Essential Idea:
The ancestry of groups of species can be deduced
by comparing their base or amino acid sequences
Understandings:
- A clade is a group of organisms that have evolved from a common ancestor
- Cladograms are tree diagrams that show the most probable sequence of divergence in clades
- Evidence for which species are part of a clade can be obtained from the base sequence of a gene or the corresponding amino acid sequence of a protein
- 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
- Traits can be analogous or homologous
- Evidence from cladistics has shown that classification of some groups based on structure did not correspond with the evolutionary origins of a group or species
Applications:
- Cladograms including humans and other primates
- Reclassification of the figwort family using evidence from cladistics
Skills:
- Analysis of cladograms to deduce evolutionary relationships