genbio

• Thomas Malthus


  Theorist who proposed that if population grew, there would be insufficient living space and food would run out
• If population grew


  1. Insufficient living space

  2. Food runs out
• Pieces of Evidence for Evolution

  • Fossils
  • Embryology
  • Anatomical Evidence
  • Biochemical
  • Biogeography
• Fossils


  • Preserved remnants of once living organisms trapped in rocks, tar pits, frozen in ice or embedded in amber
  • Most common fossils are bones, shells, and seeds or pollen grains
• Most fossils are formed in sedimentary rock
• Relative dating


  Rocks were dated by their position with respect to one another; rocks in deeper strata are generally older
• Absolute dating


  Measuring the degree of decay of certain radioisotopes contained in the rock; the older the rock, the more its isotopes have decayed
• The fossil record provides a clear record of the major evolutionary transitions that have occurred through time
• Embryo


  An organism in its initial phases of development
• Embryology


  Study of the development of the anatomy of an organism to its adult form
• During development, at some time all vertebrates have a supporting dorsal rod, called a notochord, and demonstrate paired pharyngeal pouches
• The similarities in the early stages of embryo development are evidence that living organisms have evolved from earlier living things and that they do share a common ancestry
• Homologous Structures


  Different species, similar structures (Homology indicate descent from common ancestor)
• Analogous Structures


  Different appearance, similar function
• Vestigial Structures


  Anatomical features that are reduced and have no function
• The more closely linked organisms are the more related is their biochemical genetic makeup
• DNA/Nucleic acids


  Genes are located in the chromosomes, which are made of DNA. The more closely related two living organisms are, the more similar the sequence of their DNA molecules will be
• Proteins


  Molecules that are used to build up and repair body parts. Scientists believe that the more similar the structure of protein molecules of different organisms is, the more related they are and the more recent the existence of their common ancestor
• Biogeography


  The study of the geographic distributions of organisms. The common ancestors of these organisms had come from one place, expanding out into other accessible regions
• Mechanisms of Evolution

  • Genetic Variation
  • Natural Selection
  • Gene Flow
  • Genetic Drift
• Genetic Variation

  • A random change in a gene of DNA (mutation)
  • New allele combinations form in offspring (recombination)
• Natural Selection


  Organisms that are best adapted to an environment are more likely to survive and reproduce
• Gene Flow


  The movement of alleles from one population to another. Happens when organisms migrate and breed in a new population
• Genetic Drift


  Changes in allele frequencies due to random chance. Some alleles may increase while others may be eliminated changing the gene pool