Presentiment – circadian clocks giving plants and animals a sense of time

Presentiment is that long shadow on the lawn
Indicative that suns go down;
The notice to the startled grass
That darkness is about to pass.

Emily Dickinson

Sometimes you find in literature beautiful expressions of technical terms that are otherwise dry and stuffy. Presentiment, by Emily Dickinson, is one of those beautiful expressions. Why did she decide to write a few words about twilight, and at the same time so succinctly summarise one of the key features of the circadian clock? Apparently Dickinson spent much of her adult life withdrawn from the world and, in doing so, she was probably in a position to watch and notice the hidden-in-plain-sight details of the world, such as how the length of shadows allow you to approximate the time of day and how grass may tell time without watches.

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Plants, polyploidy and producing new species

Modern wheat. A product of polyploidy.
CC Wheat field / Weizenfeld II | Christian Schnettelker

When I talk about my career and my interest in evolutionary biology, I often get asked, “How do you actually get new species?”. It’s not a stupid question; for people without a background in biology it really is very hard to imagine how the diversity of life we see today has formed from the types of ancient creatures we find in the fossil record. I normally look to my favourite fish, the Mexican blind cavefish, or point out the variety that can be produced in the single species of dog, or mention horizontal gene transfer to confer antibacterial resistance in bacteria, to show how even small changes can result in quite big differences in a species. Add to that vast amounts of time and it becomes a little easier to imagine the “hedge” of life taking shape.

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