There are very few places on Earth that are completely devoid of life. No matter how extreme the environment, there will almost always be organisms that evolve to adapt to it. Even if the cold ice tears the cell membrane and the high heat destroys the cellular mechanism, extreme temperatures have never been an obstacle to life. Some animals survive the "resurrection" experience even if they are completely frozen, while others survive even if they are not in water for decades... The existence of various strange life forms has broken our understanding of the limits of life on Earth. Let's take a look at some of the most extreme life forms on Earth.
Toughest
For them, lethal rays, absolute zero, cosmic vacuum, extreme pressure, and 120 years without water are not problems. Tardigrades ( or tardigrades ) are miniature invertebrates that can be seen almost everywhere, from freshwater to the ocean, from moss in your garden to the top of a mountain. They are one of the most powerful animals on the planet, and under harsh conditions, they can even roll themselves up and pause their metabolism until environmental conditions improve. In fact, tardigrades have set records for survival in a variety of extreme environments, but these records were achieved in a "super hibernation" state, so whether they count or not is debatable. The following is a partial survival record of tardigrades under extreme conditions:
Survives 120 days without water
Freeze to -272.8 °C (very close to absolute zero) and still survive
Heat to 151 ° C, or survive
Fearless of the vacuum of space – Several tardigrades once survived 10 days on a European Space Agency test satellite
Don't die at six times the pressure of the deepest seabed
The amount of X-rays and gamma rays that have a lethal effect on other life cannot help them
Most resistant to pressure
As soon as you reach the surface of the sea, the pressure begins to increase. For animals (including humans) adapting to life on the Earth's surface, water pressure can cause many problems, the most obvious of which is that rising water pressure squeezes the lungs and other air chambers in the body. To combat this effect, like walruses
and sperm whales
Mammals such as these can dive to depths of more than 1,000 meters by allowing their chest and lungs to collapse to squeeze out air. As a result, they can spend long periods of time without breathing, and they have higher levels of hemoglobin in their blood and higher levels of myoglobin, a similar molecule in their muscles.
The water pressure at a depth of several hundred meters has reached dozens of atmospheres, and a whole host of problems have arisen. As important "communication" channels in cell membranes are squeezed, nerves and myocardium begin to struggle, and many proteins do not fold into the correct three-dimensional shape, thus becoming physiologically deformed.
Even so, the deep sea is still full of life. Even in the deepest parts of the ocean, where the water pressure can reach 1,000 atmospheres, shrimp-like footstock, sea cucumbers, nematodes and other bugs and bacteria still thrive. The maximum depth a fish can swim to is 8,730 meters, just a few kilometers away from the deepest part of the ocean, but what scientists have not understood so far is: Why don't fish swim deeper?
To survive, deep-sea animals have evolved a series of clever cellular adaptation strategies. From bacteria to fish, deep-sea organisms typically have more flexible cell membranes, which are achieved by replacing saturated fats with unsaturated fats. They also use a compound called trimethylamine oxide to help proteins fold properly.
Once adapted to the environment, animals live in the deep sea as humans on land. And on the surface of the sea, deep-sea crabs
and footed animals
It will be as difficult to move underwater as we do, because their cell membranes will become too fragile under an atmospheric pressure, and inflatable chambers such as fish maws will swell and burst with the release of air pressure during the floating process. Obviously, when it comes to pressure, it is better to "adapt to local conditions".
Most drought tolerant
Of all the constraints on life, water is the least negotiable. All cells need water as a medium to allow their own chemical reactions to take place while keeping the cell membrane intact.
For most animals, severe dehydration means death. However, some creatures can survive by sitting and waiting for the rain to fall. Tardigrades
, Rotifers
nematode
Juvenile shrimp and a fly can roll themselves into balls after dehydration and then sit back and wait for the drought to end. Most lichens and mosses, some fungi and bacteria, and hundreds of species of flowering plants are also dehydrated and waiting for improvement, sometimes years or even decades.
All of these organisms survive by replacing water molecules inside and around cells with sugar to dehydrate themselves while maintaining the structure of the cell. As the sugar content in the cell rises, the cytoplasm transforms from a liquid state into a solid state called "sugar glass", thus temporarily "freezing the cell in time".
This is a clever survival strategy, but it is not common. Other strategies for waiting for the drought to end are less extreme. For example, some lepers and include the African bullfrog
Many frogs, including those, dug their own holes to form an impermeable cocoon to envelop themselves, leaving only their nostrils to breathe. Countless other animals, from snails to crocodiles, have adopted similar strategies. Even some mammals, including ground squirrels and a lemur, can survive dry periods by sleeping heavily.
For all of these organisms, however, dehydration and hiding are only temporary measures, and water scarcity is indeed the ultimate challenge for living things on Earth. So, most species know that the best strategy to prevent water scarcity should first and foremost be to avoid areas of severe water scarcity.
Most heat resistant
Heat is a big challenge for life. On land, too much heat means water evaporates or boils, and living things can't survive without water.
There is no concern about water shortage on the seabed, but in the deep sea thermohydrate can be as high as 400 ° C, where the seawater is "opened" by the heat of the Earth's interior. Once the maximum temperature that an organism can tolerate, complex molecules like DNA (deoxyribonucleic acid) and proteins begin to break down, and too much heat can "burn" off their chemical bonds.
The highest known temperature at which life can still grow is 121 °C, and the holder of this record is a microorganism simply called "strain 121", which usually lives at a temperature of about 100 °C in the hydrothermal port on the seabed, and when it is heated to 121 °C in the laboratory, it does not seem to care, even if it rises to 130 °C, it is still alive, but it can no longer be replicated, unless the temperature drops.
From a cytochemical point of view, extreme thermophilic organisms like "Strain 121" (thermophilic organisms are organisms that grow best at 55°C to 65°C) are not much different from you and me, except that their proteins and DNA are more closely arranged, so they can tolerate more heat before they die. However, once the temperature exceeds 100 ° C, basic metabolites like ATP (adenosine triphosphate) break down within a few seconds. Therefore, the upper temperature limit of life depends on how quickly cells renew these compounds.
Multicellular organisms are more difficult in terms of heat tolerance, and scientists have so far not understood why. Above 40°C, most of these creatures have problems. Above 60°C, no eukaryotes (organisms with membrane-encapsulated nuclei) will survive long, with one exception – Pompeii found in the 1980s in the seafloor hydrothermal vents off the Galapagos Islands.
Unusually, their tails are attached to the walls of the hydrothermal mouth and thus withstand water temperatures of up to 80 °C. However, the rest of their bodies are far enough away from the hot seawater.
Scientists still don't know how the tail of Pompeii tolerates heat, in part because the animal doesn't live long in the lab. One of the reasons they can withstand high temperatures may be their high levels of collagen, which remain relatively stable at high temperatures. In addition, Pompeii live in self-built tubes, and symbiotic bacteria also form furry lumps on Pompeii's body, which provides a certain high temperature protection for Pompeii.
On land, the animal that can tolerate the highest temperature is the desert inhabitant Sahara silver ant,
The ant can tolerate for a few minutes above 53°C while looking for other animals that die in the hot midday sun for food. Why are Sahara silver ants so afraid of heat? They store enough heat shock protein before leaving the nest, which helps other proteins stay in shape. And while out foraging, silver ants are accustomed to climbing up any height they can find to enjoy the breeze — whether it's a plant or a scientist who is observing them on the spot.
Most hardy
Below 5 °C, the work of enzymes, the biological catalysts that advance all the chemical processes of life, will be painfully slow. Below 0 °C, the situation becomes worse: ice crystals begin to form inside and around the cell, sucking up water from stem cells and cutting the cell membrane and cytoplasm into pieces. In fact, more than 80% of the habitats on Earth are colder than 5°C. However, animals that can cope with severe cold are not uncommon.
Let's look at the microbes first, which stop growing until around -15 ° C. That's not great, and more complex animals have achieved the same with a range of strategies. Mammals and birds are ahead of the curve in this regard, due to their ability to generate heat on their own, and heat is a byproduct of their metabolism. They also use fur and fat to keep the body warm. The monarch penguins are even more remarkable, with thousands of them clinging to each other to fend off Antarctic ice winds that can bring temperatures as low as -60°C.
At such low temperatures, a large number of animals that lack their own internal heat can survive. In the case of Antarctic jumpers, for example, as winter comes, they can lower their body's freezing point by synthesizing antifreeze molecules while discarding everything that might act as an ice crystal nucleation point (ice crystals form around the nucleation point), such as intestinal matter and bacteria. They also produce their own antifreeze — sugars or glycols that protect cells from the freezing process.
Some animals survive even by freezing, including many insects, the young sons of western turtles, and a variety of North American frogs such as forest frogs. These animals use antifreeze to protect the most critical parts of the body. For less critical parts, such as the body cavities and eye lenses, they promote a measured rather than runaway freeze by making proteins as ice nucleation points, or by encouraging the growth of ice nucleation bacteria (bacteria that act as nucleation points for ice).
The caterpillar on Ellesmere Island in Canada is an extreme example.
It does not hibernate until below -70°C by freezing intestinal material, blood, and other extracellular fluids. Antarctic nematodes go further, allowing the cytoplasm (the liquid part of the cell) to freeze, leaving only the nucleus and other organelles unfreezed. Scientists don't know how they cope with this bizarre state, but they are known to be able to synthesize on their own an antifreeze that may smooth the edges of ice crystals and thus prevent damage.
utmost
The largest animal in the entire history of evolution and still existing today is the blue whale. The 30-meter body length and 190 tons of weight may already be a blue whale
The upper limit of their size, a little larger, they will face the problem of hyperthermia during exercise, because their metabolic mechanisms will produce heat faster, and excess heat is difficult to dissipate through the surface of the skin. This problem is also exacerbated by a thick layer of blubber – blue whales have a layer of blubber that warms their bodies during rest.
While there may never be an animal larger than a blue whale, it is only small in the face of some other kinds of organisms. The largest of these creatures is the Pseudomelia fungus, known as the "Giant Fungus", and although it is unclear how big it is, it has now spread to 965 hectares in the Marul National Forest in Oregon.
As for plants, the biggest one today is "General Sherman",
It is a giant sequoia tree in California's Sequoia National Park, with a trunk volume of about 1500 cubic meters. The tallest surviving tree is also found in California, USA, and this coastal sequoia is 115 meters high, which is almost worthy of its name - "Hipperion", a title derived from the name of a giant god. Only one tree above this height is a downed eucalyptus tree found in Mount Popo in Victoria, Australia, which has reached a height of 143 meters. The calculations suggest that this is close to the theoretical maximum of tree height, and once this limit is exceeded, the top leaves have difficulty absorbing water from the roots through capillary action.
least
To ask how small life really is is to ask what the definition of life is. Viruses are generally considered to be the smallest life that can replicate themselves, and some viruses are only 20 nanometers in diameter (1 nanometer equals one millionth of a millimeter). But as an intracellular parasite, viruses are highly dependent on other life forms, so viruses are often not considered real life.
The smallest known bacterium is the "Taikoo Richmond Ore Acidophile Nanomicrobial" (arman) found in 2006 in the sewage of the hot arsenic-bearing pit in northern California, USA, which is only 200 nanometers long, which is 1/3 of the size of E. coli, equivalent to the size of a large virus. Contains only about 1 million base pairs. You know, the human genome contains 3 billion base pairs.
Some scientists believe that the honor of "minimal" should be given to nanobacteria,
These small, oval structures are found in human blood and saliva, only 50 to 100 nanometers in diameter, and look like cells, and they can also divide like cells. But scientists have yet to isolate the genetic material necessary for life from them. A study of the year stated that nanobacteria were nothing more than calcium carbonate particles.
Since genetic material is necessary for life, another way to explore the smallest life is to identify the smallest genome. The preferred target is Mycoplasma genitalium, a parasitic bacterium that causes urinary tract infections in humans, with a genome of only 580,000 base pairs and a genetic abundance (a case where a particular biochemical function is duplicatively encoded by two or more genes): of the 482 genes that code for proteins, 382 have been shown to be necessary for life. This makes it potentially close to the smallest viable genome, making it the first genome planned to be artificially sequenced.
Organisms can have smaller genomes, but at the cost of this, they may no longer qualify as an independent life form. For example, wood lice
(an insect that sucks sap) lives a symbiotic fungus that provides the essential amino acids for psyllids. It has only 182 genes and relies heavily on pyllid cells that it may even have evolved into a organelle—a basic unit of the cell. This is reminiscent of the way early cells "merged" bacteria, which were merged into mitochondria and chloroplasts, responsible for releasing energy and performing photosynthesis, respectively.
Longest-lived
Of all the limitations on Earth, one that no living thing can escape is death. However, some creatures still outweigh others in changing the fate of death as much as possible.
For reasons that have not yet been fully understood, animals rarely live to be 100 years old. But there are exceptions to everything, and there are some exceptions in this regard. The longest known animal to live is a sea clam caught off the coast of Iceland, which is estimated to have lived for about 400 years or more. Scientists still don't know why these clams are much longer-lived than other animals, but what they already know is that at some point in their lives, their mortality rate actually decreases, so it's not known if they will go through the same aging process as we understand it.
The way plants bypass the aging problem is by allowing cells in their oldest parts to die while continuing to produce new ones. The most extreme example of this is the so-called clone tree, which replicates itself by emitting new clusters of identical genes over large areas that share the same root system. A cloned tree in Utah, USA, is probably the longest-lived representative of this. Although its existing part appears to be no more than 130 years old, the age of some of its roots has been determined to be around 80,000 years old. The longest-lived tree on record is a foxtail pine named "Prometheus", which was about 5,000 years old when it was cut down in 1964. Its oldest part is long dead, and the surviving part is only a few hundred years old.
As for the longest-lived organisms on Earth, they may be bacteria found in the permafrost of Siberia, Canada and Antarctica, which are thought to have lived for 500,000 years, probably because of their extremely slow metabolism and extremely efficient DNA repair mechanisms, which allow them to cope with severe food shortages and live for a long, long time.
However, no one can defeat the "undead jellyfish" - lighthouse jellyfish, which can return to an immature stage after becoming sexually mature, and theoretically can continue to age and "rejuvenate" indefinitely like this. As a result, all the lighthouse jellyfish eaten by predators may not have lived to the age of the day, and scientists have not been able to measure the age of such jellyfish.