Philosophers have long pondered the concept of a brain in a jar, hooked up to a simulated world. Though this has largely remained a thought experiment, CrowdScience listener JP wants to know if it might become reality in the not-too-distant future, with advances in stem cell research. In the two decades since stem cell research began, scientists have learned how to use these cells to create the myriad of cell types in our bodies, including those in our brains, offering researchers ways to study neurological injuries and neurodegenerative disorders. Some labs have actually started 3D printing stem cells into sections of brain tissue in order to study specific interactions in the brain. Human brain organoids offer another way to study brain development and diseases from autism to the Zika virus. So, might stem cell research one day lead to a fully-grown human brain, or is that resolutely in the realm of science fiction? If something resembling our brains is on the horizon, is there any chance that it could actually become conscious? And how would we even know if it was? Host Marnie Chesterton takes a peek inside the human brain and speaks with leading scientists in the field, including a philosopher and ethicist who talks about the benefits – and potential pitfalls – of growing human brain models. Along the way, we'll pull apart the science from what still remains (at least for now) fiction. Presented by Marnie Chesterton Produced by Sam Baker for BBC World Service

Snails are a major enemy of gardeners around the world, invading vegetable patches and gobbling prize plants. CrowdScience listener Alexandre reckons he’s removed thousands of them from his garden, which got him wondering: apart from eating his garden to the core, what’s their wider role in nature? Would anyone or anything miss them if they suddenly disappeared? And for that matter, what about other creatures? We all know how complex biodiversity is, but it seems that some animals are more important than others in maintaining the balance of life on earth. Is there anything that could go extinct without having knock-on effects? CrowdScience heads to the Hawaiian mountains, a snail diversity hotspot, to discover the deep value of snails to native ecosystems there. Researchers and conservationists are working together to protect these highly endangered snails, and their natural habitats, from multiple threats. We hear why all snails – even the ones munching Alexandre’s petunias – have their role to play in the natural world, and get to grips with cascading extinctions: how the loss of a single species can trigger unpredictable effects on a whole ecosystem. With contributions from Imogen Cavadino, Dr Norine Yeung, Dr Kenneth Hayes, Dr David Sischo, Jan Kealoha, and Professor Ian Donohue. Presented by Marnie Chesterton Produced by Cathy Edwards for the BBC World Service [Image credit: Getty Images]

In the past 18 months we have heard lots about the human immune system, as we all learn about how our bodies fight off Covid-19 and how the vaccine helps protect us. But this got listener John, in Alberta, Canada, thinking about how trees and plants respond to diseases and threats. Do they have immune systems and if so, how do they work? Do they have memories that mean they can remember diseases or stressful events 5 months, or 5 years down the line, to be better prepared if they encounter the same threats again? Presenter Marnie Chesterton sets out to investigate the inner workings of plants and trees, discovering that plants not only have a sophisticated immune system, but that they can use that immune system to warn their neighbours of an attack. Some researchers are also investigating how we can help plants, especially crops, have better immune systems – whether that’s by vaccination or by editing their genes to make their immune systems more efficient. But some plants, like trees, live for a really long time. How long can they remember any attacks for? Can they pass any of those memories on to their offspring? Crowdscience visits one experimental forest where they are simulating the future CO2 levels of 2050 to understand how trees will react to climate change. Featuring: Professor Jurriaan Ton, University of Sheffield Professor Xinnian Dong, Duke University Dr Estrella Luna-Diez, University of Birmingham Peter Miles, F.A.C.E. Facility Technician, University of Birmingham Presented by Marnie Chesterton and Produced by Hannah Fisher for the BBC World Service. Photo credit: Getty Images

This year has been a weird one for UK gardeners – unpredictable spring temperatures meant flowers failed to bloom and throughout the rainy summer, slugs have been savaging salad crops. But why and when plants blossom is about more than just early cold spells and wet weather, and a listener in California has asked Crowdscience to investigate. Flowering is vital to both plants and us. Without it, they wouldn’t be able to evolve and survive (and we wouldn’t have anything to eat). Anand Jagatia hears that different species have developed different strategies for doing this based on all sorts of things, from where they’re located to how big they are to what kind of insects are around to pollinate them. The famously stinky Titan Arum, or corpse flower, for example, blooms for a single day once every decade or so before collapsing on itself and becoming dormant again. This gives it the best chance of attracting carrion beetles in the steamy Sumatran jungle. But other plants open their petals much more regularly, which is a process regulated by a clever internal clock that can sense daylight and night. It’s even possible to trick some of them into producing flowers out of season. Cold is also a vital step for some brassicas and trees, and scientists are starting to understand the genes involved. But as climate change makes winters in parts of the world warmer and shorter, there are worrying knock on effects for our food supply. Produced by Marijke Peters for BBC World Service. Featuring: Guy Barter, RHS Professor Judy Jernstedt, UC Davis Professor Dame Caroline Dean, John Innes Centre Professor Ove Nilsson, Umea Plant Science Centre (Photo credit: Getty Images)

Look into my eyes. What do you see? Pupil, lens, retina… an intricate set of special tissues and mechanisms all working seamlessly together, so that I can see the world around me. Charles Darwin called the eye an ‘organ of extreme perfection’ and he’s not wrong! But if the eye is so complex and intricate, how did it evolve? One listener, Aloyce from Tanzania, got in touch to pose this difficult question. It’s a question that taxed Darwin himself, but CrowdScience is always up for a challenge! The problem is that eyes weren’t ever designed - they were cobbled together over millions and millions of years, formed gradually by the tweaks and adaptations of evolution. How do you get from the basic detection of light to the wonderful complexity - and diversity – of visual systems we find throughout the animal kingdom? CrowdScience sent Marnie Chesterton on an 800 million year journey to trace how the different elements that make up the human eye gradually came into being; from the emergence of the first light-sensitive proteins to crude eye-cups, from deep sea creatures with simple pinhole eyes to the first light-focusing lenses, all the way to the technicolour detail of the present day. Produced by Ilan Goodman for the BBC World Service. With contributions from: Dr Adam Rutherford, Dr Megan Porter, Professor Dan Nilsson, Dr Samantha Strong (Photo Credit: Getty Images)