It's hard to imagine that once our planet looked very different. Everything was different: plants, animals, atmosphere, water. For many millions of years, the Earth has undergone changes that have led it to the current state of affairs. These changes are periodic in nature and have their own scientific name - evolution. Let's try to figure out what it is and how its processes proceeded.
The concept of evolution
If you define it in terms of biological science, then you can say so. Evolution is an irreversible change in time that occurs in living organisms and leads to the fixation at the genetic level of newly acquired traits that allow them to adapt to any environmental conditions.
At the same time, not every individual is a unit of the evolutionary process, because there are whole groups consisting of identical organisms. Therefore, the idea of an elementary link in this large-scale process was ambiguous for a long time. Modern scientists unanimously declare that the unit of evolutionaryprocess is population.
The process itself can be traced by any person on a specific example from nature, if such a goal is set. So, the appearance of adaptations for the corresponding lifestyle in moles, associated with a complete loss of vision, is very clear. After all, there is no light underground, therefore vision is not important. But the sense of smell of these creatures can be envied. They can smell the earthworm from a few tens of meters away!
At the same time, it is obvious that the ancestral forms of these animals led a terrestrial lifestyle and were not deprived of either sight or forelimbs of a normal structure. Of course, this transformation did not happen immediately. It took mother nature many centuries, millennia and even millions of years to bring moles to the form in which they are known to us now. And so it is with all organisms. At the same time, one should not think that we live in a stationary world, where the biomass is completely stable and formed.
Evolution is still ongoing, subjecting all animals, plants, microorganisms, even humans to change. It just happens at the genetic level, and cannot be seen by contemporaries.
Evolutionary terminology
There are a number of concepts that should be learned to operate in order to have an idea about evolution and the processes that accompany it. Over time, the accumulation of a base of theoretical knowledge and the generalization of all the material received, there were also terms that denoted certain organisms and changes in their states,actions, natural phenomena. Evolution includes many metamorphoses and processes, but let's define the main ones.
- Heredity is the ability of organisms to pass on to their offspring the traits fixed in the genotype. Thanks to her, there are identical individuals that form entire populations.
- Variability is such a feature in organisms that appears from birth and persists throughout life, which allows you to acquire new traits by combining the genotypes of the father and mother.
- Mutations are an important part of the phenomenon under consideration. The unit of the evolutionary process is, of course, not mutation. However, this is the driving force behind change over time.
- The struggle for existence is the natural rivalry of individuals for territory, food, a profitable place to live, water, a female, and so on. It is this struggle that determines the number of animals and plants, their strength and endurance. Those that survive grow stronger and leave behind more resilient and adaptable offspring.
- Natural selection is a process carried out by nature itself, which determines the place of each individual in life, limiting their numbers, limiting the progression in reproduction and survival.
- The unit of the evolutionary process is the population. It is a group of similar organisms that transmit within themselves a certain set of traits to offspring and have the same set of morphological, physiological and anatomical features that determines the smallest structural unit of the development process.
To fully understand the phenomenon under consideration, one should clearly understandand such ecological concepts as species, genus, population, biocenosis, biomass, biosphere and others.
History of evolutionary doctrine
The concept of evolution as a process of development did not come to people immediately. Initially, changes in plants and animals were mentioned in antiquity. Then the sages, philosophers and researchers noticed that over time, individuals change, many have similar features. Among the most famous minds were:
- Thales.
- Xenophanes.
- Heraclitus.
- Alcmaeon.
- Empedocl.
- Plato.
- Aristotle.
- Hippocrates and others.
Middle Ages and modern times
In the Middle Ages, the most common theory of the origin and development of life was Creocionist. God was considered the only creator who created the Earth as it is, and any other views were not considered possible. This slowed down the development of true concepts for a long time.
Later, when the era of geographical discoveries passed and it became known about the huge diversity of life on Earth, it was time for a theoretical explanation of this diversity. Then the theory of evolutionary transformations appeared. Her father is considered to be the world-famous Englishman Charles Darwin. However, on a par with him, almost the same discoveries were made by another scientist - Alfred Wallace. Creocionist views were replaced by transformist ones.
The essence of themconsisted in the belief that the Earth was different, and only with the passage of time many transformations took place and those organisms that exist now were formed. In addition, the process of transformation has not stopped, but continues to this day and will continue forever, as long as life exists.
The doctrine of evolution according to Darwin
What does the theory created by the Englishman say? What is the unit of the evolutionary process and why does it even occur? Let us designate several key provisions of this teaching.
- All the diversity of life that exists on the planet is the result of thousands of years of transformation, and was not created overnight by one Creator.
- Evolution is based on processes such as natural selection, hereditary transmission of information to generations, mutations that occur in populations, variability of species.
- New signs arise and are fixed as a result of the struggle for existence, which is the means of natural selection.
- The result of evolution is the formation of an organism that is maximally adapted to the conditions of its existence.
Charles Darwin gave not only a theoretical explanation of the development of life, but also supported all this with ongoing experiments. The only thing he could not understand and explain in any way was the discreteness of inherited traits. According to his views, those signs that were passed down from generation to generation should have been transformed and faded over time. However, Mendel's experiments proved that they reappear after several generations.
Darwinian evolutionary process unit
In order to explain any process, it is necessary to select its elementary cell. So it is with evolution. Charles Darwin believed that a species is a unit of the evolutionary process. Is this true today? No, after all, from the point of view of the current synthetic theory of the development of life, the species cannot be considered as the smallest particle of global change in time.
According to the views of contemporaries, the elementary unit of the evolutionary process is the population. We will discuss the reasons later.
Darwin also believed that the smallest cell is a view. He described and recorded the changes that occurred within one species of individuals, considered the entire set of factors influencing these changes.
What is a view?
Why can't we assume that the unit of the evolutionary process is the species? Because we have already indicated that the result of the process of development of life is adaptation to local factors. The acquisition and consolidation of those features that will help to exist freely in certain areas.
However, let's remember, for example, the polar region. The place where blizzards always sweep and white snow blinds, where cold and cold make you tremble. More than one specific species of animals lives in these parts, but their adaptations to such harsh conditions are extremely similar. This is thick fur with undercoat, white color, thick layer of subcutaneous fat, large size, etc.
Thus, it turns out that the species are different, but the signs of adaptation are similar. That is why the unit of the evolutionary process is not a species, it is simply an elementary cell of ecology as a science. This is a collection of individuals that have similar morphological, physiological characteristics, lifestyle, and also occupy a certain area and freely interbreed with each other, forming fertile offspring.
Population as an elementary unit of the evolutionary process
The modern theory of evolution is synthetic. It is the result of a confluence of all the views of Charles Darwin, modern research and reasoning. It has no definite author, it is the product of the work of many scientists from different countries.
So, it is this theory that determines that the unit of the evolutionary process is the population. It is she who is the smallest elementary cell of this global transformation process.
From the point of view of ecology, a population is a form of existence of certain types of organisms, in which they are best adapted to environmental conditions. One population can include both individuals of the same or different species. The features they possess may also differ. Some organisms can be small, others large, and so on.
In each population there is a struggle for existence, natural selection, mutations are formed and certain signs are fixed. And that is what evolution is.
Drivers of evolution
WeWe have already mentioned the main processes that are the engines of this macrophenomenon - evolution. Let's label them again.
- Natural selection through the struggle for existence within and between populations.
- Heritability and variability leading to the fixation of important new traits in the genotype.
- Mutations, both beneficial and harmful. Random or directed, they tend to reinforce new traits.
- Artificial selection - directed evolution carried out by man to obtain the desired species of animals and plants (this is done by plant breeding and animal husbandry).
The importance of heredity in the process of evolution
The ability to transmit traits by inheritance is an important feature of all living beings. It provides the ability to reproduce the same individuals, but at the same time get new ones. Heredity is the basis of life.
Its biological role is to maintain the number of individuals of different species and preserve them in nature. In addition, she is one of the main guiding forces of evolution.
Variability and its role
It cannot be said that variability is a unit of the evolutionary process. Is she that important to him? Of course. After all, it is in this process that the basis for acquiring new features and characteristics lies. The ability of an organism to recombine, form new traits and fix them - all this happens due to variability.
