genbio Q4W5

• Descent with modification


  Passing on of traits from parent organisms to their offspring
• Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life
• Evolution described as "descent with modification" by Charles Darwin


  Species that changed over time, giving rise to the new species and share a common ancestor
• Heredity


  The passing on of traits from parent organisms to their offspring
• According to Charles Darwin, all species descended from only a few life forms that had been modified over time
• Descent with modification


  • Forms the backbone of Darwin's Theory of Evolution, which posits that the development of new types of organisms from pre-existing types of organisms over time is how certain species evolve
• How descent with modification works

  1. Genetic mutation

  2. Individual (or natural) selection

  3. Evolution of the population (or species as a whole)
• Genes and individuals do not evolve, only populations evolve
• Natural selection


  A species adapts to its environment, thanks to its specific genetic makeup
• Darwin never used the word evolution in the first edition of The Origin of Species, instead used the phrase "descent with modification"
• Descent with modification


  • All living organisms are related to each other due to their descent from a common ancestor that lived in the distant past
  • Over evolutionary time, the descendants of that common ancestor have accumulated diverse modifications, or adaptations, that allow them to survive and reproduce in specific habitats
  • Over long periods of time, descent with modification has led to the rich diversity of life we see today
• Natural selection can act only on heritable traits, traits that are passed from organisms to their offspring
• Environmental factors vary from place to place and from time to time. A trait that is favorable in one environment may be useless or even harmful in another environment
• Modern Synthesis


  Evolutionary theory dramatically changed when Darwin's original ideas were merged with ideas from genetics
• The updated and revised theory of evolution becomes easier to understand, appreciate, and embrace
• Lamarck


  Interested in adaptation or the manner and process by which organisms are able to adapt physiologically and morphologically to their environment
• Lamarck's theory


  The use or disuse of a vital organ could lead to the development of novel but well-adapted traits, and the cumulative effect of these adaptations could eventually lead to a new species
• Transmutationism became increasingly acceptable by the early nineteenth century
• Transmutationists


  • Erasmus Darwin
  • Isidore Geoffroy Sainte Hilaire
• Isidore Geoffroy Sainte Hilaire

  Studied birth defects and suggested that through such "monstrous births" new species might suddenly arise
• Charles Darwin


  The leading transmutationist of the nineteenth century
• Darwin developed the major features of his theory as early as 1837 after returning from his five-year voyage of the HMS Beagle and after reading the famous Essay on the Principle of Population by Thomas Malthus
• Darwin did not make his work public until much later as he felt he needed to collect solid evidence to support his contentious theory
• Darwin was forced into joint publication of an abbreviated version of his theory in 1858, shortly after Alfred Russel Wallace independently formulated his own nearly identical theory
• Darwin's theory of "descent with modification"


  Darwin's theory of species change by means of the mechanism of natural selection
• The full title of Darwin's famous book was "On the Origin of Species or the Preservation of Favored Races in the Struggle for Life"
• The first edition of On the Origin of Species is considered a more accurate account of the workings of evolution because subsequent editions included a watered-down version of his original theory
• Natural selection


  Occurs when an organism with a favorable variation in some trait reproduces more as a result, thereby increasing the frequency of the variation in the next generation
• In addition to natural selection, Darwin included some four or five other mechanisms that he thought could account for species change including the inheritance of acquired characters