evidence for phylogeny knowledge test

• what are the 4 traditional evidence for phlyogeny?

  morphological

  behavioral

  embryological

  fossil record
• describe morphological evidence

  similarities in body plans/physical features suggest organisms share a recent common ancestor, therefore are closely related e.g. pentadactyl limbs as evidence for a common ancestor for mammals
• describe behavioral evidence?

  animals with similarities in mating/feeding/locomotion (movement) may have evolved from a common ancestor
• describe embryological evidence?

  at an early stage of development all animals look similar - showing we evolved from a common ancestor
• describe fossil record evidence?

  fossils are mineralised remains of organisms, preserved in rocks. by arranging fossils in chronological order, gradual changes in organisms over long periods of time can be observed.
• what are the 3 new evidences for phylogeny?

  molecular: DNA

  molecular: proteins

  cellular
• describe molecular: DNA evidence?

  evolution is caused by gradual changes in the base sequence of organisms' DNA therefore, organisms that diverged (evolved to become different species) more recently should have more similar DNA, as less time has passed for changes to occur
• describe molecular proteins evidence?

  comparing the amino acid sequences of specific proteins (e.g. haemoglobin). organisms that have diverged more recently would have more similar molecules
• describe cellular evidence?

  scientists examine the bonds within lipids in cell membranes for example. the bonds in bacteria and archaea have been found to be different

  scientists also look for similarities in cell ultrastructure e.g. the development and composition of flagella in bacteria and archaea have been found to be different
• what did molecular and cellular evidence allow scientists to discover?

  that bacteria and archaea evolved separately and that archaea are more closely related to eukarya than bacteria
• how have the new evidences affected the classification system?

  the 3 domain system has been created which split the kingdom prokaryotae into two domains: archaea and bacteria
• how are the 5 kingdoms organised into domains?

  eukaryotic organisms are placed into the domain eukarya (4 of the 5 kingdoms) and the kingdom prokaryotae was split into achaea and bacteria
• what are the 3 domains?

  Archaea, Bacteria, and Eukarya.
• why was the domain system made?

  because of new evidence, mainly molecular:

  molecular:

  1. the enzyme RNA polymerase is different in bacteria and archaea
  2. archaea but not bacteria have similar histones to eukarya

  cell membrane evidence:

  1. the bonds of lipids in the cell membrane of bacteria and archaea are different
  2. the development and composition of flagellae are different
• most scientists now agree that archaea and bacteria evolved separately and that archaea are more closely related to eukarya than bacteria, the 3 domain system reflects how different archaea and bacteria are
• define phylogeny?

  the evolutionary relationships between organisms
• define common ancestor?

  a species from which two or more new species evolved
• what does a phylogenetic tree show?

  evolutionary history of modern species

  common ancestors of modern and ancient species

  evolutionary relationships between species
• what does the first branch point of a phylogenetic tree show?

  the first common ancestor
• what does a line than branches of show on the tree?

  divergent evolution: species diverge over time into two different species resulting in a new species becoming less like the original one
• how do phylogenetic trees show evolutionary relationships?

  closely related species diverged away from each other more recently - the branches will be close together
• classification is now based on phylogeny: organisms are now classified based on their evolutionary history. the more recently the groups diverged, the more closely related they are therefore more likely to share the same taxonomic group