It is hard to imagine that once our planet looked completely different. Everything was different: plants, animals, atmosphere, water. For millions of years, the Earth has undergone changes that have brought it to the current state of affairs. These changes are periodic in nature and have their scientific name - evolution. Let's try to figure out what it represents and how its processes proceeded.
Concept of evolution
If we give a definition from the point of view of biological science, then we can say so. Evolution is an irreversible change in time that occurs in living organisms and leads to the consolidation at the genetic level of newly acquired traits that allow them to adapt to any environmental conditions.
Moreover, not every specific individual is a unit of the evolutionary process, because there are whole groups consisting of identical organisms. Therefore, the idea of the elementary link of this large-scale process has long been ambiguous. Modern scientists unanimously declare that the population is the unit of the evolutionary process.
Any person can trace the process itself on a concrete example from nature, if such a goal is set. So, the appearance of adaptations for the corresponding way of life of moles, coupled with a complete loss of vision, is very obvious. After all, there is no light under the ground, therefore, vision is not important. But the sense of smell of these creatures can be envied. Feel the smell of an earthworm a few tens of meters!
At the same time, it is obvious that the ancestral forms of these animals led a terrestrial way of life and were not deprived of either vision or the 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 with all organisms. At the same time, we should not think that we live in a stationary world where the biomass is completely stable and formed.
Evolution is proceeding now, subjecting changes to all animals, plants, microorganisms, even humans. It just happens at the genetic level, and cannot be seen by contemporaries.
Terminology of Evolutionary Learning
There are a number of concepts that should be learned to operate in order to have an idea of evolution and the processes that accompany it. With the passage of time, the accumulation of the theoretical knowledge base and the generalization of all the material obtained, there were also terms that denoted certain organisms and changes in their states, actions, natural phenomena. Many metamorphoses and processes belong to evolution, however, let us define the main ones.
- Heredity - the ability of organisms to transmit to their offspring 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 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 changes 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, become stronger and leave, respectively, more hardy and adapted offspring.
- Natural selection is a process carried out by nature itself, determining the place of each individual in life, limiting their number, limiting the progression in reproduction and survival.
- The unit of the evolutionary process is the population. It is a group of similar organisms that transfers within itself a certain set of characters to offspring and has the same set of morphological, physiological and anatomical features, determines the smallest structural unit of the development process.
For a complete understanding of the phenomenon under consideration, environmental concepts such as species, genus, population, biocenosis, biomass, biosphere and others should be clearly understood.
The history of evolutionary doctrine
The concept of evolution as a development process did not come to people right away. 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 symptoms. Among the most famous minds were these:
- Thales.
- Xenophanes.
- Heraclitus.
- Alkmeon.
- Empedocles.
- Plato.
- Aristotle.
- Hippocrates and others.
Middle Ages and the New Age
In the Middle Ages, the most widespread theory of the origin and development of life was Creoezonist. God was considered the only creator who created the Earth as it is, and all sorts of other views were not considered possible. This slowed down the development of true ideas for a long time.
Later, when the era of geographical discoveries passed and it became known about the enormous diversity of life on Earth, the time came 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, along with him almost the same discoveries were made by another scientist - Alfred Wallace. Creoceonist views were replaced by transformist ones.
Their essence was the belief that the Earth was different, and only over time did many transformations take place and those organisms that exist now were formed. Moreover, the transformation process has not stopped, but continues to this day and will always continue as long as life exists.
Darwin's doctrine of evolution
What does the theory created by the Englishman say? What is a unit of the evolutionary process and why does it even happen? We outline several key points of this teaching.
- All the diversity of life that exists on the planet is the result of millennia of transformations, 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, and variability of species.
- New signs arise and are consolidated as a result of the struggle for existence, which is a 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 the 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 arise again after several generations.
Darwin 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 an evolutionary process. Is this true today? No, because, from the point of view of the current synthetic theory of the development of life, a 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 consider the reasons later.
Darwin believed that the smallest cell is a species. He described and recorded the changes that occurred within the same species, considered the totality of factors affecting these changes.
What is a view?
Why can not we assume that a unit of the evolutionary process is a species? Because we have already indicated that the result of the development of life is adaptation to local factors. The acquisition and consolidation of those signs that will help to exist unhindered in certain areas.
However, let's recall, for example, the polar edge. The place where snowstorms always sweep and white snow dazzles, 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 a thick fur with undercoat, white color, a thick layer of subcutaneous fat, large sizes and more.
Thus, it turns out that the species are different, and the signs of adaptation are similar. That is why the unit of the evolutionary process is not a species, it is just an elementary cell of ecology as a science. This is a collection of individuals with similar morphological, physiological characteristics, lifestyle, as well as occupying a certain range and freely interbreeding, forming prolific offspring.
Population as an elementary unit of the evolutionary process
The modern theory of evolution is synthetic. It is the result of the merging of all the views of Charles Darwin, modern research and inference. She does not have a specific author; she is a 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 a population. It is she - the smallest unit cell of this global process of transformation.
From an environmental point of view, a population is a form of existence of certain types of organisms in which they are best suited to environmental conditions. One population may include both individuals of the same or different species. The symptoms they possess may also vary. Some organisms may 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. Namely, this is evolution.
Drivers of Evolution
We have already mentioned the basic processes that are the engines of this macro-phenomenon - evolution. Once again we denote them.
- Natural selection, carried out due to the struggle for existence within the population and between them.
- Heredity and variability, leading to the consolidation of important new traits in the genotype.
- Mutations, both beneficial and harmful. Random or directional, they lead to the consolidation of new signs.
- Artificial selection - directed evolution, carried out by man to obtain the necessary species of animals and plants (this is done by plant breeding and animal husbandry).
The value of heredity in the process of evolution
The ability to pass on traits by inheritance is an important feature of all living things. 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, it is one of the main directing forces of evolution.
Variability and its role
It cannot be said that variability is a unit of the evolutionary process. Is she such an important link? Of course. After all, it is in this process that the basis for acquiring new features and features lies. The body's ability to recombine, form new traits and fix them - all this happens due to variability.