Thanks to pioneering work led by Kew scientists, plants were the first major group of organisms to be re-classified based on genetic studies; all organisms have now been reclassified based on such evidence, following the lead work on plants
In 2013 the DNA Bank at the Royal Botanic Gardens, Kew is celebrating its 20th anniversary. This whirring freezer in the Jodrell Laboratory is home to a large set of samples, but there are an original set of about 500 DNA samples that 20 years ago helped to revolutionise botany – changing scientists’ understanding of how the world’s flowering plants (angiosperms) were related and resulting in a major reclassification important for unlocking the potential in plants for human use.
Traditionally, plant taxonomy was based on the physical appearance of plants. Plants were classified according to their overall similarity: those that closely resembled one another were grouped together. Until recently, flowering plants had been classified into one of two groups: the monocotyledons (single seed leaf) and the dicotyledons (two seed leaves).
In the early 1990s, DNA base sequencing, which was then cutting-edge technology, made it possible for scientists at Kew to start comparing plant species according to their DNA and assessing them for genetic similarities. Scientists used the DNA sequences of three genes found in ALL plants. The results were truly surprising, revealing relationships between the most unlikely sets of species.
The lotus was not related to the waterlily, which it so closely resembled. Straggly hedgerow weed, the nettle, was close kin to the regal rose, and the exotic, much-loved flowers of orchids were related to the vegetables asparagus and onion.
For the first time, botanists were able to begin building an accurate evolutionary ‘tree of life’.
They were able to deduce the order in which groups of plants diverged from each other as they evolved.
Our survival on the planet has depended to a large extent on the benefits we reap from plants
– medicinal, food, fuel, clothing and shelter. Knowing the pattern of plants’ evolution is a great advantage because it allows scientists to tap into the predictive power of genetics to more easily distinguish plants most likely to be beneficial to people in the future. It can also help inform conservation programmes. The loss of a species without close relatives results in a greater loss of genetic information than the extinction of a species with many related species.

1.
Give out article
2.
Ask class to use table below to classify plants on powerpoint
3.
For the exam, pupils must understand how DNA hybridization has led to a new classification system in plants.
4.
Ask pupils to read through the article in pairs. They must highlight the article, and then summarise the methodology and findings of the article in three bullet points.
5.
These bullet points must be brought to Miss Lea, checked, and then the questions below should be handed out:
1.
How were flowering plants originally classified?
2.
Look back at your notes on classification. What type of classification is it that you have name in Q1? (e.g. biochemical, phylogenetic, artificial etc)
3.
The scientist compared the sequences of three genes that are found in all plants. They chose these genes because they coded for polypeptides that are used in biochemical processes such as photosynthesis that all plants throughout the world carry out.
If scientists wanted to do the same with an animal such as a mouse, what sorts of genes could they sequence?
4.
Have these questions marked by Miss Lea, and collect a Cytochrome C worksheet