EducationThe science

Motion selection. Example of a driving selection form

In 1859, the English scientist Charles Darwin published his fundamental work, The Origin of Species by Natural Selection. In this book, the modern theory of evolution was first formulated. Its driving force is natural selection, which, in turn, is divided into several types, including driving selection. Examples of this hypothesis, given in the "Origin of Species", clearly demonstrated how the mechanism of life development on earth works.

The essence of driving selection

The principle of driving selection is that individuals who have received some differences from the general norm accepted by the species, find themselves in a predominant position and, in the end, win the struggle for survival. This is a long and complex process. Intraspecific variability affects all structures and organs in each species. It concerns both quantitative characteristics (the presence or absence of variation), and qualitative (dimensional, countable).

The history of the development of mammals gives researchers numerous examples of the driving form of selection. The most variable signs are the number of hair per unit area, the mass of various organs, the number of red blood cells in the blood. In the course of evolution, the size of the human brain increased. A huge number of variations is in the features of the attachment of different muscles, the structure of the bronchial tree of the lungs, the form of the liver.

Doubtful views

A multitude of intermediate species forms spawned a driving selection. Darwin himself cited examples of this group. This is a British red grouse, which originated from the Norwegian species, Madeira insects, birds of the Galapagos Islands. All of them can be described as "dubious species". What are their main features? These are forms that are very similar to a species, but so similar to some other forms or closely interrelated intermediate steps that biologists do not recognize them as independent species.

Such living beings are links in evolution. Doubtful views are actually emerging new ones. They are not yet so well separated from their ancestors, but have already begun the process of separation. These are examples of driving selection in animals. They result from the struggle for life. No matter how small the random changes in the form, if they are anyhow useful, they will undoubtedly remain and will be inherited by the offspring.

Bird driving selection

The struggle for existence is, first of all, the struggle for the diet. If the species can not fix its position in the food chain, it will necessarily die out. Examples of the driving form of natural selection can be clearly seen in the appetite of animals.

Consider several species of birds. Big tit one day eats a lot of insects, equivalent to the mass of their own body, and the long-tailed titmus feeds its chicks hundreds of times a day, taking 5-6 caterpillars per serving. Flycatcher-gingerbread feeds offspring to a kilogram of beetles and worms in two weeks. Korlek can eat up to 10 million insects a year in a year. The American kestrel for the same period should catch up to 300 mice and dozens of small birds. Feed, delivered by the starlings to their chicks, can fill three birdhouses.

Each of these cases is an example of the action of the driving form of natural selection. Changes in the stomach, intestines and beak gradually changed the birds. Some of them became hardier and more fertile, others became large predators, the third became extinct, left without food and turned into food for neighbors.

The dominant species

A variety is generated if the animal or plant is widely distributed throughout the world. Darwin also called these species dominant. It is these that are most often singled out by selection. An example is an ordinary fox that inhabits different parts of Eurasia . It forms several geographical forms, constantly replacing each other. Foxes living in the north are much larger than foxes living in the south, in the zone of steppes and semi-deserts. The smallest of them live in Central Asia, and especially in Afghanistan.

The wide range of the fox world is the result of the evolution that the selection has done. The example is obvious: in the north, animals need to be more enduring than in the south. This is connected with climatic conditions, and with dangerous neighbors. During the migration of foxes to the south, each new generation became less and less as a result of small natural changes. New individuals became more adapted to the steppes and deserts and continued to conquer unfamiliar territories.

Moving selection and feeding base

All examples of driving natural selection show that in each individual case, nature maintains a biological balance. Even if the new variety takes advantage and becomes dominant, its dominance always has a limit. This principle manifests itself also in the event that a person tries to interfere in natural processes.

In 1911, 25 individuals of reindeer were brought to Pribilof Island near Alaska. They are well established in a new place - in 1938 they were already two thousand. There were too many individuals, because of what the fodder base was destroyed and the entire population gradually died out. In 1950, there were only 8 deer left on the island. The characteristics of driving selection and examples show that if the species is in too good a condition, it multiplies, massages the food necessary for itself, and as a result, it dies.

A similar situation developed on the Arizona Keibab Plateau, where people, trying to restore the number of black-tailed deer, shot all coyotes and cougars and banned hunting. Exceeding the permissible population density was the starting point of extinction of the population.

Randomness of mutations

The mechanism of driving selection acts chaotically. Darwin could not understand how the changes that occur in new generations of living organisms are regulated. Scientists of the XX century came to the conclusion that new traits arise in animals and plants as a result of random mutations. They can appear unnoticeably and disappear unnoticed, but if such changes are useful to the individual, they are preserved and inherited by the offspring.

Discovered Europe, Europeans brought to the continent an ordinary bee, which quickly exterminated the native bees, who had a smaller sting. This case is artificial. His cause was human activity. But it is precisely on this principle that natural selection moves.

Intraspecific struggle

The struggle for survival is always hard, but the struggle for life between individuals and species of the same species is doubly stubborn. Affects the similarity in the habits and structure of the body.

In Scotland in the XIX century, there was a confrontation between two species of thrushes - an increase in the number of thrushes-dyub resulted in the disappearance of songbirds. An example of the action of the driving form of natural selection is the fact that in Russia the Asian cockroaches of the Prusak have everywhere ousted their larger congeners.

Interspecific struggle

It is important that the structure of any organic creature most significantly affects other living creatures nearby. As a rule, these are competitors who fight each other daily for survival. Thus, parasites living near tigers have characteristic hooks. They proved to be more convenient for sticking these predatory animals to the wool.

Examples of driving selection in plants can also be considered in the context of interspecies struggle. A dandelion familiar to everyone has tufts-fly. They carry the seeds and are closely interlinked with the dense population of the territories on which this plant is. Such a structure helps not only to survive, but also to reproduce in huge numbers. Seeds on the fly are able to carry far away through the air and get on still unoccupied soil.

Expansion

At first glance, the supply of food in the seeds of many plants has nothing to do with other plants. However, in fact they are of fundamental importance. It consists in the rate of growth of shoots, forced to fight with extraneous vegetation surrounding them. In the early stages of existence, young shoots of peas or beans develop rapidly. In the course of their evolution, their seeds began to receive a large supply of food, which helped them to occupy a significant niche in the organic world. The species-competitors of peas and beans that did not receive this advantage, lost the interspecific struggle and disappeared from the face of the earth.

The above example shows an important regularity. When an animal and plant enters a new country and finds itself among unfamiliar competitors, the conditions of its life vary greatly, even if the climate remains the same. In order to gain a foothold in the new territory, the species must necessarily deviate from its ancestors in its development.

Slow selection

Driving selection operates hourly and daily. He preserves and creates useful changes, thereby perfecting the organic being, depending on the conditions of his life. Selection is slow and imperceptible to the human eye, but it is implacable. Evolution can not be considered for several generations. For this, scientists have to study entire geological epochs and periods of thousands and millions of years.

The selection can work at the expense of signs, seemingly completely insignificant. For example, insects that eat leaves are distinguished by green color, and for bark-feeding trees a spotted-gray color is characteristic. If the color changes, these creatures will become visible and vulnerable to predators. Similarly, for the flock of white sheep, the presence of lambs is disastrous with at least a small black spot.

Correlation and adaptation

The signs of living beings change not only as a result of random mutations, but also according to the principle of correlation. What is its essence? When one part of the body changes, it will necessarily lead to changes in other parts. Often such evolutionary turns are characterized by the most unexpected properties.

The main function of changes is adaptation. They can manifest themselves at various stages of life. For example, the ostrich chicks have characteristic horny tubercles on the upper part of the beak, which are also called chicks. In the first days after hatching from the egg, they dissolve and disappear. Their only purpose is to help the chick destroy the shell. This is the so-called embryonic adaptation. It allows the species to increase its fertility and to fight more effectively for survival. Due to such seemingly insignificant features and functioning of the selection process.

Similar articles

 

 

 

 

Trending Now

 

 

 

 

Newest

Copyright © 2018 en.birmiss.com. Theme powered by WordPress.