Konstantin Sergivich Merezhkovsky (1855-1921) (also transliterated Konstantin Sergeevich Merezhkovsky, Constantin Sergeevič Mérejkovski, Constantin Sergejewicz Mereschcowsky, Konstantin Sergejewicz Mereschkovsky and Konstantin Sergejewicz Mereschkowsky) was a prominent Russian biologist and botanist active mainly around Kazan, whose research on lichens led him to propose the theory of symbiogenesis - that larger, more complex cells evolved from the symbiotic relationship between less complex ones. He presented this theory in the 1926 book Symbiogenesis and the Origin of Species. However, he had used the term as early as 1909, and the fundamentals of the idea had appeared in his 1905 work, The nature and Origins of Chromatophores in the Plant Kingdom. 1855 was a common year starting on Monday (see link for calendar). ... 1921 (MCMXXI) was a common year starting on Saturday (see link for calendar). ... A biologist is a scientist devoted to and producing results in biology through the study of organisms. ... Botany is the scientific study of plant life. ... Kazan (Tatar Qazan, Казан, Russian Казань) is the capital city of Tatarstan and one of Russias largest cities. ... For other things named Lichen, see: Lichen (disambiguation). ... Symbiogenesis refers to the merging of two separate organisms to form a single new organism. ... Complexity is the opposite of simplicity. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ... Common Clownfish (Amphiprion ocellaris) in their Magnificent Sea Anemone (Heteractis magnifica) home. ... 1926 (MCMXXVI) was a common year starting on Friday (link will take you to calendar). ... 1909 (MCMIX) was a common year starting on Friday (see link for calendar). ... 1905 (MCMV) was a common year starting on Sunday (see link for calendar). ...

He was inspired by his work as a leading lichenologist - lichens were of major interest at the time as it had recently been shown that they exhibit a symbiotic relationship between fungi and algae. Around the turn of the century he collected a sizeable lichen herbarium, containing over 2000 specimens from lands in Russia, Austria and around the Mediterranean. The collection is currently in the possession of Kazan University. He also studied hydras. Lichenology is the branch of botany that studies the lichens, symbiotic organisms made up by the association of a microscopical alga with a filamentous fungus. ... For other things named Lichen, see: Lichen (disambiguation). ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... The hobby of collecting consists of acquiring specific items based on a particular interest of the collector. ... In Botany, a herbarium is a collection of preserved plants or plant parts, mainly in a dried form. ... The Mediterranean Sea is an intercontinental sea positioned between Europe to the north, Africa to the south and Asia to the east, covering an approximate area of 2. ... Kazan State University is located in Kazan, Tatarstan, Russia. ... Species Hydra americana Hydra attenuata Hydra canadensis Hydra carnea Hydra cauliculata Hydra circumcincta Hydra hymanae Hydra littoralis Hydra magnipapillata Hydra minima Hydra oligactis Hydra oregona Hydra pseudoligactis Hydra rutgerensis Hydra utahensis Hydra viridis Hydra is a genus of simple, fresh-water animals possessing radial symmetry. ...

Merezhkovsky rejected Darwinian evolutionary theory. He did not believe that natural selection could explain biological novelty, rather the acquisition and inheritance of microbes. He was criticised by another Russian lichenologist, Alexandr Alexandrovich Elenkin. This article is about Darwinism as a philosophical concept; see evolution for the page on biological evolution; modern evolutionary synthesis for neo-Darwinism; and also evolution (disambiguation). ... Natural selection is the metaphor Charles Darwin used in 1859 to name the process he postulated to drive the adaptation of organisms to their environments and the origin of new species. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ...

There is now growing evidence that Merezhovsky had a grain of truth with his hypothesis that some evolution happened by organisms incorporating other organisms. The well known example of animal mitochondria being ancient plant cells was recently augmented by the finding of some bacteria having several "layers" of ingested cells.