[00:14.50]Antarctica... the coldest place on earth...
[00:18.17]with an air temperature of minus 50 degrees Fahrenheit.
[00:23.47]You'd think that nothing could survive here -
[00:26.64]Yet huddling together these Emperor Penguins
[00:29.61]have evolved to cope with the battle for life in the big freeze.
[00:55.27]But cold isn't the penguins' biggest enemy
[01:07.21]The leopard seal - four meters long - a Super predator.
[01:14.42]No wonder everyone's reluctant to be the first to take the plunge!
[01:30.47]Penguin and seal have a relationship forged over millions of years,
[01:35.18]that of predator and prey.
[01:47.86]It's easy to see nature as red in tooth and claw,
[01:51.66]where predators dictate who lives and dies and only the fastest and strongest survive
[02:01.27]The truth is, predators and prey are just part of life's story,
[02:06.37]our world is made up of a vast network of complex relationships.
[02:13.68]Animals -including us - have to find mates,
[02:17.52]look after families and keep up with the neighbors.
[02:25.56]All these relationships affect how we look and behave.
[02:38.67]This is the surprising story of how the relationships
[02:41.98]between all living things have shaped the whole Journey of Life.
[03:01.30]Life on earth wasn't always as complicated as it is today...
[03:05.47]There was a time when there were no relationships at all.
[03:09.50]No violence, practically no competition and no sex.
[03:19.25]Three billion years ago
[03:21.08]the pinnacle of evolution was these strange lumps on the ocean floor -
[03:27.96]made up of ancient blue green algae.
[03:39.53]They might not look much but stromatolites had the power to change the world.
[03:46.17]They produced the first oxygen in earth's history and totally transformed the planet's atmosphere.
[03:54.78]Not only did they generate the air we breathe,
[03:57.48]they set the scene for all life as we know it today.
[04:02.26]Because of them, a brand new type of cell evolved,
[04:05.99]perhaps the most important life has ever known.
[04:13.20]These revolutionary, oxygen-fuelled cells spawned our ancestors.
[04:22.44]They were 20 times more energetic than the older models -
[04:26.18]And some then discovered that the quickest way to get the extra energy
[04:29.88]they needed was to steal it - by engulfing other cells.
[04:41.06]A new force was unleashed - the predator.
[04:46.67]And the struggle between predators and prey
[04:49.17]has been going on for hundreds of millions of years.
[04:53.91]As predators find better ways to catch and kill, their prey have to improve their self-defense.
[05:03.48]The two are locked in an intense relationship which forces both sides to change,
[05:08.76]because neither can afford to be left behind.
[05:12.69]Nature selects only the winners' genes the losers genes will disappear.
[05:19.20]This arms race has helped shape the lives and bodies of just about everything alive today
[05:25.31]and pushed some creatures to extremes.
[05:50.40]This cricket might think it's on a flower.
[05:59.64]Until the flower bites it in the neck.
[06:05.31]It's actually a mantis that's evolved to look just like an orchid -
[06:09.48]beauty turns out to be a beast!
[06:19.19]Other hunting strategies are even more bizarre
[06:23.30]Over millennia the snapping turtle's efforts
[06:25.83]to reel in a fish have turned its tongue into a juicy worm!
[06:42.38]Secret weapons aren't the only winning formula sometimes more subtle tactics may be needed.
[06:51.59]Meet jumping spider Portia, one of the world's smallest assassins
[06:57.56]She's hunting the much larger web spider
[07:01.50]She might be tiny, but she has a big appetite
[07:11.34]Her first direct - approach alerts her target,
[07:14.98]who just shakes the web and forces Portia to retreat.
[07:22.32]But Portia has evolved a Plan B, a maneuver straight out of Mission Impossible!
[07:41.27]She slowly lowers herself within striking range -
[07:48.32]she leaps - bites - and leaves the poison from her tiny fangs to do the rest.
[08:01.53]This time it isn't size or secrecy that counts -
[08:04.63]but strategy - Portia may be small, but she's as deadly as they come.
[08:13.57]The relationship between hunter and hunted doesn't only shape the way the predators attack,
[08:19.25]it also drives the way that prey fight back.
[08:24.62]Sometimes it's just about using natural assets in a different way.
[08:32.29]When a hungry raven eyes their chicks, field fares fight dirty!
[08:52.41]What a way to win!
[08:58.49]After millions of years of predators and prey slugging it out pretty much anything is possible.
[09:10.13]The only problem with an evolutionary arms race is we don't see it develop,
[09:15.20]all we see is the end result.
[09:21.04]The story of the passion flower vine is a rare exception.
[09:28.11]Just like any other prey passion vines are evolving to protect themselves
[09:33.02]from hungry predators.
[09:37.42]What makes them unique is that you can pretty much watch them doing it.
[09:43.30]At home in tropical America,
[09:45.23]they're under constant attack from lethal predators that lurk deep in the jungle.
[09:59.01]The adults are harmless enough - it's what they leave behind that's the problem.
[10:08.32]Mother butterflies lay their eggs on the passion vine's leaves.
[10:12.33]Tiny time bombs which soon hatch out into very hungry caterpillars.
[10:23.30]The fate of this plant is already sealed.
[10:26.01]In a few days there'll be nothing left.
[10:40.52]If a passion vine already has a batch of eggs installed
[10:44.09]it's pointless for a mother butterfly to lay more.
[10:47.73]There'd be nothing for her caterpillars to eat.
[10:50.56]This gives the passionflower a chance to fight back.
[10:55.64]Today not all the eggs are what they appear -
[10:59.07]some are in fact just yellow spots grown by the passion vine itself as a deterrent to butterflies
[11:11.25]But as in every arms race, not every attack is foiled.
[11:21.76]So there's pressure for better and better mimics to evolve
[11:25.43]and some are now so good it's hard to tell which eggs are real!
[11:42.98]Who'd have thought the relationship between a butterfly and a vine
[11:46.35]could have produced such a sophisticated bluff.
[11:53.76]Even when you're safe from predators things don't always go your way,
[11:58.03]there's competition to contend with.
[12:04.40]In Africa lots of hungry meat eaters are on the lookout for a free meal.
[12:11.31]A Vulture has the aerial advantage of being able to spot the first signs of a kill.
[12:24.16]Though it won't feed undisturbed for long.
[12:27.53]Soon every vulture in the area is fighting for a beak full!
[12:50.28]At this buffet, only the toughest get to eat.
[12:56.86]Lappet-faced vultures are the biggest bully boys of all,
[12:59.96]they knock the smaller griffons flying.
[13:12.31]But a free lunch attracts other hopefuls too -
[13:20.35]more feathers fly as even Lappets have to make way for the mammal heavy mob.
[13:29.39]Like predators and prey, this kind of competition is a real force to be reckoned with -
[13:34.49]another influence on evolution which selects only the toughest to survive.
[13:54.88]Competition is so crucial to animals' lives,
[13:57.62]that it can have a massive impact on their body shape.
[14:03.59]Many animals in Africa feed on Acacia trees
[14:06.99]why don't they fight like vultures at a kill?
[14:10.43]Because these diners have been molded into different shapes and sizes
[14:14.20]so they don't tread on each other's toes.
[14:18.67]Tiny Dik diks can nibble around the thorny lower branches in a way no bigger animals can -
[14:31.25]Taller Impala have control over the acacia's middle zone
[14:37.42]But even they are kept in their place - by the Gerenuk -
[14:40.96]which has a poise no other antelope can match.
[14:47.43]Gerenuks look more like ballet dancers than gazelles -
[14:50.74]they even balance on points!
[14:59.68]Their specially adapted hips and spines enable them to swivel
[15:03.88]while on their hind legs.
[15:08.42]But there's one animal which can feed higher still -up to 6 meters off the ground.
[15:20.27]It has a flexible, leathery tongue
[15:22.30]it uses just like a hand to pluck the highest twigs and leaves -
[15:27.81]thanks to the longest neck in the world.
[15:40.19]So competition hasn't just pushed animals into developing different eating habits,
[15:45.22]it's helped create entirely different species that can live in harmony
[15:58.34]But what happens when neighbors want exactly the same thing?
[16:12.32]Ring-tailed Lemurs live in troops on the island of Madagascar.
[16:18.26]Each group needs their own territory to survive,
[16:21.09]for shelter, food and a safe place to rear babies.
[16:26.63]They're often under threat from other lemur gangs,
[16:29.00]who'll steal the whole thing if they can
[16:42.62]The alarm sounds - Time to rally the Troops
[16:51.49]These intruders look like they mean business.
[16:59.37]Lemur society is run by females -
[17:02.14]it's they who lead the band into the fray - soldiers with babies on their backs!
[17:29.73]When competition gets this intense, the Lemurs' answer is teamwork.
[17:57.29]Once animals are driven to work together,
[18:00.03]the close bonds that evolve can open up a whole new way of life
[18:08.40]Meerkats are high on the menu for many predators
[18:11.70]so they need to work together to protect themselves.
[18:35.33]They're one of the few mammals that take turns at doing different jobs.
[18:44.47]While the rest of the family starts digging for breakfast,
[18:48.31]one member stands guard, on the lookout for predators.
[19:03.46]The others can carry on feeding safe in the knowledge
[19:06.96]that someone is watching their backs.
[19:31.65]It's not just lookout duty that meerkats share.
[19:37.62]When a monitor lizard appears they all gang up to drive it way
[20:05.35]En masse, these little creatures make a formidable force!
[20:11.46]Being such good team players is the meerkats' winning formula...
[20:14.99]it's all for one... and one for all!
[20:27.34]Some animals have taken cooperation to even greater extreme.
[20:33.41]Certain types of insects from bees to termites to ants
[20:37.48]live together in huge social colonies.
[20:42.66]But rather than share duties like the meerkats,
[20:45.52]termites have actually evolved different shapes and sizes
[20:48.93]to make them physically specialized for certain tasks.
[20:53.73]Workers are the general dogsbodies which do a multitude of jobs
[20:57.80]from finding food to looking after the babies, and repairing the nest.
[21:04.58]A soldier's sole purpose is to defend the colony.
[21:08.41]They're twice the size of the others and are armed with pincer claws.
[21:14.65]Both these types have given up the ability to breed,
[21:17.82]that role is played by just one queen a mother of the entire colony.
[21:28.53]She has become an egg producing machine and swollen and immobile,
[21:33.57]without her extended family of servants she would die.
[21:38.31]In fact none of the termites can survive without the others help
[21:42.11]they have become one massive super organism -
[21:46.69]It's easy to see why we'd help our own relations
[21:49.89]but some animals co-operate with different species.
[21:53.23]How could that evolve.
[21:55.66]One answer is found in the sea
[22:00.30]A coral reef is a natural metropolis,
[22:02.94]a city where everyone is trying to get on and make their own way.
[22:10.28]It's full of opportunities, deals to be struck.
[22:16.22]And some entrepreneurs are cleaning up!
[22:24.42]It turns out there's a market niche for professional groomers!
[22:42.74]Cleaners - like these tiny wrasse -
[22:45.11]snaffle up their clients' parasites and dead skin.
[22:49.82]They set up their own cleaning stations
[22:51.92]and their clients come from far and wide for dental hygiene or a gill wash.
[22:57.19]In return, the cleaner gets a meal.
[23:03.33]Cleaner shrimps, too, serve a most discerning clientele.
[23:11.20]And fish are smarter than you might think,
[23:13.51]they have good memories and come back regularly to exactly the same spot to be pampered.
[23:47.51]It isn't just tropical fish though which have discovered that
[23:50.58]hiring a little help gives you the edge.
[23:55.45]Some plants have too.
[23:59.62]Flowers only exist because of an ancient alliance between insects and plants.
[24:10.26]Since plants can't move around, they need help to carry pollen
[24:14.57]between them to produce fertile seeds.
[24:18.60]So they advertise themselves as nectar feeding stations.
[24:24.34]As the insects feed, they get an extra take-away of pollen.
[24:29.32]It's a partnership that has evolved so successfully flowering plants
[24:33.62]now dominate our world.
[24:37.46]The only draw back is some insects may take pollen to the wrong plant.
[24:45.13]To get round this certain flowers have developed an exclusive contract with their pollinators.
[24:53.47]And Orchids for example can be very demanding indeed.
[24:59.78]Some, like this bucket orchid, may seem downright cruel!
[25:06.72]This Euglossine bee needs its perfumed oils to attract a mate
[25:15.29]But as he gathers the oil, he loses his grip.
[25:20.20]Exactly what the orchid wants!
[25:23.67]It has evolved a complex trap which press-gangs male bees into service
[25:30.94]The only way out is a tight squeeze via the back door
[25:34.38]and the orchid's pollen sacks
[25:57.27]The pollen sticks to the delivery bee's back.
[26:03.41]Once free, and dried off surely he'll never go near a bucket orchid again!
[26:18.46]But perhaps male bees have short memories
[26:21.03]because here he is falling for the same ploy all over again!
[26:30.47]But the only difference this time is that he's delivering pollen instead.
[26:39.45]No question who's in charge in this relationship!
[26:45.68]But there is another invisible partnership which is even more important to plants.
[26:53.43]Including the tallest trees on the planet.
[27:01.20]They can live for more than 2000 years and grow more than a hundred meters tall.
[27:08.91]Although these giants are some of the largest of all living things
[27:12.64]they rely on the tiniest of partners which live hidden underground.
[27:18.18]These secret accomplices are fungi.
[27:21.22]They penetrate the roots and then stretch out through the soil as a network of tiny threads.
[27:30.63]The giant trees can't get enough water and nutrients on their own,
[27:34.93]but the fungal network can.
[27:38.54]Its massive surface area sucks up the fluid and minerals
[27:42.41]and transports them back to the trees roots.
[27:47.31]And in return trees feed the fungi sugars produced by their leaves.
[27:53.79]90% of all plants live with fungal partners,
[27:57.06]from the redwoods to the tropical rainforests, it's a 400 million year old marriage.
[28:07.13]Without it, plants might never have been able to colonize the land.
[28:12.34]And without all this green stuff, where would all we animals be?
[28:22.28]The close relationship between plants and fungi
[28:25.35]is only one of the great alliances that have shaped life.
[28:37.63]There is one more - you'd need a microscope to see it
[28:41.43]but it is perhaps the most important partnership on earth.
[28:47.57]Because it's what gives animals their energy.
[29:10.36]Scattered throughout our cells are billions of structures known as Mitochondria.
[29:17.10]Each is a tiny furnace that releases energy from our food
[29:21.41]and generates the life force that our bodies need.
[29:25.28]It's a crucial relationship one that started out in a very unusual way.
[29:31.62]Billions of years ago, the mitochondria lived independent lives,
[29:35.79]as free-floating bacteria.
[29:41.33]Then our ancestor cell engulfed one, but instead of digesting it,
[29:46.13]formed an alliance with its prey.
[29:51.67]The two joined forces and were transformed.
[29:54.74]Bacteria became mitochondria creating a new type of hybrid super-cell.
[30:03.18]A super-cell which was the basic building block for almost everything alive today.
[30:19.20]So there are some evolutionary partnerships where all benefit.
[30:28.57]But as we know relationships aren't always that straightforward.
[30:41.25]Most grazing animals in Africa are plagued by biting insects and ticks.
[30:47.76]They have what seem to be whole squads of helpful hangers-on.
[30:55.30]Oxpeckers - insect-eating birds that reach the parts the animals themselves can't.
[31:05.24]But oxpeckers aren't quite as innocent as they appear.
[31:09.82]They don't just eat up ticks, they peck holes in the animals' skin.
[31:23.40]What appear to be honest little helpers, in fact turn out to be blood-sucking parasites.
[31:32.40]A way of life which is surprisingly common.
[31:40.41]Take the rabbit for example,
[31:42.65]you might expect predators to have the biggest impact on their lives.
[31:48.22]After all, they're hunted by a whole army of killers.
[31:58.30]But with predators at least they can run away.
[32:01.90]Rabbits face another threat they can't see, smell or hear -
[32:12.31]Each rabbit is infested with thousands of fleas, ticks and minuscule Mites,
[32:17.75]which may be small but pack a powerful bite.
[32:22.19]These tiny bloodsuckers sap the rabbits' strength and within them
[32:26.76]they harbor an even deadlier threat.
[32:30.40]A fatal virus -myxamatosis - which kills far more rabbits
[32:34.73]every year than all predators combined.
[32:42.24]A virus is a nightmare straight out of science fiction.
[32:47.48]It's an invader with one aim - to replicate.
[32:51.38]It's made up of special components it needs to fulfill its mission.
[32:57.42]A potential victim - the outer surface of a body cell.
[33:03.16]On first contact the virus docks and merges with the cell membrane.
[33:12.34]Its inner pod enters the cell, seeks out the command centre,
[33:16.44]the nucleus and then injects its secret weapon - a snake of virus genes.
[33:26.45]These then corrupt the cell making it into a virus factory.
[33:32.12]Eventually the cell dies and bursts,
[33:35.03]releasing thousands of new viruses and the real destruction begins.
[33:43.50]Each year just about every baby rabbit born in the wild will catch this deadly virus.
[33:49.81]And only one in five will survive so it's a massive selection pressure.
[33:58.55]It's not just rabbits that viruses affect.
[34:04.29]In 1918, at the end of the Great War, a flu virus struck Europe.
[34:13.67]The war killed 25 million people over four years, that's three times the population of London,
[34:20.67]the flu epidemic wiped out the same number in just four months.
[34:34.42]Against such a powerful enemy, how can anything possibly fight back?
[34:41.13]The answer is a word we're all familiar with SEX!
[35:09.62]Sexual relationships aren't just about reproduction
[35:17.40]In fact it's perfectly possible to reproduce without sex -by cloning.
[35:24.60]Aphids are baby machines - they're all female and don't need a mate.
[35:30.28]They can pump out new aphids all by themselves.
[35:34.25]One every 20 minutes - each already stocked with it's own daughters!
[35:40.69]Cloning is great for increasing numbers fast
[35:43.22]but it has one flaw: As all cloned babies are identical,
[35:48.26]a killer disease that wipes out one wipes them all out.
[35:57.10]The key thing sex does is to create variety.
[36:03.51]Although these puppies all have the same parents, they're individuals.
[36:08.65]During sexual reproduction genetic material is reshuffled
[36:13.05]so that each sperm and egg is unique
[36:16.52]and when the 2 join together to make a puppy, each puppy is unique too.
[36:22.09]What's critical in the fight against parasites though is that
[36:25.80]the puppies are unique on the inside.
[36:29.90]This one might be more resistant to parvo virus
[36:33.17]and this one to distemper virus it's the same for human diseases too.
[36:45.65]Resistant individuals have cell membranes that lock the killer virus out.
[36:50.89]So its lethal life cycle can't get started.
[36:57.80]Sex is crucial it's evolution's way of ensuring the success of future generations.
[37:05.00]No wonder animals are so desperate to have sex.
[37:12.44]Once a year in autumn, American Elk gather to breed.
[37:24.46]It's called the rut -
[37:26.19]a spectacle where stags compete for breeding rights.
[37:50.28]This rut is played out in a most unusual location.
[37:59.12]In Yellowstone National Park
[38:01.03]manicured lawns attract the herds right into the centre of Yellowstone village itself.
[38:13.34]Here humans get a ringside seat.
[38:32.42]Each stag has two aims - to impress the females and frighten off rivals.
[38:42.37]Although the males are bigger and more dominant, it's the females who really run this show.
[38:49.37]As they'll be left holding the babies they're very choosy about whom they mate with.
[38:55.68]Only the stags with the most impressive antlers and fighting ability will do.
[39:02.72]Which forces the males to fight to prove themselves.
[39:09.46]It's a knock-out contest - where only winners get the right to breed.
[39:14.00]So over generations the battles get harder and the stags stronger.
[39:20.44]Female choice means that sexual relationships
[39:23.61]can shape the bodies and behavior of their mates so they are driving evolution.
[39:35.35]The overwhelming urge to win and pass on their genes
[39:38.69]can push the stags meanwhile right over the edge.
[40:15.33]Thankfully for other males,
[40:17.00]there are other less violent ways of courting favor.
[40:21.23]Sometimes it's all just a matter of showing off.
[40:25.44]So some species put all their effort into how they look.
[40:31.51]Posers can be just as successful as fighters!
[40:50.40]Instead of proving their worth on the battleground,
[40:52.93]these peacocks flaunt fancy dress instead.
[41:03.31]The females will only mate with the ones they find the most attractive.
[41:11.82]What does all this ostentation and display actually mean?
[41:20.43]How can a female be sure she's going to have good strong healthy babies?
[41:27.43]Remarkably a little finch proves that masculine beauty isn't just skin deep.
[41:34.97]Zebra Finch males have orange legs and cheeks and bright red beaks.
[41:43.51]The females are much plainer.
[41:50.29]So why are the males so colorful.
[41:53.16]To find out we tried a little experiment.
[42:00.57]The males' red legs and beaks are full of color pigments called carotenoids,
[42:05.34]found naturally in carrots certain fruits and seeds
[42:09.97]Half the males were fed a diet high in carotenoids to make them redder.
[42:15.78]Then they were put into a special choice chamber
[42:18.45]next to a duller male who hadn't been fed the pigments.
[42:22.62]Two males in their own designer bedrooms at the back,
[42:25.69]one female at the front.
[42:27.86]The sexes were segregated by a pane of glass.
[42:31.20]The males couldn't leave their rooms,
[42:32.96]but the female at the front could move from the left to the right.
[42:37.87]She could then choose a male by perching by his window.
[42:43.37]Tiny cameras were installed to record what happened throughout the Little Bird House.
[42:53.22]The high-speed CCTV footage shows what happens next.
[42:59.22]Watch the female at the bottom of the screen.
[43:02.96]She seems to have chosen the male on the left.
[43:06.60]And the camera in his bedroom shows she spent most of her time with him.
[43:12.14]While another reveals the other male was ignored.
[43:17.24]The most popular was the one with the brightest red beak - every time.
[43:26.08]In tests 9 out of 10 females preferred him.
[43:32.16]The question is why?
[43:36.33]The same red pigments not only make the male look good,
[43:39.76]they help his body fight diseases, too.
[43:43.40]A dull male is probably weaker and not a good bet as a mate
[43:57.25]A brightly colored male is not just likely to be healthy -
[44:00.39]he'll also pass on his parasite - fighting genes to his young.
[44:08.16]So it pays for a female to demand the best.
[44:17.54]And this male zebra finch has passed his medical with flying colors!
[44:24.64]But there's an extra twist,
[44:26.74]researchers now think female choice even creates new species.
[44:33.48]This is a zebra cichlid and experiments have shown that
[44:37.26]he's a dedicated follower of fashion.
[44:42.53]These fish are only found wild in Lake Malawi in Africa.
[44:48.13]What makes them special is that males have a variety of coats of many colors
[44:52.87]which is extremely unusual in a single species.
[44:57.18]Why the males come in so many different colors was a mystery.
[45:01.61]To investigate the fish were put in choice chambers.
[45:08.39]The larger, more colorful males were confined
[45:11.39]but the little brown females could go where they liked.
[45:15.79]All they had to do was swim in with the male they liked the most,
[45:19.13]and their choice was made.
[45:23.23]The tests proved some rather surprising results.
[45:29.14]It turns out even females of the same species have different ideas about what is sexy.
[45:35.68]Some preferred white males, some yellow, others blotchy and so on.
[45:44.19]Which explains why Zebra cichlid males come in so many different colors
[45:51.43]But how does that help to create new cichlid species?
[45:58.44]If a group of females gang together and decide that one color
[46:02.17]is now highly desirable, they'll only mate with those particular males.
[46:14.22]This preference is passed on to their daughters
[46:17.39]over generations an entirely separate breeding group is formed -
[46:21.16]and eventually a whole new type of cichlid.
[46:28.67]So what exactly did happen in the wild?
[46:35.21]Lake Malawi and the other African great lakes started out
[46:38.54]with just a handful of cichlid species.
[46:48.12]Now they're home to one in 10 of all kinds of freshwater fish on the planet.
[46:55.16]An incredible 1700 cichlids species.
[46:59.33]This is the greatest explosion of new species ever discovered.
[47:03.30]All created by the relationship between females and their males
[47:29.43]Whether with families and friends, competitors or enemies -
[47:33.30]living together isn't always easy.
[47:44.38]But relationships have been a massive force for change throughout the whole journey of life
[47:57.22]And ultimately it's our connections with each other
[48:00.86]each other that have created the spectacular variety of life we see today.
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