- Early evidence for classifying organisms was based on structural and physiological similarities between organisms.
- In recent years, more sophisticated techniques have been develop which can be used to compare biochemical similarities.
- Consequently, many of the evolutionary relationships between organisms have been revised.
- Consequently, classification is frequently being revised to take account of these changes.
Comparison of DNA base sequences
- When it comes to IBDP Biology, each species has a unique set of genes.
- Differences in the genetic code occur through mutations.
- If enough changes occur, new species may evolve.
- This occurs over many generations.
- Scientists can analyse an organisms DNA base sequences using gene probes and electrophoresis.
- Computers can be used to compare the sequences of different species.
- Theoretically, the more similarities there are, the more closely related the species are.
- This information can be used to determine which taxonomic groups species should be put into.
- Also, scientists can estimate the average rate of mutations.
- Through triangulation, they can estimate how long ago two species shared a common ancestor.
- This can be used to build up a phylogenetic tree.
- The Jodrell Laboratory at the Royal Botanical Gardens at Kew have used this to reclassify plants.
- Previously classification was based on structural and physiological comparisons.
- They have produced a huge body of DNA sequences from genes in each of the three plant genomes:
- Mitochondrial – ATP synthase gene
- Nuclear – ribosomal DNA gene
- Chloroplast - ribulose bisphosphate carboxylase (RuBisCO) gene
- They analysed 580 RuBisCO sequences for advanced dicotyledons.
- They used this data to sort out the major lineages of the dicotyledons in the greatest detail.
- When it comes to IBDP Biology, they also analysed 587 species covering all major lineages and families of plants for the three genes.
- This encompassed the breadth of plant diversity.
- This data has provided major insights into patterns of flowering plant evolution and classification.
That's the end of this topic.