Learn more about the types of living things. Let's look at what it is below.

What's the point?

Speciation is the process of formation and change of new biological species.

It is also a very complex process of evolution and the emergence of a new species, which ceases any ties with its parents and turns into a special, unique community of organisms.

The essence of speciation is the change in organisms, the main force of the phenomenon is considered to be natural selection and

There are several types of speciation: allopatric, the process of which proceeds slowly and smoothly, in contrast to another type - sympatric. It can occur at different speeds, but most often it occurs chaotically and jerkily. Charles Darwin believed that the extinction of intermediate forms and the survival of extreme forms as a manifestation of competition is this process. The stages of speciation throughout the creation of a new subject alternate with a strict sequence, creating a chain of newly introduced qualitative parameters, data that will make it possible to identify a certain population or individual as a representative of a new species.

Forms of speciation

Divergent speciation is the primary division of an entire species into several new ones. The main effect of this is the accumulation of various changes at the genetic level and the disappearance of reproductive function.
Phyletic speciation is a mechanism of metamorphosis in which one species passes into another, new one. The main process is that when climate change occurs, better changes occur in the entire population. Through hybridization, different species are crossed in their habitat.

The emergence of one or more new species is subject to two main mechanisms: allopatric and sympatric. The sequence of speciation largely depends on a wide variety of factors corresponding to the form of appearance of the new individual.

Mechanics of sympatric speciation

Sympatric (ecological) speciation is the emergence of a new subject among a standard set of individuals in a species; it appears within the old habitat. This isolation process is called genetic.
Sympatric (ecological) speciation is a phenomenon carried out in a certain territory and depends on the appearance in the population of certain independent groups that do not have the opportunity to interbreed. This option is the fastest; it gives birth to species that are closest to the initial one. This is the process of speciation, as a result of which individuals of one species intensify the struggle for existence within old habitats, without expanding.

Allopatric (geographic) speciation

"Instant" speciation based on polyploidy

Where reproduction occurs asexually (as in various plants), it only takes one individual significantly different from the rest to become completely genetically isolated and give rise to an entirely new species.
Variants of sympatric speciation are polyploidy and hybridization.

Polyploidy is the name of a type of mutation when the presence of chromosomes in living cells increases, it always occurs a multiple of times. For example, completely different types of wheat form a line with the number of chromosomes 14, 28, 42. The cells of wild cotton contain 26 chromosomes, and its cultivated counterpart - already 52. ​​Hybridization is the process of crossing and obtaining new hybrids, the essence of which is to combine genetic material in the cells of an individual.

Observation of speciation

Hybridization is the crossing of organisms of different species, that is, the combination of different genomes in one individual (hybrid). One of the common examples of hybridization is the cultivated plum, which was obtained by combining the cells of sloe and cherry plum. Also in this group we can mention the mountain ash, whose habitat is the taiga of central Siberia.

Examples of speciation

Apple leaf flies Rhagoletis pomonella are one of the most striking examples of speciation. During the process of their evolution, the existence of this species was not separated by physical barriers. Initially, the habitat of these flies was the east coast of the United States of America. These flies existed in hawthorn fruits, but with the beginning of the colonization of the United States and the introduction of new crops to this territory, including the apple tree in 1647, new niches and habitats appeared. But it was only in 1864 that Rhagoletis pomonella was recorded on apple fruits, indicating the emergence of a completely new species. Over the course of long observations, the development paths of species divided.

Representatives do not interbreed with each other, since each race prefers its own type of fruit for mating. Due to the different flowering periods of plants, this process becomes simply impossible.

Scientists have identified types of speciation when dividing the old into several new ones into two main types of this process: allopathic and sympatric.

Speciation on islands

Since islands are where conditions arise for the development of groups of flora and fauna separate from the mainland, species are able to acquire new properties and characteristics. If on the mainland adaptation to the climate was not necessary for existence and survival, an easier method of survival was preferable - migration. On the islands, adaptability to the environment is a must.

On the mainland, animals throughout the entire evolutionary period could move to different climatic zones and move along with glaciers. The species existing on the islands had to adapt to local climatic conditions - this was the key to survival.

These features of existence have formed many species of unusual animals on the islands. Unfortunately, much of this amazing wildlife has disappeared, all thanks to human intervention. Hunting, the introduction of rodents, bacteria and infections have led to the mass extinction of rare amazing species. At a time when man had not yet set foot on the wild islands, each of them had its own world, absolutely unique and unlike the others. Before the advent of humans, species living on the islands could migrate to the mainland only with changes in water levels or global changes in geological position. The cause of migration could also be disasters that disrupted the island's isolation. As a result of such changes, both island and continental animal species were able to migrate in both directions. In most cases, with such movement and when mainland species arrived on the island, the island inhabitants were threatened with complete extinction. Although there were cases when local species adapted to new conditions and competed with new ones that arrived from the mainland.

Peripheral isolators

Paleontologists rarely find remains that belong to the ancestors of modern animal species. The island origin suggests that the present species of flora and fauna were originally separated and existed in limited populations. Due to their size, these populations were unable to find opportunities to search for new places, and the island itself may have ceased to exist over time.

Not all animal species began their existence on islands, which is the most common condition for geographic isolation.

Importance of Peripheral Isolators

The bottom line is that new species arise in an environment completely isolated from the outside world and in small populations. The entry of a small population of individuals into a wider habitat will certainly lead to the extinction of the population, but from the percentage of subjects that manage to adapt to new conditions, new organisms arise.

Species that manage to survive arise from small populations, engaging in a battle for dominance with dominant life forms, rather than by slowly transforming existing ones. If the dominant species cannot withstand the fight, then new forms begin to grow. The process of creating life spans periods of billions of years, during which time continents appeared and disappeared, water levels changed, and the climate became hotter and colder. Species and populations of animals were constantly separated and connected with each other, various barriers between them formed and disappeared.

Natural changes and global catastrophes, such as the fall of a meteorite, were the conductor of evolution and modification. Constant changes in the habitat conditions of species forced them to adapt to changing conditions. A huge number of organisms failed to do this. Those who were able to adapt settled and captured new territories for existence. Unlike land, the world's oceans are the largest and most stable environment in the world, in which billions of different creatures and organisms exist. There are practically no natural barriers, and relatively few new forms of life are formed.

Over the past several hundred billion years, a global event for the world's oceans has been the emergence of species of marine reptiles that are quite hardy and resistant to various changes. In further development, marine mammals and many species of seabirds arose.

Currently, the main negative event has been the increase in human presence in the world's oceans: the dumping of household, construction, industrial and radioactive waste, uncontrolled fishing of various species of fish, and the complete extermination of some species of marine predators and large mammals. Human consumption on the world's oceans can lead to a global catastrophe and the extinction of many marine species.

Speciation is the result of microevolution and occurs in a population over a certain period of time. A new group appears, ending any connection with its relatives.

But new forms can be formed in different ways. In the first place is isolation. Isolated from each other, organisms accumulate differences, supported by genes. The new population that has emerged is a different species that cannot interbreed with former relatives.

Forms of speciation

The formation of species is influenced by the usual evolutionary factors: mutations, genetic drift, natural selection, waves of life and isolation. Among the forms of education there are:

• Changing environmental conditions throughout the entire range force individuals in the population to accumulate advantageous adaptations. Gradual transformation is called phyletic speciation.
• In some cases, the ranges overlap. Then, with random crossings of individuals from different groups, hybrids are formed - this is a hybridogenic form.
• In true speciation, called divergent speciation, the original unit is divided into several. This occurs during isolation, with the accumulation of new genetic characteristics and the disappearance of reproductive functions. At the same time, a distinction is made between allopatric, or geographical, speciation and sympatric, i.e. biological.

In populations occupying a certain territory, independent groups of individuals with biological differences appear. They, not being able to cross with each other, form a new species. Reasons: - shift in timing associated with flowering, mating, spawning; - different breeding sites. With such isolation, sympatric ecological speciation occurs.

Sympatric speciation

The emerging organisms with new characteristics are slightly different from the original individuals, and the process itself proceeds quickly. The struggle for existence, in this case, intensifies. For asexual reproduction, only one individual is needed. If it is very different from other relatives, it can be isolated at the genetic level and produce offspring of a new species. Such “sudden” sympatric speciation includes:

1. Polyploidy is a genomic mutation when the number of the chromosome set increases and becomes a multiple of the haploid number.
2. Hybridization is when two different genetic materials combine to form a hybrid.

Examples of ecological speciation

Most often this applies to those organisms that depend on environmental factors where they usually live.

• There are two different shapes of alfalfa – sickle and sticky. One grows at the bottom of the mountains, the other at the top. Blackbirds. The habitat of some is deep forests, others are close to human habitation. Both are within the same range.
• Plants pollinated by insects with special adaptations to a specific flower shape. The bee is the insulating factor in snapdragon flowers.
• Big rattle. This plant comes in two forms; outwardly they are no different from each other. But one prefers to bloom in spring, and the other in August. Various forms arose from the annual mowing of the grass.
• Sevan trout is represented by 5 populations, spawning at different times and going to different depths in different parts of the reservoir.

Allopatric speciation

Geographic speciation is more accurately called allopatric. New species are formed when isolated by space (reservoirs, mountains, deserts) and differences in climatic conditions. It occurs in two ways: fragmentation during the disintegration of the parental range or the resettlement of original groups. Moreover, the emerging groups are located in areas that are not connected with their parent habitats.

Such speciation is often influenced by geological processes. Allopatric speciation takes quite a long time, hundreds of thousands and millions of years. During this time, many generations change, between which there is constantly a stubborn struggle for survival and territory.

Examples of allopatric speciation

Organisms isolated from each other cannot exchange genetic material. This leads to the formation of a new species.

• There are two subspecies of American squirrels and three subspecies of blue jays, their habitat is North America, but different geographical areas.
• The great tit settled over a large territory and formed 3 subspecies.
• New lilies of the valley, the ancestors of the original species of which occupied the forests of Eurasia, appeared in those places where there was no glacier, which divided the range into different territories.

Species and speciation

A species is a group of organisms that have the same genetic, morphological, and physiological characteristics. They interbreed freely and produce fertile offspring. In addition, inhabiting a certain territory, they descend from the same ancestors. Thanks to the special characteristics of organisms, both individuals and the entire population survive.

Due to the heterogeneity affected by mutations, within such a group there are organisms with varying degrees of fitness. In the new conditions of existence, only those who have the desired persistent trait will survive and give birth to offspring. For example, tits of the same species, but feeding on different foods, formed 5 new ones. Subspecies often cannot interbreed during reproductive isolation if they do not have the same genitals, different behavior, or incompatible genetic material.

Speciation process

Speciation is the completion of microevolution, a qualitative stage in the evolution of organisms. Speciation consists of the following stages:

• the course of natural selection within a population, depending on living conditions;
• accumulation of mutational changes;
• emergence and separation of subspecies;
• natural selection in subspecies;
• biological isolation;
• emergence of a new species.

In a changed environment, the struggle for survival between representatives of the same group always intensifies. Surviving individuals pass on successful traits that are reinforced in new conditions of existence.

Speciation is the result of evolution

Charles Darwin, who recognized the existence of a species unit, managed to prove that nature is constantly replenished with new forms of organisms descended from existing organisms. He pointed out that this process is influenced by the driving forces of evolution. Each species strives to fill its habitat as completely as possible and master different methods of survival. In this case, from one ancestral form several are formed that have mastered different habitats.

• Evolutionary scientists, based on experiments conducted, have established a very rapid acquisition of new characteristics under changing conditions. In Trinidad, guppy fish that lived in the water below a waterfall with many predators were moved to the water above the waterfall. Here predators ate only small fish. The descendants of the settlers adapted by becoming large. According to scientists, the fish needed much more time, millions of years instead of these 4.
• In the Bahamas, lizards from an island with tall trees were moved to another with bushes. In the new place, in subsequent generations, the hind legs gradually became shorter. This speed of appearance of the trait is thousands of times greater than the proven adaptation by paleontologists.

conclusions

The completion of speciation is reproductive isolation when the isolating barrier is removed. The subsequent fate of the new generation, whether it will flourish, die, or split into several groups, will depend on the complex interspecies relationships that have arisen. Without the emergence of new species, the development of nature is impossible.

Speciation is the process of the emergence of new species. Speciation is the process of changing old species and the appearance of new ones as a result of the accumulation of new characteristics. In this case, the genetic incompatibility of newly formed species, that is, their inability to produce fertile offspring or offspring at all, when crossed is called an interspecific barrier, or a barrier of interspecific compatibility.

There are various theories explaining the mechanisms of speciation, none of which is generally accepted or fully proven. One of the reasons for this is the difficulty of empirical verification due to the long-term nature of the process being studied.

According to the synthetic theory of evolution (STE), the basis for speciation is the hereditary variability of organisms, the leading factor is natural selection. In STE, two modes of speciation are distinguished: geographical, or allopatric, and ecological, or sympatric.

Sympatric (ecological) speciation

It is associated with the divergence of groups of individuals of the same species and living in the same habitat according to ecological characteristics. In this case, individuals with intermediate characteristics turn out to be less adapted. Diverging groups form new species.

Sympatric speciation can occur in several ways. One of them is the emergence of new species with a rapid change in the karyotype through polyploidization. There are known groups of closely related species, usually plants, with a multiple number of chromosomes. Another method of sympatric speciation is hybridization followed by doubling of the number of chromosomes. There are now many species known whose hybridogenic origin and genome character can be considered experimentally proven. The third method of sympatric speciation is the occurrence of reproductive isolation of individuals within an initially single population as a result of fragmentation or fusion of chromosomes and other chromosomal rearrangements. This method is common in both plants and animals. A feature of the sympatric path of speciation is that it leads to the emergence of new species, always morphologically close to the original species. Only in the case of the hybridogenic emergence of species does a new species form appear, different from each of the parental ones.

Allopatric (geographic) speciation

Caused by the division of a species' range into several isolated parts. Moreover, selection can act differently on each such part, and the effects of genetic drift and the mutation process will be clearly different. Then, over time, new genotypes and phenotypes will accumulate in isolated parts. Individuals in different parts of a previously unified range can change their ecological niche. With such historical processes, the degree of divergence of groups can reach the species level.

"Instant" speciation based on polyploidy

It does not imply division of the area into parts and is formally sympatric. Moreover, over several generations, as a result of sharp changes in the genome, a new species is formed.

Speciation occurs through saltation based on polyploidy in plants.

Hybridogenic speciation

When different species are crossed, the offspring are usually sterile. This is due to the fact that the number of chromosomes varies between species. Dissimilar chromosomes cannot pair up normally during meiosis, and the resulting sex cells do not receive a normal set of chromosomes. However, if a genomic mutation occurs in such a hybrid, causing the number of chromosomes to double, then meiosis proceeds normally and produces normal germ cells. In this case, the hybrid form acquires the ability to reproduce and loses the ability to interbreed with parental forms. In addition, interspecific plant hybrids can reproduce vegetatively.

Speciation is an evolutionary process as a result of which new species are formed from individual populations of existing species of living organisms. In living nature, speciation occurs everywhere and always. However, this is usually a fairly long process that cannot be directly observed. Thus, the formation of a new species can take millions of years.

As a result of speciation, the number of species on Earth is constantly increasing. However, many species become extinct for one reason or another (due to changing climatic conditions, as a result of human activity, etc.). Therefore, over the entire history of the Earth, the number of species of living organisms that arose on it, according to some estimates, exceeds a billion, but the number of living species is estimated at around 2 million.

There are two main methods of speciation, that is, how exactly a new species is formed from a previously existing one. One mode of speciation is called geographic (or allopatric), the other is called biological (or ecological, or sympatric).

When geographical mode of speciation one of the populations of a species finds itself in slightly different living conditions and isolated from other populations of the same species. Isolation prevents the exchange of genes, and new conditions force the population to follow its own evolutionary path. Over a series of generations, individuals develop new characteristics adapted to the existing environment. In this case, such changes may occur in the genotype that exclude the possibility of crossing with individuals of the original species of this population. As a result, a new species is formed on the basis of this population.

A classic example of a geographic mode of speciation is Darwin's finches. It is assumed that some groups of finches living in South America somehow ended up on different Galapagos Islands. Moreover, each group followed its own evolutionary path.

Biological mode of speciation usually occurs over a shorter period than geographical time, and is more typical for plants than for animals. In biological speciation, a new species is formed as a result of a random change in the genotype of an individual. At the same time, it can no longer interbreed with other individuals of the original species. This, for example, occurs in plants as a result of polyploidy (a multiple increase in the number of chromosomes). The mutant plant can then reproduce vegetatively or through self-pollination, effectively founding a new species. Polyploidy is not the only way of biological speciation. A new species can also be formed as a result of other chromosomal rearrangements.

Typically, biological speciation results in the original species splitting into species occupying different ecological niches. Therefore, it is also called ecological speciation.

3. Evolutionary changes occurring at the population, intraspecific level are called m spawning . The process of microevolution has two forms:

Phyletic evolution;

Speciation.

Phyletic evolution means gradual changes that occur over time within a single species, population, or group of populations. As a rule, as a result of these changes, the adaptability of organisms to the environment increases.

Speciationoccurs when a biological species splits into two or more new species. It is this process that provides the enormous diversity of the organic world.

Stages of speciation. Speciation usually consists of two stages: first - the occurrence of reproductive isolation,

second– its consolidation by natural selection.

At the first stage of speciation, the exchange of genes between two populations of a given species must cease; this usually occurs as a result of geographic separation, such as the occurrence between populations of a mountain range, glacier, water hazard, etc. The lack of gene exchange between two populations creates the opportunity for their genetic divergence(discrepancies). Such divergence can arise both as a result of adaptation of organisms to local conditions, and as a result of random changes in the composition of the gene pool of each population. (As genetic differences between isolated populations accumulate, due to changes in conditions and lifestyle, prezygotic isolating mechanisms arise, for example, differences in the timing of reproduction, in behavior, etc.

Subsequently, the separation of populations can be consolidated due to the development of postzygotic isolating mechanisms. The separation of species becomes irreversible. The process of the emergence of complete isolation is supported by natural selection.

The specific ways in which new species arise may vary. In general, there are two main forms of speciation: allopatric And sympatric.

Using the material presented below and the textbook, fill out the table “Characteristics of forms of speciation” independently.

Form name	Shape characteristics
allopatric	This form of speciation is associated with the expansion of the range of the original species and occurs during long-term geographic isolation of populations. The emergence of geographical barriers (mountain ranges, sea straits, etc.) leads to the emergence insulators– geographically isolated populations. Speciation associated with spatial separation of populations – geographical.
sympatric	environmental(for example, food) specialization, therefore this form of speciation is often called ecological. b) sudden, polyploidy, i.e., by multiplying the number of chromosomes of the original ancestral species.

Allopatric speciation. This form of speciation is associated with the expansion of the range of the original species and occurs during long-term geographic isolation of populations. The emergence of geographical barriers (mountain ranges, sea straits, etc.) leads to the emergence insulators– geographically isolated populations. As a rule, this occurs at the border of the range of the original species, where living conditions are somewhat different from usual and the processes of natural selection are actively occurring. As a result, the single gene pool of the species seems to be torn into pieces. Every territorial population is characterized by its own gene pool with its characteristic frequencies of occurrence of different alleles. Interruptions of gene flow between isolators, on the one hand, and the action of natural selection, on the other, ultimately lead to their reproductive isolation and the formation of independent species. Such speciation, associated with spatial separation of populations, is also called geographical.

Two kinds

Rice.Scheme of geographic speciation: A – local populations of one species; B – division of populations into two groups; B – cessation of gene exchange between populations; D – completion of speciation.

Previously, you have already familiarized yourself with examples of geographic speciation, considering the emergence of modern species of lily of the valley from the original species that lived millions of years ago in the broad-leaved forests of Europe. The invasion of the glacier tore the single habitat of the lily of the valley into several parts. It has been preserved in forest areas that escaped glaciation: in the Far East, southern Europe, and Transcaucasia. When the glacier retreated, lily of the valley spread again in Europe, forming a new species, larger, with a wide corolla, and in the Far East - a species with red petioles and a waxy coating on the leaves.

Sympatric speciation. Sympatric speciation is associated with the emergence of a new form within the original population. Such nucleation can occur as a result of: a) environmental (for example, food) specialization, therefore this form of speciation is often called ecological. It is believed that the five species of tits were formed in connection with food specialization: according to the methods of searching for and preying on them. For example, the great tit hammers branches and tree trunks; small species (blue tit) – only stems of herbaceous plants. The smallest species (coal tits, tufted tits) more often explore the terminal branches of the tree in search of food. The great tit feeds on large insects; The blue tit and the titmouse hunt for small insects in the crevices of the bark and in the buds; The tufted tit feeds on the seeds of coniferous trees.

Another form of sympatric speciation includes b) sudden , occurring as a result of chromosomal mutations, polyploidy and hybridization. It is known that closely related potato species differ from each other by a multiple set of chromosome numbers: n=12, 24, 48, 72. This allows us to assume that the corresponding species were formed as a result polyploidy, i.e., by multiplying the number of chromosomes of the original ancestral species.

In plants, as a result of polyploidy, isolating mechanisms are able to form during the life of a single generation. A multiple increase in the number of chromosomes within one species can occur spontaneously; or chromosome multiplication occurs as a result of crossing closely related organisms. In addition to potatoes, many economically valuable plants are polyploids. The chromosome sets of animals can also change rapidly. Polyploids are found among fish (sturgeon, spined loach, etc.), grasshoppers, worms, insects and other animals.

Sometimes speciation occurs due to hybridization followed by a doubling of the number of chromosomes. Thanks to the doubling of chromosomes, normal germ cells are formed in such organisms and the development of the offspring proceeds without disturbances. The cultivated plum with 2n = 48 chromosomes, for example, arose by crossing sloe (n = 16) with cherry plum (n = 8) and then doubling the number of chromosomes.

Thus, the formation of new species as a result of chromosomal rearrangements can occur in populations inhabiting the same geographical area and not separated by any barriers.

Rice. 82. Types of tits

Rice. 83. Polyploidy. A large-leaved rose with 14 chromosomes (left) and its polyploid form with 28 chromosomes (right).