Evolution

• Evolution:

  • The change in the characteristics of a species over many generations 
• Fossils: 

  • The preserved evidence in rocks or soils of organisms that were once alive
  • Could be the whole organism, or traces that it once lived (scratches, burrows, tracks)

  For a fossil to form:

  • Organism needs to be rapidly buried after death
  • Organism needs to be in a low oxygen environment, to reduce decay
  • Organism needs to remain buried and undisturbed for a long time
  • Body parts need to be made out of hard substances (bones, teeth)
• Biodiversity:

  • The number and range of species that exist on Earth or in an ecosystem 
• Rock stratigraphy: 

  • Comparing strata in different locations to determine their relative ages 

  Strata:

  • Layers of sedimentary rock 
  • Fossils of the same type indicate the strata is of the same age 
• Fossil record: 

  • All species that have been found as fossils
  • It is incomplete 
  • More water living organism than terrestrial organisms
  • More hard bodied organisms than soft bodied organisms 
• Comparative anatomy: 

  • The science of comparing physical structures of one species with another 

  Homologous structures: 

  • Structures which have a common evolutionary origin (genes from common ancestor) and similar underlying anatomy, but have evolved different functions due to evolving in different environments 
• Comparative embryology: 

  • The study of development, structure, and function of embryos
  • Comparison of vertebrate embryos can give a time line of evolutionary development 
• Comparative biochemistry: 

  • The study of the molecules and chemical reactions found in living organisms 
  • Organisms that are more closely related will have similar DNA and proteins (amino acid sequences) 
  • Comparison of these molecules can show how closely two species are related