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 resettlement (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, mollusks).
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).
1. 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
2. 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.
Answer
3. Establish a correspondence between the stages of the life cycle of plants and methods of reproduction: 1) asexual, 2) sexual. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) controversy
B) accompanied by the fusion of gametes
B) sporophytes reproduce
D) the gametophyte reproduces
D) a zygote is formed
E) meiosis occurs
Answer
4. Establish a correspondence between the characteristics and the method of reproduction: 1) asexual, 2) sexual. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) Gametes are not formed.
B) Only one organism is involved.
C) Fusion of haploid nuclei occurs.
D) Offspring are formed that are identical to the original individual.
E) The offspring show combinative variability.
E) Gametes are formed.
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 remain very similar to the parent
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
Answer
7 Sat. Establish a correspondence between 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 chlamydomonas
B) sturgeon spawning
B) sporulation in mosses
D) division of the common amoeba
E) fragmentation of mycelium in fungi
E) raspberry root suckers
Answer
8. Establish a correspondence between examples and methods of reproduction: 1) asexual, 2) sexual. Write the numbers 1 and 2 in the order corresponding to the letters
A) tissue culture
B) unfertilized eggs
B) tubers
D) eggs
D) somatic cells
E) parts of the rhizome
Answer
Choose one, the 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. Identify two terms that "fall out" from the 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, the offspring are exact copies of the 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
All of the above characteristics, except for two, are used to describe the sexual reproduction of animals. Find two characteristics that "fall out" from the general list, and write down the numbers under which they are indicated.
1) Gametes are formed as a result of gametogenesis.
2) In the reproduction of chordates, as a rule, individuals of different sexes participate.
3) The starting material for the formation of gametes are spores.
4) In the offspring, the characteristics of both parents are combined.
5) The chromosome set of the gamete is formed as a result of division by mitosis.
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
1. All the methods of crop production below, except for two, are classified as vegetative propagation. Identify two tricks that “fall out” of the general list, and write down the numbers under which they are indicated.
1) division of tubers
2) propagation by rhizome
3) obtaining seedlings from seeds
4) artificial insemination
5) layering formation
Answer
2. All the examples below, except for two, characterize vegetative propagation. Identify two examples that "fall out" from the general list, and write down the numbers under which they are indicated.
1) getting heterotic hybrids
2) propagation by dividing the bush
3) use of root offspring
4) propagation by seeds
5) rooting layering
Answer
All but two of the following organisms reproduce by spores. Identify two organisms that "fall out" from the general list. Write down the numbers under which they are indicated.
1) mukor mushroom
2) cholera vibrio
3) tuberculosis bacillus
4) fern shield
5) cuckoo flax
Answer
© D.V. Pozdnyakov, 2009-2019
Question 1. Prove that reproduction is one of the most important properties of wildlife.
The ability to reproduce or self-reproduce is one of the essential and most important properties of living organisms. Reproduction maintains the long existence of the species, ensures continuity between parents and their descendants in a number of many generations. It leads to an increase in the number of individuals of the species and contributes to its resettlement.
Question 3. What is asexual reproduction? What is the process behind it?
There are two types of reproduction: asexual and sexual.
Asexual reproduction is a type of reproduction that occurs without the production of gametes. For its implementation, only one organism is needed. As a result of asexual reproduction, a new individual develops from one or a group of somatic cells of the mother's organism. Mitosis is the basis of asexual reproduction. With asexual reproduction, the daughter organism at the genetic level
Asexual - due to mitotic division, in plants rarely due to meiotic division.
Sexual - due to meiotic division.
Question 4. List the ways of asexual reproduction; give examples.
Asexual reproduction in unicellular organisms.
Asexual reproduction in multicellular organisms.
1. Vegetative - is based on the ability of organisms to restore (regenerate) the missing parts. In plants, a variety of this form of reproduction is observed: it occurs by the formation of new buds on stems, roots, leaves, from which new plants grow. They can exist independently, without connection with the mother's body. For example, in multicellular algae, fungi, lichens, reproduction is carried out by scraps of threads, hyphae, fragments of thalli. Angiosperms can reproduce: parts of the stem (cacti, elodea), leaf (violet, begonia, lily), roots (raspberry, gooseberry, dandelion), modified shoots: tubers (potato), bulbs (onion, garlic, tulip, daffodil), rhizomes (wheatgrass, horsetail, Ivan-tea), mustache (strawberry), etc. In animals, due to the high specialization of body cells, vegetative reproduction is less common. The ciliary and annelids are divided by constrictions into several parts, in each of them the missing organs are restored and, thus, several individuals appear at once. In coelenterates, polyps begin to grow rapidly, transverse constrictions are formed, as a result of which daughter individuals are formed, and this method is called strobilation. At this point, the polyp resembles a stack of plates. The resulting individuals - jellyfish come off and begin an independent life. In some species of mammals (armadillo) and insects (wasps-riders), vegetative reproduction of embryos occurs, when at the early stages of embryonic development the dividing embryonic disk gives rise to several individuals (from 4 to 8). A similar thing can be observed in humans when blastomeres are separated from which monozygotic twins will develop (such an increase in the number of individuals is called polyembryony.)
2. Budding characteristic of coelenterates (hydra). The kidney (protrusion) includes cells of the ecto- and endoderm. The kidney enlarges, tentacles form on it, and this kidney separates from the mother.
3. Reproduction by fragments - (fragmentation) occurs when an individual divides into two or more parts, each of which grows and forms a new individual. Fragmentation is associated with regeneration, i.e. the ability to restore the whole organism. Fragmentation has been described for flatworms, nemerteans, and starfish.
4. Sporulation found in fungi, algae, mosses, club mosses, horsetails and ferns. Spores are formed by meiosis in ordinary vegetative cells of the mother organism or special organs - sporangia and are microscopic unicellular formations.
With any form of asexual reproduction - body parts or spores - there is an increase in the number of individuals of a given species without increasing their genetic diversity: all individuals are an exact copy of the mother's organism. A set of individuals descended from one ancestor by asexual reproduction is called clones (Greek clon - branch, offspring).
Question 5. Is it possible for genetically heterogeneous offspring to appear during asexual reproduction?
In asexual reproduction, the exact copying of the genetic material of the mother occurs, and the daughter organisms are identical to the mother. The appearance of genetically heterogeneous offspring during asexual reproduction is impossible. The method of asexual reproduction developed in the laboratory is cloning.
Cloning makes it possible to work with single cells or small embryos. For example, when breeding cattle, a calf embryo at the stage of undifferentiated cells is divided into fragments and placed in surrogate mothers. As a result, several identical calves with the necessary traits and properties develop.
Plant cloning can also be used if necessary. In this case, selection occurs in cell culture (on artificially cultivated isolated cells). And only then, full-fledged plants are grown from cells with the necessary properties.
The most famous example of cloning is the transplantation of a somatic cell nucleus into a developing egg. This technology in the future will make it possible to create a genetic twin of any organism (or, more importantly, its tissues and organs).
Question 6. What is the difference between sexual reproduction and asexual reproduction? Define the definition of sexual reproduction.
Sexual reproduction involves specialized sex cells that carry a haploid set of chromosomes. In most cases, a new generation arises from the fusion of two gametes from different organisms. Therefore, unlike asexual reproduction, in sexual reproduction, the daughter individual receives hereditary information from both parents (50% from the mother and 50% from the father) and has its own combination of genetic material. In many species that are characterized by sexual reproduction, there are male and female individuals that form gametes of different sizes and properties: large immobile eggs and small mobile spermatozoa. Such species are called dioecious.
In general, we can say that sexual reproduction is the process of formation of a diploid daughter organism, which occurs with the participation of germ cells that carry a haploid set of chromosomes.
Question 7. Think about the importance for the evolution of life on Earth had the emergence of sexual reproduction.
Sexual reproduction has very large evolutionary advantages over asexual reproduction. This is due to the fact that the genotype of the offspring arises from a combination of genes belonging to both parents. As a result, the ability of organisms to adapt to environmental conditions increases. The sexual process consists in the fusion of two cells - gametes. The formation of gametes is preceded by a special form of division - meiosis, which leads to a decrease in the number of chromosomes by half.
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.
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 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 unfavorable environmental conditions, therefore, animals with an external type of fertilization need to produce a large number of germ 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.
This test allows you to check the knowledge of students on cell division, individual development of the body. different types of test tasks are used: complete the sentence, choose the correct judgment, choose the correct answer, define biological concepts. these forms of knowledge control allow students to prepare for the final certification.
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Reproduction and individual development of organisms.
1.What is it?
1. the property of living organisms to reproduce their own kind.
2. type of reproduction in which only one parent individual participates.
3. the process of formation of gametes.
4. pairwise convergence of homologous chromosomes in prophase 1 of meiosis.
5. the process of fusion of gametes.
6. individual development of an individual from the moment the zygote is formed until the death of the organism.
7. stage of cell preparation for division.
9. List in order the phases of meiosis.
10. the process of formation of male gametes.
11. indirect cell division.
12. the process of crossover of homologous chromosomes, which occurs in prophase 1 of meiosis and leads to the exchange of genes.
13. a method of cell division, as a result of which gametes are formed.
14. List in order the phases of mitosis.
2. Define:
Blastula; ectoderm; sexual reproduction; organogenesis; gastrula; postembryonic development.
3. Choose the correct judgment.
- asexual reproduction occurs without the formation of gametes, it involves one individual.
- In the second division of meiosis, whole chromosomes diverge to the poles.
- during sexual reproduction, offspring arise as a result of the fusion of diploid nuclei contained in the germ cells - gametes.
- daughter cells formed as a result of mitosis contain only one of each pair of homologous chromosomes.
- the number of chromosomes in daughter cells during meiosis after the first division is halved.
4. Choose the correct answer.
- conjugation of chromosomes is the connection of two homologous chromosomes in the process: mitosis; meiosis; fertilization; pollination.
- the daughter organism is more different from the parent during reproduction: vegetative; disputes; sexual; budding.
- stages of crushing, blastula, gastrula, organ formation are characteristic of individual development: embryonic; postembryonic; direct; indirect.
- in the process of mitosis, the greatest changes undergo: cytoplasm; endoplasmic reticulum; nucleus; lysosome.
- during sexual reproduction, daughter individuals develop from: one unspecialized cell; two unspecialized cells; merged unspecialized cells; fused specialized cells.
- a single-layer spherical embryo with a cavity inside is called: gastrula; blastula; neurula; blastomere.
- conjugation and crossing over occur: in prophase1; in prophase2; in interphase; in the process of fertilization
- the egg and sperm have: a diploid set of chromosomes; haploid; contain a small supply of nutrients.
On the topic: methodological developments, presentations and notes
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