved

  11. Fossils – Methods of fossilization 4. Petrification • If the organisms body lies in water that is rich in minerals, the minerals permeate the body and when the water evaporates, the minerals remain in the shape of the organism – like turning the body to stone.

  12. Fossils – Methods of fossilization 5. Molds & Casts • If the organisms body lies in water and sand is washed over the body burying it. • The sand hardens to rock and after the body decomposes, the sand “mold” remains

  13. Fossils – Methods of fossilization 6. Imprints • Impressions in mud or tar stay after the mud hardens. Like a foot print in cement.

  14. Evidence of Evolution1. Comparative Anatomy Comparative Anatomy is the study of structural similarities and differences between organisms

  15. Evidence of Evolution1. Comparative Anatomy A. Homologous Structures – similar structures and similar embryonic development but different forms and functions - indicates evolutionary relationship

  16. Evidence of Evolution1. Comparative Anatomy B. Analogous Structure – similar external forms and function but quite different internally - indicates no evolutionary relationship

  17. Evidence of Evolution1. Comparative Anatomy C. Vestigial Structures - Remnants of structures that were functional in an ancestral form. - Tend to be reduced in size and serve little or no function.

  18. Evidence of Evolution2. Comparative Embryology • Comparisons of patterns of development • Closely related organisms show similar patterns of development.

  19. Evidence of Evolution2. Comparative Embryology • The more closely related the organisms,the longer they resemble one another during development.

  20. Evidence of Evolution3. Comparative DNA • By comparing gene and base sequences, we can identify links between organisms. • The more DNA in common, the more closely related the organisms.

  21. Evidence of Evolution3. Comparative DNA For example: The haemoglobin gene for humans is only one base pair different from that of the haemoglobin gene for a gorilla while the haemoglobin gene for a horse has 24 different base pairs.

  22. Evidence of Evolution4. Geographic Distribution • Pangaea - 165mya the continents split • Migration and continental shift. • Animals and native flowering plants of west coast US are closely related to those on east coast Asia. • Similar organisms in Africa and South America

  23. Evidence of Evolution5. Fossil record • Fossils give us snapshot of many organisms that have inhabited the earth. • To study and understand the information provided by fossils, scientists can compare body structures of different fossilized organisms with other fossils and with organisms living today. • To put the life of the organism in perspective, the fossil must be dated to provide a time-frame for its life.

  24. Evidence of Evolution5. Fossil Record - Dating A. Relative dating - if the rock layers are in the original order of deposit, then the lower the layer, the older the deposit and any fossil found in it.

  25. Evidence of Evolution5. Fossil Record - Dating B. Correlation – shows that certain rock layers in one place are older than certain rock layers in another place.

  26. Evidence of Evolution5. Fossil Record - Dating C. Index Fossils - fossils that allow relative dating of rocks within a fairly narrow time span. If you find a certain fossil of an organism in one region that matches the fossils found in another region, the rocks and other fossils are likely from the same time period.

  27. Evidence of Evolution5. Fossil Record - Dating D. Radioactive dating – most reliable The chemistry involved: • Atoms are made of protons, electrons and neutrons • Isotopes are atoms having different atomic weight because of differing numbers of neutrons.

  28. Evidence of Evolution5. Fossil Record - Dating Carbon always has 6 protons Carbon has an average atomic mass of 12.01. It could have a mass of 12, 13 or 14 as it could have 6, 7 or 8 neutrons C12has 6 protons and 6 neutrons so a mass of 12. C13has 6 protons and 7 neutrons so a mass of 13. C14has 6 protons and 8 neutrons so a mass of 14. C14 is unstable so it decays over time and can be used for dating.

  29. Evidence of Evolution5. Fossil Record - Dating • C14 is found in the atmosphere and is absorbed by living things. • After an organism dies, the C14 slowly decays into nitrogen. • If we measure the amount of C14 that remains in the organism, we can determine how long ago it died using the half-life of the C14.

  30. Evidence of Evolution5. Fossil Record - Dating Half Life – The time required for half of the nuclei in a given sample of a radioactive isotope to decay is called its half life. This rate is constant. C14 decays into nitrogen with a half life of approximately 5730 years.

  31. Evidence of Evolution5. Fossil Record - Dating

  32. Evidence of Evolution5. Fossil Record - Dating

  33. Evidence of Evolution5. Fossil Record - Dating

  34. Evidence of Evolution5. Fossil Record - Dating

  35. Evidence of Evolution5. Fossil Record - Dating

  36. Evidence of Evolution5. Fossil Record - Dating

  37. Evidence of Evolution5. Fossil Record - Dating

  38. Evidence of Evolution5. Fossil Record - Dating

  39. Evidence of Evolution5. Fossil Record - Dating How old would a fossil containing 20% C14 be? From the graph it appears to be about 13000 years old.

  40. % Carbon # of half-lives Evidence of Evolution5. Fossil Record - Dating A more precise answer can be found by using exponential decay. y = ( ½ ) n and, time = # of half-lives (n) x 5730

  41. Evidence of Evolution5. Fossil Record - Dating How old would a fossil containing 20% C14 be? y = ( ½ ) n n = 2.32 0.20 = ( ½ ) n Log0.5 0.20 = n time = 2.32 x 5730 Log 0.20 = n Log 0.5 time = 13 305 years

  42. Evidence of Evolution5. Fossil Record - Dating How much radioactive carbon would be left in a 44 000 year old fossil? This would be difficult to find from the graph

  43. Evidence of Evolution5. Fossil Record - Dating How much radioactive carbon would be left in a 44 000 year old fossil? time = n x 5730 y = ( ½ ) n y = ( ½ ) 7.68 44 000 = n x 5730 n = 7.68 y = 0.00488 0.488% of the carbon would remain.

  44. Evidence of Evolution5. Fossil Record - Dating After how many years is less than one percent of the C14 left in a fossil? y = ( ½ ) n n = 6.64 0.01 = ( ½ ) n Log0.5 0.01 = n time = 6.64 x 5730 Log 0.01 = n Log 0.5 time = 38 069 years

  45. Evidence of Evolution5. Fossil Record - Dating If a specimen was found to be 1.72 million years old, how much C14 remains in the bones? time = n x 5730 y = ( ½ ) n y = ( ½ ) 296.68 1.72 x 106 = n x 5730 n = 296.68 y = 4.9 x 10-90 This amount of carbon is too insignificant!

  46. Evidence of Evolution5. Fossil Record - Dating For any specimen that is over 50 000 years old, it is more practical to use other radioactive compounds to date the fossils. Uranium has a half life of 710 million years Potassium has a half life of 1.3 billion years

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