B14: genetics and evolution

• Fossil records can show evolution happening over millions and millions of years
• Antibiotic resistant bacteria show evolution can also happen very quickly over a few years due to random mutations
• Species


  Something that can produce fertile offspring
• Ligers are an example of a crossbred species and they are not fertile themselves
• Mendel


  Scientist who discovered that genes are the reason things get passed on, using pea plants
• Mendel's pea plant experiments

  1. Crossed green peas (pp) with yellow peas (PP)

  2. Found offspring were all green (Pp)

  3. Bred offspring together and got yellow peas again
• Lamarck's theory of evolution

  Giraffes stretch their necks to reach tall branches, and then pass this trait to their offspring
• Lamarck's theory of evolution is now commonly accepted as wrong, and has been replaced by natural selection
• Charles Darwin's theory of natural selection

  • Random mutation causes an advantageous gene
  • This gene can then be passed on through generations
• Darwin noticed different species of finches on the Galapagos islands, with variations in beak size and shape related to the food they ate
• Speciation


  Animals develop into a new species, often due to isolation from the original species
• Experiment proving speciation


  • Single species of bee fed different foods (starch vs maltose)
  • After 8+ generations, the two bee species could no longer interbreed to produce fertile offspring