Unit 2 - Evolution

• Before technology was available to show otherwise, the thought that Earth's natural surroundings changed was unimaginable and life forms were thought to be immutable (unchanged and unchanging)
• By the 19th century, there was sufficient evidence that Earth was very old (billions of years) and that life forms on Earth had undergone and continued to undergo changes
• Mutations


  Changes in genetic information, the original sources of genetic variation
• Types of mutations


  • Neutral
  • Harmful
  • Beneficial
• Neutral mutations


  Provide no benefit or harm to the individual
• Harmful mutations


  Reduce the reproductive success of an organism
• Harmful mutations


  • Cystic Fibrosis
  • Huntington's Disease
• Beneficial mutations


  Produce a change in an individual's phenotype that gives the individual an advantage
• Beneficial mutations


  • The sickle cell allele gives carriers a high degree of resistance to malaria
  • Changes as a result of human manipulation
• 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/animals
• Limitations of artificial selection

  • Breeders cannot create traits that do not already exist in some form within the population
  • If mutations arise, then breeders have new material to work with
• In the past, Evolution was not accepted within the Catholic religion
• With newer Popes, evolution has become accepted because they recognize that the Book of Genesis, and creation of all life in 7 days had to happen gradually over time
• Most evidence for evolution comes from biogeography, the observed geographic patterns of distribution of species. Darwin’s observations during the voyage of the Beagle laid the foundation for his new science. 
• Darwin’s Hypothesis

  Darwin considered evolution to be the best explanation for why isolated islands had many species that were found nowhere else, and why these species bore a resemblance to species nearest the continent. 
• Darwins hypothesis:

  1. Fossils closely resemble extinct organisms currently living in the same region; indicating that they could be ancestral. 
• Darwin's hypothesis:

  2. Many different species of finch found on the Galapagos Islands. They could have arisen from a single ancestral line and speciated due to isolation and filling different niches.
• Darwin's Hypothesis:

  3. Homologous features: structures that share a common origin but may serve different functions in different species (ex. Whale and dolphin flipper bones and human hands); could indicate a common ancestor. 
• Darwin's Hypothesis:

  4. Analogous features: features that serve the same purpose in different species, but are different in structure (e.g. Bat and bird wings, lobster and fish eyes).
• Darwin's Hypothesis:

  5. Embryology: the embryos of many animals are structurally very alike during the beginning of development despite no relationship to function as the organism grows. 
• Darwin's Hypothesis:

  6. Vestigial features and anatomical oddities: structures that are not used in living organisms (digits in dogs and horses, muscle for moving your ears, hips in whales); could indicate change over time. 
• Darwin's Hypothesis:

  7. Evidence of artificial selection: Darwin looked for a mechanism of inheritance through breeding. He found that variation was inheritable. 
• Darwin's Hypothesis:

  8. In nature, the struggle for survival dictates breeding success. Darwin read Malthus’ “Essay on the Principle of Population” (1798) which stated that nature produces far more offspring than are needed to survive, and that population depends on resource availability. Darwin applied this to speciation: successful individuals that exploit resources best survive to reproduce, and pass on their traits to the next generation. 
• On the Origin of Species

  Book published in 1859 by Darwin and Wallace
• On the Origin of Species published

  1859
• Natural Selection


  The way nature favours the reproductive success of some individuals within a population over others
• "Survival of the Fittest"


  Phrase used by Herbert Spencer describing the process of natural selection
• Adaptation


  Characteristic or feature of a species that makes it well suited for survival or reproductive success in its environment
• Darwin's Finches


  • Because the food source was limited to medium-large-sized seeds, the finches that were able to adapt for their needs were the ones that had little or no competition for food; resulting in higher survival rates and reproduction success
• Camouflage


  • Seasonal camouflage where species can change the colour of their fur to blend in with their surroundings
  • Chromatophore cells change the colour of the species skin quickly to hide from predators
• Once thought that creation was immutable (divinely designed)
• Archbishop James Ussher of Armagh declared the Earth was created on Sunday October 23, 4004 B.C.


  1650
• Radiometric dating today indicates that the Earth is about 4.5 billion years old, and the universe is about 13 billion years old
• Radioisotopes


  Atoms that undergo radioactive decay (nucleus of an atom changes and releases a subatomic particle)
• Decay rates can be measured accurately
• Half-life


  When 50% of sample of parent isotope converted to daughter isotope
• Darwin's theory could not account for how species evolve or the source of variation
• Modern Evolutionary Synthesis


  Modern genetics and biology have been combined with Darwin's theory
• Biologists define evolution as changes in the gene pool of a species over time
• Natural selection acts to favour some genetic combinations over other