In this topic of IBDP Biology, we will learn about Biochemical Comparisons for Classification --- Part 1.

• 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.

• 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.

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