Living organisms are not able to absorb mechanical energy. Creatures that feed on electricity have been discovered on earth. And at this time

Corliss suggested that hydrothermal vents could create cocktails of chemicals. Each source, he said, was a kind of atomizer of the primordial broth.

As hot water flowed through the rocks, the heat and pressure caused simple organic compounds to fuse into more complex ones such as amino acids, nucleotides and sugars. Closer to the border with the ocean, where the water was not so hot, they began to link into chains - forming carbohydrates, proteins and nucleotides like DNA. Then, when the water approached the ocean and cooled even more, these molecules collected into simple cells.

It was interesting, the theory attracted people's attention. But Stanley Miller, whose experiment we discussed in the first part, did not believe it. In 1988, he wrote that deep-sea vents were too hot.

Although extreme heat can create chemicals like amino acids, Miller's experiments showed that it can also destroy them. Basic compounds like sugars “could survive for a couple of seconds, no more.” Moreover, these simple molecules would be unlikely to form chains, since the surrounding water would instantly break them apart.

At this point, geologist Mike Russell joined the fray. He believed that the theory of hydrothermal vents may be quite correct. Moreover, it seemed to him that these sources would be an ideal home for the precursors of the Wachtershauser organism. This inspiration led him to create one of the most widely accepted theories of the origins of life.

Geologist Michael Russell

Russell's career included many interesting things - he made aspirin while searching for valuable minerals - and in one remarkable incident in the 1960s, he coordinated the response to a possible volcanic eruption despite a lack of preparation. But he was more interested in how the Earth's surface changed over the centuries. This geological perspective allowed his ideas about the origin of life to take shape.

In the 1980s, he discovered fossil evidence of a less violent type of hydrothermal vent in which temperatures did not exceed 150 degrees Celsius. These mild temperatures, he said, may have allowed life molecules to live longer than Miller thought.

Moreover, the fossil remains of these “cool” vents contained something strange: the mineral pyrite, composed of iron and sulfur, formed in tubes with a diameter of 1 mm. While working in the laboratory, Russell discovered that pyrite could also form spherical droplets. And he suggested that the first complex organic molecules could have formed inside these simple pyrite structures.

Iron pyrite

Around this time, Wachtershauser began publishing his ideas, which involved a stream of hot, chemically enriched water flowing through minerals. He even suggested that pyrite was involved in this process.

Russell put two and two together. He proposed that hydrothermal vents in the deep sea, cold enough to allow pyrite structures to form, harbored precursors of Wachtershauser organisms. If Russell was right, life began at the bottom of the sea - and metabolism came first.

Russell compiled it all in a paper published in 1993, 40 years after Miller's classic experiment. It didn't generate the same media frenzy, but it was arguably more important. Russell combined two seemingly separate ideas - Wachtershauser metabolic cycles and Corliss hydrothermal vents - into something truly compelling.

Russell even offered an explanation for how the first organisms obtained their energy. That is, he understood how their metabolism might work. His idea was based on the work of one of the forgotten geniuses of modern science.

Peter Mitchell, Nobel laureate

In the 1960s, biochemist Peter Mitchell fell ill and was forced to resign from the University of Edinburgh. Instead, he set up a private laboratory on a remote estate in Cornwall. Isolated from the scientific community, he financed his work from a herd of dairy cows. Many biochemists, including Leslie Orgel, whose work on RNA we discussed in Part 2, thought Mitchell's ideas were completely ridiculous.

Several decades later, an absolute victory awaited Mitchell: in chemistry in 1978. He did not become famous, but his ideas are in every biology textbook today. Mitchell has spent his career figuring out what organisms do with the energy they get from food. Essentially, he was wondering how we all manage to stay alive every second.

He knew that all cells store their energy in one molecule: adenosine triphosphate (ATP). A chain of three phosphates is attached to adenosine. Adding a third phosphate requires a lot of energy, which is then locked into ATP.

When a cell needs energy - for example, when a muscle contracts - it breaks down the third phosphate into ATP. This converts ATP into adenoside phosphate (ADP) and releases stored energy. Mitchell wanted to know how a cell makes ATP in the first place. How does it store enough energy in ADP to attach the third phosphate?

Mitchell knew that the enzyme that produces ATP is located in the membrane. Therefore, he assumed that the cell pumps charged particles (protons) through the membrane, so many protons are on one side, but not on the other.

The protons then try to leak back through the membrane to balance the number of protons on each side - but the only place they can get through is the enzyme. The flow of flowing protons thus provided the enzyme with the energy needed to create ATP.

Mitchell first outlined his idea in 1961. He spent the next 15 years defending her from all sides until the evidence became irrefutable. We now know that the Mitchell process is used by every living thing on Earth. It's happening in your cells right now. Like DNA, it underlies life as we know it.

Russell borrowed from Mitchell the idea of ​​a proton gradient: the presence of a large number of protons on one side of the membrane and a few on the other. All cells require a proton gradient to store energy.

Modern cells create gradients by pumping protons across membranes, but this requires a complex molecular mechanism that simply could not appear on its own. So Russell took another logical step: life must have formed somewhere with a natural proton gradient.

For example, somewhere near hydrothermal springs. But it must be a special type of source. When the Earth was young, the seas were acidic, and acidic water has a lot of protons. To create a proton gradient, the source water must be low in protons: it must be alkaline.

Corliss's sources were unsuitable. Not only were they too hot, but they were also sour. But in 2000, Deborah Kelly of the University of Washington discovered the first alkaline springs.

Kelly had to work hard to become a scientist. Her father died while she was finishing high school, and she was forced to work to stay in college. But she managed and chose underwater volcanoes and scorching hot hydrothermal springs as her subject of interest. This couple brought her to the center of the Atlantic Ocean. At this point, the earth's crust cracked and a ridge of mountains rose from the seabed.

On this ridge, Kelly discovered a hydrothermal vent field that she called the “Lost City.” They were not like those discovered by Corliss. The water flowed out of them at a temperature of 40-75 degrees Celsius and was slightly alkaline. Carbonate minerals from this water clumped together into steep white "pillars of smoke" that rose from the sea floor like organ pipes. They look creepy and ghostly, but they are not: they are home to many microorganisms.

These alkaline vents fit perfectly into Russell's ideas. He firmly believed that life appeared in such “lost cities.” But there was one problem. As a geologist, he did not know enough about biological cells to convincingly present his theory.

Column of smoke from a “black smoking room”

So Russell teamed up with biologist William Martin. In 2003, they presented an improved version of Russell's previous ideas. And this is probably the best theory of the emergence of life at the moment.

Thanks to Kelly, they now knew that the rocks of the alkaline springs were porous: they were dotted with tiny holes filled with water. These tiny pockets, they theorized, acted as “cages.” Each pocket contained basic chemicals, including pyrite. Combined with the natural proton gradient from the sources, they were an ideal place to start metabolism.

Once life learned to harness the energy of spring waters, Russell and Martin say, it began to create molecules like RNA. Eventually, she created a membrane for herself and became a real cell, escaping from the porous rock into open water.

Such a plot is currently considered as one of the leading hypotheses about the origin of life.

Cells escape from a hydrothermal vent

In July 2016, he received a boost when Martin published a study reconstructing some of the details of "" (LUCA). This is an organism that lived billions of years ago and from which all existing life originated.

It is unlikely that we will ever find direct fossil evidence of the existence of this organism, but nevertheless we can make educated guesses about what it looked like and what it did by studying the microorganisms of our day. This is what Martin did.

He examined the DNA of 1,930 modern microorganisms and identified 355 genes that were shared by almost all of them. This strongly suggests that these 355 genes were passed down, through generations and generations, from a common ancestor - around the time when the last universal common ancestor lived.

These 355 genes include some for using the proton gradient, but not for generating it, as predicted by Russell and Martin's theories. Moreover, LUCA appears to have been adapted to the presence of chemicals such as methane, suggesting that it inhabited a volcanically active environment, such as a vent.

Proponents of the RNA world hypothesis point to two problems with this theory. One can be fixed; the other can be fatal.

Hydrothermal vents

The first problem is that there is no experimental evidence for the processes described by Russell and Martin. They have a step-by-step history, but none of these steps have been observed in the laboratory.

“People who believe that everything started with reproduction are constantly finding new experimental data,” says Armen Mulkijanyan. "The people who are pro-metabolism don't do that."

But that may be changing, thanks to Martin's colleague Nick Lane at University College London. He built an "origin of life reactor" that simulates the conditions inside an alkaline spring. He hopes to see metabolic cycles and maybe even molecules like RNA. But it's still early.

The second problem is the location of the sources in the deep sea. As Miller noted in 1988, long-chain molecules like RNA and proteins cannot form in water without helper enzymes.

For many scientists this is a fatal argument. “If you're good at chemistry, you won't be sold on the idea of ​​deep sea springs because you know the chemistry of all those molecules is incompatible with water,” Mulkijanian says.

Still, Russell and his allies remain optimistic.

It is only in the last decade that a third approach has come to the fore, backed by a series of unusual experiments. It promises something that neither the RNA world nor hydrothermal vents have been able to achieve: a way to create an entire cell from scratch. More on this in the next part.

The Proterozoic eon is the longest era in the history of the Earth. It began 2.5 billion years BC. e. and ended 541 million years BC. During this time, the Earth turned from an oxygen-free planet of microbes and prokaryotes into an oxygen-rich planet of multicellular organisms.

1. The Great Oxygen Event

Biologist Alexander Markov about the oxygen crisis, greenhouse gases and the emergence of eukaryotes

In the early Proterozoic, over several hundred million years, there was a fairly rapid increase in the amount of free oxygen in the atmosphere and hydrosphere. The prerequisites for this arose at the end of the Archean era. About 2.45 billion years ago, the so-called great oxygen event began, when oxygen levels rose from almost 0% to about 1% of current oxygen levels.

Why do geologists believe that oxygen levels increased during this period? This is indicated by a number of signs, for example the ratio of sulfur isotopes in sedimentary rocks. Apparently, volcanic gases entering the atmosphere, if there is no oxygen in this atmosphere, participate in certain photochemical reactions, during which fractionation of sulfur isotopes occurs and a changed isotopic composition is obtained. But when oxygen appears in the atmosphere, these processes stop. And at the beginning of the Proterozoic, these processes just stopped.

A. Markov. 2010. The Birth of Complexity. Evolutionary biology today: unexpected discoveries and new questions. M.: Astrel: CORPUS.

2. Crisis in microbial communities

There are also a number of minerals in sedimentary rocks that can only form in anoxic conditions—they oxidize in the presence of oxygen. And such unoxidized minerals are also found in rocks before the beginning of the Proterozoic, and then they are no longer formed.

In those days, all microbes were adapted to life in oxygen-free conditions, and oxygen is a strong oxidizing agent, it is actually a strong poison, from which it is necessary to protect itself in some special way. The increase in oxygen content in the atmosphere was supposed to cause some kind of crisis in microbial communities, which then constituted virtually the only form of life on Earth.

E. Kunin. 2014. Logic of chance. On the nature and origin of biological evolution. M.: Tsentrpoligraf.

3. Causes of the Huronian glaciation

At the same time, the first major glaciation on Earth occurred - it is called the Huronian.
The reasons for the onset of warm or cold eras in the history of the Earth, apparently, were quite diverse. But one of the important reasons for their occurrence is the amount of greenhouse gases in the atmosphere such as CO2, methane, water vapor. However, the development of life affects the content of carbon dioxide, and then methane.

7 facts about the stages of abiogenesis and the problem of the origin of life on Earth

Why does glaciation occur at a time when oxygen levels increase? First, for oxygen levels to increase, carbon must be removed from the cycle. During the biogenic carbon cycle, photosynthetic organisms remove carbon dioxide from the atmosphere and convert it into organic matter. Then heterotrophic organisms that feed on finished organic matter oxidize this organic matter with the help of oxygen released by photosynthetics and convert it back into CO2. Thus, photosynthetics release oxygen and take carbon from the atmosphere, and heterotrophic organisms, on the contrary, take oxygen and release carbon.

If the activity of photosynthetics is not fully balanced by the activity of heterotrophs, that is, the consumption of organic matter lags behind the production of organic matter, then this excess organic matter will be buried in the earth's crust. This leads to the fact that carbon is gradually removed from the atmosphere, the CO2 content in the atmosphere drops, the greenhouse effect weakens, and it becomes colder.

At the moment of rapid increase in oxygen content, glaciation occurred. In addition, the released oxygen could oxidize methane, which, apparently, was still present in significant quantities in the atmosphere. And methane is also a very strong greenhouse gas.

K. Eskov. 2000. History of the Earth and life on it. M.: MIROS – MAIK “Nauka-Interperiodika”.

4. The appearance of the first eukaryotic cell

Towards the end of the first glaciation and the end of the period of rapid growth of oxygen, the most important event in the evolution of earthly life occurs - the first eukaryotic cell appears.
Until now, only prokaryotes have lived on Earth - these are bacteria that do not have a cell nucleus and other membrane structures or organelles. In the cell they do not have mitochondria, plastids and any other complexities. Even at the dawn of cellular life, prokaryotes were divided into two large groups: bacteria and archaea (formerly they were called archaebacteria).

Eukaryotes are the third large group of living organisms that appear for the first time in the early Proterozoic, most likely in connection with the increase in oxygen. Eukaryotes are organisms that have a cell nucleus, mitochondria, and are initially adapted specifically to an oxygen environment. Mitochondria are organelles of a eukaryotic cell that are precisely needed for oxygen respiration, since they use oxygen to oxidize organic matter and produce energy. It was the eukaryotic cell that became the basis for the development of all complex forms of multicellular life on our planet: animals, plants, fungi.

Prokaryotes have tried several times and continue to sometimes try to transition to multicellularity, but these attempts do not go far for a number of technical reasons. For example, in a multicellular organism, different cells perform different functions, and accordingly, different genes work in different tissues. The genome of a eukaryotic organism contains all the genes necessary for the formation of all tissues of a multicellular organism, but in each tissue only part of them works - the one that is needed. In order for this to work, a very complex effective system of gene regulation is needed. And for this it is very important to have a cell nucleus in which genes are isolated from the violent biochemical processes occurring in the cytoplasm. There it is possible to develop effective systems for regulating gene function, which prokaryotes do not have, since they have simpler regulatory systems.

5. Structure of a eukaryotic cell

Some researchers believe that the emergence of the eukaryotic cell is the most key event in the evolution of life on Earth. And maybe it only happened once, since all modern eukaryotes apparently descend from a single ancestor. Perhaps there were some other attempts at such evolutionary experiments, but they did not survive to this day.

7 facts about the most basic system of the body

The eukaryotic cell is chimeric in nature. It appeared as a natural result of the evolution of Precambrian microbial communities, which constituted the main form of life in the Archean era and continued to dominate in the Proterozoic. If you look at what proteins a eukaryotic cell is made of, you get a very interesting thing. The central system of the eukaryotic cell, associated with DNA replication, work with genetic information, and protein synthesis, is served by proteins similar to archaeal proteins. But on the periphery - metabolism, receptors, interaction with the external environment, signal transmission - proteins similar to bacterial proteins dominate. That is, a eukaryotic cell has an archaeal core and a bacterial periphery. In other words, in the process of evolution, a certain merger occurred, a combination of the genomes of representatives of two great branches of prokaryotes.

N. Lane. 2014. Ladder of life. Ten greatest inventions of evolution. M.: AST: CORPUS.

6. Adaptation of ancient microbes to oxygen

During the oxygen crisis, when ancient microbes had to adapt to a new poison that had appeared - to free oxygen, some archaea, apparently, actively borrowed foreign genes, including bacterial ones, and as a result acquired a number of bacterial properties. The result was a kind of chimeric unicellular organism capable, for example, of ingesting other prokaryotes. Perhaps they turned to predation, perhaps they merged with other cells to exchange genetic material. Most likely, sexual reproduction was formed at this stage. Another key feature of eukaryotes is true sexual reproduction, associated with the fusion of germ cells and reduction division (meiosis).

This chimeric organism at some point ingested bacteria, representatives of the alpha-proteobacteria group, which became the ancestors of mitochondria - organelles for oxygen respiration. Thus, this organism, having acquired such a symbiont, protected itself from the toxic effects of oxygen. After this, oxygen was utilized by these symbiotic mitochondria. The free-living ancestors of mitochondria learned to deal with oxygen and invented a system of oxygen respiration. Probably, at first they simply burned organic matter to neutralize oxygen, and then they learned to extract benefit from this in the form of energy.

7. Development of the fauna of unicellular eukaryotes in the ocean

Biologist Evgeny Kunin on the view of genes from the point of view of statistical physics, a change in the evolutionary paradigm and the connection of cosmology with the origin of life

As ancient organisms adapted to oxygen, microbes evolved into proto-eukaryotic cells with mitochondria. At some point, a nucleus appeared in the cell. There is a theory that the nucleus appeared as a result of symbiosis with viruses. Scientists have discovered very large viruses, which in a number of properties resemble the cell nucleus, from which we can conclude that perhaps the cell nucleus was also acquired during evolution through symbiosis.

At the beginning of the Proterozoic, two billion years ago, the eukaryotic cell appears. The first eukaryotes were unicellular, heterotrophs, that is, they consumed ready-made organic matter. Somewhat later, some eukaryotes entered into symbiosis with cyanobacteria and swallowed them. Thus, these cyanobacteria gave rise to plastids, which led to the emergence of plants.

During the Middle Proterozoic, we already see remains of single-celled eukaryotes in the fossil record. Gradually, phytoplankton developed from eukaryotic unicellular algae. And at the same time, apparently, the first multicellular algae begin to appear.

Below is a list of 10 amazingly hardy creatures that are able to survive in conditions that no other creature can survive.

Jumping spiders are a family of spiders containing more than 500 genera and about 5,000 species, which is approximately 13% of all spider species. Jumping spiders have very good eyesight and are also capable of jumping distances much greater than their body size. These active daytime hunters are widely distributed throughout the world, including deserts, rainforests and mountains. In 1975, a representative of this family was discovered even at the peak highest mountain in the world- Everest.

Ninth on the list is the Giant Kangaroo Hopper, a critically endangered rodent found only in California, USA. Its lifespan is 2–4 years. Throughout its short life, a rodent is able to live without a single drop of drinking water. They get the moisture they need to survive from food, which is mainly seeds.

Pompeii worm (Alvinella pompejana)

The Pompeii worm is a species of deep-sea worm that was discovered in the early 1980s in the northeastern Pacific Ocean. These pale gray worms can grow up to 13 cm in length. The Pompeii worm remained unstudied for a long time, since when trying to bring it to the surface it inevitably died. This is explained by the fact that during the ascent, the usual pressure for the Pompeian worm decreased. However, recently, French scientists, with the help of special equipment that maintained the necessary environmental pressure, managed to deliver several individuals to the laboratory alive and healthy. It turned out that these worms are able to survive at fairly high temperatures. The optimal temperature for them is 42 °C, but when heated to 50-55 °C, the worm died.

Greenland sharks are among the largest and least studied sharks in the world. They live in the waters of the North Atlantic at temperatures ranging from 1–12 °C and depths of up to 2,200 meters, where the approximate pressure is 220 atmospheres or about 9,700 kilograms per square centimeter. Greenland polar sharks are very slow, their average speed is 1.6 km/h, and their maximum speed is 2.7 km/h, hence the second name “sleeping sharks”. They feed on almost anything they can catch. The largest individuals of these sharks can reach up to 7.3 m and weigh up to 1.5 tons, but the average length varies from 2.44 to 4.8 m, and the average weight does not exceed 400 kg. Their exact lifespan is unknown, although it is theorized that they can live up to 200 years. Is one of longest living animals on the planet.

For decades, scientists believed that only single-celled organisms could survive at very great depths underground due to high pressure, lack of oxygen and extreme temperatures. However, after Gaetan Borgoni and Tallis Onstott discovered these multicellular organisms in ore at the Beatrix and Prefontaine gold mines in South Africa in 2011 at depths of 0.9 km, 1.3 km and 3.6 km below the surface of the Earth , the hypothesis was refuted. The discovered worms, 0.52–0.56 mm long, lived in small accumulations of water at a temperature of 48 °C. Halicephalobus mephisto may be the deepest living multicellular organisms on the planet.

Some species of frogs were found literally frozen, but with the onset of spring they “thawed” and continued their life activities. There are five known species of such frogs in North America. The most common is the tree frog, which simply hides under leaves and freezes to overwinter. The most interesting thing is that during such hibernation the frog’s heart stops.

Many people know that the deepest point of the World Ocean, as well as least explored place on the planet is the Mariana Trench, 11 km deep, where the pressure is approximately 1072 times normal atmospheric pressure. In 2011, scientists using a high-resolution camera and a modern bathyscaphe discovered giant amoebae at a depth of 10,641 meters, which are several times larger (10 cm) than their relatives.

Bdelloidea

Bdelloidea is a rotiferous animal that lives in fresh water, moist soil and wet moss throughout the world. They are microscopic organisms, the length of which does not exceed 150–700 microns (0.15–0.7 mm). They are invisible to the naked eye, but when viewed through a magnifying glass, the Bdelloidea animal can be seen as small white dots. They are able to survive in harsh, dry conditions thanks to anhydrobiosis, a condition that allows this animal's body to quickly dehydrate and thus resist desiccation. As it turned out, the animal can stay in this state for up to 9 years, waiting for favorable conditions to return. Interestingly, since the discovery, not a single male representative has yet been found.

Cockroaches

A popular myth states that in the event of a nuclear war, the only survivors on Earth will be cockroaches. It is not surprising because they are considered one of the hardiest insects, capable of living without food and water for one month. And the lethal dose of radiation for these insects is 6-15 times greater than, for example, for humans. However, they are still not as resistant to radiation as, for example, fruit flies. Found fossils of cockroaches show that they lived 295-354 million years ago, thus ahead of dinosaurs, although these cockroaches certainly differed in appearance from modern cockroaches.

Tardigrades are microscopic animals first described by the German pastor Johann August Ephraim Goeze in 1773. They are distributed throughout the world, including the ocean floor and polar regions at the equator. Most often they inhabit lichen and moss cushions. The body size of these translucent invertebrates is 0.1-1.5 mm. Tardigrades have incredible endurance. Scientists have found that tardigrades are able to survive for several minutes at a temperature of 151 °C, and can also live for several days at a temperature of minus 200 °C. They were also exposed to radiation of 570,000 roentgens and approximately 50% of the tardigrades remained alive (for humans, a lethal dose of 500 roentgens). They were also placed in a special high-pressure chamber filled with water and exposed to 6,000 atmospheres, which is 6 times more than the pressure at the bottom of the Mariana Trench - the animals remained alive. There is a known case when moss taken from the desert about 120 years after it dried up was placed in water, and one of the tardigrades that were in it showed signs of life.