Biological evolution defined as any genetic change in a population that occurs over several generations. These changes may be small or large, very noticeable or not significant.
For an event to be considered an example of evolution, changes must occur at the genetic level of the species and be passed on from one generation to the next. This means that , or more specifically, alleles in a population change and are passed on. These changes are noted in the (pronounced physical features that can be seen) of the population.
Change genetic level population is defined as small-scale change and is called microevolution. Biological evolution also includes the idea that all living organisms are related and can descend from a common ancestor. This is called macroevolution.
What is not biological evolution?
Biological evolution does not determine the simple change of organisms over time. Many living things experience changes over time, such as loss or increase in size. These changes are not considered examples of evolution because they are not genetic and cannot be passed on to the next generation.
Evolution theory
How does genetic diversity occur in a population?
Sexual reproduction can create favorable combinations of genes in a population or remove unfavorable ones.
A population with more favorable genetic combinations will survive in its environment and reproduce more offspring than individuals with less favorable genetic combinations.
Biological evolution and creationism
The theory of evolution has generated controversy since its inception, which continues to this day. Biological evolution contradicts religion regarding the need for a divine creator. Evolutionists argue that evolution does not address the question of whether God exists, but rather attempts to explain how natural processes occur.
However, there is no escaping the fact that evolution contradicts some aspects of certain religious beliefs. For example, the evolutionary account of the existence of life and the biblical account of creation are completely different.
Evolution suggests that all life is connected and can be traced back to a single common ancestor. A literal interpretation of biblical creation suggests that life was created by an omnipotent supernatural being (God).
However, others have tried to combine the two by arguing that evolution does not rule out the possibility of God, but simply explains the process by which God created life. However, this view still contradicts the literal interpretation of creativity presented in the Bible.
For the most part, evolutionists and creationists agree that microevolution does exist and is visible in nature.
However, macroevolution refers to the process of evolution that is at the species level, where one species evolves from another species. This is in sharp contrast to the biblical view that God was personally involved in the formation and creation of living organisms.
For now, the evolution/creationism debate continues, and it appears that the differences between the two views are unlikely to be resolved any time soon.
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Biological evolution is historical development organic world. The word “evolution” is Latin and translated means “unfolding”, and in in a broad sense- any change, development, transformation. In biology, the word “evolution” was first used in 1762 by the Swiss naturalist and philosopher C. Bonnet.
Life arose on Earth about 3.5 billion years ago. The predecessors of the first organisms were complex organic protein compounds that formed gelatinous lumps, the so-called coacervate droplets. These droplets, floating in the primordial ocean, were able to grow by absorbing from environment various nutrients. They disintegrated into daughter droplets, of which more perfect ones existed longer. The structure of coacervates gradually became more complex; they formed a nucleus and other elements of a living cell. This is how the simplest single-celled organisms appeared.
Millennia passed, and the structure of living beings became more and more improved as a result of natural selection. Some of these simplest organisms have developed the ability to absorb energy sunbeam and build in your body from carbon dioxide and water organic matter. This is how the first unicellular plants, blue-green algae, arose.
Other living beings retained the same way of eating, but primary plants began to serve them as food. These were the first animals.
Subsequently, as a result of evolution, the first multicellular organisms-sponges, archaeocyaths (extinct invertebrate animals), coelenterates. Gradually, the world of plants and animals became more complex and diverse, and they also populated the land.
Based on their fossil remains - prints, fossilized skeletons - scientists have established that what ancient organisms, the simpler they are arranged. The closer we get to our time, the more complex organisms become and more and more similar to modern ones.
As a result of the development of the organic world, higher plants and highly organized animals. From mammals - fossils great apes- a man happened.
This is brief outline evolution of life on our planet.
Evolution is one of the forms of movement in nature. It continuously and gradually leads to high-quality and quantitative changes living organisms that are exposed to inanimate nature, as well as other organisms.
The study of the causes and patterns of evolution in biology is the study of evolutionary science, a complex of knowledge about the historical development of living nature. The basis of this doctrine is evolutionary theory.
Even the philosophers of the ancient world - Empedocles, Democritus, Lucretius Carus and others - expressed brilliant guesses about the development of life. But many more centuries passed before science accumulated enough facts that allowed scientists to discover the variability of species, and then create a theory that explains the evolutionary process occurring in nature.
In the second half of the 18th - first half of the 19th centuries. J. Buffon and E. J. Saint-Hilaire in France, E. Darwin in England, J. V. Goethe in Germany, M. V. Lomonosov, A. I. Radishchev, A. A. Kaverznev, K. F. Roulier in Russia and others created the doctrine of the changeability of animal and plant species, which contradicted the teaching of the church about their creation by God and immutability. However, they did not consider the reasons that lead to these changes.
First attempt to create evolutionary theory was made by the French naturalist J. B. Lamarck (1744-1829). In his work “Philosophy of Zoology” (1809), he outlined a holistic theory of the origin of species, but he could not correctly explain what driving forces development of the organic world.
A truly scientific evolutionary theory was created by the English naturalist Charles Darwin. It was set out in the book “The Origin of Species by Means of Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life,” 1859). Darwin managed to identify the driving forces - the factors of the evolutionary process. This is indefinite variability, the struggle for existence, natural selection.
As a result of the struggle for existence, the organisms most adapted to living conditions survive, while the less adapted, weak ones are eliminated from reproduction or die. Thanks to natural selection, beneficial hereditary changes accumulate and are summed up in plants and animals, and new adaptations also arise.
The struggle for existence and natural selection are the most important driving factors evolution, they are interconnected. They determine the further existence of the organism. In the process of biological evolution, the number of species of living organisms increases. The formation of new species in nature - the most important stage in the process of evolution.
As a result of the evolutionary process, the genetic composition of populations changes, biocenoses and the biosphere as a whole are transformed.
Evolutionary doctrine and its core is the biological evolutionary theory - the basis of modern progressive biology.
Evolution is a process historical development organic world. The essence of this process is the continuous adaptation of living things to diverse and constantly changing environmental conditions, and the increasing complexity of the organization of living beings over time. In the course of evolution, the transformation of some species into others occurs.
The main ones in evolutionary theory– the idea of historical development from comparatively simple shapes life to a more highly organized one. The foundations of the scientific materialist theory of evolution were laid by the great English naturalist Charles Darwin. Before Darwin, biology was mainly dominated by the incorrect concept of the historical immutability of species, that there are as many of them as were created by God. However, even before Darwin, the most insightful biologists understood the inconsistency of religious views on nature, and some of them speculatively arrived at evolutionary ideas.
The most prominent natural scientist and predecessor of Charles Darwin was the famous French scientist Jean Baptiste Lamarck. In his famous book“Philosophy of Zoology” he proved the variability of species. Lamarck emphasized that the constancy of species is only an apparent phenomenon; it is associated with the short duration of observations of species. Higher forms life, according to Lamarck, originated from lower ones in the process of evolution. Lamarck's evolutionary doctrine was not sufficiently conclusive and did not receive wide recognition among his contemporaries. Only after the outstanding works of Charles Darwin did the evolutionary idea become generally accepted.
Modern science has many facts that prove the existence of the evolutionary process. This is data from biochemistry, embryology, anatomy, systematics, biography, paleontology and many other disciplines.
Embryological evidence– similarity of initial stages embryonic development animals. Studying the embryonic period of development in various groups, K. M. Baer discovered the similarity of these processes in different groups of organisms, especially in the early stages of development. Later, based on these conclusions, E. Haeckel expresses the idea that this similarity has evolutionary significance and on its basis the “biogenetic law” is formulated - ontogenesis is a brief reflection of phylogeny. Each individual in its individual development (ontogenesis) goes through the embryonic stages of ancestral forms. Study only early stages The development of the embryo of any vertebrate does not allow us to determine with accuracy which group they belong to. Differences are formed at later stages of development. How closer group, to which the studied organisms belong, the longer common features will be preserved in embryogenesis.?
Morphological– many forms combine the characteristics of several large systematic units. When studying different groups of organisms, it becomes obvious that in a number of features they are fundamentally similar. For example, the structure of the limb in all four-legged animals is based on a five-fingered limb. This basic structure is various types transformed due to different conditions existence: this is the limb of an equid animal, which when walking rests on just one finger, and the flipper of a marine mammal, and the burrowing limb of a mole, and the wing of a bat.
Organs built according to a single plan and developing from single rudiments are called homologous. Homologous organs cannot in themselves serve as evidence of evolution, but their presence indicates the origin of similar groups of organisms from a common ancestor. A striking example evolution is served by the presence vestigial organs and atavisms. Organs that have lost their original origin are called vestigial. initial function, but persist in the body. Examples of rudiments include: in humans, which performs the digestive function in ruminant mammals; the pelvic bones of snakes and whales, which do not perform any function for them; coccygeal vertebrae in humans, which are considered to be the rudiments of the tail that our distant ancestors had. call the manifestation in organisms of structures and organs characteristic of ancestral forms. Classic examples Atavisms are multi-nipple and tailedness in humans.
Paleontological– the fossil remains of many animals can be compared with each other and similarities can be detected. Based on the study of fossil remains of organisms and comparison with living forms. They have their advantages and disadvantages. The advantages include the opportunity to see firsthand how this group of organisms changed in different periods. Disadvantages include that paleontological data are very incomplete due to many reasons. These include such as the rapid reproduction of dead organisms by animals that feed on carrion; soft-bodied organisms are extremely poorly preserved; and finally, that only a small fraction of the fossil remains are being discovered. In view of this, there are many gaps in paleontological data, which are the main object of criticism by opponents of the theory of evolution.
Nature improves itself all the time. But evolutionary changes proceed extremely slowly. Compared to human life, of course. Only over billions of years of the Earth’s existence was nature able to achieve such perfection and diversity of life as we see now.
Darwin suggested that the driving forces of evolution, or factors influencing the development of living nature, are:
- heredity and variability of individuals of one species;
Heredity and variability
It is known that individuals of the same species are similar, but still not the same. They differ slightly in terms of appearance and internal structure, behavior. These differences may influence the possibility of survival. More chances those individuals who survive and leave offspring have features which correspond to the habitat. These changes can be inherited by offspring. As a result, the number of individuals with such characteristics increases in the next generation.
Struggle for existence
Natural selection
The struggle for existence leads to natural selection - the preferential survival and reproduction of more adapted individuals of the species and the death of less adapted ones.
The action of natural selection over the course of many generations leads to the accumulation of small useful hereditary changes and the formation of adaptations of organisms to their environment.
An inhabitant of European forests, the hedgehog has sharp spines that serve as protection from predators. Their emergence is the result of natural selection. Even a slight hardening of the skin could help to survive distant ancestors hedgehog For many generations, individuals with more developed spines had an advantage in the struggle for existence. It was they who could leave offspring and pass on their hereditary changes to them. Gradually, new useful traits spread within the species, and all individuals European hedgehog became the owners of thorns.
Acting long time, the driving forces of evolution lead to the formation of adaptations of living organisms to various environmental conditions, to the transformation of some species into others, to the emergence of more complex forms of life on the basis of simpler ones.
Adaptation (adaptability)
Adaptations are features of living organisms, thanks to which they exist in nature. Useful traits, arising in individual organisms as a result of variability, help them survive in the struggle for existence. These characteristics are preserved as a result of natural selection and are inherited by descendants. Thus, generation after generation, the characteristics of animals and plants gradually change for the better for them. evolutionary changes. And that is why all living organisms are so well adapted to the conditions in which they live.
Speciation
Speciation is the result of evolution. Over the course of many generations, a population can be isolated from other populations of a given species (for example, located at a great distance from them). Acting for a long time, natural selection leads to the accumulation of many differences between the isolated and other populations.
As a result, individuals from different populations lose the ability to interbreed and produce offspring. The emergence of insurmountable biological barriers to crossing leads to the process of speciation.
Speciation led to the emergence of two types of foxes - the common fox and the corsac fox. In the north, natural selection favored the survival of the largest individuals (than larger size body, the less heat the body loses). As a result, the species Common fox was formed. In the southern regions, on the contrary, natural selection was aimed at preserving the smallest individuals (than smaller size body, the more heat the body gives off without overheating). As a result, the species Corsac fox was formed.
To date, biological evolution has been fully confirmed based on scientific facts, accumulated in various industries biological science. Evidence of evolution is based on a comparative study of external and internal structure, development and life processes modern representatives ancient extinct species. For this purpose there are scientifically based cytological,
The natural phenomenon of changes in populations, species, higher taxa, biocenoses, flora and fauna, genes and characteristics over time during the history of the Earth.
Scientific theories of evolution explain how evolution occurs and its mechanisms.
general characteristics
Strictly speaking, biological evolution is the process of change over time in hereditary characteristics, or the behavior of a population of living organisms. Hereditary milestones are encoded in an organism's genetic material (usually DNA). Evolution, according to the synthetic theory of evolution, is primarily a consequence of three processes: random mutations of genetic material, random genetic deviation (eng. genetic drift) and not random natural selection within groups and species.
Natural selection, one of the processes that governs evolution, results from differences in the chances of reproduction between individuals in a population. This necessarily follows from the following facts:
- Natural, hereditary variation exists within groups and among species
- Organisms are supernatural (the number of offspring exceeds the limit of guaranteed survival)
- Organisms are excellent in their ability to survive and regenerate
- In any generation, those that reproduce successfully necessarily pass on their hereditary traits to the next generation, while unsuccessful reproducers do not do this.
If traits increase the evolutionary fitness of the individuals who carry them, then those individuals are more likely to survive and reproduce than other organisms in the population. This way they pass on more copies of successful inherited traits to the next generation. A corresponding decrease in fitness due to harmful products leads to their existence. Over time, this can lead to adaptation: the gradual accumulation of new ones (and the preservation of existing ones), which generally adapt the population of living organisms to their environment and ecological niche.
Although natural selection is not random in its form of action, other capricious forces have strong influence on the process of evolution. In sexually reproducing organisms, random genetic variation leads to hereditary ones that become quite common simply through coincidence and random mating. This purposeless process may be influenced by natural selection in certain situations(especially in small groups).
In different environments, natural selection, random genetic variations, and a tiny bit of randomness in the mutations that appear and persist can cause various groups(or parts of a group) evolve in different directions. Given enough disagreement, two groups of sexually reproducing organisms can become different enough to form individual view, especially if the ability for interspecific crossing between two groups is lost.
Experiments show that all living organisms on Earth have a common ancestor. This conclusion was made based on the total presence of L-amino acids in proteins, the presence of total genetic code in all living beings, the possibility of classification by inheritance into categories, nested, homology of DNA sequences and commonality of biological processes.
Although the first mentions of the idea of evolution date back to recent times, modern form she acquired in the writings of Alfred Wallace and Charles Darwin in their joint paper at the Linnean Society in London (Linnean Society of London) and later in Darwin's On the Origin of Species (1859). In the 1930s Synthetic theory evolution combined evolutionary theory with the genetics of Gregor Mendel.
The evolution of organisms occurs due to changes in hereditary traits. For example, a person's eye color is a hereditary trait that an individual receives from his parents. Hereditary traits are controlled by genes. The set of genes of one organism is its genotype.
The set of all characteristics that form the structure and behavior of an organism is called a phenotype. These traits arise as a result of the interaction of the genotype of that organism with the conditions external environment. That is, not every phenotypic trait of an organism is inherited. For example, tanning is caused by the interaction of a person's genotype with sunlight, this way the tan will not fade. In general, people tan differently based on their genotype. For example, some people have a hereditary trait such as albinism. Albinos do not sunbathe and are very sensitive to solar radiation- They get sunburned easily.
Reasons for evolution
Matrix copying with errors
The basis of life on Earth is the process of copying molecules nucleic acids- DNA and RNA. The copying process is carried out by the matrix principle of complementarity: one nucleic acid molecule can form a pair for itself, and from this paired molecule a molecule is read that is identical to the original one. Thus, DNA and RNA molecules are capable of unlimited reproduction.
When copying, errors will certainly occur due to imperfections in the replication system. Through these errors, copies of DNA and RNA contain small differences, which, however, increase over time. This process of self-creation with changes is called convariant redupication.
Some inanimate systems, for example, crystals or some chemical cycles, are capable of unlimited reproduction with errors. But living things are different in that they can transmit these errors unchanged to subsequent generations. These errors, or mutations, practically do not change physicochemical characteristics molecules of nucleic acids, but affect the information read from them by living organisms. Thus, living organisms exhibit heredity and variability in their characteristics, which are led, respectively, by copying and mutations in nucleic acid molecules.
Homeostasis and stability of ontogeny
The constant reproduction of DNA with errors leads to what is present in every molecule genetic information changes a lot over time. Modern living organisms have systems to protect against excessive changes in the nucleotide sequence of the DNA molecule. These include repair enzymes, suppressors of mobile genome elements, antiviral defense mechanisms etc.
However, genes are still passed on to the next generation with some changes, with the result that a population of living organisms of the same species usually does not contain individuals in which all the DNA sequence is the same. At the same time, phenotypic variability is often less than genetic variability, since interactions between various genes in ontogenesis suppress the influence of changes in individual genes. Thus, multicellular organisms achieve stability individual development, leads to the preservation of the species norm.
Selective survival and reproduction
RNA and DNA molecules, as well as living organisms, reproduce with varying efficiency depending on their own properties and environmental conditions. Organisms may die before they reach the time of reproduction, and those that survive leave different quantities descendants. Those organisms that survived and reproduced effectively were able to do this through two groups of reasons: the compliance of their gene variants with environmental conditions or a combination of circumstances not related to the “quality” of the alleles. According to the influence of the first group on the distribution of alleles in a population, it is described by the concept of natural selection, and of the second group by the concept of genetic drift.
Natural selection
Natural selection is the selective survival (long-term survival) and reproduction of individuals in a population that are most adapted to environmental conditions. The more adapted a plant or animal is, the more likely her survival to reproductive age, as well as the more offspring she will leave. Fitness depends on the presence in the individual’s genotype of alleles of genes that contribute to survival and reproduction. Since all organisms in a population have different genotypes, when stable conditions the number of carriers of gene alleles that are more advantageous under these conditions will increase over generations.
In addition, environmental conditions create competition for survival and reproduction between organisms. Because of this, organisms that possess alleles that give them an advantage over their competitors pass on those alleles to their offspring. Alleles that do not provide this advantage are not passed on to subsequent generations.
Genetic drift
Genetic drift is a process of changes in allele frequency that is caused by reasons that are not related to the influence of alleles on the fitness of individuals. Therefore, genetic drift is considered a neutral mechanism in the evolution of genes and populations. The relationship between the influence of natural selection and genetic drift in a population varies depending on the force of selection and the effective size of the population (the number of individuals capable of reproduction). Natural selection usually plays big role in large populations, and genetic drift predominates in small ones. The predominance of genetic drift in small populations can even lead to the fixation of harmful mutations. As a result, changes in population size can significantly alter the course of evolution. The bottleneck effect, when the population declines sharply and as a result is lost genetic diversity, leads to greater homogeneity of populations.
General course of evolution
The first traces of life on Earth are dated 3.5-3.8 billion years ago. These are the remains of prokaryotic life - stromatolites. About 3 billion years ago, the first photosynthetics appeared, which were cyanobacteria. The first eukaryotes appeared about 1.6-1.8 billion years ago. It leads to " oxygen catastrophe"- a sharp increase in oxygen concentration in the Earth's atmosphere. Multicellular eukaryotes arose many times in different groups, however, the first reliable fossils date back to about 750 million years ago (Cryogenian period), and the appearance of diverse oceanic biota is associated with the Vendian period (Ediacaran biota, about 600 million years ago). The appearance of skeletal animals and their rich remains occurred in the Cambrian period about 550-520 million years ago. Then the majority appeared modern types animals.
In the Silurian period, plants first came onto land. In the Devonian, the first amphibians and arthropods settled on land. The Permian period gave rise to reptiles that dominated the Earth throughout the Mesozoic era. Several groups of therapsid reptiles further evolved into mammals. During the Cretaceous period, birds appeared and flowering plants began to flourish. IN Cenozoic era Mammals dominated, and insects also flourished. In the Anthropocene, one of the groups of primates, hominids, gave rise to human evolution. In the Pleistocene-Holocene, man becomes geological force, influencing the evolution of the entire biosphere.
Properties of evolution
The course of the evolution of life reveals several cross-cutting patterns that are objective and often described mathematically. Evolutionary biology studies additional mechanisms evolution or new possibilities for the implementation of the original principles, which will allow us to fundamentally understand the essence of these patterns. The main properties of evolution are as follows: the emergence of organisms adapted to the environment, morpho-functional progress, the appearance of new organs and structures (emergence), the transition to sexual reproduction, the extinction of species, the growth of biodiversity.
Adaptation
Modern species appear to be well adapted to the environment in which they exist. At the same time, adaptations are limited to the environment where they are usually used: when the organism moves into new environment he often becomes completely maladapted, or at least less adapted than the "native" inhabitants of other conditions. Before the appearance evolutionary picture world, the fairly clear correspondence of the properties of an organism to the conditions of its “native” environment so amazed researchers that they considered it a consequence of the action of supernatural forces. However, adaptation is an almost necessary consequence of evolution, since organisms less adapted to environmental conditions make an increasingly smaller contribution to the genetic diversity of the population due to natural selection. At the same time, the origin of the adaptations themselves does not necessarily depend on selection, but may be a side consequence of other adaptations or even a coincidence of circumstances (a consequence of genetic drift).
Progress and Autonomy
During evolution, anucleate bacterial cells give rise to complex eukaryotic cells. Eukaryotes subsequently acquire multicellularity and form tissues and organs. Animals develop nervous system, have complex behavior that allows them to survive in many environments. Man, as the pinnacle of animal evolution, has achieved the ability to live in any environment, including extraterrestrial ones.
Emergence
In the course of evolution, recombination of parts of organisms and genes often occurs, changing the function of old structures. However, some processes and parts of organisms arose for the first time. Photosynthesis in cyanobacteria, DNA replication proteins, translation apparatus, fish scales and the like.
Dioecy
The first animals were hermaphrodites, and among the higher hermaphrodites there are almost no hermaphrodites.
Sex and recombination
IN asexual organisms genes are inherited together (they vaccinated) and do not mix with the genes of other individuals during reproduction. The descendants of sexual organisms contain a random mixture of the chromosomes of their parents due to independent sorting. During the related process of homologous recombination, sexual organisms exchange DNA between two homologous chromosomes. Recombination and independent sorting do not change the frequencies of alleles, but they change their association with each other, producing offspring with new combinations of alleles. Sex generally increases genetic variation and can increase the rate of evolution. However, asexuality may have advantages in certain environments because it has re-evolved in some organisms. Asexuality may allow two sets of alleles to diverge in the genome and, as a consequence, lead to the emergence of new functions. Recombination allows equal alleles that are found together to be inherited independently. However, the frequency of recombination is low (approximately two events per chromosome per generation). As a result, genes located nearby on the same chromosome are not always separated from each other during the process of genetic recombination and tend to be inherited together. This phenomenon is called gene linkage. Gene linkage is assessed by measuring the frequency of two alleles on the same chromosome (a measurement of gene linkage disequilibrium). A set of alleles that tend to decline together is called a haplotype. This is important when one of the alleles of a particular haplotype provides a large advantage in the struggle for existence: positive natural selection will lead to selective purification (English) Selective sweep), which will lead to the fact that the frequency of other alleles of this haplotype will also increase. This effect is called genetic hitchhiking. When alleles cannot be separated by recombination (for example on the Y chromosome of mammals), then harmful mutations accumulate (cm. Mueller ratchet). By changing combinations of alleles, sexual reproduction leads to the removal of harmful and the spread of beneficial mutations in the population. In addition, recombination and gene sorting can provide organisms with new beneficial combinations of genes. But this one positive effect balanced by the fact that sex reduces the rate of reproduction (cm. The evolution of sexual reproduction) and can cause the destruction of advantageous gene combinations. The reasons for the evolution of sexual reproduction still remain not entirely clear and this issue is still an active area of research in the field evolutionary biology. It stimulated new ideas about the mechanisms of evolution, such as the Red Queen hypothesis.
Extinction
There have been many times in the history of the Earth mass extinctions living organisms. These were the extinctions at the border of the Vendian and Cambrian periods, when the Ediacarian biota died, the Permian and Triassic periods, the Cretaceous and Eocene periods. After mass death old groups of organisms began to flourish those groups that survived extinction. Extinctions on a smaller scale, such as the post-glacial extinction of large mammals after the last ice age, also lead to changes in groups of organisms. Humans have led to the extinction of species that are most vulnerable to its anthropogenic activities.
Increased biodiversity
Paleontological findings, although incomplete and limited, demonstrate an increase in biodiversity both in the ocean and on land.
Levels of evolution
On different levels Organizations of living properties of evolution and its mechanisms play different roles.
- genetic
- genomic
- population
- species
- taxonian
- ecosystem
- biosphere
Mutations
Genetic variation occurs due to random mutations occurring in the genomes of organisms. Mutations are changes in the sequence of DNA nucleotides caused by radioactive radiation, viruses, transposons, chemical mutagens, and copying errors that occur during meiosis or DNA replication. These mutagens produce several various types changes in the sequence of DNA nucleotides: they may have no effect, change the gene product, or even stop the gene from functioning. Studies in fruit flies have shown that if mutations cause changes in a protein that is encoded by a particular gene, the consequences are likely to be detrimental. Approximately 70% of such mutations lead to certain disorders, the rest are neutral or beneficial. Since mutations often have a harmful effect on cells, in the process of evolution organisms have developed DNA repair mechanisms that eliminate mutations. Thus, the optimal mutation rate is a compromise between the cost of paying for a high frequency of deleterious mutations and the cost of metabolic costs (for example, the synthesis of repair enzymes) to reduce this frequency. Some organisms, such as retroviruses, have such a high mutation rate that almost every one of their descendants will possess a mutated gene. This high mutation rate may be an advantage because these viruses evolve very quickly, thus evading immune system responses.
Mutations can involve large stretches of DNA, such as gene duplications, which provide the raw material for the evolution of new genes. In animals, on average, duplications of tens to hundreds of genes occur every million years. Most genes that share a common ancestor belong to the same genetic family. New genes are formed in several ways, generally through duplication of ancestral genes, or through recombination of parts of different genes, resulting in the formation of new combinations of nucleotides with new functions. New genes form new proteins with new functions. For example, to form the structures of the human eye that are responsible for the perception of light, four genes are used: three for color vision (cones) and one for night vision (rods), all of these genes descended from one ancestral gene. Another advantage of duplicating a gene, or even an entire genome, is that it increases the redundancy (redundancy) of the genome; this allows one gene to acquire new functions while a copy of that gene performs the original function. Changes in chromosomes can occur as a result of large mutations, when segments of DNA within a chromosome are separated and then reinserted elsewhere on the chromosome. Nariklad, two chromosomes of the genus Homo fused to form human chromosome 2. This merger did not take place in the phylogenetic series of other monkeys, that is, they have these chromosomes separated. The most important role Such chromosomal rearrangements in evolution accelerate the divergence of populations with the formation of new species due to the fact that fewer interpopulation crossings occur.
DNA sequences that can move around the genome (Transposable genetic elements), such as transposons, form most genetic material genetic material of plants and animals and are important in the evolution of genomes. For example, more than a million Alu sequences are present in the human genome, and these sequences now serve to regulate gene expression. Another effect of these mobile DNAs is that they can cause mutations in existing genes, or even remove them, thus increasing genetic diversity.
The problem of the origin of life
Recognition of evolution by the Catholic Church
The Catholic Church recognized the Latin in the encyclical of Pope Pius XII. Humani Generis, that the theory of evolution can explain the origin of the human body (but not his soul), calling, however, for caution in judgment and calling the theory of evolution a hypothesis. 1996 Pope John Paul II, in a letter to the Pontifical Academy of Sciences, confirmed the acceptance of theistic evolutionism as a valid position for Catholicism, stating that the theory of evolution is more than a hypothesis. Therefore, among Catholics, literal, young-earth, liquid creationism (J. Keene can be cited as one of the few examples). Leaning toward theistic evolutionism and the theory of “intelligent design,” Catholicism, represented by its highest hierarchs, including the elected 2005 pope Benedict XVI, however, certainly rejects materialistic evolutionism.