Mechanism of Evolution

• Evolution


  Gradual developmental modification to establish diversity and complexity in the living world
• Evolution


  Present day complex plants and animals evolved from earlier simpler forms of life by gradual changes
• Aristotle was a very great organizer of knowledge, studied and classified more than five hundred animal species, and showed an awareness of the interrelatedness of species
• Aristotle's classification of living things was later used by Darwin as evidence for the theory of evolution
• Charles Darwin is known as the architect of the theory of evolution by natural selection
• Charles Darwin advanced a view of the development of life on earth with the publication of On the Origin of Species in 1859
• Jean Baptiste Lamarck believed that living things evolved in a continuously upward direction and that species changed into other species
• Jean Baptiste Lamarck believed in the theory of acquired characteristics
• Charles Lyell was a prominent geologist in the nineteenth century known for the theory of uniformitarianism and significant influences on Darwin
• Charles Lyell's theory that slow processes created the earth influenced Darwin's theory of species creation
• Alfred Russel Wallace co-discovered the theory of evolution with Charles Darwin and proposed natural selection as the driving force of evolution
• Alfred Russel Wallace hypothesized that natural selection can contribute to reproductive isolation of incipient species
• Alfred Russel Wallace worked on his theory of evolution by natural selection in the mid-1800s
• Charles Darwin defined evolution as descent with modification
• CHARLES DARWIN: 'Descent with Modification'
• Evolution


  Defined as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor
• 3 principles of descent with modification

  1. Traits are inherited

  2. These traits lead to different levels of fitness

  3. Traits that increase fitness become more dominant in the population
• Traits that are inherited get passed on to the next generation. Traits of an individual will affect their ability to find food, shelter, and mates. Traits that increase their ability will continue to be passed on to the next generation. Traits that decrease their ability will not continue
• Natural selection

  Process in nature through which living organisms adapt and change in response to an environmental condition. Organisms better suited to their environment tend to survive longer and produce more offspring
• Natural selection

  Individuals in a population are naturally variable, meaning that they are all different in some ways. Some individuals have traits better suited to the environment than others. Individuals with adaptive traits are more likely to survive and reproduce, passing the adaptive traits on to their offspring. Over time, advantageous traits become more common in the population
• Peacock


  • Peacock females pick their mate according to the male's tail. Males with the largest and brightest tails mate more often, leading to most breeding males having large, bright tails. Tail characteristics are passed from adult breeding peacocks to their offspring
• Peppered moths


  • Most peppered moths used to be light-colored with black spots. When London's atmosphere became soot-filled during the Industrial Revolution, light-colored moths were eaten by birds more readily. Within months, most moths became darker. After factories reduced soot output, light-colored moths increased in number
• Artificial selection


  Identification by humans of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations. Works similarly to natural selection, but with human interference making the decisions
• Dog breeding


  • Artificial selection has allowed humans to drastically alter the appearance of dogs. Dogs have been bred for various desired characteristics, leading to a wide range of breeds from tiny Chihuahuas to massive Great Danes
• Agriculture

  • Artificial selection has been used to produce animals and crops with desirable traits. Meats sold today are the result of selective breeding of chickens, cattle, sheep, and pigs. Many fruits and vegetables have been improved or created through artificial selection
• Fruits and vegetables improved through artificial selection


  • Broccoli
  • Cauliflower
  • Cabbage
• Artificial selection


  Faster than natural selection and allows humans to mold organisms to their needs
• Gene flow


  Movement of individuals and/or genetic material from one population to another, introducing genetic variation
• Events of gene flow

  • Pollen being blown to a new destination
  • People moving to new cities or countries
• Genetic variation in modern human populations has been critically shaped by gene flow
• Neanderthal gene flow introduced new genetic variation to the human population
• Neanderthal gene versions have been linked to immune functions, metabolic functions, and skin color in modern humans
• Genetic drift

  Affects genetic makeup of the population through a random process, not producing adaptations
• Genetic drift affects the genetic makeup of the population through a random process
• Mutation


  Change in DNA base pair sequence due to environmental factors or mistakes during DNA replication
• Mutation is a sudden, heritable modification in an organism's traits
• Exposure to radioactive iodine (131I) from the Chernobyl accident increased the risk of thyroid cancer
• Radioactive iodine (131I) gives off radiation that breaks the chemical bonds in DNA, leading to mutations
• Theories learned today

  • Theory of Acquired Characteristics
  • Theory of Survival of the Fittest
  • Descent with Modification
  • Theory of Evolution by Natural Selection
  • Theory of Evolution by Artificial Selection
• Theory on evolution of organisms

  • Natural Selection
  • Artificial Selection
  • Gene Flow
  • Genetic Drift
  • Mutation