Indicators artificial selection natural selection table. Natural selection

Artificial selection. To substantiate the historical principle of the development of wildlife, Darwin deeply studied the centuries-old practice of agriculture and animal husbandry and came to the conclusion: the variety of breeds of domestic animals and cultivated varieties of plants is the result of variability, heredity and artificial selection.

Artificial selection is carried out by a person and can be twofold: conscious (methodical) - in accordance with the goal set by the breeder, and unconscious, when a person does not set goals for breeding a breed or variety with predetermined properties, but simply eliminates less valuable individuals and leaves the best for the tribe. Unconscious selection was carried out by man for many millennia: even savages during a famine left more useful animals for the tribe, and killed less valuable ones. In unfavorable periods, primitive man first of all used hard fruits or smaller seeds, and in this case he also made selection, but unconscious. In all cases of such selection, the most productive forms of animals and more productive varieties of plants were preserved, although man here acted as a blind factor of selection, which can be any other factor of the environment. .one

Many valuable forms have been bred by centuries of artificial selection. In particular, by the middle of the XIX century. more than 300 varieties of wheat have been registered in agricultural practice, 38 varieties of date palm were cultivated in the deserts of North Africa, in Polynesia - 24 forms of breadfruit and the same number of varieties of banana, in China - 63 varieties of bamboo. There were about 1000 varieties of grapes, more than 300 of gooseberries, about 400 breeds of cattle, 250 breeds of sheep, 350 breeds of dogs, 150 breeds of pigeons, many valuable breeds of rabbits, chickens, ducks, etc. or the breed originates from its direct ancestor. However, Darwin proved that the source of the diversity of animal breeds and varieties of cultivated plants is one or a small number of wild ancestors, the descendants of which were transformed by man in different directions in accordance with his economic goals, tastes and interests. In this case, the breeder used the hereditary variability inherent in the selected forms.

Darwin distinguished definite (now called modification) and indefinite variability. With a certain, or group, variability, all or almost all of the offspring of individuals exposed to the same conditions change in one direction; for example, when there is a shortage of food, animals lose weight; in a cold climate, wool in mammals is thicker 1 t. one ort, one breed, one species. Currently, this form of variability is called genotypic. Variability is transmitted to offspring not only during sexual reproduction, but also during vegetative reproduction: often a plant grows shoots with new properties or buds develop, from which fruits with new qualities (grapes, gooseberries) are formed - the result of a mutation in the somatic kidney cell.

In the phenomena of variability, Darwin discovered a number of important regularities, namely: when one organ or sign changes, others may change. For example, a crest develops at the site of attachment of the exercised muscle to the bone; in wading birds, the neck is lengthened simultaneously with lengthening of the limbs, and the thickness of the hair in sheep changes accordingly with an increase in the thickness of the skin. This variability is called correlative or correlative. On the basis of correlative variability, the breeder can predict deviations from the original form and select in the desired direction.

Natural selection unlike artificial, it is carried out in nature itself and consists in the selection within the species of the most adapted individuals to the conditions of a particular environment. Darwin discovered a certain commonality in the mechanism of artificial and natural selection: in the first form of selection, the conscious or unconscious will of man is embodied in the results, in the second, the laws of nature prevail. In both cases, new forms are created, however, with artificial selection, despite the fact that variability affects all organs and properties of animals and plants, the resulting animal breeds and plant varieties retain traits that are useful for humans, but not for the organisms themselves. On the contrary, natural selection preserves individuals in which the changes are useful for their own existence in the given conditions.

Certain and indefinite variability is constantly observed in nature. Its intensity is less pronounced here than in domestic forms, since the change in the natural environment is subtle and extremely slow. The emerging qualitative heterogeneity of individuals within species, as it were, brings many "applicants" to the evolutionary arena, leaving natural selection to reject those less adapted to survival. The process of natural "culling", according to Darwin, is carried out on the basis of variability, the struggle for existence and natural selection. The material for natural selection is provided by the undefined (genotypic) variability of organisms. It is for this reason that the offspring of any pair of wild (as well as domestic) organisms turns out to be heterogeneous. If the changes are beneficial, it increases the chances of survival and procreation. Any change harmful to the organism will unconditionally lead to its destruction or the impossibility of leaving offspring. Survival or death of an individual is the final result of the "struggle for existence", which Darwin understood not literally, but figuratively. He distinguished three forms of struggle for existence:

A) intraspecific - the most fierce, since individuals of the same species need similar food sources, which are also limited, in similar conditions for reproduction, the same shelters;

C) the struggle of living organisms with factors of inanimate nature - environmental conditions during drought, floods, early frosts, hail, many small animals, birds, worms, insects, grasses die.

As a result of all these complex relationships, many organisms die or, being weakened, do not leave offspring. Individuals with at least minimal beneficial changes survive. Adaptive traits and properties do not appear immediately, they are accumulated by natural selection from generation to generation, which leads to the fact that the descendants differ from their ancestors at the species and higher systematic level.

The struggle for existence is inevitable due to the intensive reproduction existing in nature. This pattern knows no exceptions. There are always more organisms born than those capable of living to adulthood and leaving offspring. Calculations show: if all born mice survived, then within seven years the offspring of one pair would occupy the entire land. the globe... A female cod fish lays up to 10 million eggs at a time, one plant of a shepherd's purse gives 73 thousand seeds, henbane - 446 500, etc. However, " geometric progression reproduction "never takes place, since there is a struggle between organisms for space, food, shelter from enemies, competition in choosing a sexual partner, a struggle for survival with fluctuations in temperature, humidity, lighting, etc. In this" fight "most of the born die , leaving no offspring, and therefore in nature the number of individuals of each species remains constant on average.

Table Forms of selection (T. L. Bogdanova. Biology. Tasks and exercises. A guide for applicants to universities. M., 1991)

Indicators	Artificial selection	Natural selection
Source material for selection		Individual signs of an organism
Selection factor		Environmental conditions (wildlife and inanimate nature)
Change path:
favorable	Get selected, become productive	Remain, accumulate, inherited
unfavorable	Selected, rejected, destroyed	Are destroyed in the struggle for existence
The nature of the action	Creative - directed accumulation of traits for the benefit of a person	Creative - selection of adaptive characters for the benefit of an individual, population, species, leading to the emergence of new forms
Selection result	New varieties of plants, breeds of animals, strains of microorganisms	New species
Selection forms	Mass; individual; unconscious (spontaneous); methodical (conscious)	Motive, supporting evasion in changing environmental conditions; stabilizing, maintaining the constancy of the average reaction rate under constant environmental conditions

Natural selection is the main, leading, directing factor of evolution, underlying the theory of Charles Darwin. All other factors of evolution are random, only natural selection has a direction (towards the adaptation of organisms to environmental conditions).

Definition: selective survival and reproduction of the fittest organisms.

Creative role: choosing useful traits, natural selection creates new ones.

Efficiency: the more there are various mutations in the population (the higher the heterozygosity of the population), the greater the efficiency of natural selection, the faster evolution proceeds.

Forms:

Stabilizing - acts under constant conditions, selects average manifestations of the trait, retains the characteristics of the species (cross-finned coelacanth fish)
Motive - acts in changing conditions, selects extreme manifestations of a trait (deviation), leads to a change in traits (birch moth)
Sexual - competition for a sexual partner.
Breaking - selects two extreme shapes.

Consequences of natural selection:

Evolution (change, complication of organisms)
The emergence of new species (increase in the number [diversity] of species)
Adaptation of organisms to conditions environment. Any fitness is relative, i.e. adapts the body to only one specific conditions.

Choose the one that is most correct. Natural selection is based on
1) mutation process
2) speciation
3) biological progress
4) relative fitness

Answer

Choose the one that is most correct. What are the consequences of the action of stabilizing selection
1) preservation of old species
2) change in the rate of reaction
3) the emergence of new species
4) preservation of individuals with altered traits

Answer

Choose the one that is most correct. In the process of evolution, a creative role is played by
1) natural selection
2) artificial selection
3) modification variability
4) mutational variability

Answer

Choose three options. What are the characteristics of driving selection?
1) acts under relatively constant living conditions
2) eliminates individuals with an average value of the trait
3) promotes the reproduction of individuals with an altered genotype
4) preserves individuals with deviations from the mean values of the trait
5) preserves individuals with a steady rate of trait reaction
6) promotes the appearance of mutations in the population

Answer

Choose three characteristics that characterize the driving form of natural selection
1) provides the emergence of a new species
2) manifests itself in changing environmental conditions
3) the adaptation of individuals to the original environment is improved
4) individuals with a deviation from the norm are rejected
5) the number of individuals with an average value of the trait increases
6) individuals with new traits are preserved

Answer

Choose the one that is most correct. The starting material for natural selection is
1) the struggle for existence
2) mutational variability
3) change in the habitat of organisms
4) the adaptability of organisms to the environment

Answer

Choose the one that is most correct. The starting material for natural selection is
1) modification variability
2) hereditary variability
3) the struggle of individuals for survival conditions
4) the adaptability of populations to the environment

Answer

Choose three options. The stabilizing form of natural selection is manifested in
1) constant environmental conditions
2) change in the average reaction rate
3) preservation of adapted individuals in the original habitat
4) culling of individuals with deviations from the norm
5) preservation of individuals with mutations
6) preservation of individuals with new phenotypes

Answer

Choose the one that is most correct. The effectiveness of natural selection decreases when
1) the occurrence of recessive mutations
2) an increase in homozygous individuals in the population
3) a change in the rate of reaction of a sign
4) an increase in the number of species in the ecosystem

Answer

Choose the one that is most correct. In arid conditions, in the process of evolution, plants with pubescent leaves were formed due to the action
1) relative variability

3) natural selection
4) artificial selection

Answer

Choose the one that is most correct. Pest insects acquire resistance to pesticides over time as a result
1) high fertility
2) modification variability
3) conservation of mutations by natural selection
4) artificial selection

Answer

Choose the one that is most correct. The material for artificial selection is
1) genetic code
2) population
3) gene drift
4) mutation

Answer

Choose the one that is most correct. Are the the following judgments about the forms of natural selection? A) The emergence of resistance to pesticides in insects - pests of agricultural plants - an example of a stabilizing form of natural selection. B) Driving selection contributes to an increase in the number of individuals of the species with an average value of the trait
1) only A is true
2) only B is true
3) both statements are true
4) both judgments are neurons

Answer

Establish a correspondence between the results of the action of natural selection and its forms: 1) stabilizing, 2) driving, 3) disruptive (disruptive). Write down the numbers 1, 2 and 3 in the correct order.
A) Development of antibiotic resistance in bacteria
B) The existence of fast and slow growing predatory fish in one lake
C) A similar structure of the organs of vision in chordates
D) The emergence of fins in waterfowl mammals
E) Selection of newborn mammals of average weight
F) Retention of phenotypes with extreme deviations within one population

Answer

1. Establish a correspondence between the characteristic of natural selection and its form: 1) driving, 2) stabilizing. Write down the numbers 1 and 2 in the correct order.
A) keeps the average value of the feature
B) promotes adaptation to changed environmental conditions
C) preserves individuals with a trait that deviates from its average value
D) helps to increase the diversity of organisms
E) contributes to the preservation of species characteristics

Answer

2. Compare the characteristics and forms of natural selection: 1) Motive, 2) Stabilizing. Write down the numbers 1 and 2 in the correct order.
A) acts against individuals with extreme values of traits
B) leads to a narrowing of the reaction rate
B) usually acts in constant conditions
D) occurs during the development of new habitats
E) changes the average values of the trait in the population
E) can lead to the emergence of new species

Answer

3. Establish a correspondence between the forms of natural selection and their characteristics: 1) driving, 2) stabilizing. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) acts in changing environmental conditions
B) acts in constant environmental conditions
C) is aimed at preserving the previously established average value of the feature
D) leads to a shift in the average value of the trait in the population
E) under its action, both an increase in the characteristic and a weakening can occur

Answer

4. Establish a correspondence between the signs and forms of natural selection: 1) stabilizing, 2) driving. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) forms adaptations to new environmental conditions
B) leads to the formation of new species
C) preserves the average rate of the feature
D) rejects individuals with deviations from the average norm of traits
E) increases the heterozygosity of the population

Answer

5. Establish a correspondence between the characteristics and forms of natural selection: 1) stabilizing, 2) driving. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) manifestation in constant living conditions
B) death of individuals with new traits
C) preservation of individuals with new mutations
D) preservation of individuals with an aromorphic trait
E) an increase in the number of individuals with a steady rate of reaction

Answer

Establish a correspondence between examples and forms of natural selection, which are illustrated by these examples: 1) driving, 2) stabilizing. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) an increase in the number of dark butterflies in industrial areas in comparison with light ones
B) the emergence of insect pests of resistance to pesticides
C) the preservation to the present of the reptile tuatara inhabiting New Zealand
D) a decrease in the size of the cephalothorax in crabs living in troubled water
E) in mammals, the mortality of newborns with an average weight is less than with a very low or very high
E) the death of winged ancestors and the preservation of insects with reduced wings on islands with strong winds

Answer

Establish a correspondence between examples and types of natural selection: 1) driving, 2) disruptive. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) long neck in a giraffe
B) white and orange wings of jaundice butterflies
C) different forms of beak of finches
D) the presence of early and late flowering rattle forms
E) an increase in the number of light-colored butterflies in a birch forest
E) an increase in the average height of a person from generation to generation

Answer

Establish a correspondence between the forms of the struggle for existence and examples illustrating them: 1) intraspecific, 2) interspecific. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) fish eat plankton
B) seagulls kill chicks when there are a large number of them
C) current wood grouse
D) nosed monkeys try to shout down each other, blowing huge noses
E) chaga mushroom settles on birch
E) the main prey of the marten is squirrel

Answer

Analyze the table "Forms of natural selection". For each letter, select the appropriate concept, characteristic and example from the list provided.
1) sexual
2) driving
3) group
4) preservation of organisms with two extreme deviations from the mean value of the trait
5) the emergence of a new feature
6) the formation of bacterial resistance to antibiotics
7) preservation of the relict species of gingko biloba plant 8) increase in the number of heterozygous organisms

Answer

Changes in species diversity are influenced by the actions of natural and artificial selection. Natural selection takes place in nature and can change direction depending on changing environmental conditions. Artificial selection is guided by man.

Definition

Natural selection is the driving force behind evolution, thanks to which new, more adapted species are formed. The term was coined by naturalist Charles Darwin.
The reasons for natural selection are:

unfavourable conditions;
interspecies competition;
intraspecific competition.

Rice. one. Different kinds sparrow.

Artificial selection is the selection and fixation in the genome of individuals of certain traits that are useful for humans. Artificial selection is at the heart of breeding. Selecting "workers" individuals, a person independently produces food, materials, medicines. Initially, without knowledge of genetics and selection, the development of new breeds, varieties, strains by humans was spontaneous. Gradually, with the help of selection and genetic engineering, people learned to clearly achieve their goals.

An example of artificial selection is all agricultural activities, natural - the emergence polar bear, pesticide-resistant insects, nylon-eating bacteria. Thanks to selection, man has brought out lines of dairy and beef cows, dogs, corn, wine bacteria, high-performance cotton.

Rice. 2. Comparison of wild and cultivated corn.

Comparison

Despite the peculiarities of the course of the processes, between the two types of selection there are certain similarities:

source material are individual characteristics organism and hereditary variability;
favorable, necessary (for a person or for the body itself) signs are fixed, inherited;
individuals with unfavorable traits are destroyed, rejected either by humans or in the process of evolution.

A description of the differences is presented in the comparison table of artificial and natural selection.

*Selection signs*	*Comparative characteristics*
*Selection signs*	Natural selection	Artificial selection
	Population	Individual or group
	Natural ecosystems	Farms, breeding stations, nurseries
Duration	Continuously for several millennia	Several years, on average - 10 years to obtain a new breed or new variety
	Conditions and environmental influences	Human actions
Criterion	Population fitness	Obtaining traits that are beneficial to humans
	Driving selection - directed towards better adaptation of the population to the changed environmental conditions; Stabilizing selection - the retention of useful traits under relatively constant conditions; Disruptive selection - consolidation of opposite variants of one trait in a population	Unconscious selection is the fixation of the best traits in a population by chance, without a specific goal; Methodological selection - purposeful human actions to preserve a certain trait in the population
Result	The emergence of new species	Obtaining new breeds, varieties, strains

Rice. 3. Graphs of natural selection forms.

Meaning

Despite the difference in approaches, the types of selection should not be opposed. Artificial selection is inextricably linked with natural selection, because initially, humans used to select wild individuals that formed in natural conditions. At the same time, nature can independently influence the breeds and varieties already bred by man.

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The action of artificial or natural selection affects the change in biological diversity and the improvement of existing species. In addition, a person can grow more productive individuals in artificial conditions, depending little on environmental factors.

In most cases, individuals bred by humans are not capable of independent life in the wild.

What have we learned?

From the lesson, we learned about the similarities and differences between artificial and natural selection. A person is responsible for artificial selection, cultivating a trait of an individual useful for himself. Thanks to artificial selection, a person receives food, medicine, tissue, etc. Natural selection has been taking place without human participation in the process of evolution for thousands of years. Both types of selection are based on hereditary variation.

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Assessment of the report

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1. Natural selection - the process of survival of individuals with hereditary changes useful in the given environmental conditions and their leaving offspring is the main driving force of evolution. The non-directional nature of hereditary changes, their diversity, the predominance of harmful mutations and the guiding nature of natural selection - the preservation of individuals only with hereditary changes useful in a certain environment.

2. Artificial selection - the main method of selection, which deals with the development of new varieties of plants and animal breeds. Artificial selection is the preservation by humans for subsequent reproduction of individuals with hereditary changes of interest to the breeder.

3. Comparison of natural and artificial selection.

4. The role of natural selection in the creation of new varieties of plants and animal breeds - increasing their adaptability to environmental conditions.

36. Basic methods of animal breeding.

The creation of breeds of domestic animals began after their domestication and domestication, which began 10-12 thousand years ago. Keeping in captivity reduces the effect of the stabilizing form of natural selection. Various shapes artificial selection (first unconscious, and then methodical) lead to the creation of a whole variety of breeds of domestic animals.

In animal breeding, in comparison with plant breeding, there are a number of features. Firstly, animals are mainly characterized by sexual reproduction, therefore, any breed is a complex heterozygous system. Assessment of the qualities of males that do not appear outwardly in them (egg production, butterfat content) are assessed by offspring and pedigree. Secondly, they often have late maturity, the generation change occurs after a few years. Thirdly, the offspring are few.

The main methods of animal breeding are hybridization and selection... There are the same crossing methods - closely related crossing, inbreeding, and unrelated - outbreeding... Inbreeding, as with plants, results in depression... Selection from animals is carried out according to exterior(to certain parameters of the external structure), because it is he who is the criterion of the breed.

1. Intra-breed breeding: aimed at preserving and improving the breed. Practically expressed in the selection of the best producers, culling of individuals that do not meet the requirements of the breed. In breeding farms, herd books are kept, reflecting the pedigree, exterior and productivity of animals for many generations.

2. Interbreeding used to create a new breed. At the same time, closely related crossbreeding is often carried out, parents are crossed with offspring, brothers and sisters, this helps to get a larger number of individuals with the necessary properties. Inbreeding is accompanied by strict constant selection, usually several lines are obtained, then different lines are crossed.

A good example is the breed of pigs developed by Academician M.F. Ivanov - the Ukrainian white steppe. When creating this breed, sows of local Ukrainian pigs were used with a small mass and low quality meat and lard, but well adapted to local conditions. The breeding males were white English boars. The hybrid offspring were again crossed with English boars, inbreeding was used for several generations, clean lines were obtained, when crossed, the founders of a new breed were obtained, which did not differ from the English breed in terms of meat quality and weight, and from Ukrainian pigs in endurance.

3. Using the effect of heterosis... Often, with interbreeding in the first generation, the effect of heterosis is manifested, heterotic animals are distinguished by early maturity and increased meat productivity. For example, when crossing two meat breeds of chickens, heterotic broiler chickens are obtained, when crossing Berkshire and Durokersay pig breeds, early maturing pigs with a large mass and good quality meat and lard are obtained.

4. Test for offspring are carried out for the selection of males, which do not show some qualities (milkiness and butterfat content of bulls, egg production of roosters). For this, male producers are crossed with several females, the productivity and other qualities of the daughters are assessed, comparing them with maternal and medium-sized ones.

5. Artificial insemination used to obtain offspring from the best male producers, especially since the sex cells can be stored at liquid nitrogen temperature at any time.

6.Using hormonal superovulation and transplantation dozens of embryos can be taken from outstanding cows per year, and then implanted in other cows; embryos are also stored at liquid nitrogen temperature. This makes it possible to increase the number of offspring from outstanding producers by several times.

7. Distant hybridization, interspecific crossing, has been known since ancient times. Most often, interspecific hybrids are sterile, their meiosis is disturbed, which leads to a violation of gametogenesis. Since ancient times, people have used a hybrid of a mare with a donkey - a mule, which is distinguished by its endurance and longevity. But sometimes gametogenesis in distant hybrids proceeds normally, which made it possible to obtain new valuable animal breeds. An example is the archaromerino, which, like the argali, can graze high in the mountains and, like the merino, produce good wool. Fertile hybrids were obtained from the crossing of local cattle with yaks and zebu. When crossing beluga and sterlet, a fertile hybrid - bester, ferret and mink - honorik was obtained, a hybrid between carp and crucian carp is productive.

A) intraspecific - the most fierce, since individuals of the same species need similar food sources, which are also limited, in similar conditions for reproduction, the same shelters;

C) the struggle of living organisms with factors of inanimate nature - environmental conditions during drought, floods, early frosts, hail, many small animals, birds, worms, insects, grasses die.

The struggle for existence is inevitable due to the intensive reproduction existing in nature. This pattern knows no exceptions. There are always more organisms born than those capable of living to adulthood and leaving offspring. Calculations show: if all born mice survived, then within seven years the offspring of one pair would occupy the entire land of the globe. A female cod fish lays up to 10 million eggs at a time, one plant of a shepherd's purse gives 73 thousand seeds, henbane - 446 500, etc. However, the "geometric progression of reproduction" is never realized, since there is a struggle for space between organisms , food, shelter from enemies, competition in choosing a sexual partner, the struggle for survival with fluctuations in temperature, humidity, lighting, etc. the average remains constant.

Table Forms of selection (T. L. Bogdanova. Biology. Tasks and exercises. A guide for applicants to universities. M., 1991)

Indicators	Artificial selection	Natural selection
Source material for selection		Individual signs of an organism
Selection factor		Environmental conditions (wildlife and inanimate nature)
Change path:
favorable	Get selected, become productive	Remain, accumulate, inherited
unfavorable	Selected, rejected, destroyed	Are destroyed in the struggle for existence
The nature of the action	Creative - directed accumulation of traits for the benefit of a person	Creative - selection of adaptive characters for the benefit of an individual, population, species, leading to the emergence of new forms
Selection result	New varieties of plants, breeds of animals, strains of microorganisms	New species
Selection forms	Mass; individual; unconscious (spontaneous); methodical (conscious)	Motive, supporting evasion in changing environmental conditions; stabilizing, maintaining the constancy of the average reaction rate under constant environmental conditions