Botanists are scientists who study plants. The number of people studying botany at university has fallen by 50% since the late 1980s. Maybe it’s not seen by some as an exciting science to study but there is no doubt that it is important – we are dependent on plants for our very survival! Charles Darwin, who is best known for developing the theory of evolution by natural selection, was also a botanist and it is very obvious that it was studying plants that sowed the seeds for this momentous work.

Darwin’s love of plants would have started in his childhood as both his parents were keen gardeners and kept a varied collection of plants in their garden. When he attended Cambridge University in 1828 he was greatly influenced by the botanist John S Henslow who was studying patterns of variation with and between plant populations, this work is believed to have given Darwin material for his later theories.

Henslow arranged for Darwin to be employed as the naturalist on the HMS Beagle, where Darwin collected more than 2000 plant specimens which, along with the famous finches, helped him to understand how species evolved on the different Galapagos islands.

Darwin also studied the reproduction of orchids. He made many observations of bee orchids and how they attract a pollinator. The flowers look like female bees, wasps or beetles and also emit pheromones, chemicals which have a strong scent to attract male insects. The male, fooled into thinking that the flower is an attractive female, will land on it and try and mate! In doing so, he will be covered with pollen and take this along to another flower when he repeats his mistake and tries to mate with another.

The orchid must have evolved to look like the female insect, the plant having the most realistic flower being pollinated and reproducing to pass on these genes. If the bee evolves to look different then the flower also evolves. This mechanism is called co-evolution.

Darwin was also fascinated by an orchid native to Madagascar called Angraecum sesquipedale. At the base of each flower is a long tube, about 20-35 cm long with a pool of nectar at the bottom. This is the reward for a butterfly or moth which lands on the flower. The insect inserts its long proboscis (mouth part) down the flower and sucks up the nectar. Whilst it is feeding, it gets covered in pollen.

Darwin hypothesised that there must be an, as yet undiscovered, insect with a proboscis this long. In 1903, after Darwin’s death a moth fitting this criteria was discovered, proving his hypothesis correct.

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It’s not just insects which rely on flowers for food – we do too. Your students can find out more by completing Homework activity: Which bit?

By Gemma Young for Smart Learning