How many types of life on earth. Classification of living organisms on earth. Natural conditions affecting the abundance, disappearance and emergence of organisms
Life on Earth, thanks to natural selection and evolutionary biology, is incredibly diverse. It can be found everywhere: from the tops of volcanic islands to the dark depths of the earth's crust.
Assessing the biodiversity of our planet
Now the researchers have taken on the Herculean task: they are going to count how many different types of living organisms exist on our planet. Their conclusion is that in a microbe-dominated world, there are more than a trillion different kinds of living beings. Incredibly, this means that only one thousandth of one percent of all species has actually been identified.
Previous estimates of all kinds can be called arbitrary. However, a new study by the US National Academy of Sciences demonstrates a universal mathematical law that allowed the authors to come up with the most reliable biodiversity research method to date.
Just as mapping the Milky Way and other galaxies helps us understand and appreciate our place in the universe and its history, understanding the vast diversity of species will help us understand and appreciate our place in evolution and life on Earth. 
Gaps in modern classification
Databases for all the kingdoms of life, from bacteria to animals and from archaea to plants, already exist, but they are incomplete. The team of scientists initially wanted to see if the same biodiversity patterns exist in the microbial world as they do in the animal and plant kingdoms. To do this, they collected the most up-to-date databases into one large collection, the largest of its kind.
The efforts of scientists have shown that about 5.6 million species have been classified, but this is clearly not all. In particular, they believe that microbial life databases have many gaps that need to be filled. With more adventurous search methods and better equipment, new types of microbes could be seen in the most unlikely places, scientists say. 
For example, in a recent study, a water sample from a fairly average flow contained 35 new groups. This means that the tree of life of microbes that we knew before changed in an instant.
Diversity of microbial life
In order to estimate how many types of microorganisms exist on Earth, scientists turned to scaling laws, mathematical relationships. They describe the relationship between two quantities, such as species and abundance. The researchers realized that the law of similarity, which also applies to a wide range of fields, including economics, applies to all forms of life, including the microbiome. 
Using this universal law of similarity, they could not only predict which types of microorganisms would dominate in different environments, but also confirm that there are over a trillion different types of microorganisms on Earth. This makes them the most dominant life form on the planet, far ahead of the relatively small variety of animals and plants.
Scaling law
Using a known set of data, the universal scaling law can be applied to estimate how many species of living organisms exist in different ecosystems on the planet. Dominance is a measure of how common a species is in a variety of ecosystems, whether we are talking about microbes or large species of organisms.
The research conducted by scientists allows us to understand how much we still do not know about the world in which we live. Microorganisms drive the natural ecosystems of the Earth, so understanding all the information about them is a paramount task for researchers. Everything literally depends on them. 
A living organism is the main subject studied by such a science as biology. It is made up of cells, organs and tissues. A living organism is one that has a number of characteristic features. He breathes and eats, stirs or moves, and also has offspring.
Life Science
The term "biology" was introduced by J.B. Lamarck - a French naturalist - in 1802. At about the same time and independently of him, the German botanist G.R. gave such a name to the science of the living world. Treviranus.
Numerous branches of biology consider the diversity of not only currently existing, but also already extinct organisms. They study their origin and evolutionary processes, structure and functioning, as well as individual development and links with environment and with each other.
Sections of biology consider particular and general patterns that are inherent in all living things in all properties and manifestations. This applies to reproduction, and metabolism, and heredity, and development, and growth.
The beginning of the historical stage
The first living organisms on our planet differed significantly in their structure from those currently existing. They were incomparably simpler. Throughout the entire stage of the formation of life on Earth, He contributed to the improvement of the structure of living beings, which allowed them to adapt to the conditions of the surrounding world.
At the initial stage, living organisms in nature ate only organic components that arose from primary carbohydrates. At the dawn of their history, both animals and plants were the smallest single-celled creatures. They were similar to today's amoebas, blue-green algae and bacteria. In the course of evolution, multicellular organisms began to appear, which were much more diverse and more complex than their predecessors.
Chemical composition
A living organism is one that is formed by molecules of inorganic and organic substances.
The first of these components is water, as well as mineral salts. found in the cells of living organisms are fats and proteins, nucleic acids and carbohydrates, ATP and many other elements. It is worth noting the fact that living organisms in their composition contain the same components that objects have. The main difference is in the ratio of these elements. Living organisms are those ninety-eight percent of whose composition is hydrogen, oxygen, carbon and nitrogen.
Classification
The organic world of our planet today has almost one and a half million diverse animal species, half a million plant species, and ten million microorganisms. Such diversity cannot be studied without its detailed systematization. The classification of living organisms was first developed by the Swedish naturalist Carl Linnaeus. He based his work on the hierarchical principle. The unit of systematization was the species, the name of which was proposed to be given only in Latin.
The classification of living organisms used in modern biology, indicates family ties and evolutionary relationships of organic systems. At the same time, the principle of hierarchy is preserved.
The totality of living organisms that have a common origin, the same chromosome set, adapted to similar conditions, living in a certain area, freely interbreeding and producing offspring capable of reproduction, is a species.
There is another classification in biology. This science divides all cellular organisms into groups according to the presence or absence of a formed nucleus. it
The first group is represented by nuclear-free primitive organisms. A nuclear zone stands out in their cells, but it contains only a molecule. These are bacteria.
The true nuclear representatives of the organic world are eukaryotes. The cells of living organisms of this group have all the main structural components. Their core is also clearly defined. This group includes animals, plants and fungi.
The structure of living organisms can be not only cellular. Biology studies other forms of life. These include non-cellular organisms, such as viruses, as well as bacteriophages.
Classes of living organisms
In biological systematics, there is a rank of hierarchical classification, which scientists consider one of the main ones. He distinguishes classes of living organisms. The main ones include the following:
bacteria;
Animals;
Plants;
Seaweed.
Description of classes
A bacterium is a living organism. It is a unicellular organism that reproduces by division. The cell of a bacterium is enclosed in a shell and has a cytoplasm.
Mushrooms belong to the next class of living organisms. In nature, there are about fifty thousand species of these representatives of the organic world. However, biologists have studied only five percent of their total. Interestingly, fungi share some characteristics of both plants and animals. An important role of living organisms of this class lies in the ability to decompose organic material. That is why mushrooms can be found in almost all biological niches.
The animal world boasts a great diversity. Representatives of this class can be found in areas where, it would seem, there are no conditions for existence.
Warm-blooded animals are the most highly organized class. They got their name from the way they feed their offspring. All representatives of mammals are divided into ungulates (giraffe, horse) and carnivores (fox, wolf, bear).
Representatives of the animal world are insects. There are a huge number of them on Earth. They swim and fly, crawl and jump. Many of the insects are so small that they are not even able to withstand water tension.
Amphibians and reptiles were among the first vertebrates that came to land in distant historical times. Until now, the life of representatives of this class is connected with water. So, the habitat of adults is dry land, and their breathing is carried out by lungs. The larvae breathe through gills and swim in the water. Currently, there are about seven thousand species of this class of living organisms on Earth.
Birds are unique representatives of the fauna of our planet. Indeed, unlike other animals, they are able to fly. Almost eight thousand six hundred species of birds live on Earth. Representatives of this class are characterized by plumage and oviposition.
Fish belong to a huge group of vertebrates. They live in water bodies and have fins and gills. Biologists divide fish into two groups. These are cartilage and bone. Currently, there are about twenty thousand different types of fish.
Within the class of plants there is its own gradation. Representatives of the flora are divided into dicots and monocots. In the first of these groups, the seed contains an embryo consisting of two cotyledons. You can identify representatives of this species by the leaves. They are pierced with a mesh of veins (corn, beets). The embryo has only one cotyledon. On the leaves of such plants, the veins are arranged in parallel (onions, wheat).
The class of algae includes more than thirty thousand species. These are water-dwelling spore plants that do not have vessels, but have chlorophyll. This component contributes to the implementation of the process of photosynthesis. Algae do not form seeds. Their reproduction occurs vegetatively or by spores. This class of living organisms differs from higher plants in the absence of stems, leaves and roots. They have only the so-called body, which is called the thallus.
Functions inherent in living organisms
What is fundamental for any representative of the organic world? This is the implementation of the processes of energy and matter exchange. In a living organism, there is a constant transformation of various substances into energy, as well as physical and chemical changes.
This function is an indispensable condition for the existence of a living organism. It is thanks to metabolism that the world of organic beings differs from the inorganic. Yes, in inanimate objects there are also changes in matter and the transformation of energy. However, these processes have their fundamental differences. The metabolism that occurs in inorganic objects destroys them. At the same time, living organisms without metabolic processes cannot continue their existence. The consequence of metabolism is the renewal of the organic system. The cessation of metabolic processes entails death.
The functions of a living organism are varied. But all of them are directly related to the metabolic processes taking place in it. This can be growth and reproduction, development and digestion, nutrition and respiration, reactions and movement, excretion of waste products and secretion, etc. The basis of any function of the body is a set of processes of transformation of energy and substances. Moreover, this is equally relevant to the capabilities of both tissue, cell, organ, and the whole organism.
Metabolism in humans and animals includes the processes of nutrition and digestion. In plants, it is carried out with the help of photosynthesis. A living organism in the implementation of metabolism supplies itself with the substances necessary for existence.
An important distinguishing feature of the objects of the organic world is the use of external energy sources. An example of this is light and food.
Properties inherent in living organisms
Any biological unit has in its composition separate elements, which, in turn, form an inextricably linked system. For example, in the aggregate, all organs and functions of a person represent his body. The properties of living organisms are diverse. In addition to a single chemical composition and the possibility of implementing metabolic processes, the objects of the organic world are capable of organization. Certain structures are formed from the chaotic molecular movement. This creates a certain order in time and space for all living things. Structural organization is a whole complex of the most complex self-regulating processes that proceed in a certain order. This allows you to maintain the constancy of the internal environment at the required level. For example, the hormone insulin reduces the amount of glucose in the blood when it is in excess. With a lack of this component, it is replenished by adrenaline and glucagon. Also, warm-blooded organisms have numerous mechanisms of thermoregulation. This is the expansion of skin capillaries, and intense sweating. As you can see, this is an important function that the body performs.
The properties of living organisms, characteristic only for the organic world, are also included in the process of self-reproduction, because the existence of any has a time limit. Only self-reproduction can sustain life. This function is based on the process of formation of new structures and molecules, due to the information that is embedded in DNA. Self-reproduction is inextricably linked with heredity. After all, each of the living beings gives birth to their own kind. Through heredity, living organisms transmit their developmental features, properties and signs. This property is due to constancy. It exists in the structure of DNA molecules.
Another property characteristic of living organisms is irritability. Organic systems always react to internal and external changes (impacts). As for irritability human body, then it is inextricably linked with the properties inherent in muscle, nervous, and glandular tissue. These components are able to give impetus to the response after muscle contraction, the departure of a nerve impulse, as well as the secretion of various substances (hormones, saliva, etc.). And if a living organism is deprived of the nervous system? The properties of living organisms in the form of irritability are manifested in this case by movement. For example, protozoa leave solutions in which the salt concentration is too high. As for plants, they are able to change the position of the shoots in order to absorb light as much as possible.
Any living system can respond to the action of a stimulus. This is another property of the objects of the organic world - excitability. This process is provided by muscle and glandular tissues. One of the final reactions of excitability is movement. The ability to move is a common property of all living things, despite the fact that outwardly some organisms are deprived of it. After all, the movement of the cytoplasm occurs in any cell. Attached animals also move. Growth movements due to an increase in the number of cells are observed in plants.
Habitat
The existence of objects of the organic world is possible only under certain conditions. Some part of space invariably surrounds a living organism or a whole group. This is the habitat.
In the life of any organism, organic and inorganic components of nature play a significant role. They have an effect on him. Living organisms are forced to adapt to existing conditions. So, some of the animals can live in the Far North at very low temperatures. Others are able to exist only in the tropics.
There are several habitats on planet Earth. Among them are:
Land-water;
ground;
soil;
Living organism;
Ground-air.
The role of living organisms in nature
Life on planet Earth has been around for three billion years. And during all this time organisms developed, changed, settled and at the same time affected their environment.
The influence of organic systems on the atmosphere caused the appearance of more oxygen. At the same time, the volume of carbon dioxide. Plants are the main source of oxygen production.
Under the influence of living organisms, the composition of the waters of the World Ocean has also changed. Some rocks are of organic origin. Minerals (oil, coal, limestone) are also the result of the functioning of living organisms. In other words, the objects of the organic world are a powerful factor that transforms nature.
Living organisms are a kind of indicator indicating the quality of the human environment. They are connected by complex processes with vegetation and soil. With the loss of at least a single link from this chain, an imbalance of the ecological system as a whole will occur. That is why it is important for the circulation of energy and substances on the planet to preserve all the existing diversity of representatives of the organic world.
Specialists of the largest project to study the World Ocean Census of Marine Life - "Census of Marine Life" - published the latest data on calculations of the number of species of living organisms on Earth. The most accurate calculations showed that
6.6 million species live on land and another 2.2 million plow the ocean depths.
“The question of how many species of living organisms exist on Earth has been of interest to scientists for centuries. We answered it based on data on the distribution and distribution of species, which is especially important now that human activity has significantly increased the rate of extinction of species. Many of them disappear from the face of the Earth even before we know about their existence, place in food chains and potential benefits that they bring to nature and man,” says Camilo Mora, lead author of the work from the University of Hawaii (USA) and the University of Halifax (Canada).
Previous estimates of Earth's "population" have been much more vague:
figures were given both in 3 million and in 100 million species.
However, the narrowing of the interval does not mean that everything on Earth is already known. 86% of the inhabitants of the land and 91% of the inhabitants of the seas have yet to be discovered, described and catalogued.
“This work shortens the most total number species that must be known to describe our biosphere. If we don't know (at least in order of magnitude) the number of people in a country, how can we plan for the future? The same is true for biodiversity. Humanity has committed itself to protecting species from extinction, but until now we did not know how many of these species there are,” says Boris Worm, co-author of the work.
The international Red Book now includes 59,508 species, 19,625 of which are classified as endangered. This means that the most detailed document on the protection of species on Earth covers only 1% of the total "population".
How did scientists manage to count undiscovered species? To do this, they had to collect all the principles of taxonomy - the science of classification. In 1758, the Swedish scientist Carl Linnaeus created a classification system that now bears his name and helps scientists group species. Today, 253 years later, about a million terrestrial and 250,000 marine species have been described and catalogued.
Professor Mora and his colleagues calculated the total number of species based precisely on the taxonomy.
They studied the numerical structure of taxa, which form a pyramid-like hierarchical structure, narrowing from species, genera and families to subkingdoms and kingdoms.
By categorizing the 1.2 million species known today, the researchers found a significant numerical relationship between the most completed taxonomic levels and the total number of species. Using the developed method, scientists independently calculated the number of species in the most fully studied groups - mammals, fish and birds. The obtained data confirmed the reliability of the method.
Applying this approach to all eukaryotes (organisms containing a formed nucleus in cells), scientists obtained the following numbers for their main groups:
- 7.77 million animal species (953434 described and cataloged);
- 298 thousand plant species (215644 are described and cataloged);
- 611 thousand species of mushrooms (described and cataloged 43271);
- 36.4 thousand species of unicellular animals (8118 are described and catalogued).
|
|||||||||||||||||||||
|
How many species are on the planet?
The result of almost three hundred years of work of taxonomists - zoologists, botanists, microbiologists - is more than a million found and described species of living creatures that inhabit the Earth. Findings of new species do not stop, every year taxonomists describe dozens and hundreds of new species. How to estimate how many species have not yet been found? Different calculation methods give very different results. One of possible ways solution to this problem is the analysis of taxonomic diversity on different levels hierarchical classification of living things.
How many species of animals, plants, fungi and microorganisms live with us on Earth? The question seems simple, but there is no exact answer to it. Every year, taxonomists describe new, previously unknown species of not only protozoa or insects, but also vertebrates: amphibians, reptiles, fish, and sometimes even mammals. All experts agree that the number of not yet known, not found and not described species exceeds the number of species known. The currently accepted figure - about 1.2 million species known to science - is only a fraction of the real diversity of life on the planet. The problem is to determine how many species have not yet been found.
Another attempt to answer this question was made by an international group of researchers (Mora et al., 2011). Another - because from time to time different experts offer their own assessments of the species diversity of the Earth. These estimates differ by two orders of magnitude - from 3 to 100 million species, depending on the method of counting: since it is impossible to directly enumerate all the species, most of which have not yet been discovered, the only way left is to find some kind of rule that will allow you to go from a known number species to the general.
Attempts to discover universal patterns for all living things or for individual taxonomic groups have been made repeatedly. The simplest relationship "number of species - area" works satisfactorily only in homogeneous biotopes, but does not take into account their mosaic nature. An estimate of the rate of increment of new species by the time of description makes it possible to judge the limiting number of species for small, rather well-studied taxa; in poorly studied groups, the number of taxonomic descriptions does not decrease with time, and the graph goes to infinity. There were attempts to use dependencies based on private observations, for example, on the ratio of the number of beetles to the number of trees in a tropical forest (5: 1), on the ratio of the number of known species to the number of new ones found in a local area, etc. However, particular patterns, with extrapolations to other groups of organisms or other regions lead to large errors. The rules that apply to some groups of organisms are not always suitable for others. This is where the scatter in estimates comes from.
In search of a more universal regularity, the authors of the article under discussion turned to the ratio of the diversity of taxa in their hierarchy. It is assumed that on large data sets the ratio of the number of taxa in the series "type - class - order - family - genus - species" is more or less constant. It must be said that the approach itself is not new: back in 1976, A. N. Golikov noted that for several very different groups organisms (ciliates, mollusks, mammals) in semilogarithmic coordinates, the relationship between taxon rank and diversity is linear, and the slopes of the straight lines are close for different groups of organisms. Richard Warwick proposed a quantitative index based on the ratio of the number of taxa of different ranks (taxonomic distinctness index) and used it to identify possible sources of origin for local faunas of hypersaline lakes (Clark and Warwick, 1998, 1999; Warwick et al., 2002 ).
To assess the total species diversity of the planet, the ratio of the number of taxa of different ranks can be used if the assumption is correct that all or almost all taxa of higher ranks have already been counted, and only the number of species is unknown. The authors tested this assumption using two datasets, the Catalog of Life and The World's Register of Marine Species. The first of them contains about 1.24 million marine and terrestrial species, the second - 194 thousand only marine organisms, mostly mentioned in the first catalog.
Since the date of its description is known for each taxon from phylum to species, it is easy to construct the dependence "cumulative number of taxa - time" and, using various methods of approximation, find the limit to which this number tends. As can be seen from fig. 2, A-F, in the animal kingdom, graphs for higher taxa (from types to families) are close to saturation, and by extrapolating them, one can find the limit of the function - the expected total number of taxa of a given rank. This does not work only for species - the graph of the accumulated number of species over the past century and a half is linearly directed to infinity.
To find a limit to the number of species, the authors calculated the relationship between the number of taxa of the highest ranks and the number of species. Different approximation models for the higher data taxa give slightly different results, so the authors took the average of the obtained results and obtained a family of lines that coincided rather closely with each other (Fig. 1, G). The first five points on the graph are the limits of the functions that describe the increase in the number of taxa over time, and the sixth point is the expected number of animal species on the planet.
Interesting data are given in additional materials to the article under discussion. It follows from them that the proposed method gives satisfactory results for eukaryotes (best for the animal kingdom, worst for protozoa), but is absolutely inapplicable to prokaryotes, in which the accumulation curves of higher taxa are very far from saturation.
The authors estimated the diversity of the planet's eukaryotes at 8.74 (±1.3) million species. Of these, about 7.7 million animals, 298,000 plants, 611,000 fungi and 36,400 protozoa (Fig. 3). Thus, today we know "by sight" about 14% of the species that live on Earth. The eukaryotic fauna of the Ocean has been studied by 9%.
Scientists do not know the exact number of living species that exist in the world. In fact, after several centuries of classification of living things, scientists have managed to document only 14% of living species. The remaining 86% of the species that exist have yet to be discovered.
According to the latest estimates, there are about 8.7 million species on planet Earth. As the rate of extinction has increased, thousands of living species have become extinct without being documented, and we will never know of their existence. This is just one of the reasons why it is difficult to estimate the exact number of species living on Earth.
How many species are there on Earth?
To date, scientists have been able to register about 1.2 million species. However, the total number of species that exist is approximately 8.7 million. Unfortunately, due to extinction, we will never be able to know about all the species.
Extinction problem
While discovering new species is the easier part of documenting living things, classifying them is the hard part. Researchers must match specimens with available specimens, analyze their anatomy and DNA, and find their classification lineage. This process takes a long time and often becomes unreliable. The biggest problem with species classification is extinction. Extinction takes away key components of the classification chain, meaning that scientists may encounter unrelated species.
As of March 2018, the IUCN Red List has listed thousands of animal species as critically endangered, meaning that the ability to further classify species may be at risk. This leads to the fact that the exact number of species will never be available to us.
Difficulties in counting
The size of the animal often makes it difficult to detect and count the species. In most cases, the smaller the animal, the harder it is to find and count them.
Uncertainties in counting, terminology and scientific classification of species. How are individual animal species identified? It's not as easy as it seems at first glance. Some classifications place birds in the reptile group, thus raising the number of reptiles by as much as 10,000 species.
Despite these problems, it is useful to have an idea of how many species of animals live on our planet. This knowledge gives us the perspective of a balanced study, so as not to let certain groups of animals slip out of our sight.
If we divided all animals into two groups, and animals, then about 97% of all species would be invertebrates. They include animals that do not have a skeleton, such as sponges, coelenterates, mollusks, annelids, flatworms, arthropods, and insects. Of all the invertebrates, insects are by far the most numerous group. There are many types of insects that we have yet to discover. Vertebrates represent the remaining 3% of all species and include the classes of animals that are most familiar to us: amphibians, reptiles, birds, fish, and mammals.
The list below contains rough estimates of the number of species in various groups of animals.
Animals: 3-30 million species:
+ Invertebrates: 97% of all known species:
- : 10000 kinds;
Intestinal: 8,000-9,000 species;
