bio 1

• Evolution


  Any change in the heritable traits within a population across generations
• Aristotle's Scala Naturae


  • Believed species were fixed and organized them on a scale of increasing complexity
  • This view aligned with the Old testament's idea of species being individually deigned by God
• Carolus Linnaeus


  • In 1700's, scientist saw evidence of divine design in the well-suited organisms to their environments
  • Introduces the binomial system for naming species
  • Developed a nested classification system, grouping similar species into increasingly inclusive categories
  • Aims to classify glory of God, not considering evolutionary relationships but rather attributing resemblances among species to divine creation
• How animals are classified (from top to bottom in the hierarchy)

  • Domain (domains)
  • Kingdom (kingdoms)
  • Phylum (phyla)
  • Class (classes)
  • Order (orders)
  • Family (families)
  • Genus (genera)
  • Species (species)
• Charles Darwin challenged Carolus Linnaeus' idea, arguing organizing living things based on how closely related they are in terms of evolution
• Charles Darwin


  • A British naturalist who proposed the theory of biological evolution by natural selection
  • Defined evolution as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor
• Lamarckian Theory of Evolution


  • Use and Disuse: Body parts that are used extensively become stronger while those not used deteriorate
  • Inheritance of Acquired Characteristics: Organisms can pass modification acquired during their lifetime to their offspring
• Descent with modification


  By natural selection explains the adaptations of organisms and the unity and diversity of life
• Species accumulate differences from their ancestors as they adapt to different environments over many generations
• Shared features from one organism illustrate the unity of life, hence, all organisms share characteristics
• Three observations about life

  • Organisms are well suited (adapted) for life in their environments
  • Many shared characteristics of life
  • The rich diversity of life
• Charles Darwin


  • A keen observer of nature set out to explain three broad observations about evolution
  • At Cambridge, he became the protégé of John Henslow, a botany professor
  • After Darwin graduated, Henslow recommended him to Captain Robert FitzRoy, who was readying the survey ship HMS Beagle for a voyage around the world
  • During the voyage of the beagle, Darwin observed many example of adaptations, inherited characteristics of organisms that enhance their survival and reproduction in specific environments
• Beak variation in the Galapagos finches


  • Skinny beak – specialized in eating insects
  • Sharp beak – specialized in eating fruits
  • Large beak – specialized for cracking seeds
• Artificial selection


  • Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits
• Natural selection and Adaptation

  • Members of a population often vary in their inherited traits (Variation)
  • Natural selection may only act variations if (1) they are heritable (2) they affect the organisms ability to survive and reproduce
  • All species can produce more offspring than their environment can support and many of these offspring fail to survive and reproduce. If all of these offspring and their descendants survived to maturity, they would carpet the surrounding land surface
• Darwin's Inferences


  • #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than do other individuals
  • #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations
• Natural Selection


  • Is a process in which individuals that have certain heritable traits survive and reproduce at a higher rate than do other individuals because of those traits
  • Over time, natural selection can increase the frequency of adaptations that are favorable in a given environment
  • If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species
  • Although natural selection occurs through interactions between individual organisms and their environment, individuals do not evolve. Rather, it is the population that evolves over time
  • Natural selection can amplify or diminish only those heritable traits that differ among the individuals in a population. Thus, even if a traits is heritable, if all the individuals in a population are genetically identical for that trait, evolution by natural selection occur
  • Environmental factors vary from place to place and overtime
• Charles Darwin: 'It is not the strongest of the species that survives, nor the most intelligent. It is the one that is most adaptable to change.'