Evolution - PowerPoint PPT Presentation

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  1. Definition: The Scientific theory that describes changes in species overtime and their shared ancestry. Evolution Darwin’s Findings and the Evidence for Evolution

  2. Darwin’s Voyage • Darwin was apart of a mission that was commissioned to survey and map the coastal waters of South America • His role: • Observe • Record • Collect specimens

  3. The route taken by the HMS Beagle

  4. Darwin’s Discoveries • Discovered the fossils of giant Glyptodon and Megatherium in S.A.

  5. Darwin’s Discoveries • He documented that the fossils he found resembled modern day sloths and armadillos currently living in the same region • He found other examples of fossils that bare close resemblance to modern animals that shared similar geographical distributions

  6. Darwin’s Discoveries

  7. Darwin’s Discoveries • He also discovered fossils of marine organisms high in the Andes Mountains • Added support to idea that the Earth was dynamic and changing

  8. Darwin’s Discoveries • Next big discovery occurred on the Galapagos Islands • Darwin noted that several islands contained unique species that are similar, yet different, to ones in neighbouring islands

  9. Distribution of Galapagos Tortoises

  10. Examples of Galapagos Tortoises • Isabela Island • Santa Cruz • Abingdon Island • Pinzon Island

  11. Darwin’s Discoveries • Species on Islands resembled species on mainland

  12. Evidence for Evolution • Evidence from Biogeography = the study of the past and present geographical distribution of species populations • Geographically close environments are more likely to be populated by related species than are locations that are geographically separate but environmentally similar

  13. Evidence for Evolution • Biogeography continued • Animals found on islands often closely resemble animals found on the closest continent • E.g. lizards found on the Canary Islands, are very similar to those on mainland in West Africa

  14. Darwin’s Discoveries • In Darwin’s observations he noticed many species have structures that similar in anatomy, but they serve different function in each organism

  15. Homologous features • Homologous features serve different functions, but are similar anatomically • E.g. a fin of whale is for swimming • Hand of person for grasping • Wing of bat for flying • Evidence based on anatomy

  16. Darwin’s Discoveries • Darwin also observed features in organisms that have a similar function but have a different structure

  17. Analogous features • Serve the same function in different organisms, yet are anatomically distinct • E.g. wing of butterfly and bird • Eye of fly and eye of fish • Evidence based on anatomy

  18. Darwin’s Discoveries • Organisms with analogous features did not share such a recent common ancestor • Analogous traits evolved independently and arose independently in evolutionary history • Darwin concluded that organisms with homologous features share a recent common ancestor

  19. Darwin’s Discoveries • Vestigial Features = feature that no longer serve a function in one species, but do serve a function in a similar species • (e.g. vestigial toes on dogs and pigs)

  20. Darwin’s Discoveries • Further support - Evidence from Embryology (the study of early, pre-birth stages of an organism’s development) • Closely related species share homologous developmental processes and patterns • Similarities between embryos and related groups point to a common ancestral origin

  21. Darwin’s Discoveries How he put it all together

  22. What Darwin Observed • Darwin made many observations on his trip and identified different patterns • Fossil evidence • Galapagos Island observations (biogeography) • Anatomical observations: • Homologous features • Analogous features • Vestigial features

  23. Previous Knowledge • Darwin had observed artificial selection • Directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation • Used to produce new breeds or varieties of plants and animals • This is how the domestication of crops and animals took place

  24. Examples of Artificial Selection

  25. Examples of Artificial Selection

  26. What he did • Darwin used this knowledge to put together his theory of natural selection • A paper by Thomas Malthus was influential • Malthus stated that in nature, plants and animals have more offspring than can survive or be supported by nature

  27. Theory of NS – based on the struggle for survival • Most offspring will die, therefore there is a constant struggle for survival • Only individuals with traits favourable to their environment will live to reproduce and pass on their genes • The others will die • Coined “survival of the fittest”

  28. Modern Theory of Evolution What proof is there that his theory is valid?

  29. What’s been going on since Darwin • There have been more fossils unearthed • Transitional fossils • Repeated patterns have been observed • Our ability to interpret fossilized remains has improved • We have a better idea of the age of the earth

  30. Evidence from the Fossil Record • Transitional fossils – fossil that show links between groups of organisms and shares characteristics common to two now separate groups • E.g. Archaeopteryx

  31. Evidence for Evolution • Evidence from the Fossil Record • Fossils from more recent geological periods are usually much more similar to species alive today than fossils found in older, deeper layers of rock • Older fossils are simpler

  32. Evidence from Fossil Record • Evidence from the Fossil Record cont. • Not all organisms appear in the fossil record at the same time • E.g. fossil history of vertebrates show that fish appear in fossil record first

  33. Fossils of the same species can be found on the coastline of neighbouring continents

  34. Age of the Earth – how might this help? • We know the earth has changed drastically in its 4.5 billion years of existence • It is hypothesized that the universe is 14 billion years old

  35. Age of the Earth – how might this help? • This data comes from combined information from different streams of science

  36. Palaeontology and Geology • How do we know the age of rocks? • We use radiometric dating • How does this work? • Rocks are composed of matter…some of that matter contains…. • Carbon

  37. Radiometric Dating • Carbon (the ‘normal’ one) contains 6 protons, 6 neutrons • In this state Carbon is Stable (12C) • However Carbon is also present in an unstable form • Unstable forms contain 6 protons, but more or less neutrons • This is called an isotope • 14C – contains 6 protons, 8 protons

  38. Isotope Example

  39. Atoms want to be stable, so the nucleus will undergo change • To do this it gives off particles • In the case of 14C it will eventually break down to • 14C is the parent isotope • 14N is the daughter isotope

  40. Naturally known radioactive materials, like 14C, break down at constant rates • This is called radioactive decay

  41. Rate is described as a half-life • The time required for one-half of the parent (unstable radioactive element) to be converted to a more stable daughter element • The half-life of carbon-14 is 5,730 ± 40 years. • The percentage of carbon-14 present in remains of plants, animals, fossils, and rocks can be used to roughly determine age

  42. Half-life: Carbon Dating Activity • Objective – to figure out the age of different rock samples using the radioactive isotope carbon-14