Biology - Chp 15 - Darwins Theory Of Evolution - PowerPoint

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Biology - Chp 15 - Darwins Theory Of Evolution - PowerPoint

  1. 1. Chapter 15Darwin’s Theory of Evolution
  2. 2. 15 – 1 The Puzzle of Life’s Diversity
  3. 3. • There are A LOT of different organisms• This variety of living things is called Biological DiversityQ: What scientific explanation can account for the diversity of life?A: A collection of scientific facts, observations, and hypotheses known as Evolutionary Theory
  4. 4. Evolution• Change over time
  5. 5. Theory• A well supported testable explanation of phenomena that have occurred in the natural world
  6. 6. Charles Darwin• Born in England, February 12, 1809• Ships naturalist on a trip around the world aboard the HMS Beagle• During his travels, Darwin made numerous observations and collected evidence that lead him to propose a revolutionary hypothesis about the way life changes over time
  7. 7. Charles Darwin
  8. 8. The Voyage of the Beagle
  9. 9. Darwin’s Observations• Darwin saw far more diversity during his travels than he saw in his native country
  10. 10. Patterns of Diversity• Darwin was intrigued by the fact that so many plants and animals seemed remarkably well suited to whatever environment they inhabited• He was also impressed by the ways in which organisms survived and produced offspring• He was also puzzled by where different species lived and did not live
  11. 11. Fossil• Preserved remains of ancient organisms• Some looked like organisms that were still alive• Others looked completely unlike any creature he had ever seen• Darwin wondered, why had so many species disappeared, and how were they related to living species
  12. 12. The Galapagos Islands• Of all the Beagles ports of call, the one that influenced Darwin the most was a group of islands off the coast of South America called the Galapagos Islands• Although they were close together they all had different climates and differences between the species
  13. 13. Galapagos Tortoises
  14. 14. The Journey Home• While heading home, Darwin spent a great deal of time thinking about his findings• Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos• Darwin began to wonder if animals living on different islands had once been members of the same species
  15. 15. 15 – 2 Ideas that Shaped Darwin’s Thinking
  16. 16. • To understand how radical Darwin’s thoughts appeared, you must understand a few things about the world in which he lived• Most Europeans belived the world was only a few thousand years old• Nothing had changed since creation• Rocks and major geological features were thought to have been produced suddenly by catastrophic events that humans rarely ever witnessed• Slowly after studying many scientific theories of his time, Darwin began to change his thinking dramatically
  17. 17. Hutton and Lyell• Geological forces that have shaped Earth form very slowly, often over millions of years
  18. 18. Hutton and Geological Change• Geological forces that have shaped Earth form very slowly, often over millions of years• Therefore Earth had to be much more than a few thousand years old
  19. 19. Lyell’s Principles of Geology• Charles Lyell – author “Principles of Geology”• Process that shaped the Earth millions of years earlier continue in the present• Darwin Thought: If the earth could change over time, could life be changing as well?
  20. 20. Lamarck’s Evolution Hypothesis• Jean – Baptiste Lamarck• French naturalist• One of the first scientists to recognize that living things have changed over time, and that all species were descended from other species• Also realized, that organisms were somehow adapted to their environments
  21. 21. Lamarks theory had 3 aspects to it1. Tendency toward perfection• Organsims continually change and acquire features that help them live more successfullyEx.) Birds wanted to fly, so their wings grew and became suited to flying
  22. 22. 2. Use and Disuse• Body parts that were used developed, and those that were not went awayEx.) Reptiles stopped using their legs and evolved into snakes3. Evolution of Acquired Traits• Organsims that changed a characteristic in their lifetime, would pass that change on to its offspring
  23. 23. • This theory is WRONG!• He will forever be known in this class as Lamark the Loser!
  24. 24. Population Growth• Thomas Malthus - English economist• Published an essay in which he noted that babies were being born faster than people were dying
  25. 25. Malthus reasoned• That if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone
  26. 26. • Darwin realized that this applied even more to plants and animals than it did to humans because animals and plants had more offspring than humans did
  27. 27. 15 -3 Darwin Presents His Case
  28. 28. Publication of On the Origin of Species • Darwin did not rush to publish his thoughts • Darwin was not only stunned by his discoveries, he was disturbed by them • In 1858 Alfred Russel Wallace wrote to Darwin about a theory of evolution that was similar to his • Suddenly Darwin had an incentive to publish his own work
  29. 29. Inherited Variation and Artificial Selection• One of Darwin’s most important insights was that members of each new species vary from one another in important ways• Ex.) some trees have bigger fruit, some cows give more milk
  30. 30. Artificial Selection• Selection by humans for breeding of desired characteristics
  31. 31. Evolution by Natural Selection• Darwin was convinced that a process like artificial selection occurs in nature• High birth rates and a shortage for resources would force organisms into a competition for resources
  32. 32. Survival of the Fittest• A key factor in the struggle for existence, was how well suited an organism is to its environment• Darwin called the ability of an organism to survive and reproduce in its environment fitness• Darwin purposed that fitness is the result of adaptations
  33. 33. Adaptation• Any characteristic that increases an organisms chance of survival
  34. 34. • Adaptations can be• Anatomical – Speed, protection, camouflage• Physiological – The way it goes through photosynthesis• Behavioral – The way it hunts
  35. 35. • Individuals with low levels of fitness die and do not reproduce, and those with high levels of fitness survive and reproduce successfully• He called this process Survival of the fittest
  36. 36. Natural Selection• Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness in its environment
  37. 37. Descent with Modification• Darwin proposed that each living species has descended, with changes from other species over time• He called this Descent with Modification
  38. 38. The Fossil Record• By comparing fossils from older rock layers with fossils from younger layers, scientists could document the fact that life on Earth has changed over time
  39. 39. Geographical Distribution of Living Species• Many species share similar characteristics because they inhabit similar environments
  40. 40. Homologous body structures• Structures that have different forms but develop from the same embryonic tissue
  41. 41. Vestigial structures• Structures that are reduced in size and seem to no longer have a functionEx.) appendix, tailbone, wisdom teeth• Scientists think that vestigial structures are parts that once functioned in an ancestor
  42. 42. Similarities in Embryology• Many embryos look especially similar during early stages of development• All vertebrates go through a stage in which they have gill pouches• Similarities suggest an evolutionary relationship among all vertebrate species
  43. 43. Summary of Darwin’s Theory1. Individual organisms in nature differ from one another. Some of this variation is inherited2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce.3. Because more organisms are produced than can survive, members of each species must compete for resources.4. Because each organism is unique, each has different advantages and disadvantages in the struggle for existence.
  44. 44. Summary of Darwin’s Theory5. Individuals best suited to their environment survive and reproduce most successfully. The characteristics that make them best suited to their environment are passed on to offspring. Individuals whose characteristics are not as well suited to their environment die or leave fewer offspring.6. Species change over time. Over long periods, natural selection causes changes in the characteristics of a species, such as in size and form. New species arise, and other species disappear.7. Species alive today have descended with modification from species that lived in the past.8. All organisms on Earth are united into a single tree of life by common descent.

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