Cladistics Corrects Traditional Classification Errors
Definition
Cladistics
Cladistics is a method of classifying organisms into groups (clades) based on common ancestry, determined by analysis of base sequences of DNA or amino acids.
- Traditional classification often placed organisms in groups that were not true clades (i.e., did not include all descendants of a common ancestor).
- Cladistics allows scientists to:
- Verify whether traditional classifications match evolutionary history.
- Reclassify groups when evidence shows they are not monophyletic (true clades).
- Detect convergent evolution that misled earlier taxonomists.
How Cladistics Reveals Evolutionary Relationships
- Data Collection:
- Analyze base sequences of genes or amino acid sequences of proteins.
- Identify shared derived characteristics among species.
- Identifying Sequence Differences:
- Compare DNA or protein sequences. Variations in these sequences reflect evolutionary changes over time.
- Constructing a Cladogram:
- Use software to generate a cladogram.
- Apply the principle of parsimony, which favors the simplest explanation requiring the fewest evolutionary changes.
- Imagine birds and crocodiles.
- At first glance, they seem vastly different in appearance.
- However, molecular data reveal that birds are more closely related to crocodiles than crocodiles are to other reptiles, such as snakes.
- This discovery has led to the reclassification of birds as a subgroup within reptiles, reflecting their shared ancestry with dinosaurs.
