- Classification based on evolutionary history, or phylogenetic classification, enables scientists to make reliable predictions.
- It also helps them understand the biological connections between species.
Criteria for Evolutionary Classification
- For classification to correspond to evolutionary relationships, it must satisfy two conditions:
- All organisms that share a common ancestor must be placed within the same taxonomic group.
- Each taxonomic group should include only species derived from that same ancestor.
- This ensures that each taxon represents a monophyletic group (a clade), not a mixture of unrelated organisms.
This approach ensures groups are monophyletic (include all descendants of a common ancestor).
Key Advantages of Evolutionary Classification
1. Predictive Power of Evolutionary Classification
- Because clades share inherited traits, discovering a new species within a clade allows scientists to predict its characteristics before direct study.
- This predictive value makes evolutionary classification especially useful in medicine, agriculture, and ecology.
- Bats:
- If a new species of bat is discovered, classification within mammals immediately allows predictions:
- Four-chambered heart
- Presence of hair and mammary glands
- Placenta and therefore a navel
- Endothermy (warm-blooded metabolism)
- If a new species of bat is discovered, classification within mammals immediately allows predictions:
- Daffodils (Narcissus):
- Some daffodils produce galanthamine, a drug used for treating Alzheimer’s disease.
- Because all Narcissus species share a common ancestor, it was predicted that other species would also produce alkaloids.
- Over 80 alkaloids have now been identified in daffodils, some with potential pharmaceutical applications.
2. Avoiding Errors from Superficial Similarities
- Organisms may appear similar due to convergent evolution, not shared ancestry.
- Classification by evolutionary relationships prevents mistakes caused by relying on analogous traits.
Both sharks (fish) and dolphins (mammals) have streamlined bodies, but they are not closely related.
3. Role of DNA and Molecular Evidence
- DNA sequencing has revolutionized classification by revealing true evolutionary relationships.
- Organisms previously grouped by morphology have been:
- Reclassified into different clades (e.g., giant pandas reclassified with bears, not raccoons).
- Split into separate groups when genetic divergence was discovered.
- Merged into one clade when previously separated organisms were shown to share ancestry.
The reclassification of fungi into distinct kingdoms based on molecular evidence overturned their earlier grouping with plants.
Self review- How does classification of bats as mammals allow predictions about their physiology?
- Describe one case where DNA evidence has led to the reclassification of a species.
- Explain how evolutionary classification supports conservation biology.
