The existence of species diversity - that's what microevolution is

The concept of evolution as a constant development of all life on the planet, the complication of life forms and the emergence of its new forms is widely used today in popular literature and in the media. Speculation on the theme of evolution and microevolution, the use of the term in populist forms blurs its meaning, drawing attention to the very essence of the process. What is microevolution in biology, its forms and the end result are the questions that are covered in this article.

Evolution as a biological process

Evolutionary teaching distinguishes two conventional forms - macroevolution and microevolution - as mechanisms for the development of life on earth. The division is conditional and is based on the size of the taxonomic units, to which the evolutionary movement leads. Macroevolution implies the formation of large taxa (genus, family, class, etc.) over a long period of time. The result of microevolution is the formation of a new species, the smallest taxonomic unit. Therefore, microevolution is called otherwise speciation, the formation of a new species in the middle of the source by achieving reproductive isolation and isolation into a separate taxon.

Regularities of development

All the laws of evolution as speciation pass in macrotaxons in the same scenarios and according to the same rules as for elementary units of evolution - populations. What is microevolution, it is easy to illustrate on the example of the formation of related phylogenetically close species within the same genus. For example, in the Arctic live three closely related species of seals - the seal of Witt, the sea leopard and the seal of Ross. In addition to minor external differences, their food bases are completely different, they led to the formation of closely related, but different species.

Types of microevolution

Speciation, which leads to reproductive incoherence as the last stage of the evolutionary isolation of a group within a species, has several mechanisms. By the type of the mechanism of isolation, several forms are distinguished. To microevolution is:

• Geographic speciation.
• Speciation on the ecological division of populations.
• Speciation by proper reproductive isolation (dopupulation and post-copulation).

What is geo-environmental and microevolution?

In this case, the mechanism of isolation in the panmictic (sexually reproducing) groups of organisms is considered when a new species is formed under the influence of geographic or environmental factors. Geographic factor of population isolation is considered to be changes in the landscape, which lead to temporary or complete isolation of populations of one species. A good example is the formation of island species. And the most, perhaps, known in this context are Galapagos convolvulus, the description and study of which led Charles Darwin to his theory of the origin of species. An example of what microevolution is like an ecological speciation has already been cited - the Arctic seals. In the case of seals, the ecological factor of isolation became the fodder base. But the environmental factor is also the discrepancy between breeding seasons, various ecological races within the species and so on.

Dokopulyatsionnaya form of isolation as a kind of microevolution

In the case of the impossibility of free crossing of individuals as a result of isolation associated with the lack of formation of a zygote (embryo) of the body, they speak of pre-isolation. Its forms are different:

• Isolation arising from the characteristics of sexual behavior (ethological). An example is closely related tropical frogs, differing in timbre and species-specificity of mating singing.
• Isolation caused by a different structure of copulatory or reproductive organs. Example - different types of orchids have a specific structure of the flower, which allows them to pollinate only a certain species of hummingbird.

Isolation caused by discrepancy gametes. Examples are only in experiments, nature is difficult to trace this mechanism.

Post-population isolation as a mechanism of speciation

In this case it is understood that the zygote was formed. What is microevolution in this case, show the following forms of achieving complete reproductive isolation of populations within a species:

• Non-viability of the zygote at the first stages of ontogeny.
• Death of a born calf or young individual before reaching reproductive age.
• Sterility of hybrids.

The biological mechanism of this form of isolation is complex and associated with cytological, biochemical and humoral features.

Microevolution as a process of achieving complete reproductive isolation of a group within one species leads to the formation of new species of organisms other than parental forms. But this is in theory. Not every isolation of the population will lead to reproductive isolation and not every reproductive isolation will lead to the formation of new forms. What in dogma evolution is that microevolution begins with isolation and ends with it.