There are not many people left in the world who continue to believe in the biblical story about the creation of all life on our planet. Everyone is familiar with the concept of evolution. Numerous evidence of the development of all life on Earth leaves no doubt about the origin of changes in the world around us. Who is Charles Darwin, even younger students know. But when it comes to what is the result of evolution, there is no clear answer.
Academic foundations
Let's start with the definition of evolution in biology. This word is derived from the Latin evolutio, which means literally "deployment". The process of evolution is often depicted as an unfolding spiral. In biology, this concept refers to the irreversible process of development of organicworld in all aspects of its manifestation. The result of evolution is the diversity of the organic world and the improvement of the adaptability of organisms to environmental conditions.
Darwinism as the basis of the doctrine of evolution
The founder of the doctrine - Charles Darwin (1809-1882) - formulated the following principles of evolutionary doctrine:
- All species are capable of unlimited reproduction of their own kind.
- The lack of life-supporting resources limits the unlimited growth of the species. Natural selection as a result of evolution is the limiter that regulates the number of organisms.
- Success, as well as the death of an individual in the struggle for existence, is selective. And it was this selectivity that he called natural selection.
- The main results of evolution - according to Darwin - is the improvement of the organism's adaptability to the conditions of the biotope and, as a result, an increase in the diversity of species.
Variety as a consequence
Since the results of evolution, according to Darwin, is the fitness of the organism, as a result of natural selection, individuals with the most useful qualities for survival survive and thrive. Natural selection is the "creative" mechanism of evolution. The result is the emergence of new traits that increase the chances of an individual to leave fertile offspring and pass on these traits to him.
Evolution Material
If the result of evolution is fitness anddiversity of species, then mutations and combinative variability within the genome serve as the material for it. It is mutations that cause the appearance of new traits that natural selection will creatively evaluate for suitability and necessity in the specific living conditions of the species. Genetic variability and fluctuations in the number of individuals in populations (population or life waves) provide material for turning on the mechanisms of the struggle for existence and the survival of the fittest.
"Creative" directions
The struggle for existence as a result of natural selection leads to the fact that the result of evolution is the emergence of new species from the progenitor. And natural selection can go in three directions:
- Motive - occurs when changes in the environment, and then the result of evolution is a shift in the average values of the trait in the direction of its increase or decrease.
- Stabilization - this is the way the evolution of the species will go under unchanging environmental conditions. With this type of selection, the optimal norm is preserved, and all extreme manifestations of the trait are eliminated from the population.
- Population-tearing selection begins with sudden changes in the environment. Then most of the population with normal traits dies abruptly, and the carriers of extreme trait indicators are the most adapted to the changed conditions.
Genetic or reproductive isolation
Whateverno way evolution proceeded, the main condition for the formation of new species is reproductive isolation - the impossibility of free crossing of individuals for panmictic species (sexually reproducing). It is worth saying that the achievement of reproductive isolation in nature proceeds in two ways: allopatric (reproductive isolation is achieved by geographical separation of populations) and sympatric (isolation occurs in the same area with the maternal species). In any case, as soon as the regime of the impossibility of free interbreeding is established between populations, it can be said that the result of the evolution of the organic world is the formation of a new species, and this process is completed.
Examples of successful animal fitness
As soon as trait changes appear in the genome, they are tested by natural selection. The most successful are fixed morphologically and become adaptive. There are many examples in nature. Successful morphological adaptations include protective and warning coloration, camouflage and passive protection. Protective coloration, such as the white plumage of a partridge in winter, makes the animals invisible against the background of the environment. Those organisms that have in their arsenal chemical defenses against enemies have a warning coloration. For example, the red-black color of poisonous poison dart frogs or the yellow-black color of poisonous salamanders. Disguise as a defense against enemies can be truly passive (the body shape of a stick insectreally resembles a stick) or imitative (for example, the belly of a glass butterfly is very similar to the belly of a wasp, so the birds don’t touch it).
Evolutionary Fitness Relativity
All evolutionary scientists agree that the nature of fitness is relative. There are no absolutely useful signs, just as there are no absolutely useless ones. All devices are developed in specific environmental conditions and, if changed, may be useless or even harmful. Defense against one enemy may be useless against another (stinging wasps and hornets are not eaten by most birds, but flycatchers and bee-eaters eat mostly them). Behavioral features may be meaningless (for example, the maternal instinct that causes a starling to feed a cuckoo). And a useful organ or skill in other conditions becomes a burden (for example, a flying fish jumps out of the water and escapes from aquatic predators, but becomes the prey of an albatross).
Summing up
About 7.5 million animal species, about 300 thousand plant species and 600 fungi species, add 36 thousand species of unicellular organisms - all this diversity is the main result of the evolution of life on planet Earth. And all of them are perfectly adapted to the conditions of their habitat. For 3.7 million years of the existence of life on the planet, living organisms have constantly evolved and adapted to environmental conditions, andthis process continues today.
