evidence for evolution

• why was Darwin's theory controversial?

  religious implications, Darwin going against the belief that God created all beings/organisms
• who wrote the book which inspired Darwin on his theory of evolution?

  Lyell
• how did Darwin develop his evolution theory?

  • began with principle that evolution is a slow process that occurs gradually over long periods of time
  • observed finches in Galapagos islands
  • noticed design on finches beaks were related to foods available on the islands
  • birds with beaks more suitable to food available would survive for longer than birds without, more likely to produce offspring with same desirable characteristic
• how did Darwin and Wallace propose their evolution theory to the public?

  • both working on evolution theory at same time
  • when they exchanged ideas they were very similar, Darwin published a book called on the origin of species
  • in this book he named the theory that he and Wallace presented as the theory of evolution by natural selection
• what are the three sources/methods used to study the theory of evolution?

  • palaeontology (study of fossils)
  • comparative anatomy
  • comparative biochemistry
• how are fossils formed? describe the formation of the fossil record

  • fossils are formed when animal and plant deposits are preserved in rocks
  • sediment deposited on the earth in layers
  • most recent layer on top
  • forms a sequence of oldest to youngest fossils, known as the fossil record
• how does the fossil record provide evidence for evolution?

  • fossils of simplest organisms are found in the oldest rocks, of the more complex ones found in younger rocks, shows complex organisms evolved gradually from simpler ones
  • sequences in which organisms are found matches their ecological link to each other
  • similarities in fossil anatomy help scientists to correctly identify how closely related organisms are
  • allows relationships between extinct and living organisms to be correctly identified
• why is the fossil record not complete?

  • many organisms are soft-bodied so they decompose quickly before they fossilise
  • conditions needed for fossils to form aren't always present
  • other fossils are destroyed by movements of the earth, eg volcanoes
• how does comparative anatomy provide evidence for evolution?

  • studies similarities and differences between anatomy of different living species
  • similarities suggest divergent evolution - suggesting the species evolved from a common ancestor
• what is homologous structure and how does it provide evidence for evolution?

  • identified when looking at comparisons between anatomy (comparative anatomy)
  • a structure that appears different in different organisms but has the same underlying structure
  • therefore implying that the organisms evolved from a common ancestor
  • presence of homologous structure explains divergent evolution- which explains how, from a common ancestor, different species have evolved, each with a different set of adaptive features as a result of moving to different habitats
• what is comparative biochemistry?

  • study of similarities and differences in proteins and other molecules that control life processes
  • some of these molecules are highly conserved among species
• how is the relationship between two species identified by studying the DNA?

  • looking at the order of DNA bases, or of AAs in a protein
  • number of differences compared against the rate the molecule undergoes neutral base pair substitution
  • from this scientists can estimate the point at which the species last shared a common ancestor
  • species that are closer related have more similarities between DNA and proteins, whereas species that are not closely related have fewer similarities