Macroevolution

Macroevolution: Large scale changes in the appearance of species are referred to as macroevolution. Usually these changes occur more slowly, over many generations. Evidence of macroevolution comes from a variety of fields of study:

• Biogeography: differences in a species over geographic space. example: Darwin's finches in the Galapagos Islands
• The Fossil Record: differences in a species over time. example: the changes in the skeletal structure of the horse lineage.
• Comparative Anatomy
• • Homologous structures: structures that may have diverged due to different selective pressures, but which continue to share similarities due to common ancestry. example: bones of the arm and hand in a human, a bird, a bat, and a whale.
  • Analogous structures: structures which have converged in multiple lineages to perform a similar function, but which are dissimilar in origin. example: the wings of insects and birds, the tails of fish and marine mammals.
• Vestigial structures: remnants of structures that used to serve a purpose, but which no longer do so, thus giving clues to an organism's ancestry. example: the vestigial hind limbs of whales, the non-functional eyes of cave dwelling fish, the pectoral and pelvic vestiges in snakes.
• Artificial Selection: directional selection imposed on a species by humans, for a desired (non-natural) outcome. example: selection on dogs to create breeds as distinct as the chihuahua and the great dane, selection on farm animals for greater yields of milk, meat, fur, eggs, etc. A great example from agriculture is the range of varieties created from Brassica oleracea, the wild mustard plant, including cabbage, kale, kohlrabi, brussels sprouts, cauliflower, and broccoli.
• DNA Comparison: comparison of DNA sequences of species to determine relatedness. example: DNA comparisons of human, chimpanzee, and orangutan.