Science Podcasts

Naked Scientists episode

Sun, 19th Nov 2006

Science in Antarctica

Iceberg (c) Uwe Kils @wikipedia

As winter approaches, we take a trip down south to look at some of the cool research going on in Antarctica. Dr Jane Francis from Leeds University talks about six-foot penguins and a time when Antarctica was warm and ice-free, Kate Hendry from the University of Oxford describes what it's like to work in Antarctica today, and Derek and Dave bring a welcome injection of heat as they find out how hand warmers work. We then dive into the waters around Antarctica with Dr Povl Abrahamsen from the British Antarctic Survey, who uses automated subs to look under the ice sheets and find out how they're changing, and Dr Mike Fedak from the University of St. Andrews describes how his team have attached data collection instruments to the fur of elephant seals to explore completely unchartered depths of the Southern Ocean.

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In this edition of Naked Scientists

Condensed Transcript

  • The Fever That Came in From The Cold

    "Feed a cold and starve a fever", stated the doctors of yester-year, possibly wrongly, but now there's proof that running a temperature really does help the body to fight off infections. A paper in this month's edition of the journal Nature Immunology from Sharon Evans and her team at Roswell Park Cancer Institute in New York shows that, as well as making it more difficult for bacteria to multiply, an elevated body temperature also acts to rally bug-battling white blood cells called lymphocytes. The researchers found that when the body runs a fever, cells lining the blood vessels supplying the lymph glands start to produce large numbers of sticky molecules, called ICAM and CCL21, which act like molecular grappling hooks to snare passing white blood cells and drag them into the lymph node. Once inside, antigen presenting cells recruit and stimulate lymphocytes capable of tackling the culprit infection. The team carried out the work in experimental mice which were kept in hotter than normal conditions (39.5 C, 2.6 degrees above their normal body temperature). This had the effect of doubling the numbers of lymphocytes which entered lymph nodes around the body. So perhaps reaching to the pill packet next time you're running a temperature might not be such a good idea...

  • More Reasons For Red Wine Being Good For Us

    Here on the Naked Scientists we've often talked about how scientists are uncovering more ways in which enjoying an occasional glass of red wine might be good for us - and in particular a compound found in grape skins and red wine called resveratrol. It has already been shown to increase the life span of mice by 15% and clinical trials are currently underway involving people with diabetes. Now we have news this week from scientists who have discovered yet another possible health-giving benefit of the red stuff - it could boost athletic performance and even help keep us thin. That's according to a new study, led by scientists from the Institute of Genetics and Molecular and Cell Biology in Illkirch in France, who have shown that high doses of resveratrol given to mice improves their muscle endurance and also stops them getting overweight. The researchers fed a group of mice on a very high fat diet, and then gave half of them a very high dose of resveratrol - the equivalent to a hundred glasses of wine each day for a human being. After 3 weeks, the mice that were taking the red-wine like supplements, only weighed 20% more than mice on normal diets. While the high fat diet mice that weren't taking the supplements weighed 60% more than the normal mice. To test their fitness endurance, the mice were put on treadmills, and it turned out that the ones taking the resveratrol supplements could run twice as far as mice on normal diets that hadn't taken any of the compound and there didn't seem to any nasty side affects of taking such large amounts of it. The researchers think this muscle boosting affect is likely to be linked to the affect resveratrol has on those tiny energy producing units inside living cells called Mitochondria - essentially what they do is burn the food we eat and convert it into energy that we use to move and grow. Now, it's thought that resveratrol might trigger the process that gives each cell more mitochondria - and with more mitochondria, more energy can be produced - a little bit like building more wind turbines to harness more wind energy. The amount of red wine you would have to drink to have these affects are unfortunately, rather huge, so taking resveratrol in wine form may be little use to us. But it may be possible to take supplements of the compound in the future - athletes may even start taking it to boost their performance - could red wine become a banned substance in the Olympic Games?

  • Climate Change Is Making Frogs Sick

    On the show a few weeks ago, we heard about frogs communicating to each other with ultrasound, but sadly these week I have rather more gloomy frog news - it seems that climate change is making European frogs very sick. A team of Herptologists lead by Jaime Bosch at the National Museum of Natural Science in Madrid has studied midwife toads living in Spain's Penalara Natural Park where they used to thrive but now are virtually extinct. The team looked back through records kept of the midwife toads going back 26 years, and compared them to meteorological data covering the same time period. And what they found was that rising air temperatures between 1976 and 2002 were very strongly linked to the impact of a deadly fungus on the toads. The chytrid fungus called Batrachochytrium dendrobatidis interferes with the toad's ability to stop themselves drying out. With their thin moist skins, frogs and toads are incredibly susceptible to changes in global temperature, and it's thought that the increasingly warm dry conditions may allow this fungus to survive over winter when previously it would have died out. This is the first evidence for a European species being wiped out by a disease linked to climate change, although the fungus is already known to be the culprit for amphibian declines in Australia and South America. Since the 1980s, the disease has killed 74 out 100 harlequin frog species in C and S America alone. It's not obvious why these fungal diseases have spread so rapidly and so devastatingly around the world, but the pet trade may be partly to blame. And the really bad news is that trying to save frogs and toads inside protected nature parks like the one in Spain, is not going to be enough to ensure their survival in the face of climate change.

     

  • Science Update

     


    Bob - This week for the Naked Scientists, Science Update goes polar. I'll talk about some singing Antarctic icebergs, but first, Chelsea takes us up near the North Pole, where we find not Santa Claus, but something that to some scientists seems almost as unlikely.

    Chelsea - In the Arctic, plants and animals have to survive three months of total darkness in the winter. Today, very few species are up to that task; but 45 million years ago, during a period called the Eocene, vast forests thrived there. Earth scientist Hope Jahren of Johns Hopkins has found that they were home to conifers that grew to 100 feet tall and 10 feet wide, thanks to an unusual ability.

    Hope - We believe that they went into a dormant state, not unlike a deciduous tree like the maples that you see today that are losing their leaves. However, these were conifer forests, and the conifers that we see today are evergreen all year round. So the idea of a conifer forest that shuts down and loses its leaves once a year is a very different ecosystem than anything we have on Earth today.

    Chelsea - She adds that the Earth was warmer in the Eocene, so studying its ecosystems could help scientists predict what might happen if today's Earth continues to warm.

    Bob - Thanks, Chelsea. This low, restless moan is the song of an Antarctic iceberg, sped up so that humans can hear it. Northwestern University seismologist Emile Okal and his colleagues are studying these strange, ultra - low-frequency melodies with seismic microphones they've planted on the ice. Okal says each iceberg resonates on a surprisingly specific note, which fluctuates over time.

    Emile - And this creates a kind of symphony: like, if you slightly adjust the length of a violin string, you're going to be able to slightly change the musical note that you play.

    Bob - It's not clear where the rumbling comes from. Okal says it may be the sound of icebergs scraping together, or the vibrations of water flowing through cracks like air through an organ pipe. He says figuring out what these songs are, and understanding why an iceberg might change its tune, could help scientists keep tabs on the shrinking polar ice.

    Chelsea - Thanks, Bob. We'll be back next week with more stories from the left side of the Atlantic. Until then, I'm Chelsea Wald.

    Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists.

  • Ancient Antarctica And Six-foot Penguins

    Chris - Now, lots of people when you say "Antarctica" think very very cold. But it wasn't always that way, was it?

    Jane - No, I mean like you say most people when they think of Antarctica they think of ice caps and glaciers and very cold temperatures but for most of Antarctica's history and I'm talking about millions of years now in geological time it was actually green and it was covered with lush, dense forests.

    Chris - How warm was it?

    Jane - Well the interesting thing is that even though more than 99% of Antarctica's covered in ice, the most common fossil that you can find in Antarctica is probably fossil wood. And what we can do is use fossil plants that we find in the rocks, so fossil wood, leaves, even the flowers. We can use those to reconstruct the vegetation and from there we can work out what the temperature was. So if we go back say 50 million years ago, to what we call sub-tropical to warm temperate which means very nice indeed thank you, warm summers and warm winters.

    Chris - Not that grossly dissimilar to here then?

    Jane - Well, even warmer than here actually, much more pleasant. And no signs of ice at all. A very different world.

    Chris - And the point is that was 50 million years ago. It's very different today. So what's changed to make such a profound shift in the way that things happen in Antarctica now?

    Jane - Well the most interesting thing is that Antarctica actually has been over the South Pole for at least 100 million years so when I say that there were forests in Antarctica people usually say to me "oh well does that mean the Antarctic continent was on the equator?" And that's not the case at all. Geologists have looked at the rocks and they've found signals in the rocks to show us Antarctica was over the South Pole. So that means the earth's climate was much warmer in those days. Probably that's partly because there was higher levels of carbon dioxide. So that's one reason why we look into the past and do these paleoclimate studies, it really is a mirror image of what we might be seeing in future with higher carbon dioxide levels. But also Antarctica was part of a much bigger landmass in the past called Gondwana. And all the southern hemisphere continents were amassed together so there was this big landmass over the pole. So Antarctica wasn't sort of isolated in its icy tomb of water as it is now.

    Chris - So presumably because there were all those land masses jammed together, the ocean circulations would have been quite different then, and that may have had an impact on the temperatures.

    Jane - Yes. Well what we think happened is that the ocean currents that flowed around the equator were warmed up by the equatorial temperatures and because of the position of the coastlines around Gondwana, those warm water masses were pushed all the way down to Antarctica. So they could get rid of all this warm moist air over the continent and keep the continent warm. And then those water currents went back to the equator again and warmed up. Whereas today you see Antarctica is completely isolated, South America, South Africa and Australia moved away millions of years ago. And now we have the circum - Antarctic current and it flows around Antarctica and that keeps it really cold. That water, that current never gets the chance to warm up, and so Antarctica is just frozen inside.

    Chris - Doesn't the same thing happen in the air above Antarctica in the sense that you end up with this big sort of whirlpool going round in the air which is why you end up with CFCs and things dumping there which is why we ended up with an ozone hole.

    Jane - Yeah it's a very specific, small, climate of it's own above Antarctica. I always think of it as a big deep freeze. It has a big block of ice on it that's up to 3, 4 kilometres thick and it's just sitting there. It's so big it has it's own internal freezer in it.

    Chris - Now the last vestige of the connection between those other big continents and the Antarctic continent was that the corner of Australia where Tasmania is and that kind of thing?

    Jane - No actually that split away some 100 million years ago. The last connection actually was with South America. And that wasn't very long ago, geologically speaking; probably the deep water flowed between Patagonia and the Antarctic Peninsula, the bit that sticks up like a finger, about sort of 20 million years ago. Before that it was joined, so that's why, when we find a lot of fossils of animals and plants we also find quite close relatives of them in South America today. And no doubt in the past, millions of years ago they could have quite easily walked all the way from South America into Antarctica. And if you go further back in time when Gondwana existed you could have had a nice holiday walking all the way from the equator all the way through Antarctica and out to Australia and you wouldn't have had to get your feet wet.

    Chris - So how deep would you now have to go through the ice to find the kinds of fossilised specimens that you've been looking at?
    Jane - Well it's really easy actually, just pick them up off the surface. Because like I said most of it is covered in ice and people usually think I have to look in ice cores but that's not the case. There are small bits of rock just sticking up as mountains that stick above the ice sheet, or some of the islands have cliffs that are exposed so the rocks are exposed, and the fossils are just lying there waiting for me to come along and pick them up.

    Chris - now when somewhere gets isolated like that for a considerable period, the wildlife that evolves tend to be pretty specialised doesn't it, so do those fossils give you and revelations as to some pretty funky animals that would have been living there at that time?

    Jane - Well the history of Antarctica's really interesting because the fossil history is quite different from the animals and plants that live there now so for example the plants we have in the forests, we have a lot of tropical plants that are mixed with plants that grow today, in say Tasmania. So we get sort of Tropical vines, and some really big bushy plants. In terms of animals, we have dinosaurs of course. We've got dinosaur bones from Antarctica, and we also have some primitive mammals. Some colleagues of mine in Argentina have been finding primitive mammals like Sloths and little rat-like animals. And then of course, penguins. But the penguin fossils that we find, actually the interesting this is that we find penguin bones in the same bed of rock as we find our sub-tropical plant fossils. So penguins that first lived in Antarctica certainly didn't live on the ice, as you can imagine them today. They lived in the seas around the edges of these forests.

    Chris - So they didn't evolve to live in icy conditions at all, they evolved to live in much warmer environments

    Jane - They certainly did, yes.

    Chris - So how the hell have they coped with that sudden and dramatic shift in how they go about their life? How would they have foraged, what would they have eaten? Or would they have had pretty much the same foraging lifestyle, they simply would have done it in the warmer water?

    Jane - Well I'm not sure how they lived, I mean what we know from the penguin fossils that we find in Antarctica is that… well there's one very famous penguin fossil of a type of penguin that had toe bones, when we construct the penguin that had these large toe bones, it was at least 6ft high, so can you just imagine that, a 6ft high penguin wandering around in the warm waters of tropical Antarctica?

    Chris - And the fact that it was 6 feet high, is that a reflection on the fact that it was a lot warmer? Have penguins shrunk down to minimise their heat losses now, because it's so cold, is that what's forced them to be smaller?

    Jane - I have no idea because I'm not a penguin expert but I don't think so. If you look at an emperor penguin today, I met some emperor penguins a few years ago, and I'm not a very tall person but they came up to above my waist and they've got big curved beaks, so they look pretty formidable.

    Chris - As someone said to me the other day Jane, that's a lot of chocolate, isn't it, a 6 foot high penguin?

    Jane - It sure is!

    Chris - That's Jane Francis from the University of Leeds.

  • Living in Antarctica

    Helen - We have now on the line Kate Hendry from the University of Oxford, who's going to tell us a little bit about what it's like to be down there. Hi Kate.

    Kate - Hi Helen.

    Helen - Hi, Now, is it a problem, the fact that it's very, very cold down in Antarctica, that makes research possibly quite hard down there, or are there other things as well that we need to think about?

    Kate - Well certainly the cold is one of the important problems, just trying to keep warm when you're out in the field.

    Helen - Is it really that cold?

    Kate - Well, at the moment it's summer in Antarctica of course so it's not actually that cold. Where I work at Rothera research station, it's usually average between about - 5 and +5 degrees centigrade.

    Helen - Oh, so quite warm then.

    Kate - In the winter of course it can get to -30, and -40, and it's even worse with the wind chill. So yes, it's certainly very important then.

    Helen - Well I suppose we have a lot of modern technology to keep us warm so it's not that bad. Do you ever use hand warmers like we described in kitchen science?

    Kate - Unfortunately no, I was listening to that thinking it was a wonderful idea. I might have to try and find some of those

    Helen - Apparently people even take them diving which sounds great to me. So yes, it's very cold. Now what other things are problematic about being down in Antarctica?

    Kate - Well one of the main things is the isolation really, I mean you're a long way away from anywhere else, so you can't just pop down the shops to pick up spare supplies or anything.

    Helen - So psychologically do people tend to get quite loopy down there?

    Kate - Not at all, it's quite a good community spirit. I mean the base down there is self-sufficient. There are people there who are the electricians, who are the plumbers and chefs and everyone kind of looks after each other.

    Helen - So there's a whole team of people keeping you alive and getting the research done down there. It sounds like you have a good support system. So I suppose you have to plan very carefully because everything has to be brought in, and I assume everything has to be taken out as well. Are there very tight environmental regulations? Because we hear stories sometimes about how tourism has to be regulated quite carefully so as to not cause any more damage in Antarctica than we can possibly help. Is research very tightly coordinated and controlled as well?

    Kate - Oh very much so yes the British Antarctic Survey are really careful about making sure all the waste is taken out, so we recycle everything we can, everything separated on base, and it ships out at the end of the season.

    Helen - So you take everything back, you don't leave anything behind?

    Kate - No, nothing at all

    Helen - Excellent. That sounds great. And you enjoy working down there I guess, one final question, to me it sounds a very cold, barren place to be but you always say (I'll admit now that Kate's my sister so I know all about this already, and she comes back just bubbling about the place) so what is it about the place that's so addictive do you think?

    Kate - Oh it's very difficult to describe but I suppose it's living in one of the most beautiful places on the planet really. It's a pristine wilderness, I'm sharing my living space with penguins, seals and whales, and in my spare time I can go off skiing and in the mountains so it's a pretty cool place to live.

    Helen - Sounds fantastic. So thanks so much Kate for giving us a little glimpse into what life in the Antarctic is like, and good luck with the rest of your research.

  • Automated Subs And Melting Ice Sheets

    Chris - One of our next guests is from the British Antarctic Survey, and that's Povl Abrahamsen and he's going to take us under the ice. Hi Povl.

    Povl - Hi.

    Chris - Welcome to the Naked Scientist. So how are you exploring what's going on under the surface of Antarctica?

    Povl - Well, Antarctic ice shelves can be hundreds of meters thick, floating glaciers. And underneath, they're some of the hardest areas to actually access. So a recent approach has been using robot submarines, AUVs, Autonomous Underwater Vehicles, to go down beneath the ice shelves and explore there.

    Chris - And what's down there?

    Povl - Well, it's seawater. It's extremely cold. And we're trying to trace what kind of water actually flows beneath there. Is it melting the ice shelves from below? And the only way to really get answers to that question is either to drill in from above or to get submarines, or instruments in from the ice shelf front.

    Chris - So what are you actually seeing when you're down there, what have you discovered so far? What are the findings?

    Povl - Well some of the most interesting findings were that we have an upward looking sonar that will actually give us a profile of what the base of the ice looks like. We've always assumed that this is completely smooth, that is the surface is completely smooth. But it turns out that actually there are extremely rough areas at the base of the ice shelves.

    Chris - Why is that so critical?

    Povl - Well it's critical because if we have a rougher area then you get more turbulence at the base of the ice shelf, more heat exchange recurring here.

    Chris - Almost like fins on a heat sink. So that speeds up melting does it?

    Povl - Yes. That would speed up melting.

    Chris - Is it a symptom of melting though, does that mean that the problem is becoming more acute?

    Povl - Well we don't exactly know what is causing these areas. We can see that they seem to correspond to some surface features called flow stripes on the surface of the ice shelves, but we're not exactly sure what their significance is, or how they were created, or how they're maintained.

    Chris - How do you actually control a submarine down under water? Because one thing that you can't do is have a radio controlled boat, you can't do radio waves can you, so how do you tell your submarine where to go and what to look at, and how do you get it back?

    Povl - Well you tell it where to go in advance, so all of that is programmed in, and it will try to then follow these instructions. If it does encounter any obstacles it will try to get around them on the way. And we can track where it is while it's out there. And then it's supposed to come back out to the ship. Or if there's any problem then the ship can tell it to use a homing beacon, to get it to return to the ship.

    Chris - And how deep is it going down?

    Povl - The deepest we sent it down beneath the ice shelf was about 800 meters, but the deepest it can go is 1500. There's a new version on the drawing board now that goes down to 6000 meters.

    Helen - That's an awful long way isn't it. So how long do these things go off on their own for, do you wave goodbye to it for days at a time or is it just a few hours?

    Povl - I think the longest mission it's ever been off on was about 30 hours.

    Helen - And you're really crossing your fingers it's going to come back.

    Povl - Yes.

    Chris - Povl have you ever lost one of these, presumably they must cost quite a few million. Has one ever gone AWOL?

    Povl - Ah, yes. Unfortunately that has happened.

    Chris - Who's the insurance company?

    Povl - it's actually not insured.

    Chris - Now there's a confession

    Povl - Yes, well I think it was determined at the start of the project, that the cost of insuring it would be about the same amount as building a new one. So it wasn't deemed worth it.

    Chris - So how many have you lost then?

    Povl - There has only been one that was lost.

    Chris - So a once in a lifetime experience for the person who lost it, was it? They went shortly afterwards.

    Povl - yes there was a fairly gloomy atmosphere on board afterwards.

    Chris - Sure. That's Povl Abrahamsen from the British Antarctic Survey.

  • Exploring The Southern Ocean With Seals

    Chris - From the University of Saint Andrews, we have Mike Fedak. Thank you for joining us on the Naked Scientist. Now tell us how you're exploring the Antarctic.

    Mike - We're taking advantage of some really expert Antarctic explorers namely elephant seals, to help us examine the oceanography that they're dealing with. As they sort of wander around the entire polar ocean, they're excellent candidates for that kind of a job.

    Chris - I suppose that one benefit of doing this, Mike, is that if we send a ship, or one of Povl's subs down there then there's always a risk that we may change the environment that we're trying to explore. And therefore we won't get a real picture of what's really there. Whereas if you use a part of nature itself, a seal, an animal, then you might stand a chance of getting a better view.

    Mike - Well I'm less concerned about the ships making a sort of disturbance that affects their measurements, they're quite careful about that. I think it's more a case of these animals going places that ships are unlikely to be able to go, and spending time out there, much greater periods of time than a ship would be able to do. It wouldn't be economically feasible to do it. And they can visit bits of the Antarctic that just would not be visited otherwise. We can get data from those places and thereby help the other oceanographic observation techniques to be more successful.

    Chris - So technically speaking Mike how are you actually doing this?

    Mike - Well we're attaching instruments to the fur of these elephant seals. We glue them on with a fastening epoxy and these instruments basically give us a good idea of where the animal is, they describe the animal's behaviour by looking at the animal's depth, and they also do basic oceanographic measurements, they get solidity and temperature measurements and provide these profiles just in the way you might do from a ship but in places where ships are not likely to go.

    Chris - So how deep can a seal go?

    Mike - Elephant seals are amazing divers. They can get down to about 2000 metres in the extreme, which is an unthinkable kind of depth. It's a depth so great that you can imagine if you were to open a scuba tank magically at that depth, water would rush in rather than air bubbling out. It's 200 atmospheres of pressure. So amazingly deep divers. And they also dive all the time, they're almost never at the surface. So they're really great ocean explorers.

    Chris - And these actual units that you apply with the glue onto the seals fur, how big are they and do they disable the animal in any way?

    Mike - No, they don't harm the animal at all, we are able to use animals over several years and running so you can see how well the animals are doing. They're behaving in every way normally and getting just as fat as they ought to get so it doesn't seem to bother them in a way that they can't make up for. And in comparison to an elephant seal they're really not that big. They're about the size of your fist I guess. They weigh about 450 or 400 grams.

    Chris - And how do you get the data back from the animals to find out where they've been and what they've been doing?

    Mike - Well, the devices have a little computer on board which will allow them to do all the sampling, and then they package that information up into nice little compact radio messages that they send out to a satellite and the satellite then relays it down to us and we can then decode the information and turn it into the data that we need.

    Chris - And what have you found so far by doing this? Have there been any things that really jumped out and you thought "Gosh that's surprising, we would never have thought of that".

    Mike - Well I think there's a couple of different areas, I mean we started this from the point of view of trying to understand what it is that elephant seals need from the ocean, not really to do the oceanographic exploration for the sake of oceanographers but really to learn for the sake of the animals which bits of the ocean were important to them. We've identified the kind of places that they require. We now know that they're quite diverse in the sense that there's three basic strategies they use. Some are real deep ice explorers, that go way down to the Antarctic continent and sort of visit the benthos down on the continental shelf around the Antarctic margin, well into the ice. And another group effectively are animals that explore the frontal zones that are slightly lower latitudes, up around 45 degrees, to 50 degrees North or so. Areas anywhere from the Polar front down the Southern Antarctic front, and explore a much more sort of pelagic part of the ocean.

  • How can frogs survive freezing?

    Andy on the A120 asked:

    I saw a documentary about frogs, which during the winter literally freeze solid. Come spring, they seem to de-freeze and come back to life. How do they do this?

    If you put a human in the freezer, the first thing that would happen is that all of our tissues would freeze. About 60 or 70% of the weight of a human being and most mammals is water. Water forms crystals of ice, and those crystals are often jagged and sharp. These sharp ice crystals destroy the cellular structure, burst holes in the cells and make the tissue fall apart. This is the same reason why when you put a strawberry in the freezer and then get it out again it doesn't resemble a strawberry anymore - it just turns into a sort of mess. Some animals that resist this cellular destruction have managed to evolve a natural antifreeze, which works by stopping crystals forming these big jagged shapes. So that's part of it. They form much smaller crystals that have softer edges. There was a very elegant piece of research published about this time last year in the journal "Science", and they were looking at the snow flea, which lives in Canada. The snow flea makes another form of anti-freeze, and when you zoom in on the body of those animals, which can survive down to about minus 10 or something, you see that the tiny crystals of ice which form in their cells look almost like a grain of rice. They don't look sharp and jagged at all, which means that the cells don't get damaged in the same way. These antifreezes also allow them to resist lower temperatures, which means that their blood doesn't actually turn solid until a much lower temperature than it would do normally. So it works a bit like the antifreeze that you would put into your car. The other part of the survival mechanism is that frogs and other amphibians are cold blooded. So unlike us, where we have to stay warm, or we die, those animals absorb a lot of energy from their environment. Doing a little bit of exercise does put their temperature up a bit but they largely rely on absorbing energy from the environment, and that determines their metabolic rate. So how metabolically active they are can go up or down enormously depending upon the temperature. So if you cool a frog down, it just slows down to near stand still metabolically, and doesn't do anything, until you warm it up again, and they're well adapted to being able to survive like that.

  • Is odour is a matter of fact or opinion?

    Roger via email asked:

    I am having an argument with a friend, about whether or not body odour is a matter of fact or opinion. Can you recommend any relevant articles?.

    We have our body odour to thank for lots of things. One person we interviewed on this programme earlier this year, was John Pickett from Rothamsted Research, who has actually bottled "eau de human", and specifically bottled those components coming off your skin that mosquitoes hate! So there are some people in the population that exude odours that mosquitoes really cannot stand. And some people carry those genes, which enable them to make those chemicals, whereas others don't. By bottling those chemicals you can turn it into the world's best insect repellent, and that's what he's done. So I think that in that respect, body odour is extremely useful and not only mosquitoes but it works against the Scottish Biting Midge as well. People also done research on how attractive women find the smell of sweat from men. They get them to wear a shirt for while and the women sniff them and I think they've shown that you're actually more attracted to people who are less genetically similar to you. This is definitely true in mice and the studies are very robust. We know that if possible, they will try to find a mouse partner who is as genetically different from themselves as possible. If you put two mice together and they're brother and sister, and you don't give them any choice then the female will mate with the male, and have pups with her brother. But if you then introduce a third mouse, which is genetically totally different from the first two mice, then the female can abort her babies and re-mate with the different male. Mice have this very strong and well developed sense of smell, and we know that the smell receptors are on the same chromosome as the structures that control how the immune system works. So we think that mice can use smell as the surrogate marker of how your immune system is working and so you can use that smell to guide you as to how different you are genetically from someone, and therefore go for someone who is as genetically different to you as possible which should make you healthier. The problem is that we humans tend to have very well developed frontal lobes in our brain. Which means we're very social, we think things through very carefully and we're very, very likely to get the argument skewed by things like social pressures, and likes and dislikes and how big someone's wallet is.

  • Why is there a lake under the antarctic?

    David via email asked:

    Since the Antarctic is landlocked, is it believed that underneath the ice but above the land (in other words sandwiched between the two), there is an ocean of water? And where does it come from? Also, what's melting the ice? Is it energy or heat coming from within the earth that's making the ice melt?

    Well that's really interesting because one of the most exciting projects that people are involved with on Antarctica at the moment is looking for what's called sub-glacial lakes. They're using radar waves from the surface of the ice to look down. And they think what they've found is a whole series of lakes that are sitting above the rock but below the ice. Of course the really exciting question is, are they ancient life forms in there, and are they unique? And so that's what everybody's hoping to find the near future. As for what's melting the ice, that's a very good question and one that we all want to know the answer to. It is possible that it is what we call geothermal heat from the rocks underneath causing the bottom of the ice sheet to melt. It may be water that's been trapped there for millions of years, and that's what everybody is hoping for.

  • How can beer freeze immediately?

    Steve from New Zealand asked:

    Sometimes when I put my beer (330mL glass bottle) in the deep freeze to rapidly chill it, I can take it out and it's still liquid. If I then leave it for a few minutes on the side and come back to drink it, it goes all icy. Why is this? Surely once I've taken it out of the fridge it should instantly start getting warmer, not turning to ice!

    I reckon it's down to something similar to our kitchen science that we did this evening. That was all about nucleation. What you need is one tiny crystal to kick start the process. But where does this first crystal come from? Well, say he puts the glass bottle of this stuff in the freezer, and the glass where it's not in contact with the liquid, gets that little tiny bit colder because the liquid's not taking away the heat. This means that the glass on one side of the bottle is at a much cooler temperature than the rest of the bottle containing the liquid. Then, when you take the bottle out, because you've had it in the freezer on it's side, and you turn it the right way up, suddenly lots and lots of beer gets in contact with the side that's much colder, which might be enough to kick-start a small crystal forming, which then nucleates it makes it much more energetically favourable for lots of other ice crystals to form and the beer goes slushy.

 

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