An employee of the Zoom Museum of Moscow State University proposed a new classification of living beings

Alexander Martynov brought out the concept of distinguishing organisms, similar to the theories of scientists of the 19th-20th centuries

Instead of the concept of “species”, the broader term MOD (Multilevel Organismal Diversity) or the concept of multilevel diversity of organisms, emphasizing a greater number of distinctive features in different species of living beings, was proposed by the employees of the Zoological Museum of Moscow State University and the Institute of Developmental Biology of the Russian Academy of Sciences. Their work on the subject was published recently in a well-known Cambridge University book series.

It so happened that biologists have not yet found a universal definition for the term “species”. And this despite the fact that at different times more than 30 different interpretations were proposed.

For a long time the so-called biological concept of species ruled the roost. She attributed both individuals to the same species if, when mating, they could produce fertile offspring. For example, a horse can be crossed with a donkey – they will have a mule, but he will not give offspring. So the horse and donkey are not the same species. This concept was strong even in the middle of the last century, before the advent of molecular genetics. However, it is now obsolete, as examples of fertile offspring have been found in nature between two seemingly different species, such as a wolf and a dog.

Today, biologists rely mainly on the morphological method of defining one species – according to similar features of the structure of animals (for example, by the number of legs, outgrowths on the back, the shape of the skeleton), as well as on the method of molecular difference between species that appeared 10 years ago. That is, now they are looking not only at external similarities, but also at the structure of the DNA of compared living beings. Deepening into the genetic level showed that in the animal world everything is much more complicated: where morphologists distinguish 3-4 types of worms, geneticists can find 9-10! This phenomenon has been termed “hidden biodiversity”. For example, before everyone thought that the clouded leopard was one species. But after looking at the sequence of the genomes of its various representatives, they found out that there are three different types of smoky leopard. Therefore, for the last 3-4 years, some scientific journals no longer accept papers that rely only on morphological features in determining the species.

So why is there a need to introduce yet another theory? The thing is, scientists say, that so far there is difficulty in determining the similarity of two individual creatures, even by the genome. It is clear that one to one in two different creatures, it cannot coincide. Then what should be considered a sign of one species – the similarity of the genome by 98% or by 97.5%? There is no consensus yet. In addition, each group of animals has its own practice and its own idea of ​​a single species at the molecular level.

Alexander Martynov from the Zoom Museum of Moscow State University and Tatiana Korshunova from the IBR RAS proposed instead of the concept of “species” to introduce a more universal one – MOD (Multilevel Organismal Diversity), that is, to rely on the concept of a multi-level diversity of organisms, which would rather consider each animal as an individual. Similar theories of classification of organisms and, in particular, the problem of species, have been discussed and are being discussed at the present time in many monographs and collections by other scientists around the world.

Just like previous taxonomists, Martynov and Korshunova suggested taking into account in the biological classification of organisms, in addition to morphology and genetics, also ontogeny – the life cycle of an animal from the embryo, larva to the adult stage. Since the organism is a developing system, ontogeny is its main characteristic. This factor would make it possible to very accurately understand all the hidden features of a particular species from the beginning of fertilization – the fusion of female, male genes, the appearance of a unicellular, then a two-celled organism, and so on, up to development into an adult. Each species has similar patterns of development.

As Martynov’s colleagues from Moscow State University commented to MK, when the theory of systematics develops, this is normal. In particular, the idea of ​​using ontogenesis was first proposed back in the 18th century by the Russian naturalist, the founder of embryology, Karl von Baer. In the 50s of the last century, it was promoted by the American Grace Orton, then there was the Englishman Colin Peterson, who defended a similar theory in the 80s. Each generation puts forward a leader in this direction.

However, the difficulty lies in the fact that scientists can now trace the paths of ontogeny from the zygote to the adult state only in a small number of organisms. This requires a large amount of research material, large funding and expensive equipment. It is one thing to dissect at each stage of development of the embryo in a mollusk or worm, and quite another, for example, in an elephant. “Imagine how many pregnant elephants would have to be killed in order to study the development of her fetus at different stages of its development! It’s simply impossible. Who will allow elephants to be killed, and pregnant females at that?!”, one zoologist told us.

So for now, molecular and morphological methods still remain working tools for determining species characteristics. Someday, scientists will begin to take into account ontogenesis, because science is moving forward, but so far we are not ready for this.