Methods of asexual reproduction in organisms are simple division. Types of reproduction of organisms, their classification

asexual reproduction

asexual reproduction, or agamogenesis - a form of reproduction in which the organism reproduces itself independently, without any participation of another individual. Should be distinguished asexual reproduction from same-sex reproduction(parthenogenesis), which is a special form of sexual reproduction.

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Reproduction is a universal property of the living, which ensures material continuity in a number of generations. The evolution of reproduction methods.

reproduction the ability of organisms to reproduce themselves. The properties of organisms to produce offspring. This is a condition for the existence of the species, which is based on the transfer of genetic material. The evolution of reproduction went, as a rule, in the direction from asexual to sexual reproduction, from isogamy to oogamy, from the participation of all cells in reproduction to the formation of germ cells, and from external fertilization to internal fertilization. intrauterine development and care for offspring. In the course of evolution, different groups of organisms have developed different ways and strategies of reproduction, and the fact that these groups have survived and exist proves the effectiveness of different ways of carrying out this process. All the variety of methods of reproduction can be divided into two main types: asexual and sexual reproduction.

Asexual reproduction, its types and biological significance.

At asexual reproduction one individual is involved; individuals are formed genetically identical to the original parent; sex cells are not formed. Asexual reproduction enhances the role of stabilizing natural selection, ensures the preservation of fitness in changing habitat conditions.

There are two types asexual reproduction: vegetative and spore formation (Table 10). A special case is polyembryony in vertebrates - asexual reproduction in the early stages of embryonic development. First described by I.I. Mechnikov on the example of the splitting of blastulae in jellyfish and the development of the cells of the whole organism from each aggregate. In humans, an example of polyembryony is the development of identical twins.

Table 10 - Types of asexual reproduction at the organism level

Sexual reproduction, its types and advantages over asexual reproduction.

Evolutionary sexual reproduction was preceded by the sexual process - conjugation. Conjugation ensures the exchange of genetic information without increasing the number of individuals. It occurs in protozoa, eukaryotes, algae and bacteria.

sexual reproduction - the emergence and development of offspring from a fertilized egg - a zygote (Table 11). In the course of historical development, sexual reproduction of organisms has become dominant in the plant and animal world. It has a number of advantages:

High reproduction rate.

Renewal of genetic material. Source hereditary variability. Success in the struggle for existence.

Large adaptive abilities of daughter individuals.

Sexual reproduction is characterized by the following features:

Two individuals are involved.

The source of the formation of new organisms are special cells - gametes with sexual differentiation.

For the formation of a new organism, the fusion of two germ cells is necessary. One cell from each parent is enough.

Irregular types of sexual reproduction (Table 11):

1. Parthenogenesis -development of an embryo from an unfertilized egg. It occurs in lower crustaceans, rotifers, bees, wasps. There are somatic or diploid and generative or haploid parthenogenesis. With somatic - the egg either does not undergo reduction division, or two haploid nuclei merge together, restoring the diploid set of chromosomes. With generative - the embryo develops from a haploid egg. Thus, in the honey bee, drones develop from unfertilized haploid eggs. In wasps and ants during parthenogenesis, the diploid set is restored in somatic cells due to endomitosis.

Table 11 - Types of sexual reproduction in eukaryotes

2. Gynogenesis – a type of sexual reproduction in which spermatozoa participate as stimulants for the development of the egg, but fertilization (karyogamy) does not occur in this case. The development of the embryo is carried out at the expense of the female nucleus. It is observed in roundworms, in the viviparous fish Molinesia. The sperm nucleus is destroyed and loses the ability to karyogamy, but retains the ability to activate the egg. Offspring receive genetic information from mother.

3. Androgenesis – a type of reproduction in which the development of an egg occurs due to the male nucleus and maternal cytoplasm. The haploid embryo is characterized by low viability, which is normalized when the diploid set of chromosomes is restored. With polyspermy, the fusion of two paternal pronuclei is possible and the formation of a diploid nucleus, as in the silkworm.

Gametogenesis. Features of oogenesis and spermatogenesis in humans, its hormonal regulation.

The process of formation of germ cells is called Gametogenesis . This process takes place in the sex glands (testes and ovaries) and is divided into permatogenesis – sperm production and oogenesis – the formation of eggs.

Spermatogenesis takes place in the convoluted seminiferous tubules of the testes and includes four phases (Table 12):

breeding;

1. maturation;

   formations.

breeding phase: repeated mitosis of spermatogonia.

Growth phase: cells lose their ability to mitosis and increase in size. Now they are called spermatocytes of the first order, which enter into a long (about 3 weeks) prophase of the 1st division of meiosis.

Table 12 - Stages of spermatogenesis

maturation phase: It includes two consecutive divisions of meiosis: as a result of the 1st (reduction) division, haploid spermatocytes of the second order (1n 2 chromatids 2c) are formed from spermatocytes of the 1st order. They are smaller than the first order spermatocytes and are located closer to the lumen of the tubule. The second division of meiosis (equation) leads to the formation of four spermatids - relatively small cells with a haploid set of DNA (1n 1 chromatid 1c).

Formation phase: It consists in the transformation of spermatids into spermatozoa. The chromatin in the nucleus is compacted, the size of the nucleus decreases. The Golgi complex is converted into an acrosome containing lytic enzymes necessary for the breakdown of the egg membranes. The acrosome is adjacent to the nucleus and gradually spreads out over it in the form of a cap. Centrioles move to the opposite pole of the cell. A flagellum is formed from the distal centriole, which then becomes the axial thread of the developing spermatozoon. Excess cytoplasm is shed into the lumen of the tubule and phagocytosed by Sertoli cells.

Spermatogenesis in humans is carried out throughout the entire period of puberty in the convoluted seminiferous tubules. The development of the sperm lasts 72-75 days.

Oogenesis - a set of successive processes of development of the female germ cell. Oogenesis includes periods of reproduction, growth and maturation (Table 13). During the period of reproduction, by mitosis, the number of diploid germ cells - oogonia increases; after the cessation of mitosis and DNA replication in the premeiotic interphase, they enter the prophase of meiosis, coinciding with the growth period of cells called oocytes of the first order. At the beginning of the growth period (slow growth phase), the oocyte increases insignificantly, conjugation of homologous chromosomes and crossing over occur in its nucleus. The number of organelles in the cytoplasm increases. This phase lasts for years. In phase rapid growth the volume of oocytes increases hundreds or more times, mainly due to the accumulation of ribosomes and yolk. During maturation, 2 divisions of meiosis occur. As a result of the 1st division, an oocyte of the second order and a reduction body are formed. By the end of the maturation period, oocytes acquire the ability to be fertilized, and further division of their nuclei is blocked. Meiosis ends in the process of fertilization with the formation of one egg and the release of 3 reduction bodies. The latter subsequently degenerate.

Table 13 - Stages of oogenesis

Differences between oogenesis and spermatogenesis:

The breeding season of oogonia ends by the time of birth.

The growth period during oogenesis is longer than during spermatogenesis and has a period of slow growth, when the size of the nucleus and cytoplasm increases, and a period of rapid growth - the accumulation of yolk inclusions.

During oogenesis, one full-fledged germ cell is formed from one oocyte I, while during spermatogenesis, four are formed from spermatocyte I.

The formation phase is characteristic only for spermatogenesis. The formation of the egg occurs during the period of fertilization.

In humans, eggs and sperm develop from primary germ cells that form in the extraembryonic mesoderm. Primary germ cells subsequently migrate to the place of their final localization - to the bisexual gonad. In many animals, the areas of the cytoplasm responsible for the secretion of primary germ cells differ in pigmentation or granules. These are gender determinants. The sex cytoplasm is concentrated at the vegetative pole of the cell.

Specific signs of the female sex (ovarian development) become noticeable at the end of the 8th week. By the end of the 3rd month of intrauterine development, oocytes are formed in the depths of the gonads (prophase 1). By the 7th month, the differentiation of the ovary will acquire a rapid pace. By the 9th month, there are 200-400 thousand oocytes in the ovary.

During oogenesis, the mitotic division of the primary female germ cells (oogonia) stops by the 5th month of intrauterine development. Their number reaches almost 7 million. Oogonia in the process of its development turns into oocytes of the first order. Further intrauterine reproduction of oogonia ceases. Therefore, by the time of birth, the girl's ovary already contains about 2 million oocytes in the primary follicles. However, an intense process of atresia occurs among them. Therefore, by the beginning of puberty, about 400-500 thousand remain in the ovary of a woman, capable of further development, oocytes.

The formation of primary follicles is completed by the end of the 3rd month of intrauterine development, when the follicular cells completely cover the oocyte. By the time the formation of the primary follicle is completed, the oocytes are at the stage of meiosis I, at the dictyoten stage (diplotene phase). From this point on, there is a long break in their further development. The arrest of oocyte division I persists until puberty.

Shortly before ovulation, the first stop at the diplotene stage of the first division of meiosis is interrupted. The division is quickly completed with the formation of an oocyte of the second order and one so-called reduction body. An ovulated oocyte is called a second order oocyte. After ovulation, the oocyte begins the second division of meiosis, which lasts until metaphase II. If fertilization has occurred, then the second phase of meiosis ends almost simultaneously with it. As a result, an egg is formed. If fertilization does not occur within 48 hours after ovulation, then the ovulated egg (oocyte II) dies.

Every month, one follicle matures in the ovary, inside of which there is a gamete capable of fertilization. The maturation of the follicle has several stages. Initially, oocytes of the first order are surrounded by a layer of cells, and a primary follicle is formed. Further, in the period before puberty, the follicles increase in size due to the growth of the oocyte, the formation of a transparent zone and a radiant crown. Then the secondary follicle grows, turns into a tertiary or mature one, containing an oocyte of the second order. In total, during the childbearing period, a woman matures 400-800 follicles.

After maturation of the ovarian follicle, its walls rupture, and the oocyte II enters the body cavity. The funnel of the oviduct (fallopian tubes) is located near the ovary. Cilia ensure the movement of the egg through the oviduct, where fertilization occurs. After ovulation, the destroyed ovarian follicle contracts and, as a result of the division of follicular cells, a "corpus luteum" is formed that fills the cavity of the vesicle. If fertilization does not occur, it degenerates, and new follicles begin to grow in another part of the ovary. When pregnancy occurs, the "yellow body" is preserved, and new follicles are formed after childbirth. During the juvenile and mature periods of ontogeny, oocytes in the ovaries are in prophase I (diplotene stage: chromosomes in them in the form of lampbrushes, intensive RNA synthesis on certain genes). The block of prophase 1 is periodically removed from oocytes, meiosis I is completed and meiosis II begins. At fertilization, after 24 hours, meiosis II is completed, and after another 10 hours, a synkaryon is formed and synkaryogamy occurs.

Blocking is adaptive. Conjugation and crossing over in meiosis are under the protection of the maternal organism, which guarantees fewer embryonic anomalies. In the postembryonic period, the body is exposed to various influences. environment, which increases the frequency of formation of abnormal gametes.

The growth of follicles, their ovulation are hormonally dependent processes that are regulated by three gonadotropic hormones of the pituitary gland: follicle-stimulating (FSH), luteinizing (LH), luteotropic (LTH), ovarian hormones - estrogens and progesterone. Under the influence of FSH, the development and maturation of follicles in the ovary occurs. With the combined action of FSH and LH, a mature follicle ruptures, ovulation, and the formation of a "corpus luteum" occur. After ovulation, LH promotes the production of the hormone progesterone in the ovary by the “yellow body”.

The secretion of LH and FSH by the pituitary gland is regulated by the neurohumoral activity of the hypothalamus, which produces neurohormones: vasopressin, oxytocin. These centers, in turn, are under the influence of ovarian hormones - estrogens. They affect the development of secondary sexual characteristics, metabolism (increase protein dissimilation) and thermoregulation. In addition, the ovaries also produce androgens - male sex hormones. The latter are also formed in the adrenal cortex.

Specific signs of the male sex, the development of the testicles are observed at the end of the 7th week of intrauterine development.

The male sex gland - the testis - consists of seminiferous tubules surrounded by connective and loose interstitial tissue that produces hormones.

spermatogenesis - this is the process of transformation of primary germ cells - spermatogonia into spermatozoa in the testes. The process occurs in the seminiferous tubules of the male gonads. Spermatogonia are located at the outer wall of the seminiferous tubules. At a certain moment, they begin to grow and move from the periphery to the center of the tubules, passing to mitotic division, resulting in the formation of spermatogonia. Spermatogonia grow and, after numerous mitotic divisions, form spermatocytes, passing to meiosis, two successive divisions of which culminate in the formation of full-fledged cells - spermatids, which differentiate into spermatozoa. Two consecutive divisions of meiosis are often called the division of maturation.

In humans, the first division of meiosis lasts several weeks, the second - 8 hours. During the second division, spermatocytes of the second order give rise to four immature haploid (1n1c) germ cells - spermatids. In the formation zone, they become spermatozoa.

Spermatogenesis is carried out throughout the entire period of puberty of the male. Full maturation of the cell is 72 days.

The functions of the testes are regulated by the endocrine glands and the pituitary gland. The main male sex hormone produced in the Leydig cells of the testes is testosterone. Under the influence of male sex hormones, the formation and breakdown of protein in the body is enhanced, which leads to the development of muscles, bone tissue, and body size.

Morphofunctional characteristics of mature gametes in humans.

Egg - oval, large, sedentary or motionless. Most animals lack a centrosome and are not capable of independent division. According to the content and distribution of the yolk, several types of eggs are distinguished (Table 14).

Table 14 - Types of eggs

The distribution of the yolk determines the spatial organization of the embryo. Isolecithal eggs are characterized by a small amount of evenly distributed yolk, for example in the lancelet. Polylecithal – with moderate (amphibian) and excessive content of yolk (reptiles, birds). Telolecithal eggs are characterized by an uneven distribution of the yolk and the formation of poles: animal , on which there is no yolk, vegetative – with yolk. Centrolecithal - are characterized by a large amount of evenly distributed yolk in the center of the egg and are characteristic of arthropods.

The egg cell forms 3 types of protective membranes:

Primary - yolk, a waste product of an oocyte or egg, is in contact with the cytoplasm. In humans, it is part of the dense shell, forming it inner part. Its outer zone is formed by follicular cells and is secondary (radiant crown).

Secondary - is formed as a derivative of follicular cells (their isolation) surrounding the oocyte (cells of the granular layer). In insects - the chorion, in humans - the radiant crown. The dense shell is penetrated by the microvilli of the egg from the inside, and from the outside - by the microvilli of the follicular cells. Thus, a radiant crown and a brilliant zone are formed in a person.

Tertiary - is formed after fertilization due to the secretion of glands or mucous epithelium of the genital tract as it passes through the female's oviduct. These are the gelatinous shells of amphibian eggs, protein, subshell and shell in birds.

During fertilization, the sperm cell overcomes the secondary and primary membranes.

Sperm. The gamete is small, mobile. It has parts: head, neck, middle part and tail. The head consists of an acrosome and a nucleus. The acrosome is formed from the Golgi complex of the spermatid. The acrosome ensures the penetration of sperm into the egg and activation of the latter with the help of the enzyme hyaluronidase.

The sperm nucleus contains compactly packed deoxynucleoproteins. Such packaging of the haploid set of chromosomes is associated with protamine proteins. Its meaning is the almost complete inactivation of the genetic material.

The neck has proximal and distal centrioles located at right angles. Proximal - participates in the formation of the spindle of division of the fertilized egg, and from the distal - the axial thread of the tail is formed.

Mitochondria are concentrated in the middle part, forming a compact cluster - a mitochondrial helix. This part provides energy and metabolic activity of the spermatozoon.

The basis of the tail is an axial thread surrounded by a small amount of cytoplasm and a cell membrane.

The viability of the sperm depends on the concentration of sperm (thick suspension), the concentration of hydrogen ions (highest activity in an alkaline environment) and temperature.

Fertilization, its phases, biological essence.

The process of fertilization (fusion of the nuclei of male and female gametes) is preceded by insemination. Insemination – processes that cause the meeting of the sperm and the egg. The interaction of gametes is provided by the release of special substances – gamons (gynogamones and androgamones). Gynogamon I stimulates sperm motility. Gynogamon II blocks the motor activity of spermatozoa and promotes their fixation on the egg cell membrane. Androgamone I inhibits the movement of spermatozoa, which protects them from premature waste of energy. Androgamone II promotes the dissolution of the egg cell membrane.

There are two types of insemination: external and internal. In some animals, dermal insemination is observed, which is a transitional form. This is typical for nemerteans, leeches.

Fertilization stages:

Convergence of gametes, acrosomal reaction and penetration of the spermatozoon;

Activation of the egg, its synthetic processes;

Fusion of gametes (syngamy).

outer phase. Rapprochement gametes belong to the outer phase. Female and male gametes secrete specific compounds called gamons. Gynogamones I and II are produced by ovules, and androgamones I and II are produced by spermatozoa. Gynogamones I activate the movement of spermatozoa and provide contact with the egg, and androgamones II dissolve the egg shell.

The viability period of eggs in mammals is from several minutes to 24 hours or more. It depends on the internal external conditions. The viability of spermatozoa is 96 hours. The ability to fertilize remains 24-48 hours.

At the moment of contact of the spermatozoon with the outer shell of the egg, the acrosomal reaction begins. The enzyme hyaluronidase is secreted from the acrosome. At the site of contact of the spermatozoon with the plasma membrane of the egg, a protrusion or fertilization tubercle is formed. The fertilization tubercle helps to draw the sperm into the egg. The membranes of the gametes fuse. The fusion of male and female germ cells is called syngamy. In some cases (in mammals), the sperm enters the egg without the active participation of the fertilization tubercle. The nucleus and centriole of the spermatozoa pass into the cytoplasm of the egg, which contributes to the completion of meiosis II in the oocyte.

internal phase. It is characterized by a cortical reaction from the side of the egg. There is a detachment of the yolk membrane, which hardens and is called the fertilization membrane. At the end of meiosis, male and female pronuclei are formed. Both pronuclei fuse. Fusion of gamete nuclei synkaryogamy is the essence of the process of fertilization, resulting in the formation of a zygote.

Modern human reproductive strategy.

Modern human reproductive strategy includes:

Prenatal diagnosis of hereditary diseases;

Using methods to overcome infertility:

artificial insemination;

fertilization of the egg in vitro;

embryo transplantation using "surrogate motherhood".

egg and embryo donation.

Asexual reproduction is such a reproduction of organisms in which there is no participation of another individual, and the reproduction of their own kind occurs by separating several or one cell from the mother organism. A single parent takes part in this process. cells are fully consistent with the original maternal.

Asexual reproduction is extremely simple. This is due to the fact that the organization of the structure of unicellular organisms is also relatively simple. Organisms with this method of reproduction reproduce their own kind very quickly. Under favorable conditions, the number of such cells doubles every hour. Such a process can continue indefinitely until a random change, the so-called mutation, occurs.

In nature, such reproduction occurs both in plants and in

Asexual reproduction of organisms

Simple division is also observed in animals, for example, in ciliates, amoebas, and some algae. First, the nucleus in the cell is divided in half by mitosis, and then a constriction is formed, and the parent individual is divided into two parts, which are daughter organisms.

In animals, asexual reproduction has been preserved only in some forms: sponges, coelenterates, tunicates. In these organisms, a new individual is obtained as a result of budding or division, after which the part separated from the parent organism is completed to the whole. In some cases, parts of the body have the ability to develop into a separate organism in animals. A whole hydra, for example, can develop from a two-hundredth part. In asexual reproduction, newly created individuals originate from several cells or one through mitotic divisions, receiving the same hereditary information that the cell of the mother's organism possessed.

Asexual reproduction of plants

This way of reproduction is widespread in flora. There are a number of plants that reproduce well by tubers, cuttings, cuttings, and even leaves, which makes it possible to use the vegetative organs of the parent plant for growing new organisms. This type of asexual reproduction is called vegetative, and it is inherent in highly organized plants. An example of such reproduction can be considered one that occurs with a mustache, for example, in strawberries.

Sporulation - asexual reproduction that occurs in many plants, for example, algae, ferns, mosses, fungi at some stage of development. In this case, special cells take part in the reproduction mechanism, often covered with a dense membrane that protects them from adverse effects. external environment: overheating, cold, drying. As soon as favorable conditions arise, the spore shell bursts, the cell begins to divide many times, giving life to a new organism.

Budding is a method of reproduction, when a small part of the body is separated from the parent individual, from which the child organism is later formed.

A group of individuals that are descended from one common ancestor with the help of this type of reproduction, in biology they are called clones.

Asexual reproduction is widely used in agriculture in order to obtain plants with a set necessary features useful for human life. Long "whiskers", shoots spread strawberries, and trees - cuttings. Scientists are studying the mechanisms of reproduction in order to learn how to control them and manage their development. necessary hereditary information they are first propagated, and then the necessary whole plant is grown from them.

1) Division of unicellular(amoeba). At schizogony(malarial plasmodium) it turns out not two, but many cells.

2) Sporulation

• Spores of fungi and plants serve for reproduction.
• Spores of bacteria do not serve for reproduction, because. One spore is produced from one bacterium. They serve to experience adverse conditions and settlement (by wind).

3) Budding: daughter individuals are formed from outgrowths of the body of the mother organism (kidneys) - in intestinal (hydra), yeast.

4) Fragmentation: the mother organism is divided into parts, each part turns into a daughter organism. (Spirogyra, coelenterates, starfish.)

5) Vegetative propagation of plants: reproduction using vegetative organs:

• roots - raspberry
• leaves - violet
• specialized modified shoots:
• bulbs (onion)
• rhizome (wheatgrass)
• tuber (potato)
• mustache (strawberry)

Methods of sexual reproduction

1) With the help of gametes, sperm and eggs. Hermaphrodite- this is an organism that forms both female and male gametes (most higher plants, coelenterates, flat and some annelids, shellfish).

2) Conjugation at green algae spirogyra: two threads of spirogyra approach each other, copulatory bridges are formed, the contents of one thread flows into another, one thread is obtained from zygotes, the second - from empty shells.

3) Conjugation in ciliates: two ciliates approach, exchange sex nuclei, then diverge. The number of ciliates remains the same, but recombination occurs.

4) Parthenogenesis: the child develops from an unfertilized egg (in aphids, daphnia, bee drones).

Establish a correspondence between the feature of sexual and vegetative reproduction and the method of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) forms new combinations of genes
B) forms combinative variability
B) produces offspring that are identical to the parent
D) occurs without gametogenesis
D) due to mitosis

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Bacterial spores, unlike fungal spores,
1) serve as an adaptation to the transfer of adverse conditions
2) perform the function of nutrition and respiration
3) DO NOT serve for reproduction
4) provide distribution (settlement)
5) are formed by meiosis
6) are formed from the mother cell by the loss of water

Answer

Choose three options. Asexual reproduction is characterized by
1) offspring have only the genes of the mother organism
2) the offspring is genetically different from the mother's body
3) one individual participates in the formation of offspring
4) in the offspring there is a splitting of signs
5) offspring develop from an unfertilized egg
6) a new individual develops from somatic cells

Answer

Establish a correspondence between the characteristic and the method of reproduction of the plant: 1) vegetative, 2) sexual
A) carried out by modified shoots
B) is carried out with the participation of gametes
C) daughter plants retain great resemblance with maternal
D) is used by humans to preserve valuable traits of mother plants in offspring
D) a new organism develops from a zygote
E) the offspring combines the characteristics of the maternal and paternal organisms

Answer

Establish a correspondence between the feature of reproduction and its type: 1) vegetative, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) due to the combination of gametes
B) individuals are formed by budding
B) provides genetic similarity of individuals
D) occurs without meiosis and crossing over
D) due to mitosis

Answer

1. Establish a correspondence between an example of reproduction and its method: 1) sexual, 2) asexual. Write the numbers 1 and 2 in the correct order.
A) sporulation in sphagnum
B) spruce seed propagation
B) parthenogenesis in bees
D) propagation by bulbs in tulips
D) birds lay eggs
E) spawning in fish

Answer

2. Establish a correspondence between a specific example and the method of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct sequence.
A) fern sporulation
B) the formation of chlamydomonas gametes
B) the formation of spores in sphagnum
D) yeast budding
D) fish spawning

Answer

3. Establish a correspondence between a specific example and the method of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) hydra budding
B) bacterial cell division into two
B) the formation of spores in fungi
D) parthenogenesis of bees
D) the formation of strawberry whiskers

Answer

4. Establish a correspondence between examples and methods of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) live birth in a shark
B) dividing infusoria-shoes in two
B) parthenogenesis of bees
D) propagation of violet leaves
D) spawning by fish
E) hydra budding

Answer

5. Establish a correspondence between the processes and methods of reproduction of organisms: 1) sexual, 2) asexual. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) lizards lay eggs
B) sporulation penicillium
C) propagation of wheatgrass by rhizomes
D) Daphnia parthenogenesis
D) division of euglena
E) propagation of cherries by seeds

Answer

6. Establish a correspondence between examples and methods of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) raspberry cuttings
B) the formation of spores in horsetail
C) sporulation in cuckoo flax
D) lichen fragmentation
D) parthenogenesis of aphids
E) budding in a coral polyp

FORMED 7. Match the examples and methods of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the correct order.
A) the formation of gametes in chlorella
B) sturgeon spawning
B) sporulation in mosses

D) division of the common amoeba

Choose the one most correct option. Reproduction, in which the daughter organism appears without fertilization from the cells of the body of the mother organism, is called
1) parthenogenesis
2) sexual
3) asexual
4) seed

Answer

All but two of the terms below are used to describe the sexual reproduction of organisms. Define two terms that "drop out" of general list, and write down the numbers under which they are indicated.
1) gonad
2) dispute
3) fertilization
4) ovogenesis
5) budding

Answer

Write down the numbers under which it is indicated what happens during the sexual reproduction of animals.
1) usually two individuals participate
2) germ cells are formed by mitosis
3) somatic cells are initial
4) gametes have a haploid set of chromosomes
5) the genotype of the offspring is a copy of the genotype of one of the parents
6) the genotype of the offspring combines the genetic information of both parents

Answer

Choose three traits that are characteristic of sexual reproduction of seed plants, and write down the numbers under which they are indicated.
1) Sperm and eggs are involved in reproduction
2) As a result of fertilization, a zygote is formed
3) In the process of reproduction, the cell divides in half
4) The offspring retains all the hereditary characteristics of the parent
5) As a result of reproduction, new signs appear in the offspring
6) The vegetative parts of the plant are involved in reproduction

Answer

Choose two differences between sexual and asexual reproduction.
1) sexual reproduction is energetically more profitable than asexual
2) two organisms are involved in sexual reproduction, one asexual
3) during sexual reproduction, offspring exact copies parents
4) somatic cells are involved in asexual reproduction
5) sexual reproduction is possible only in water

Answer

1. All but two of the following terms are used to describe asexual reproduction. Identify two terms that "fall out" from the general list, and write down the numbers under which they are indicated.
1) schizogony
2) parthenogenesis
3) fragmentation
4) budding
5) copulation

Answer

2. All of the following terms, except for two, are used to describe the asexual reproduction of living organisms. Identify two terms that "fall out" from the general list, and write down the numbers under which they are indicated.
1) fragmentation
2) seed reproduction
3) sporulation
4) parthenogenesis
5) budding

Answer

Establish a correspondence between the characteristics and the method of reproduction of plants: 1) sexual, 2) vegetative. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) is carried out with the participation of gametes
B) a new organism develops from a zygote
C) carried out by modified shoots
D) offspring have signs of paternal and maternal organisms
D) offspring have characteristics of the mother's organism
E) is used by humans to preserve the valuable traits of the mother plant in the offspring

Answer

All but two of the examples below refer to the asexual reproduction of organisms. Identify two examples that "fall out" from the general list, and write down the numbers under which they are indicated.
1) reproduction by spores of ferns
2) reproduction of earthworms by fragmentation
3) ciliate-shoe conjugation
4) budding of freshwater hydra
5) parthenogenesis of bees

Answer

Establish a correspondence between the characteristics and methods of reproduction: 1) asexual, 2) sexual. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) Haploid nuclei fuse.
B) A zygote is formed.
C) Occurs with the help of spores or zoospores.
D) Combinative variability is manifested.
E) Offspring are formed that are identical to the original individual.
E) The genotype of the parent individual is preserved in a number of generations.

The ability to reproduce is one of key features alive. In the process of reproduction, genetic material is transferred from parents to offspring. The significance of reproduction for the species as a whole consists in the continuous replenishment of the number of individuals of a given species that die according to various reasons. In addition, reproduction allows, under favorable conditions, to increase the number of individuals.

In some cases, reproduction occurs continuously throughout the life of the organism, in others - only once. Sometimes reproduction begins after the cessation of growth of the individual, and sometimes it is possible in the process of growth. Reproduction methods can be divided into three groups: asexual, vegetative and sexual. Often the first two forms are combined into asexual reproduction in general sense this word.

Fragmentation. The division of an individual into several parts, each of which grows and forms a new individual. It is closely related to regeneration - the ability to restore lost organs and body parts. Filamentous algae, many worms,