The Theory of Evolution

1. The Theory of Evolution Chapter 7

2. What is Evolutionary Theory? • Evolution describes changes in species over time and their shared ancestry • Prior to the theory of evolution, species and their traits were considered to be immutable • This means that traits / species were unable to change

3. How does Biological Change Occur? • Mutations • Neutral mutations • Does not result in any advantage or disadvantage • Harmful mutations • Reduces reproductive success of an individual • Beneficial mutations • Increases the reproductive success of an individual • Selective Breeding • Also known as artificial selection is the process of choosing individuals with a desired trait to create individuals with this trait • Eventually leads to new breeds and species being created • Adaptation / Heredity

4. Mutations • The source of variation in species • New or altered traits arise by • Mutations creating new genes or alleles • Duplicate copies of genes • Caused my misaligned chromosomes • Often neutral • Mutation rate is typically 1 per million bases • Duplications, inversions, insertions and deletions

5. Mutations (Continued) • Homologous Genes • Closely related species inherit many homologous genes • Genes that code for the same function and are very similar in structure Rat CCATC TTTCC TAAGC TCAAA Hippo CTATC CTTCC TAAGC ATAAA Deer CTATG GTTCC TAAGC ACGAA • Pseudogenes • A vestigial or useless gene that no longer codes for a functioning protein • Dolphins with genes for smell

6. Example of how one plant species was artificially selected to create six new plants

7. Artificial Selection • Artificial selection is used to enhance or express a trait that is considered “desirable” • This method is traditionally used by plant and animal breeders • However… • Breeders using artificial selection can only create traits that already exist within the population • Mutations cannot be forced (naturally) • It can decrease genetic diversity within a population • A harmful trait can accompany a beneficial one that is selected and bred • Hip Dysplasia in Golden Retrievers • Cancer in St. Bernards

8. Adaptation / Heredity • Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1744 – 1829) • He was the first scientist to offer a possible mechanism for how creatures evolved, his theory included: • “Use it or lose it”  he believed that structures that were used often became bigger and stronger, while one’s not used became smaller or were lost • Inheritance of acquired traits • Changes are passed from generation to generation • Giraffes • All species evolve over time • Provided a basis for the theory of evolution

9. How do we know evolution has occurred? • FOSSILS! • Ancient remains, traces or impressions of an organism or it’s activity preserved in rocks or other mineral deposits • Made by the organisms’ remains being gradually replaced by mineral deposits Footprints Bones Preserved in Amber Impressions

10. What do fossils tell us? Catastrophism vs. Uniformitarianism

11. Catastrophism • George Cuvier (1769 – 1832) conducted the first detailed studies of fossils • His conclusions from his studies were: • Many species occur in one rock layer that never occur in any other layers • Fossils found in layers closer to the surface are more likely to resemble living species • Simple organism fossils are found in all layers, and the closer to the surface you get, the more complex organisms become. • Cuvier theorised that the pattern of fossils could be explained by a series of global catastrophes that wiped out most life on earth • Believed that species themselves did not change

12. Uniformitarianism • Charles Lyell (1797 – 1875)  known as the father of modern geology postulated that: • The Earth has been changed in the past by the same processes that occur today • Geological change is slow and gradual rather than fast and catastrophic • The Earth was much older than science at the time believed it to be

13. DARWIN (1809 – 1882) http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_2.html

14. Darwin continued… • Charles Darwin was a naturalist who spent 5 years on the HMS Beagle mapping and surveying the South American coast for the British navy • He used biogeography to help explain evolution • The scientific study of the geographic distribution organisms based on both living species and fossils • His most infamous work is his findings on the Galapagos Islands • Spent over 20 years gathering and examining his findings HMS Beagle’s Route 

15. Evidence • If the theory of evolution is correct, and all living things are related through a common ancestor, we would expect to find evidence of this relationship by examining organisms anatomies • Physical evidence is shown in organisms: • Homologous Features • Analogous Features • Vestigial Features

16. Homologous Features • Darwin wondered why and how the bones in most mammals were so similar in umber and arrangement? • The similarities that he noticed are now referred to as homologous features • Homologous features are structures with a common evolutionary origin, that may serve different functions in difference organisms • Mammalian limbs • Mammalian skulls • 28 bones

17. Analogous Features • A structure that performs the same function in different organisms, but is not similar in origin or anatomical structure • The features have evolved independently from each other • Ex: Bird eyes and wings vs. insect eyes and wings

18. Vestigial Features • A non-functioning or marginally functioning structure, that is homologous to a fully functioning structure in a closely related species • Vestigial Appendages • Dogs dew claw • Whale hip bone

19. A frogs legs and a kangaroos legs • Bird wind and a dragonfly wing • The human appendix • Dolphin flipper and a human hand • Wings on an ostrich Homologous embryo features

20. Natures Influence on Evolution • Reverend Thomas Malthus • Mathematician who showed that all populations were limited in size by their environment, and in particular their food supply • After reading Malthus’ paper, Darwin realised the implication this had on his theory • More offspring are born than can survive, which leads to competition between members of the same species • Ex. Frogs

21. Natural Selection • Darwin’s book “On the Origins of Species” states that natural selection is the method of evolution • He describes natural selection as the way in which the environment favours the reproductive success of certain individuals over others • Ex. Anteater, longer nose / tongue more food  healthier  more likely to have reproductive success • Herbert Spencer used the phrase “survival of the fittest” to describe natural selection • Problem?

22. Modern Theory of Evolution • Modern science has allowed us to confirm and build upon Darwin’s theory • Radiometric Dating • Used by scientists to obtain precise estimates of ages of rocks by measuring radioisotopes level of radioactive decay • Based on the ratio of parent to daughter isotopes in a rock • Half-life • C14 N14

23. Modern Theory of Evolution (Continued) • Darwin’s theory of natural selection accounted for how species changed, but not the specific source of the variation • Modern Evolutionary Synthesis • Theory of evolution that takes all branches of biology into account • Anatomy, genetics, neurology etc. • Gene Pool and Mutations

24. How Has The World Changed? • Plate Tectonics • The scientific theory that describes the large-scale movements and features of the Earths crust • Pangaea • http://www.youtube.com/watch?v=WaUk94AdXPA • The idea of continental drift can be used to explain fossil distributions • Whale fossils found in Pakistan

25. Proof of continental drift is shown in the pattern of fossil discovery around the world • The science of plate tectonics and paleontology have greatly enhanced our understanding of evolution