Not much left in the world of people whocontinue to believe in the biblical story of the creation of all life on our planet. Everyone is familiar with the concept of evolution. Multiple 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 single answer.
Academic Foundations
Let's start with the definition ofevolution in biology. This word is derived from the Latin evolutio, which means literally "deployment." The process of evolution is often portrayed in the form of a developing spiral. In biology, this concept means the irreversible process of development of the organic world in all aspects of its manifestation. The result of evolution is the diversity of the organic world and the improvement of the adaptation of organisms to environmental conditions.
Darwinism as a basis for 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 shortage of life-supporting resources limits the unlimited growth of the species. Natural selection as a result of evolution is the limiter that governs the number of organisms.
- Success, as well as the death of an individual in the struggle for existence, is selective. And it was precisely 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 a biotope and, as a result, an increase in the diversity of species.
Diversity as a result
Since the results of evolution, according to Darwin,is the fitness of the organism; as a result of the action of natural selection, individuals with the most beneficial qualities for survival survive and thrive. Natural selection is the “creative” mechanism of evolution. The result is the emergence of new signs that increase the chances of an individual to leave fertile offspring and pass on these signs to it.
Material evolution
If the result of evolution isfitness and diversity of species, then the material for it are mutations and combinational variability within the genome. It is mutations that cause the appearance of new features that will creatively evaluate natural selection for suitability and the need for specific habitats of the species. Genetic variability and fluctuations in the number of individuals in populations (population or life waves) provide material for the inclusion of mechanisms for the struggle for the existence and survival of the fittest.
"Creative" directions
The struggle for existence as a resultnatural selection leads to the fact that the result of evolution is the emergence of new species from the ancestral. And natural selection can go in three directions:
- Driving - occurs with 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 way will gospecies evolution under unchanging environmental conditions. With this type of selection, the optimal rate is maintained, and all extreme manifestations of the trait are eliminated from the population.
- Disruptive population selection begins at abruptenvironmental changes. Then most of the population with signs normally dies sharply, and the carriers of the extreme indicators of the trait turn out to be the most adapted to the changed conditions.
Genetic or reproductive isolation
Whatever way evolution goes, the mainthe condition for the formation of new species is reproductive isolation - the impossibility of free crossing of individuals for panmictichnyh species (sexually reproduced). It should be said that the achievement of reproductive isolation in nature follows two paths: allopatric (reproductive isolation is achieved by geographical separation of populations) and sympatric (isolation occurs on the same range with the maternal species). In any case, as soon as the mode of impossibility of free crossing is established between populations, one can say 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 ingenome, 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 patronizing and cautionary coloring, masking, and passive protection. Protective coloration, such as white plumage in a partridge in winter, makes animals invisible against the backdrop of the environment. Warning organisms possess those organisms that have in their arsenal chemical means of protection against enemies. For example, the red and black color of poisonous tree frogs or yellow and black in poisonous salamanders. Disguise as protection against enemies can be truly passive (the form of a stickman’s body really resembles a wand) or imitative (for example, the belly of a butterfly-glass bowl is very similar to the belly of wasps, so the birds don’t touch it).
Relativity of evolutionary fitness
All evolutionary scientists agree with the statementthat the nature of fitness is relative. There are no absolutely useful signs, as there are no absolutely useless ones. All adaptations are produced in specific environmental conditions and, if they change, may be useless or even harmful. Protection from one enemy can be useless when protecting from another (most birds do not eat stinging wasps and hornets, but flycatchers and bee-eaters mainly feed on them). Behavioral features may be meaningless (for example, maternal instinct, which causes the starling to feed the cuckoo). 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 an albatross prey).
Summarizing
About 7.5 million animal species, about 300thousands of plant species and 600 species of fungi, add 36 thousand species of unicellular organisms - all this diversity is the main result of the evolution of life on planet Earth. And they are all perfectly adapted to the conditions of their habitat. Over 3.7 million years of life on the planet, living organisms have constantly evolved and adapted to environmental conditions, and the process continues today.
