1. What is fertilization? What is its biological significance? What are the stages of the fertilization process?

Fertilization is the process of fusion of germ cells (gametes), as a result of which a zygote is formed. In the nucleus of the zygote, all chromosomes become paired: in each pair of homologous chromosomes, one is paternal, the other is maternal. Consequently, fertilization leads to the restoration of the diploid set of chromosomes and the unification of the hereditary information of parental individuals in the zygote.

The fertilization process includes several stages:

● Penetration of the sperm into the egg, which causes the egg to peel off the fertilization membrane, preventing the penetration of other sperm.

● The fusion of the haploid nuclei of both gametes with the formation of a diploid zygote: the sperm nucleus increases and reaches the size of the egg nucleus, then the nuclei converge and merge, resulting in the formation of a zygote.

● Activation of the zygote for further development.

2. What animals are characterized by external fertilization? Internal? What is the advantage of internal fertilization over external fertilization?

External fertilization is characteristic of most organisms that permanently live (or only reproduce) in the aquatic environment - bony fish, amphibians, and many aquatic invertebrates. Internal fertilization is characteristic primarily for the inhabitants of the land - many invertebrates (for example, roundworms, spiders, insects) and all terrestrial vertebrates (reptiles, birds, mammals). This type of fertilization is also observed in some aquatic animals, for example, in cartilaginous fish and cephalopods.

During external fertilization, germ cells are released into the water (i.e., into the external environment), where they merge. A significant part of the gametes die from adverse environmental conditions, therefore, animals with an external type of fertilization need to produce a large number of sex cells. Internal fertilization occurs in the mother's body, for this spermatozoa are introduced into the female genital tract. The probability of meeting male and female gametes is much higher than with external fertilization, therefore, in animals with internal fertilization, a smaller number of germ cells are formed.

3. How does fertilization occur in flowering plants? Why is it called double?

In flowering plants, fertilization is preceded by pollination - the transfer of pollen grains from the stamens to the stigma of the pistil. The pollen grain soon begins to germinate, forming a pollen tube that reaches the ovule (ovule).

Each ovule contains an embryo sac containing seven cells - a haploid egg, a diploid central cell, and five auxiliary haploid cells. When entering the embryo sac, the end of the pollen tube bursts, and the internal contents with two male gametes, sperm, pour out of it.

One of the sperm fuses with the egg, forming a zygote, and the other with the central cell of the embryo sac. Thus, almost simultaneously, two fusions of germ cells are carried out, which is why fertilization in flowering plants is called double.

Subsequently, the seed embryo develops from the zygote, having a diploid set of chromosomes, and from the fertilized central cell, the endosperm, the cells of which have a triploid set of chromosomes. The endosperm stores the nutrients needed by the embryo. After fertilization, each ovule turns into a seed, and as a result of the growth of the ovary, a fetus is formed.

The process of double fertilization in angiosperms was discovered by the Russian scientist S. G. Navashin in 1898. As a result of double fertilization, not only the embryo is formed, but also the nutritive tissue (endosperm), which accelerates the entire process of seed development.

4. How does diploid parthenogenesis differ from haploid?

5. What are the advantages and disadvantages of parthenogenesis over the usual forms of sexual reproduction?

An important advantage of parthenogenesis is the absence of the need to find a partner. This helps to maintain the population size in conditions where it is difficult to meet individuals of different sexes, or in conditions of intensive extermination of organisms (for example, aphids - predatory insects, daphnia - fish).

In a number of insects, such as bees, the ability to reproduce both by haploid parthenogenesis and with fertilization underlies the formation of various castes of organisms. This mechanism of reproduction allows you to regulate the number of male and female offspring.

The main disadvantage of parthenogenesis is the low genetic diversity of daughter individuals, which limits their ability to adapt to environmental conditions.

6. Name the distinctive features, as well as the advantages and disadvantages of asexual and sexual reproduction.

Distinctive features of asexual reproduction:

● Occurs without the participation of gametes.

● Only one parent organism is involved in all cases.

Distinctive features of sexual reproduction:

● Occurs with the participation of gametes.

● In most cases, two parental individuals are involved (exceptions are self-fertilization in some hermaphroditic species and parthenogenesis).

The main advantages of asexual reproduction:

● There is no need to search for a partner, almost any individual can leave offspring.

● "Good" combinations of genes and traits are passed on to the next generation. This feature is widely used by man, for example, to obtain homogeneous offspring of cultivated plants (the offspring retain all varietal qualities).

The main advantage of sexual reproduction:

● Genetic diversity of offspring, which increases the ability of organisms to adapt to changing environmental conditions and is of paramount importance in the evolution of wildlife.

The main disadvantages of asexual reproduction:

● In most cases (except for the method in which spore formation is preceded by meiosis), the offspring are genetically identical to the parent, which reduces the adaptive capabilities of organisms.

● All "unsuccessful" combinations of parental genes and traits (in some cases, harmful mutations) are passed on to the next generation.

The main disadvantages of sexual reproduction:

● Not every individual can leave offspring, certain conditions are necessary for the meeting of partners, the formation of parental pairs, and the breeding of offspring.

● In some individuals, "unsuccessful" (unsuitable for given environmental conditions) combinations of parental genes and traits may occur, harmful mutations that have arisen in the germ cells of the parents (for example, Down's syndrome in humans) can appear.

7*. Aphids produce several parthenogenetic generations during the summer, consisting only of wingless females. Under overpopulation or other unfavorable circumstances, females begin to lay eggs, from which winged individuals of both sexes develop. What is the biological significance of this?

The appearance of offspring of different sexes determines the high genetic diversity of individuals of the next generation (compared to previous parthenogenetic generations), which increases the adaptive capabilities of organisms. The presence of wings contributes to the resettlement of individuals in new habitats. All this increases the chances of survival.

* Tasks marked with an asterisk require students to put forward various hypotheses. Therefore, when setting a mark, the teacher should focus not only on the answer given here, but take into account each hypothesis, evaluating the biological thinking of students, the logic of their reasoning, the originality of ideas, etc. After that, it is advisable to familiarize students with the answer given.

The ability to reproduce, i.e. to produce a new generation of individuals of the same species is one of the main features of living organisms. In the process of reproduction, the genetic material is transferred from the parent generation to the next generation, which ensures the reproduction of traits not only of one species, but of specific parental individuals. For a species, the meaning of reproduction is to replace those of its representatives who die, which ensures the continuity of the existence of the species; in addition, under suitable conditions, reproduction allows you to increase the total number of the species.

1. Introduction. one

2. reproduction in general. 3-4

3. Reproduction and human development. five

4. Male reproductive organs. 5-6

5. Female reproductive organs. 6-7

6. The beginning of life (conception). 7-8

7. intrauterine development. 8-11

8. Birth, growth and development of an infant. 12-13

9. Growth and development of the breast in a child from a year. 14-15

10. Beginning of maturation. 16-19

11. Used literature. twenty

BREEDING IN GENERAL

There are two main types of reproduction - asexual and sexual. Asexual reproduction occurs without the formation of gametes, and only one organism participates in it. In asexual reproduction, identical offspring are usually produced, and random mutations serve as the only source of genetic variability.

Genetic variability is beneficial to the species, as it supplies the "raw materials" for natural selection, and hence for evolution. The offspring that are most adapted to the environment will have an advantage in competition with other members of the same species and will have a better chance of surviving and passing on their genes to the next generation. Thanks to this species, they are able to change, i.e. speciation process is possible. Increased variation can be achieved by shifting the genes of two different individuals, a process called genetic recombination, which is an important feature of sexual reproduction; in a primitive form, the genetic recommendation is already found in some bacteria.

SEXUAL REPRODUCTION

During sexual reproduction, the offspring is obtained as a result of the fusion of the genetic material of the haploid nuclei. Usually these nuclei are contained in specialized sex cells - gametes; during fertilization, gametes merge, forming a diploid zygote, from which a mature organism is obtained in the process of development. Gametes are haploid - they contain one set of chromosomes obtained as a result of meiosis; they serve as a link between this generation and the next (during sexual reproduction of flowering plants, not cells, but nuclei merge, but usually these nuclei are also called gametes).

Meiosis is an important stage in life cycles involving sexual reproduction, as it leads to a halving of the amount of genetic material. Due to this, in a number of generations that reproduce sexually, this number remains constant, although it doubles each time during fertilization. During meiosis, as a result of the random birth of chromosomes (independent distribution) and the exchange of genetic material between homologous chromosomes (crossing over), new combinations of genes that fall into one gamete arise, and this shuffling increases genetic diversity. The fusion of the halide nuclei contained in the gametes is called fertilization or syngamy; it leads to the formation of a diploid zygote, i.e. a cell containing one chromosome set from each parent. This association in the zygote of two sets of chromosomes (genetic recombination) is the genetic basis of intraspecific variability. The zygote grows and develops into a mature organism of the next generation. Thus, during sexual reproduction in the life cycle, an alternation of the diploid and haploid phases occurs, and in different organisms these phases take on different forms.

Gametes are usually of two types, male and female, but some primitive organisms produce only one type of gamete. In organisms that form two types of gametes, they can be produced by male and female parental individuals, respectively, or it may be that the same individual has both male and female reproductive organs. Species that have separate male and female individuals are called dioecious; so are most animals and man.

Parthenogenesis is one of the modifications of sexual reproduction in which the female gamete develops into a new individual without fertilization by the male gamete. Parthenogenetic reproduction occurs in both the animal kingdom and the plant kingdom, and has the advantage of increasing the rate of reproduction in some cases.

There are two types of parthenogenesis - haploid and diploid, depending on the number of chromosomes in the female gamete.

REPRODUCTION AND HUMAN DEVELOPMENT

MALE GENITAL ORGANS

The male reproductive system consists of paired testicles (testicles), vas deferens, a number of accessory glands, and the penis. The testis is a complex tubular ovoid gland; it is enclosed in a capsule - a protein shell - and consists of about a thousand highly convoluted seminiferous tubules, immersed in a connective tissue that contains interstitial (Leydig) cells. In the seminiferous tubules, gametes are formed - sperm (spermatozoa), and interstitial cells produce the male sex hormone testosterone. The testicles are located outside the abdominal cavity, in the scrotum, and therefore spermatozoa develop at a temperature that is 2-3 degrees C lower than the temperature of the internal regions of the body. The lower temperature of the scrotum is partly determined by its position and partly by the choroid plexus formed by the artery and vein of the testis and acting as a countercurrent heat exchanger. Special muscle contractions will move the testicles closer or further away from the body, depending on the air temperature, to maintain the temperature in the scrotum at a level optimal for sperm formation. If a man has reached puberty and the testicles have not descended into the scrotum (a condition called cryptorchidism), then he remains sterile forever, and in men who wear too tight underpants or take very hot baths, sperm production can drop so much that it leads to infertility. Only in a few mammals, including whales and elephants, the testes are in the abdominal cavity all their lives.

The seminiferous tubules are 50 cm long and 200 microns in diameter and are located in areas called testis lobules. Both ends of the tubules are connected to the central region of the testis - the testis network (rete testis) - short straight seminiferous tubules. Here the sperm is collected in 10 - 20 efferent tubules; along them, it is transferred to the head of the epididymis, where it is concentrated as a result of reabsorption of the fluid secreted by the seminiferous tubules. In the head of the epididymis, spermatozoa mature, after which they come along a convoluted 5-meter efferent tubule to the base of the epididymis; here they remain for a short time before entering the vas deferens. The vas deferens is a straight tube about 40 cm long, which, together with the artery and vein of the testis, forms the seminal quantum and carries the sperm to the urethra (urethra), which runs inside the penis. The relationship between these structures, the male accessory glands and the penis is shown in the figure.

FEMALE GENITAL ORGANS

The role of the female in reproduction is much larger than that of the male and involves interactions between the pituitary, ovaries, uterus and fetus. The female reproductive system consists of paired ovaries and fallopian tubes, uterus, vagina and external genitalia. The ovaries are attached to the abdominal wall by a fold of the peritoneum and perform two functions: produce female gametes and secrete female sex hormones. The ovary is almond-shaped, consists of an outer cortex and an inner medulla, and is enclosed in a connective tissue sheath called the tunica albuginea. The outer layer of the cortical substance consists of cells of the bud epithelium, from which gametes are formed. The cortex is formed by the developing follicles, and the medulla is formed by the stroma containing connective tissue, blood vessels, and mature follicles.

The fallopian tube is a muscular tube about 12 cm long, through which female gametes leave the ovary and enter the uterus.

The opening of the fallopian tube ends with an extension, the edge of which forms a fringe that approaches the ovary during ovulation. The lumen of the fallopian tube is lined with ciliated epithelium; the movement of female gametes to the uterus is facilitated by peristaltic movements of the muscular wall of the fallopian tube.

The uterus is a thick-walled bag of potatoes about 7.5 cm long, 5 cm wide, consisting of three layers. The outer layer is called the serosa. Under it is the thickest middle layer - the myometrium; it is formed by bundles of smooth muscle cells, which are sensitive to oxytocin during childbirth. The inner layer - the endometrium - is soft and smooth; it consists of epithelial cells, simple tubular glands, and spiral arterioles that supply the cells with blood. During pregnancy, the uterine cavity can increase 500 times - from 10 cm3. up to 5000 cm3 The lower entrance to the uterus is its neck, which connects the uterus to the vagina. Vagina. The entrance to the vagina, the external opening of the urethra and the clitoris are covered by two skin folds - the large and small labia, forming the vulva. The clitoris is a small, erectile structure that is homologous to the male penis. In the walls of the vulva are Bartholin's glands, secreted during sexual arousal mucus that moisturizes the vagina during intercourse.

Asexual reproduction is carried out with the participation of only one parent and occurs without the formation of gametes. The daughter generation in some species arises from one or a group of cells of the maternal organism, in other species - in specialized organs. There are the following methods of asexual reproduction Key words: fission, budding, fragmentation, polyembryony, sporulation, vegetative reproduction.

Division- a method of asexual reproduction, characteristic of unicellular organisms, in which the mother individual is divided into two or more daughter cells. We can distinguish: a) simple binary fission (prokaryotes), b) mitotic binary fission (protozoa, unicellular algae), c) multiple fission, or schizogony (malarial plasmodium, trypanosomes). During the division of paramecium (1), the micronucleus is divided by mitosis, the macronucleus by amitosis. During schizogony (2), the nucleus is first repeatedly divided by mitosis, then each of the daughter nuclei is surrounded by cytoplasm, and several independent organisms are formed.

budding- a method of asexual reproduction, in which new individuals are formed in the form of outgrowths on the body of the parent individual (3). Daughter individuals can separate from the mother and move on to an independent lifestyle (hydra, yeast), they can remain attached to it, in this case forming colonies (coral polyps).

Fragmentation(4) - a method of asexual reproduction, in which new individuals are formed from fragments (parts) into which the parent individual breaks up (annelids, starfish, spirogyra, elodea). Fragmentation is based on the ability of organisms to regenerate.

Polyembryony- a method of asexual reproduction, in which new individuals are formed from fragments (parts) into which the embryo breaks up (monozygous twins).

Vegetative reproduction- a method of asexual reproduction, in which new individuals are formed either from parts of the vegetative body of the mother individual, or from special structures (rhizome, tuber, etc.) specially designed for this form of reproduction. Vegetative propagation is characteristic of many groups of plants, it is used in horticulture, horticulture, plant breeding (artificial vegetative propagation).

Vegetative organ	Method of vegetative propagation	Examples
Root	root cuttings	Rosehip, raspberry, aspen, willow, dandelion
Root offspring	Cherry, plum, thistle, thistle, lilac
Aerial parts of shoots	The division of the bushes	Phlox, daisy, primrose, rhubarb
stem cuttings	Grapes, currants, gooseberries
layering	Gooseberries, grapes, bird cherry
Underground parts of shoots	Rhizome	Asparagus, bamboo, iris, lily of the valley
Tuber	Potato, weekday, Jerusalem artichoke
Bulb	Onion, garlic, tulip, hyacinth
Corm	Gladiolus, crocus
Sheet	leaf cuttings	Begonia, Gloxinia, Coleus

sporulation(6) - reproduction through spores. controversy- specialized cells, in most species are formed in special organs - sporangia. In higher plants, spore formation is preceded by meiosis.

Cloning- a set of methods used by humans to obtain genetically identical copies of cells or individuals. Clone- a set of cells or individuals descended from a common ancestor through asexual reproduction. Cloning is based on mitosis (in bacteria, simple division).

The convergence of two individuals and the exchange of genetic material through the cytoplasmic bridge is.

copulation

parthenogenesis

conjugation

Conjugation- convergence of chromosomes during meiosis; sexual process, which consists in the partial exchange of hereditary information. Haploid gametes formed during the division of a diploid cell by meiosis contain one chromosome of each homologous pair (paternal or maternal origin), i.e. only half the original number of chromosomes. In this regard, an additional requirement is imposed on the apparatus of cell division: homologues must learn

each other and pair up before they line up on the equator of the spindle. Such pairing, or conjugation, of homologous chromosomes of maternal and paternal origin occurs only in meiosis. During the first division of meiosis, DNA replication occurs, and each chromosome then consists of two chromatids, homologous chromosomes are conjugated along their entire length, and crossing over occurs between the chromatids of paired chromosomes.

The basis of sexual reproduction is

ability of DNA to replicate

template synthesis of i-RNA

ATP synthesis process

The transfer of hereditary information to the next generation is carried out due to the ability of DNA to duplicate ( reduplication). A special enzyme unwinds the DNA molecule, the hydrogen bonds between the bases break and the chains diverge. Then, on each strand of DNA, the enzyme DNA polymerase builds a new strand according to the principle of complementarity. As a result, two completely identical DNA molecules are formed, in each of which one strand is the parent (matrix), and the second is the daughter. This way ( reduplication) is called semi-conservative. Later, in the process of division, the resulting DNA molecules are distributed between daughter cells, ensuring the accurate transmission of hereditary information.

The process of fusion of gametes is called.

gametogenesis

fertilization

sexual reproduction

Fertilization- the process of fusion of male and female germ cells (gametes), as a result of which a fertilized egg (zygote) is formed. That is, one diploid cell (zygote) is formed from two haploid gametes. In flowering plants, in addition to the fusion of haploid gametes - one of the sperm with the egg, and the formation of a diploid zygote, from which the seed embryo develops, the second sperm fuses with a diploid secondary cell and the formation of triploid cells, from which the endosperm is formed. This process is called double fertilization.

Some groups of organisms are characterized by the so-called irregular types of sexual reproduction (without fertilization): parthenogenesis, gynogenesis, androgenesis, apomixis.

Spores in bacteria and fungi serve to

enduring adverse conditions

resettlement

breeding and dispersal

Spores in bacteria and fungi serve to breeding and dispersal.

The bacterial cell is covered with a dense membrane formed by the polymeric carbon murein. Some species form spores under unfavorable conditions - a mucous capsule that prevents the cell from drying out. Remain viable for hundreds and even thousands of years. Maintain fluctuations of temperature from — 243 to 140 °C. When favorable conditions occur, the spores germinate and give rise to a new bacterial cell. The cell wall can form outgrowths that promote the association of bacteria into groups, as well as their conjugation. Hereditary material is contained in a nucleotide in the form of a circular DNA molecule. Asexual reproduction of fungi is associated with sporulation. Spores are produced in sporangia or at the ends of hyphae.

Asexual reproduction promotes.

emergence of adaptations

increase in the number of individuals

appearance of modifications

Asexual reproduction is reproduction that involves only one individual. A distinction is made between asexual and vegetative reproduction. Actually asexual reproduction is characteristic of the simplest animals (amoeba, ciliate shoe, green euglena), in which it is carried out as a result of mitotic cell division. Of multicellular animals, asexual reproduction is characteristic of the sessile form - polyps that form colonies. Plants reproduce asexually by producing spores and zoospores. Spores are usually characteristic of land plants, while zoospores with flagella are characteristic of aquatic plants. Mushrooms and algae reproduce asexually, while the same individual can grow from spores. Asexual reproduction usually provides increase in the number of genetically homogeneous offspring.

Plants are involved in sexual reproduction.

gametes

pollen grains

disputes

Gametes- germ cells. They have half the number of chromosomes as somatic (body cells) cells. In animals, they are formed as a result of meiosis, and in higher plants, as a result of mitosis.

In horticulture, fruit trees are used for propagation.

cloning

vaccination

budding

Graft in cut - the simplest and most effective type of side grafting. It is widely used for propagation of deciduous and evergreen plants.

This method consists in grafting the cutting on the side of the stock into a notch or a pin ( in side cut). At the same time, the top of the stock can remain intact or be cut into a spike. Grafting into the side cut is used on rootstocks of any thickness. When grafting, a greater strength of fusion of the scion with the stock is achieved.

The development of a new organism from an unfertilized egg is called.

ontogeny

parthenogenesis

phylogenesis

In some species of organisms, a special form of sexual reproduction occurs - without fertilization. This development is called parthenogenesis, or virgin development.

An egg ready for fertilization contains half the set of chromosomes. The ovum, ripe for fertilization, is divided into two halves. Then, having united, the egg with a full set of chromosomes begins to split up. An embryo is formed. In this case, the daughter organism develops from an unfertilized egg based on the genetic material of one of the parents, and individuals of only one sex are formed. Natural parthenogenesis enables a sharp increase in the number of offspring and exists in those populations where the contact of heterosexual individuals is difficult. Parthenogenesis occurs in animals of different systematic groups: in bees, aphids, lower crustaceans, rock lizards, and even in some birds (turkeys).

The figure shows the process

regeneration

copulation

budding

In summer, a small tubercle appears on the body of the hydra ( bud), which grows and stretches rapidly. After some time, outgrowths (tentacles) appear, and a mouth forms between them. The kidney at the base of the mother's body is laced and when the little hydra grows up, it falls to the bottom and lives on its own.

After a copious budding process the hydra's body is depleted. For some time, buds do not form on it, but if there is enough nutrition, the budding process is restored quite quickly.

In flowering plants, as a result of double fertilization, a fertilized central cell is formed.

germ

zygote

endosperm

Endosperm- tissue inside the seed, performing a storage function. In gymnosperms, the endosperm is haploid ( 1n), it is formed before fertilization from the megaspore and is the female gametophyte.

Endosperm cells in flowering plants have ... a set.

Endosperm is a tissue inside the seed that performs a storage function. In the gymnosperm seed, the endosperm is haploid (1n), it is formed from the megaspore before fertilization and is the female gametophyte. In angiosperms (flowering triploid endosperm (3n)), which is formed as a result of double fertilization of the fertilized central nucleus of the embryo sac. Due to the endosperm, the seed embryo feeds, absorbing reserve carbohydrates, proteins, fats.

The triploidity of the nuclei of endosperm cells, carrying the hereditary information of the maternal and paternal organisms, increases the adaptability of the young plant to various environmental conditions.

The figure shows the process

double fertilization

pollination

sporulation

This is natural pollination. In addition, there is artificial pollination produced by man for breeding or production purposes.

Pollination The process of transporting pollen with the help of wind or insects. observed in seed plants. Subdivided.

reproduction - the ability of organisms to reproduce their own kind.

There are two types of reproduction in nature: asexual and sexual.

I. asexual reproduction - reproduction of organisms that occurs without the formation of gametes with the participation of only one parent organism.

Identical offspring from the same parent is called clone.

Members of the same clone can be genetically different only if a random mutation occurs.

The basis of asexual reproduction is mitotic division .

Types of asexual reproduction:

Types of asexual reproduction	Characteristics	Examples of organisms
1. Simple (binary)	From one cell, two daughter cells are formed by mitosis, each of which becomes a new organism, identical to the parent.	Bacteria, many protozoa (amoeba), all single-celled algae (chlorella)
2. Multiple division (schizogony)	There is a multiple division of the cell nucleus, after which the cell itself is divided into many subsidiaries. The stage at which multiple division occurs is called schizont, and the process itself is called schizogony.	Sporozoans (a group of protozoa, which includes the causative agent of malaria - malarial plasmodium); some algae
3. Sporulation (spore formation)	A spore is a single-celled reproductive unit of microscopic size, consisting of a nucleus and a small amount of cytoplasm. Spores can be formed by mitosis or meiosis. There are also sexual spores (chlamydomonas zoospores), they perform the functions of gametes.	Algae, mosses, ferns, horsetails, club mosses; mushrooms
4. Budding	A new individual is formed in the form of an outgrowth (kidney) on the body of the parent individual, and then separates from it, turning into an independent organism.	Intestinal, unicellular fungi (yeast)
5. Fragmentation	The division of an individual into two or more parts, each of which grows and gives rise to a new organism. This method is based on the ability of organisms to regenerate (restoration of missing parts of the body).	Planaria flatworm (under unfavorable conditions); nemertines (sea worms); filamentous algae (spirogyra)
6. Vegetative propagation	Reproduction by individual organs, parts of organs or the body. It is not uncommon for plants to form structures specifically designed for this: s bulbs(short stem, fleshy leaves); s corms(swollen underground stem, no fleshy leaves); s rhizome(underground stem growing horizontally); s stolon(creeping horizontal stem, creeping along the surface of the soil; s mustache (lash)- varieties of stolons that grow rapidly in length; s tuber(underground storage shoot); s root tubers (cones) - swollen adventitious roots; s fleshy taproots; s leaves.	tulip, narcissus, onion; saffron, gladiolus; iris, couch grass, aster, mint; blackberries, gooseberries, black and red currants; strawberry, ranunculus creeping; potato; dahlias;
7. Cloning	Growing an individual genetically identical to a given organism by transplanting a nucleus from a somatic cell into an egg from which the nucleus has been previously removed.	higher plants and some animals.

asexual reproduction, evolved before sexual , is a very efficient process.

Meaning of asexual reproduction:

Advantages of asexual reproduction:

Disadvantages of asexual reproduction:

1. Only one parent required . Two individuals participate in sexual reproduction, and this involves spending time and energy searching for a partner or, in immobile organisms (plants), special mechanisms, such as pollination, in which many gametes die. 2. Genetically identical offspring . With a good adaptation of the species to the conditions of existence, this is an advantage, since successful combinations of genes are preserved. 3. Dispersal and distribution of the species . Microscopic and light spores are carried by the wind over long distances, rapid growth of rhizomes, etc. 4. Reproduction rate . Under favorable conditions, the population of the species increases rapidly

1. Lack of genetic variation among offspring. 2. If reproduction is associated with the formation of spores, then many of them fail to find a suitable place for germination, so that the energy and materials spent on their creation are wasted. 3. If a species settles in one area, then overpopulation and nutrient depletion may occur.

II. sexual reproduction - the process of obtaining offspring as a result of the fusion of the genetic material of the haploid nuclei of two gametes.

Gametes - sex haploid cells.

spermatozoa - male gametes.

Oocytes - female gametes.

Fertilization - the process of fusion of gametes.

Zygote - the result of the fusion of gametes (fertilized egg), the first diploid cell of the future organism.

Species that have separate males and females are called dioecious (most animals and humans).

Species in which the same individual is able to produce both male and female gametes are called bisexual (bisexual) or hermaphroditic (protozoa, coelenterates, flatworms, oligochaetes (earthworms), crustaceans, mollusks such as snails, some fish and lizards, most flowering plants).

Parthenogenesis (virgin reproduction) - one of the modifications of sexual reproduction, in which the female gamete develops into a new individual without fertilization by the male gamete. Thus, parthenogenesis is sexual but same-sex reproduction. Parthenogenesis occurs in both the animal kingdom and the plant kingdom.

Distinguish :

s facultative parthenogenesis, in which eggs can develop both after fertilization and without it (bees, ants, rotifers - females develop from fertilized eggs, and males from unfertilized ones);

s obligate parthenogenesis (mandatory), in which eggs are only capable of parthenogenetic reproduction (Caucasian rock lizard).

In many species, parthenogenesis is cyclical, for example, in aphids, daphnia, and rotifers, only females exist in summer, and in autumn, parthenogenesis is replaced by reproduction with fertilization.

Sexual reproduction is based on the process of formation of germ cells - gametogenesis .

Gametogenesis - the process of formation and development of germ cells.

spermatogenesis - the process of formation of male germ cells - spermatozoa.

Ovogenesis (oogenesis) - the process of formation of female germ cells - eggs.

In the process of formation of germ cells, a number of stages are distinguished:

gametogenesis	Type and phase of division	spermatogenesis (in testicles)	Ovogenesis (in ovaries)
reproduction		Primary sex cells divide by mitosis; diploid cells with single chromatid chromosomes (2 n 2 c ) – gametocytes I order (spermatocytes and oocytes)
	Interphase	Gametocytes of the first order increase in size. DNA synthesis and completion of the second chromatid occurs; diploid cells with two chromatid chromosomes (2 n 4 c )
Maturation		spermatocytes I order shared with education spermatocytes II order ( n 2 c ) . As a result of the second division, four haploid spermatids -cells with single chromatid chromosomes ( nc ) .	During the first (reduction) division oocytes I order shared with education oocytes II order ( n 2 c ) and directional body ( n 2 c ). During the second division, an ovum is formed from an oocyte of the second order ( nc ) and guide body ( nc ) ; from the first directional body - two new ones. As a result of meiosis, an egg and three directional (reduction) bodies are formed. All cells are haploid with single chromatid chromosomes. Reduction bodies soon die
Formation		The acquisition by cells of a certain shape and size, corresponding to their specific function
Sperm formation: the Golgi apparatus is located at the front edge of the head, transforming into acrosome (secretes enzymes that dissolve the egg membrane); mitochondria are compactly packed around the emerging flagellum, forming a neck.	Increase in the amount of yolk. In many animals - the formation of additional membranes (protection of the egg and the developing embryo from adverse effects)

Fertilization - the process of fusion of the sperm with the egg and the formation of a fertilized egg - zygotes .

Zygote - the initial unicellular stage of development of a new organism.

III. Ontogenesis - individual development of the organism - the period of life of an individual from the moment the zygote is formed to the death of the organism. In the process of ontogenesis, hereditary information received from parents is realized.

Ontogeny includes two periods:

Embryonic period - from the formation of a zygote to birth or exit from the egg membranes. Postembryonic period from birth to death of an organism.

The embryonic period includes three main stages:

Splitting up - the formation of a single-layer multicellular embryo as a result of mitotic division of the zygote.

At the stage of two germ layers, development in sponges and coelenterates ends. In other animals, the third germ layer is laid - mesoderm - from the endoderm and is located between the ectoderm and endoderm.

During gastrulation, cell differentiation begins organogenesis :

from ectoderm :

s nervous system;

s components of the organs of vision, hearing, smell;

s skin epithelium and its derivatives (mammary, sweat and sebaceous glands, hair, feathers, nails, tooth enamel);

s anterior and posterior sections of the digestive system (epithelium of the oral cavity and rectum);

s external gills;

s thyroid gland;

from endoderm:

s epithelium of the digestive, respiratory and genitourinary systems;

s digestive glands (liver, pancreas);

from mesoderm:

s cartilage and bone skeleton;

s muscle tissue (striated skeletal and smooth muscles of internal organs);

s circulatory system and blood;

s excretory system;

s gonads;

s all connective tissue;

s adrenal glands.

At different types animals, the same germ layers give rise to the same organs and tissues. So they homologous . Homology - proof of the unity of the origin of the animal world.

The postembryonic period is of two types:

direct postembryonic development - goes without transformations, when the born organism resembles an adult and differs only in size, underdevelopment of a number of organs and body proportions (birds, mammals, reptiles, some insects, crustaceans, etc.) Indirect postembryonic development- proceeds with metamorphosis, i.e. with the transformation into an adult. The larva is adapted to active nutrition, movement, growth and development, but cannot reproduce (exception: axolotl - the larva of the amphibian ambistoma - with a lack of thyroid hormone does not turn into an adult, but is able to reproduce at this stage). The biological meaning of metamorphosis lies in the fact that larvae and adults eat different foods, are adapted to different conditions, which eliminates competition between them and contributes to the survival of juveniles.

The postembryonic period ends with aging and death.