Seventy thousand species.
That’s the best guess for the count of life, including plants, animals and fungi, found in Great Britain and Ireland.
And it’s the target of one of biology’s most ambitious projects – scientists want to map the DNA of each of these organisms.
Having these genomes – each a complete set of genetic information for a species – could transform the way we understand the natural world. And there may also be benefits for us in the search for medicines and materials inspired by nature.
In Plymouth, the starting point for this immense task is thick, sticky mud.
Sediment collected from the bottom of Plymouth Sound was hoisted onto the deck of the research vessel owned by the Marine Biological Association.
It is placed in a sieve and washed, revealing a series of writhing creatures.
“You can see that we have some bivalves, which are related to clams and mussels. We also have a gastropod shell – these are quite similar to terrestrial garden snails. And we have some brittle stars. taxa (groups of organisms), many different types animals, which is great,” explains marine biologist Patrick Adkins.
Today he is focusing on marine worms known as polychaetes, and there are many living in the sediment.
Some look like earthworms and others are covered in tiny, squirming bristles. But the strangest is the mud owl. If you squint, its markings look a bit like an owl’s face, until it extends a tubular proboscis, breaking the illusion.
All of them will have their genomes sequenced for the project, which is called Darwin’s Tree of Life and has the participation of the Museum of Natural History.
“Even if you look at polychaetes, which is just a group of worms, it’s a huge task with hundreds and hundreds of species,” says Patrick.
“We now have over 100 species of polychaetes collected – it sounds like a lot, but it’s actually just the beginning.”
The search covers all types of habitat.
In Oxfordshire, forests are the focus.
As dusk falls, a family of badgers emerge from their set. They sniff around in the darkness, hunting for some snacks after sleeping.
The animals here at Wytham Woods have been studied in detail for over 30 years, but now their genomes have also been sequenced.
“The genome can answer so many questions that we couldn’t answer before,” says Ming-Shan Tsai of the University of Oxford.
“We can explore why the badger is so different from other animals – and its unique behavior.”
This includes the late implantation puzzle, where badgers mate and an egg is fertilized, but the pregnancy process is put on hold until it is the best time of year to have a cub.
“Obtaining a genome will also help us understand why badgers are more susceptible to tuberculosis, for example, than other animals,” he added.
At the heart of this project is the Wellcome Sanger Institute in Cambridge.
Every day, samples arrive from all over the British Isles.
Whether it’s a leaf from a tree or some blood taken from an animal, the material is weighed, then frozen with liquid nitrogen and finally pulverized into a fine powder. From there, DNA can be extracted and the genome sequenced.
Sanger played a leading role in the human genome project, which took years to complete. Now, sequencing a species takes a few days.
Mark Blaxter, who leads the Tree of Life project, says, “When the human genome was sequenced, it changed the way we do human biology forever. And it really transformed the way we see ourselves and how we work with our health and disease.
“And we want to make that possible for all of biology. So we want everybody, working on any species, or any group of species, anywhere in the world, to be able to have this definitive foundation.”
Genetic work must show how species are related, reveal their similarities and also where their differences lie.
“It’s filling the library of life,” explains Mark.
But the smallest forms of life are presenting the biggest challenges.
Jamie McGowan of the Earlham Institute in Norwich is looking through a microscope at a single drop of lake water. It is full of single-celled organisms known as protists.
“There are two little green cells here – both are microalgae. They are photosynthetic, just like plants,” he says.
They are the smallest organisms being sequenced for the project, but it’s not easy.
“They’re really difficult to identify, because some of them look very similar. And they’re also difficult to sequence because they’re starting with very, very small amounts of DNA.”
Life on Earth began with single-celled organisms, and we couldn’t exist without them.
“We are completely dependent on them for survival,” explains Jamie.
“Protists occupy a very important position in the food chain, where they eat organisms smaller than themselves, such as bacteria and viruses. And then they, in turn, are eaten by larger organisms.
“And many protists can produce oxygen – in fact, they produce about half of the planet’s oxygen supply.
“So having their genome sequenced is really important to be able to identify them. Their biodiversity is so poorly understood. And we need to protect them, because they’re so critical for everything else for life.”
Back in Plymouth, marine biologists moved ashore to take a look at some rock pools.
Each is a colorful microcosm, containing an infinity of species.
Something passes quickly through the seaweed.
“It’s a pipefish,” says Kes Scott-Somme, research assistant on the Darwin Tree of Life project. “It’s basically like a stretched out seahorse. They’re beautiful – and they’re very, very well adapted to their environment. They can live high up on the coast like that.”
But learning about the DNA of creatures like this will not only help us understand the species better – it can also help us.
“Marine environments are incredibly volatile and therefore the animals that live here need to be even more adapted to their space than we are. And that means they have very specific ways of dealing with their environment,” says Kes.
“This can help us find things like antibiotics, drugs and materials. The marine environment is a great place to look for that information.”
The Darwin Tree of Life project has a tough deadline – all 70,000 species sequenced by the end of 2030.
There’s a lot of work to do, but this project could give us our most detailed understanding yet of the diversity of life.
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Produced by Alison Francis, Senior Journalist, Climate and Science