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  • When you think of the most dominant  creatures on earth - what comes to mind?  

  • If considering sheer size, perhaps you  immediately thought of the ocean - and the  

  • largest animal that's ever lived - the blue whaleOr perhaps thinking of strength and ferocity,  

  • you imagined lush forests full of fearsome big  cats. Or maybe, quite sensibly, you thought of  

  • us - human beings- the most intelligent, and one  of the most widespread creatures on the planet.  

  • But if you were to walk down the sidewalk, or lean  against a tree, the first animal that you would  

  • likely encounter is something small - ants. Their  total population is around ten thousand trillion,  

  • and when combined their total weight would be  about the same as the weight of all human beings.  

  • in biomass and in impact on ecosystemsthese small animals are arguably the most  

  • successful creatures to have ever lived. Ants have colonized almost every landmass on  

  • earth. Their presence is so significant that they  have directed the evolution of countless other  

  • plant and animal species. Aggressive, warlikebut also cooperative, altruistic - ants living  

  • in colonies exhibit some of the most complex  behaviors of all insects. And the colony is the  

  • only thing that matters in the lives of antsTheir loyalty to it is absolute. And in their  

  • service to it, they exhibit some of the most  complex social behavior in the animal kingdom,  

  • giving rise to their nearly complete  ecological conquest of the earth.  

  • How do ant societies work, and what is it about  the colony that has made ants so successful?  

  • Is it as simple asstrength in numbers?”  Or is it something more profound?  

  • Even though insects were among the first  animals to colonize land, cooperative insect  

  • societies are a relatively recent development. The first insects emerged around 400 million  

  • years ago - but ants didn't emerge until  much later, around 100 million years ago.  

  • They lived amongst the dinosaurs, and for a long  time did not rule the landscape. This was the  

  • era of the giant dragonflies, cockroaches, and  termites. It wasn't until 60 million years ago  

  • that they became the dominant insects. And since  then, they have truly flourished. Today there are  

  • around 16,000 different species of ant, and they  are found on every continent except Antarctica.  

  • The competitive edge that allowed ants  to become a world-dominant group is their  

  • highly developed colonial existence  and specialized social structure.  

  • Ant societies are broken up into two castes: a  non-reproductive worker caste, and a reproductive  

  • royal caste. The queen is the only reproducing  female of the entire colony, and the colony  

  • exists to serve her, and her alone. The birth  of a colony begins with the birth of a queen.  

  • The life of a queen begins when its mother queen  lays a special kind of egg, different from the  

  • millions of regular worker eggs the queen ant  will lay in her lifetime. These special eggs  

  • are laid when the colony passes a certain sizeand when they hatch, they produce ants that are  

  • larger than regular workers and have wings. These  are the reproductive males and young queens.  

  • During what is called a nuptial flight  these winged ants take to the air and  

  • mate with each other, after which the males  die and the females drop to the ground,  

  • scrape off their wings and begin to search for  a place to dig their nest. Few get far in this  

  • journey. Predators snag most of these young  queens before they can establish themselves.  

  • Only around 1 in 500 new queens has a chance  at success. But those that do succeed become  

  • the single egg-laying queen of their new colony. Over the course of her life, a queen ant can lay  

  • up to 300 million eggs, depending on the species  of ant. And the vast majority of these eggs  

  • hatch into dedicated worker ants - female ants  whose lives are devoted to the queen's welfare  

  • and reproductive activity. At any given timethere are millions of worker ants maintaining  

  • the colony. There can be many different typesand many different sizes of workers even within  

  • a single colony. Some care for larvae, others  excavate tunnels, others build amazing structures,  

  • while others leave the nest and search for  food, or go to war with neighboring colonies.  

  • And surprisingly, it is the ant workers themselves  who ultimately decide the fate of the young,  

  • choosing which worker caste they  will develop into. Larvae develop  

  • into different types of workers based  largely on the nutrition they receive.  

  • Those fed more insects than seeds are  more likely to become larger individuals.

  • For leaf cutter ants, the polymorphism  that exists among the workers is extreme.  

  • The largest workers, called soldiers, defend  the colony, while the medium sized workers  

  • collect leaves, excavate tunnels, or collect  garbage, and the smallest workers raise the  

  • young and cultivate and farm fungus - the  only food source for the whole colony.  

  • The workers toil away in a flawless synchrony  - in a flow that looks chaotic to our eyes,  

  • but is in fact based oncomplex system of communication,  

  • a chemical and physical language invisible  to us, but binds these societies together.  

  • For years, scientists knew that ants must  have some way to talk to each other in order  

  • to organize their intricate societiesBut ants have poor vision and hearing,  

  • so scientists knew that ant communication must  work in a fundamentally different way to ours.  

  • It was a mystery for years, but in 1962 leading  entomologist EO Wilson began to crack the code  

  • of ant communication. He started with the  question of how ants tell other members of  

  • the colony the location of a new food source. He  noticed that ants often tap their abdomen to the  

  • ground when travelling, so wondered if they  were leaving some sort of chemical trail.  

  • He began painstakingly dissecting fire ant  abdomens, crushing each of the organs with  

  • an applicator stick. He would then spread  the ant juice on a piece of paper in front  

  • of other fire ants, to see if they would reactAs he worked through each of the known organs,  

  • the ants showed no interest. But then he stumbled  upon an organ that had never been studied  

  • before - something called Dufour's gland. When he  crushed this gland and spread it across the paper,  

  • the ants went wild. They followed the  trail immediately and completely.  

  • Over time, scientists have discovered over 20  different pheromones that ants use to communicate.  

  • And by combining different signals, ants  have created a complex pheromonal language.  

  • African weaver ants, in particular, have the most  sophisticated pheromone communication system ever  

  • studied in animals. Some of their thoughts are  expressed by spreading pheromones on the ground,  

  • like previously mentionedcombined with physical gestures.  

  • When a worker wishes to say 'follow me I have  found some food' she deposits a trail from the  

  • rectal gland, while running from the food back  to the nest. When she encounters other workers,  

  • she waves her head and touches the other ant  with her two antennae. Or when a worker wishes  

  • to raise the alarm about an enemy, she lays  short looping trails around the intruder with  

  • secretions from the sternal gland. Other signals are sent through the  

  • air. When an African weaver ant worker  encounters an enemy in her own territory,  

  • she releases a mixture of four chemicals that  not only convey a message but elicit a response  

  • from all other workers in her vicinity. The first tells the other ants to 'be alert'.  

  • The next one tells them to search for the  trouble. The next one tells them to come  

  • closer and bite anything in their path, and the  final compound tells them to go nuts and attack.  

  • Scientists believe that the combination of  these signals very closely resembles syntax  

  • that we see in human language. A main reason ants  are so successful in the world then, is the same  

  • reason that humans are. Like us, communication  gives ants the amazing capacity to cooperate.  

  • Of all ants, weaver ants are among the most  impressive. They dominate the forests in  

  • Africa and Australia, in large part due to their  complex and efficient chemical communication.  

  • But perhaps more remarkable than their  ability to communicate so effectively,  

  • is what they can achieve with it. Weaver  ants are a species of ant that do not live  

  • in or on the ground, but in the trees. And  to keep their huge populations safe there,  

  • they construct their own housing. They weave  branches and leaves together to create an  

  • architectural feat, full of a network of different  rooms complete with roofs, walls, and floors.  

  • To begin the process, a single ant searches for  a nice, bendy looking leaf. It will pull on the  

  • edges, testing to see if the leaf will curlIf the ant has some measure of success, other  

  • ants will be attracted to the endeavor, and begin  pulling the edge as well. As the leaf bends more,  

  • more workers arrive. They line up in precise rowsgripping the edge, pulling it towards another  

  • leaf. If the gap is too large for a single row of  ants to seal, they perform an impressive acrobatic  

  • tactic: they chain their bodies together to form  a bridge. Workers climb down the bodies of others,  

  • until the chain can reach the other leaf edge, up  to 10 workers long. Once the leaf edges are within  

  • reach, the workers move into position to seal the  leaves together. But what looks like glue on the  

  • finished structure is something more surprising. Once the bent leaves are ready to be sealed,  

  • the workers will collect larvae who are  in their final stages of development,  

  • and use their threads of silk to bind the leaves  together. Holding the larvae in their mandibles,  

  • the workers move the larvae back and forth across  the leaf edges - using their babies like a hot  

  • glue gun. The larvae seem okay with this, as they  respond to this motion by exuding thousands of  

  • threads of silk. This silk becomes a sheet between  the edges, and works as a powerful adhesive.  

  • Structures like this speak to ants capacity  to organize their labor effectively, millions  

  • of individuals combining their abilities into  something much greater. It's easy to assume, then,  

  • that their effectiveness comes down to a strength  in numbers, along with the communication to  

  • orchestrate the work. But this can't account for  all of their behavior, and all of their success.  

  • There is something more unifying in the world of  the ants. And the individual ant's cooperation  

  • with one another is so profound, that it makes  scientists rethink the idea of individuality.  

  • The power of a group is evident - with more ants  working together, they can find food more quickly,  

  • build more impressive structures, and  defend against enemies more effectively.  

  • And working together is common in naturebirds in flocks, or bison in herds live longer  

  • when they live in groups. But in cooperative  animal groups like these, individuals still  

  • look out for their personal interestsFor them it's not just about the group.  

  • But this is not the case for ants. Worker ants  die young, and usually don't create offspring.  

  • Their existence is sacrificial. They have no self  interest. Certain ants have been found to suffer a  

  • death rate of 6% per hour when outside the nestdue to fighting with neighboring colonies. On  

  • average each forager survives for only a week. But  during that time, she manages to collect 20 times  

  • her own body weight in food for the colony - all  to support the group, and ultimately, the queen.  

  • This unwavering loyalty to the queenand the self sacrifice to her cause,  

  • becomes more evident when a queen dies. Logic  would assume that when the queen dies the workers  

  • would raise another queen to replace her. But this  is not at all what the workers do. In most cases,  

  • the colony fails to produce a royal successorand it declines until the last worker dies. They  

  • simply do nothing until there is no one left. This level of altruism and self sacrifice is so  

  • rare in the animal kingdom, that it has  made scientists rethink what it means  

  • to be an individual. If ant individuals incolony are not competing against each other,  

  • if they are bound tightly by communication andcaste-division of labor, if they cannot survive  

  • out of the colony for very long - does the  concept of the individual break down?  

  • The idea of the superorganism is one that has  been debated for decades. With ants, it's the  

  • idea that the colony is the organism, where the  queen is the reproductive organ, the workers the  

  • supporting brain, heart, and gut. The exchange of  food among the workers is like the circulation of  

  • blood. [6] The most advanced ant societies, like  weaver ants, driver ants, or leafcutter ants,  

  • fall into this category, where their workers  do not compete amongst themselves at all,  

  • and do not reproduce outside of royalty. This capacity of the colony to act like a single  

  • superorganism has made scientists reconsider  evolutionary theory as a whole. In the 1960s  

  • and 70s, the conventional way of thinking  about evolution was centered around genes,  

  • and genes alone. Largely popularized by Dawkin's  book The Selfish gene, it follows that the more  

  • two individuals are genetically related, the more  sense it makes for them to behave selflessly with  

  • each other - that all altruistic group behavior  comes down to each individual's competitive desire  

  • to improve chances of their kin's survival. But some ant biologists, like EO Wilson,  

  • believed that this couldn't be the whole storyInstincts from social species like ants go far  

  • beyond the urge to protect their immediate kinThe group must also have a role in evolution,  

  • whether or not the group members are related  to each other. And this idea gave rise to the  

  • theory of multi-level evolution, or group  selection, where natural selection acts  

  • at the level of the group, instead of at the  more conventional level of the individual.  

  • The way ant societies function, in their daily  lives and within evolution, has entranced us as  

  • humans for decades. They have created heated  debates among the world's top scientists,  

  • and been the focus of every kid's backyard  curiosity. Their world operates in ways our  

  • brains can barely conceive - with chemical  signals painted on the ground, instincts that  

  • drive them to fatal endeavors - and yet, their  sociality, cooperation, and complexity in many  

  • ways mirrors our own. Studying ants will continue  to reveal answers about the nature of evolution,  

  • and in turn, will reveal answers about our  own society, and our own individuality.  

  • Studying the animal kingdom gives insight into  our world, and brings researchers on all sorts  

  • of journeys - both intellectual and physical. Some  of the research about ants happens in the field,  

  • in the steamy tropics or the  frigid parts of northern Finland.  

  • And some of it is done in the lab, with  complex apparatuses engineered to study  

  • ant's chemical trails or their inclination to  go to war with each other. Hearing about what  

  • it takes to carry out research like this is often  just as interesting as the science itself. I love  

  • hearing the human stories behind the scienceand this is why we decided to start a podcast.  

  • Modulus - hosted by me, and Brian from  Real Engineering, is a podcast about the  

  • people behind the science we explore here on  YouTube. We talk to the scientists who are on  

  • the cutting edge of research, and the people  who are affected by the topics we discuss.  

  • The second episode of Modulus is out now. It's an  episode where I talk to two pioneers of the ocean:  

  • some of the world's first saturation divers. They  discuss what it's like to live at the bottom of  

  • the ocean, and how it affects both your body and  your mind. Their personal accounts of the effects  

  • of the immense pressure on their bodies very much  makes you realize that the profession of deep sea  

  • diving is not for the faint of heart. This episode is available now on Nebula,  

  • the streaming platform made by me and several  other educational YouTube content creators.  

  • It's the place to watch and listen to our videos  and podcasts ad free, along with original content  

  • that is not available anywhere else like the  Real Engineerings' the Logistics of D-day,  

  • or Sam from Wendover's new trivia showwhich features creators like Brian competing  

  • in sometimes silly tasks and trying not  to make fools out of themselves. We can  

  • take more risks and have more fun on Nebulawhere we don't have to worry about the YouTube  

  • algorithm. There is so much original content  there, with more being added all the time.  

  • And to make it even better, Nebula has partnered  with CuriosityStream, the streaming platform  

  • with thousands of high budget, high quality  documentaries. There are loads of the best  

  • nature films, like David Attenborough's Ant  Mountain - which explores one of the largest  

  • animal societies in the world - a supercolony  of ants, with more than a billion members,  

  • nestled within the Swiss Alps. It dives intowhole new area of ant biology that I never knew,  

  • and since it's a David Attenborough  film you know it's going to be good.  

  • And for a limited timeCuriosityStream is still offering 26%  

  • off their annual plans, makingyearly subscription just 14.79.  

  • So by signing up at  curiositystream.com/realscience,  

  • you will get a subscription to CuriostyStream  and a subscription to Nebula, for just $14.79  

  • for the entire year. Signing up is also the best  way to support this channel, and all of your  

  • favorite educational content creators. Thanks for watching, and if you would  

  • like to see more from me the links to my  instagram, twitter, and patreon are below.

When you think of the most dominant  creatures on earth - what comes to mind?  

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The Insane Biology of: Ant Colonies

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    joey joey に公開 2021 年 06 月 10 日
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