Strategy of Life | Part 1: Nature's Selection | Free Documentary Nature

For the past 4 billion years, organisms managed to stay alive in the Earth's battleground for survival. Only the fittest survives, and those who fail to adapt perish. So which organisms were the chosen ones? Organisms use unique reproductive strategies to leave stronger offspring. Nature demands them to choose the most effective survival method, and they respond with ongoing perseverance and effort. A relentless struggle to pass down more genes efficiently in the endless cycle of evolution. Survivors are the final winners. Organisms practice extraordinary and amazing reproductive strategies to avoid extinction. Even now, nature's choice for successful reproduction keeps the Earth's circle of life going. South America's luscious rainforests are called the lungs of the Earth. There is a swamp with brown water in the jungle. This unique shade was created by the fallen dead leaves. But there is something living here, hiding among the dead leaves. She disguises herself as a dead leaf, and spends most of her time at the bottom of the swamp. Her flat body is unique enough, but her back is shaped like a honeycomb. At that moment, something breaks through the skin and swims out. The baby toads burst out of their mother's back like little sprouts. These toads with a bizarre reproductive method are the Suriname toads, Pipa pipa. The rainy season has arrived. When the rain passes, the swamp becomes rich with plankton. For the aquatic animals and plants, this is the perfect opportunity for healthy breeding. For the Pipa pipa that feed on small fish, it is also the best time to reproduce. The Pipa pipa lying flat on the floor like a leaf has a broad back with small spikes. Because it's flat, it can hide very easily from its natural enemies. The male climbs on the back of the female to mate. There are about 7,000 and 700 amphibian species in the world, but these little toads' reproduction method is the most bizarre. After mating, the back of the female looks very rough. Like the volcanic rocks formed when lava cools down, the toad's back is full of holes. Inside these holes, that resemble a honeycomb, are the Pipa pipa's eggs. The female's flat back slowly fattens up and reaches an ideal condition to protect the eggs. The female raises her offspring in her back for up to five months. The offspring spend their tadpole stage inside their mother's back and are born as tiny toads. The female must swim to the surface of the water to breathe every 30 minutes, and to provide oxygen to her offspring, she becomes a bit more diligent. Taking care of a hundred or so eggs is a very serious responsibility. It's food. Her tiny eyes capture the prey. She waits motionless and sucks in the fish in a flash. Her big mouth and long front legs increase her success rate. By becoming one with their offspring, the Pipa pipa practices a self-sacrificing reproductive strategy. Compared to the simple method of laying a massive amount of eggs, this nurturing method takes more care but ensures a higher survival rate. The offspring, born after receiving unrivaled protection from their mother, they dash out into the world as a breaking of their umbilical cords. Toward the end of the breeding season, the female's back is covered in scars from giving birth. No matter how painful the process is, for the sake of successful reproduction, nature doesn't even flinch. For if you fail to survive, the evidence of your existence becomes a faint memory in the history of life. While Suriname toads invest heavily in nurturing their offspring, Korean toads invest all their energy into producing more eggs instead of nurturing them. This is breeding season for toads. Male toads compete aggressively to win the female. The female toad is in the process of mating, but the other male toads are unable to give up and they are battling. That unrelenting male toad may never be able to have any offspring if he gives up now. Female toad lays more than 30,000 eggs at a time. She lays black eggs encased in a jelly-like tube and it is over 60 meters in length. Instead of nurturing, these toads spend all their energy in producing massive amounts of eggs. The male's strong urge to mate makes him hang on to the back of the female and encourage her to keep laying eggs. But another male appears in an attempt to steal his mate. His reckless attempt earns him a powerful kick on his head, knocking him away. The toads compete fiercely to find a mate as if their lives depended on it, but once the eggs are laid, they don't look after them. Their reproductive strategy focuses solely on quantity. Darkness has fallen over the riverbank. There's a nymph that has been waiting for a chance to mate for a very long time. The name of this little guy that spends three years as a nymph is mayfly. There are about 80 species of mayflies in Korea. The mayflies are dancing in the air after the metamorphosis. It looks as if the male mayflies are holding a dance festival. The males are desperately dancing their hearts out, trying to capture the female's interest. The mating takes place in mid-air, in a flash. The mayflies try to mate in large groups just after they get their wings. That lies in their lack of flying skills. They must fly the moment they molt, so they are literally flying for the first time. No wonder many of them fall into the traps set by predators and meet a tragic end. But with such a short lifespan, these mayflies have no time to waste on flying practice. So they chose to overwhelm their predators by flying in swarms. And this is why we can enjoy their spectacular balls. Mayflies invest their entire lifetime on breeding. Is that why, when they reach their adult form, they end up with only a trace of a mouth? The mouth degenerated so they can focus on reproduction. Reproduction is their only reason for existence. After mating, the mayflies pour out massive amounts of eggs. There is a predator even in the final moments of the mayfly's life. The only way the descendants of these fragile mayflies can survive is to rely on quantity. Mayflies use every ounce of their energy to lay more fertilized eggs into the water before they die. Most of these eggs end up as fish food. But even if a small number of these fertilized eggs survive, the deaths of these mayflies won't be in vain. Life and death coexist. And every night these mayflies in love decorate the night sky with flutters of their wings. The mayflies first appeared 330 million years ago, and the secret of their continued existence might lie in their massive group mating ritual. Reproduction is the final and ultimate goal of every living organism. Organisms are chosen according to nature's demand, and they evolve accordingly. Sometimes that choice might prove disadvantageous to survival. Nature is the mysterious power that leads the organism to make unpredictable choices. An insect smaller than one centimeter. He's busily climbing the leaves, looking for food. The long antennae and the narrow waist make him look like an ant. But he's actually a stock-eyed fly. His antennae stand out. However, these long stalks aren't antennae, but eyes. They allow stock-eyed flies to cover a wider field of vision than regular flies. Because the eyes are so far apart, the face with only a mouth gives the stock-eyed fly a grotesque appearance. Eyes are very special to these stock-eyed flies. You can tell by how they clean their eyes every chance they get. When a stock-eyed fly is molting, the eyes are closer to the face. This fragile fly that can't fly climbs up, looking for a leaf to keep him safe. He starts to transform as time passes. And his two eyes are the first to transform. He takes a breath, and as if blowing up a balloon, he lets the eye stalks out. So why were these long, extended eye stalks selected? Like regular flies, stock-eyed flies have compound eyes that let them detect objects quickly and efficiently. The eyes placed far apart allow for a wider field of vision. But while flying, it's a different story. The eyes actually get in the way. This wide field of vision makes it impossible to detect fatal danger right ahead. This little guy suffered the unfortunate fate of becoming spider food. So why were these long eye stalks selected when they are a disadvantage to survival? This stock-eyed fly is busy cleaning his eyes with his front legs. He looks like a warrior preparing for battle. These males are fighting. They are competing to win a single leaf. The rules are very simple. The fly with longer eye stalks and longer front legs wins. They face each other and compare the length of their eye stalks. And realizing he has no chance at all, one quickly accepts defeat. This time, they are similar in size. The one on the left attacks first, using his long front legs. But the excitement is short-lived. He backs down at the opponent's counter-attack. He gets punched and flees the scene. The defeated can't protest. He leaves without a word. Having long eye stalks is a symbol of strength for these stock-eyed flies. But this trait is a disadvantage for survival. So why were these long eye stalks selected? The choice wasn't up to the environment or the male stock-eyed flies. The answer becomes clear during their mating ritual. The length of the male's eye stalks plays an important role in mating. The males are fighting aggressively to win a female. And females prefer the males with eyes that are far apart. Another male makes an attempt to change the female's mind. He attacks when the other male lets his guard down, but his opponent is stronger than he thought. He gets back to the female. The male's eye stalks grew longer because the females were more attracted to that trait. To become attractive, males must risk inconvenience and danger. But if they want to breed, they have no other choice. They have to go with what the females want, since only females can reproduce offspring. A choice made blindly for the purpose of mating. Was it a foolish move? This male stock-eyed fly cleans his eyes, preparing to go out and meet that one female that will give him offspring. What other kinds of evolutionary changes will the females' preference make? Downtown in midday is always crowded. The exciting city belongs to humans and cars. But when darkness falls, the city's ownership changes. When the humans start sleeping, the little guys that were waiting for this moment get into action. The moment she falls asleep unknowingly, the creature of the night gets a whiff of human smell and climbs onto the bed. It's a bed bug. The bed bugs that were hiding in the corners sense the human body heat. They crawl out of the layers and quickly sneak under the blanket. This bed bug finally reached the human's skin. Excited by the strong aroma of human blood, the bed bug gets ready to eat. After cleaning the mouth that is shaped like a syringe needle, the bed bug makes a quick stab. The bed bug's flat body plumps up. The meal lasts about eight minutes. The bed bug continues to feed until its body doubles in size. Unlike other blood-sucking insects that feed on pooled blood, bed bugs suck fresh blood from the blood vessels. But how are they able to drink their fill without being detected? Their saliva contains protein that acts as a painkiller, so they finish their meals without being discovered by the hosts. Feeling full, the bed bug goes back in hiding. Full from feeding on human blood, the next item on the agenda is mating. Freshly fed females are sluggish, and their plump bodies make the mating more convenient. But the bed bug's mating rituals are notorious for being the messiest and the most violent. The male stabs the female's abdomen with his reproductive organ shaped like an ice pick and ejaculates sperm into her body. The bed bug's mating is more like an assault than romance. It's because females don't have a reproductive organ to receive the male's sperm. When the male punctures the female's abdomen and ejaculates sperm into her body, the sperm travels through the hemolymph to seminal concepticals and is stored there until fertilization. But why do male bed bugs have to use such a violent method? The male tries to mate dozens of times, and things become even more violent. Whenever they spot a female, they climb on top of her and stab her abdomen. And without enough time to recover from the wounds, some females end up dying. So why did nature force the bed bugs to select such a violent and ruthless breeding method? Because it allows them to have an advantage in the competition over other males. The more times they mate, the better their sperm's chance of becoming the winner. It is an extremely self-centered reproductive strategy. But come to think of it, for bed bugs that always live in the face of death, such a ruthless but effective reproductive strategy might be necessary. It is spring, and flowers are blooming everywhere, covering the earth with fragrant aroma. Flowers signal the perfect season for mating, and the first to react to the flowers' fragrance are the insects. Bees have a keen sense of smell, and they can smell any flower within one kilometer. After receiving honey from the flowers, the insects return the favor by transporting pollen from one plant to another. Flowers with intense fragrance provide a meeting place for the insects. They don't even have to go searching for a mate. After meeting naturally, they mate. While drinking honey, talk about killing two birds with one stone. For insects with lives unrelated to flowers, they need a different mating strategy. This little guy is busy searching around the rugged ground. He is looking for a mate. He looks ferocious with his sharp jaws. But the colorful, gorgeous exterior makes him look like a work of art. This little guy, that can fly quickly but not very skillfully, is named Tiger Beetle. Tiger beetles jump, fly briefly, and drop only a few feet away. And their landing is anything but smooth. They have wings, but their flying skills are nothing to boast about. But crawling is a different story. Converted to human scale, they can move at about 300 kilometers per hour. So a male tiger beetle wanders endlessly in search of a mate. The tiger beetle feeds on the carcass of a larva using his powerful jaws. Now that he's replenished, he gets back on the road. The tiger beetle wanders for long, but then suddenly comes to a halt. He finally met a female tiger beetle. He carefully sneaks up behind the female. It took him a very long time to find her, so what will the courtship look like? But he charges at her as if he is hunting a prey. Stunned, the female starts to struggle, and he gets even more violent. The male uses his strong jaws to pin the female down. This is a pretty brutal mating practice. Tiger beetle females have no say in mating. The entire process depends on the male's desire to mate. The male tries to mate with every female he runs into, hence the nickname Casanova of insects. When the number of female tiger beetles goes down, the male's appetite for mating grows stronger. Sometimes, the male keeps his jaws locked on the female he just mated with, making sure no other male will try to mate with her. That's how strongly he feels about passing down his genes. When the mating season is over, a small change takes place in the tiger beetle's habitat. There are tiny round holes in the ground. They are the holes dug by the female tiger beetles. She sticks her bottom into the hole and lays eggs. For better protection, she sticks her bottom deep into the hole when she lays eggs. A female tiger beetle usually lays one egg per hole. Tiger beetles spend one year of their two-year life cycle as larvae. It may be a larva, but it also has sharp jaws. Tiger beetles are carnivores, and they hunt even in their larva form. Larva blocks the hole with its head. An ant passes by, and the larva snatches it and drags it into the hole. It used its powerful jaws to hunt. The tiger beetle's violence could be the most ideal survival strategy for small insects like them. However, there are insects that practice a classier lifestyle. There are some fallen trees. Inside the rotting tree trunk is a new life, preparing to venture out into the world. Spotted longhorn beetles spend a year inside a rotting tree trunk before reaching their adult stage. Starved, the spotted longhorn beetle goes searching for honey or sap the moment he comes outside. Using his long antennae to smell, the spotted longhorn beetle searches for food. The smell of flowers guides him like a map, and he explores the right path. The beetle finally caught a whiff of flowers. There are flowers everywhere. They're a white false spirea with plenty of honey and pollen. A perfect first meal. It's time to enjoy the feast. He must have been starving. He's busy gulping down honey. The long antennae get in the way of feeding. But since he found the flowers thanks to them, he can't complain. After the feast, the spotted longhorn beetle male uses his long antennae to find a mate to make love with. His antennae are excellent tools for sensing female pheromones. He found a lovely female beetle. He carefully climbs on her back and starts wooing her. During the mating process, the male uses his mouth to massage the female softly, expressing his love. It isn't a brutal, violent mating, but a beautiful and tender one based on mutual consideration. The reproductive strategies of organisms take different styles and forms, and they evolve. There are tens of millions of species living on Earth. And as they all have different appearances, they have different breeding methods, some beyond our imagination. Ways of avoiding extinction and preserving the species in the endless wave of evolution. Advantages for breeding, even if inconvenient or dangerous, are selected without hesitation. Natural selection occurs in the direction that provides better protection for offspring from predators or better chance of giving birth to more offspring. This unusual looking guy is a mantis shrimp. His eyes can detect ultraviolet and infrared light and rotate 360 degrees. And he also has powerful claws. After mating, the female mantis shrimp spends most of her time in a cave. She carries around her eggs all day long, and when she does, she becomes very sensitive to movement and quite aggressive. She has to carry her eggs at all times, so it's not easy to hunt or flee from predators. She chose safe nurturing over convenience. She cares more about her eggs hatching than herself. She must be willing to make sacrifices for the sake of reproduction. To the species with low population, nurturing is as important as mating. Jawfish is made for life, and it is the male jawfish's job to protect the eggs. The males are very sensitive to trespassing. He holds 500 eggs inside his mouth, and for the seven days it takes for the eggs to hatch, he even stops feeding. What other nurturing strategy could guarantee more success? Organisms display extraordinary and crafty reproductive strategies. Birthing a life takes patience and perseverance. A female spider is on the move while carrying her eggs. There's a sack that looks like a walnut attached to the end of her abdomen. There are spiderlings inside. She's a wolf spider that can move quite swiftly, but because she is carrying an egg sack, her movement is limited. The spiderlings break open the sack and come out into the world. But instead of scattering, they climb onto their mother's back and stay there. The spiderlings won't leave their mother for even a minute. It must be a lot of work, but the spider doesn't seem bothered. Could it be extreme motherly love? Afraid her offspring might fall off, the spider doesn't budge until every last one of them reaches her back. The weight of her offspring is almost unbearable, but she endures it. She goes looking for food, carrying the extra weight. She can't move freely, so it could get dangerous. But natural selection and the powerful desire to reproduce force the wolf spiders to take on the burden of motherly love. Spiderlings excited to see the world. They've been staying at the home their mother built for them, and now they are venturing out into the world. They were staying in the tiny place created with the reed leaf. Someone has folded the reed leaf in a crafty way. Actually, all the reed leaves are folded at the tip in a shape of a sack. So who was the architect that built these amazing homes? A space completely cut off from the outside world, the architect of this special home built to protect spiderlings was a leaf-curling sack spider. A perfect home built on the spot without any blueprints. With amazing construction technique, a safe hideout is built in no time at all. The edges meet precisely. It's as if she used a ruler for measurement. The female covered her eggs with spider silk by going back and forth thousands of times. Thanks to the mother's hard work, the eggs develop safely. The mother stands guard all day long, without feeding in case her eggs are attacked by predators. Thanks to their mother's love and care, the eggs begin to hatch. Inside the spider web are the spiderlings wiggling around. The leaf-curling sack spiderlings break out of the spider silk sack. Thanks to the mother's strict nurturing strategies, a large number of spiderlings hatch successfully. The moment they come into the world, the spiderlings must find their own food. To face the harsh world, they must feed themselves first. The spiderlings are unable to hunt just yet, so how will they survive? Surprisingly, the mother offers herself to her hungry offspring. She doesn't budge until her offspring suck her dry. The leaf-curling sack spider chooses death for the sake of reproduction. The death of their mother seems atrocious and brutal. And for the sake of reproduction, never leads to an end. It is a new beginning for new life. Reproduction must continue for the cycle of life, which should never come to an end. Even if it is selfish, violent, and leads to death. In order to be chosen in the ever-changing battleground called Earth, organisms instinctively leave their fates to natural selection. This is the essence of cold-hearted nature, different from human society. Behind the mystery of birth, there are amazing strategies we haven't quite noticed. Organisms continue to reproduce by making the most ideal choices for the future. Organisms constantly ask nature how to survive and which choice is correct, as they search for the answer to survival.