topic 5.4: cladistics
Nature of science:
- Falsification of theories with one theory being superseded by another—plant families have been reclassified as a result of evidence from cladistics. (1.9)
- The ancestry of groups of species can be deduced by comparing their base or amino acid sequences.
U 5.4.1 A clade is a group of organisms that have evolved from a common ancestor.
U 5.4.2 Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein.
U 5.4.3 Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor
U 5.4.4 Traits can be analogous or homologous.
U 5.4.5 Cladograms are tree diagrams that show the most probable sequence of divergence in clades.
U 5.4.6 Evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species.
A 5.4.1 Cladograms including humans and other primates.
U 5.4.2 Reclassification of the figwort family using evidence from cladistics
S 5.4.1 Analysis of cladograms to deduce evolutionary relationships.
In the News:
In the News:
- A major step forward in the study of bacteria was the recognition in 1977 by Carl Woese that Archaea have a separate line of evolutionary descent from bacteria. Famous scientists, including Luria and Mayr, objected to his division of the prokaryotes. To what extent is conservatism in science desirable