Hermaphroditism is the presence of both types of gonads in an individual. In a person, clothes, makeup, perfume, etc. play a big role. Phenotype. Examples of determining gender by environmental factors. True synchronous hermaphroditism in an earthworm. In most animals, sex is determined genetically. Hormonal and gametic sex. In humans and other mammals, the homogametic sex is female. Examples of asexual reproduction. Males are dimly colored.
“Mechanisms of genetic sex determination” - Inheritance of traits. Sex determination in bees. Sex chromosomes. Sex determination in birds. Bees and ants do not have sex chromosomes. Determination of sex in humans. Genetics of sex. Diseases. Chromosomal sex determination. Hemophilia. Male gender. Birth of a sick girl. Chromosomes. Female. Carrier of the hemophilia gene.
"Chromosomes" - Deletion. Chromosomes like lamp brushes. Structure and functions of chromosomes. Loss of internal area. Types of chromosomes. Centromere. Chromosome structure disorders. Chromosome layout. Inversions. Polytene chromoosmata. All human chromosomes. Chromatid. Homologous chromosomes. Translocation. Duplications. Diploid set of chromosomes in plants. The meaning of the centromere. Karyotype. Giant chromosomes. Karyotype of a domestic cat.
“Applied genetics” - Live 30% longer. Biotechnological methods must develop, BUT clear regulation is required! Use of genetically modified bacteria. Complexity: Nitrogen fixation is controlled by 15 different genes. Animals and ethics. Banks of information. 4) Direct introduction of DNA, stimulated by calcium or electric shock. 5800 markers: diabetes, hypoglycemia, muscular dystrophy. Benefits and risks of using GMOs.
“Determination of genetics of sex” - Hens and roosters. Diploid set of chromosomes. Classic hemophilia. Human X chromosome. Genetics of sex. Red eye color. Reciprocal crossing. Brown-eyed woman. Genes localized on the Y chromosome. Chromosomes. Zygote. Autosomes. The gene responsible for plumage color. Black coloration in cats. The mother is a carrier of the hemophilia gene. Chickens are black. Hemizygous genes. Determination of gender. Sex in Drosophila.
“Methods of genetic analysis” - Parents. Gregor Johann Mendel. Karyotype. Literature. Karyotypes of humans and guppies. Mendel's laws. Genetic analysis algorithm. Phenotype. Genetic problems. Basic principle of genetic analysis. First generation analysis. The trait is determined by at least 5 genes. Kirpichnikov Valentin Sergeevich. Color. It is necessary to select parents who are homozygous for the characteristics being studied. Life. Second generation analysis.
Teacher: Hello, dear guys.
Teacher: Today we have new topic, and which one you tell me yourself.
Wildlife is diverse. But nothing lasts forever. An astronomical number of living beings die on Earth every second. What are the causes of these tragedies?
Student answers:
Question: Due to what universal property of organisms
does life continue on earth?
- Teacher: That's right, thanks to reproduction. Reproduction of organisms is the main property of living things.
Teacher: You know that there are two types of reproduction. Which?
(students' answers).
Means, The topic of our lesson is “Asexual reproduction and its forms”
Life on Earth began millions of years ago. In the process of evolution, some organisms were replaced by others. Why are those organisms that lived in ancient times similar to living organisms today? What is the mechanism of transmission of hereditary information from ancestors to offspring?
Teacher: Today we will remember the features and methods of asexual reproduction.
Teacher: What do you think characterizes asexual reproduction?
It is characterized by the fact that a new individual develops not from reproductive cells, but from somatic cells, thereby ensuring the homogeneity of the offspring.
Teacher: So, reproduction is….
Thereby unique property All living organisms, life on our planet exists and continues. This is the only path to immortality; reproduction is the meaning of life for any living organism. They also say about this process: “This is the process by which Life manages to fool Time.”
Teacher: What is the basis of reproduction? (cell division)
Teacher: What type of reproduction is called asexual?
One individual takes part
Without the participation of germ cells
Based on mitosis
Daughter organisms are a copy of the parent
Advantage- rapid increase in numbers
Flaw?- does not ensure survival in an unstable environment.
Teacher: What forms of asexual reproduction do you know? (student answers)
Cell division, sporulation, vegetative, budding, fragmentation
Teacher: So, let’s draw up a diagram, you in your notebooks, and on my board.
Asexual reproduction is widespread in nature, it is most common in unicellular organisms, but is also common in multicellular organisms. The following features are characteristic of asexual reproduction:
In asexual reproduction, only one individual takes part;
It is carried out without the participation of germ cells;
Reproduction is based on mitosis;
Daughter organisms arising from the mother are its exact copy. The offspring are identical and are exact genetic copies of the mother.
The advantage is a rapid increase in numbers.
Parthenogenesis is the only form of reproduction from a reproductive cell “egg”, without fertilization (notes are made in a notebook).
Hermaphroditism is the presence of male and female characteristics in one individual. Translated as “Mythical bisexual creature”, from the names of the Greek gods “Hermes and Aphrodite”.
Teacher: Let's give brief description each method of reproduction. Giving a description of each method, you fill out the table for yourself.
Division – method of asexual reproduction, in which the mother is divided into two or more daughter cells. This method is typical for unicellular organisms.
We can distinguish: a) simple binary fission (prokaryotes)
b) mitotic binary fission (protozoa, unicellular algae)
c) multiple fission, or schizogony (malarial
plasmodium, trypanosomes).
Budding is a method of asexual reproduction, in which new individuals are formed in the form of outgrowths on the body of the parent individual
Fragmentation - method of asexual reproduction, in which new individuals are formed from fragments (parts) into which the maternal individual breaks up ( annelids, starfish, spirogyra, elodea). Fragmentation is based on the ability of organisms to regenerate. If we accidentally split a jellyfish or a worm, what will happen? Proper restoration of lost body parts. And this is called regeneration.
We can safely cut the hydra
Restore your body
This is not a sensation
And regeneration.
Sporulation or sporulation is reproduction through spores. Spores are specialized cells; in most species they are formed in special organs called sporangia. (mosses, lichens, fungi) In higher plants, the formation of spores is preceded by meiosis. (horsetails, mosses, ferns)
For 10th grade information:
Polyembryony is a method of asexual reproduction in which new individuals are formed from fragments (parts) into which the embryo breaks up.
This method of reproduction occurs during embryonic development, in which several embryos develop from one zygote - twins (identical twins in humans). Offspring are always the same sex.
|
Methods of asexual reproduction |
Features of asexual reproduction |
Organisms |
|
1. Mitotic cell division |
Mitotic division of the nucleus occurs, followed by division of the cytoplasm. In this case, daughter cells receive an equal amount of hereditary information. Organelles are usually distributed evenly in daughter cells. After division, the daughter individuals grow and, having reached the size of the mother’s body, divide again. |
Amoeba, flagellated protozoa, algae, and others. |
|
2.Spore formation |
It is carried out through spores - specialized cells, fungi and plants. If the spores have a flagellum and are motile, they are called zoospores (Chlamydomonas). The spore consists of a cell covered with a membrane that protects it from unfavorable environmental conditions. |
Sporozoa, protozoa, unicellular algae, mosses, ferns, mushrooms, lichens. |
|
3. Budding. |
On the maternal individual, an outgrowth is formed - a bud (containing a daughter nucleus), from which a new individual develops. The bud grows, reaches the size of the mother and then separates from it. |
Bacteria, yeast fungi, hydra, sponges, sucking ciliates. |
|
4. Vegetative propagation. |
Characteristic of many groups of plants. A new individual develops either from a part of the mother or from special structures(bulb, tuber, layering, shoots, dividing the bush). In multicellular animals, a new organism is formed from a group of cells that separates from the mother organism (coelenterate sponges). |
Geranium, tradescantia, begonia, Uzambara violet, sansevieria, aspidistra, bulbous plant. |
Teacher: As we saw from previous examples, the process of asexual reproduction is possible not only in plants, but also in animals. Such reproduction is rare (due to the high specialization of cells), but occurs in sponges, flatworms and some annelids.
Teacher: Another method of asexual reproduction that we have not considered is vegetative. Vegetative - what is it?
Vegetative propagation is widespread among plants. We often see thickets of fern, willow, lily of the valley, nettle and other plants. New individuals are formed from above-ground or underground parts of the mother’s body. Many cultivated plants reproduce in a similar way. There are many methods of vegetative propagation, you will get acquainted with some of them today, and, I hope, in the future you will use them in your garden, garden, or home.
Teacher: The process of reproduction is inextricably linked with the properties of living organisms: heredity, variability, discreteness.
Heredity– the ability of organisms to transmit their characteristics, properties and developmental characteristics from generation to generation.
Variability- the universal property of living organisms to acquire differences from individuals, both other species and their own species.
The process of reproduction is extremely complex and is associated not only with the transfer of genetic information from parents to offspring, but also with the anatomical and physiological properties of organisms, their behavior, and hormonal control.
The basis of reproduction and individual development of an organism is cell division. The cell is not only a unit of structure, but also a unit of reproduction and a unit of development, the cell is the genetic unit of the living.
Teacher: Today we looked at asexual reproduction - its advantages and disadvantages. We also know the benefits of sexual reproduction. But I had a question while preparing for the lesson.
Question:
What form of asexual reproduction is characteristic of mosses and ferns?
What form of asexual reproduction is most characteristic of hydra and yeast?
What form of asexual reproduction is characteristic of planaria and some annelids?
Is the statement true: Asexual reproduction increases the hereditary variability of organisms?
Is the statement true: in asexual reproduction, all daughter individuals are an exact copy of the mother?
A1. For asexual reproduction:
Only one parent
Two parents
The same organism plays the role of both parents
There are no parents at all
A2. Asexual reproduction occurs:
Involving germ cells
Without the participation of germ cells
Only with the help of dispute
Only by budding
A 3. As a result of reproduction, they change
Body size
Body size
Body weight
Body shape
A4. Tulips are multiplying
Tubers
Bulbs
Cuttings
By layering
Are the statements true? (The whole class works at the same time: yes - green, no - red)
Sporulation is characteristic of hydra. -
Green euglena reproduces by cell division. +
Asexual reproduction involves one individual. +
A hermaphrodite is a bisexual organism. +
Mosses and ferns reproduce by budding. -
In asexual reproduction, the offspring are genetically very different from the parent organisms. –
Protozoa are characterized by halving. +
Reproduction is the process of reproducing others like themselves. +
Hydra reproduces by budding. +
Grapes, currants, gooseberries, and willows are propagated by cuttings. +
Asexual reproduction involves one individual. +
Reproduction is the ability of all organisms to reproduce their own kind, which ensures the continuity and acceptability of life. The main methods of reproduction are presented:
Asexual reproduction is based on cell division through mitosis, in which two equal daughter cells (two organisms) are created from each mother cell (organism). Biological role asexual reproduction consists in the emergence of organisms identical to the parents in the content of hereditary material, as well as anatomical and physiological properties (biological copies).
The following are distinguished: methods of asexual reproduction: division, budding, fragmentation, polyembryony, sporulation, vegetative propagation.
Division- a method of asexual reproduction characteristic of unicellular organisms, in which the mother 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 the paramecium (1), the micronucleus is divided by mitosis, the macronucleus by amitosis. During schizogony (2), the nucleus is first divided repeatedly 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), or 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 maternal individual breaks up (anneli, 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 (monozygotic twins).
Vegetative propagation- 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.) specifically designed for this form of reproduction. Vegetative propagation is typical for many groups of plants and is used in gardening, vegetable gardening, and plant breeding (artificial vegetative propagation).
Sporulation(6) - reproduction through spores. Controversy- specialized cells, in most species they 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 collection of cells or individuals descended from common ancestor by asexual reproduction. The basis for obtaining a clone is mitosis (in bacteria - simple division).
During sexual reproduction in prokaryotes, two cells exchange hereditary information as a result of the passage of a DNA molecule from one cell to another along a cytoplasmic bridge.
Sexual reproduction is carried out with the participation of two parent individuals (male and female), in which specialized cells are formed in special organs - gametes. The process of gamete formation is called gametogenesis, the main stage of gametogenesis is meiosis. The daughter generation develops from zygotes- a cell formed as a result of the fusion of male and female gametes. The process of fusion of male and female gametes is called fertilization. An obligatory consequence of sexual reproduction is the recombination of genetic material in the daughter generation.
Depending on the structural features of the gametes, the following can be distinguished: forms of sexual reproduction: isogamy, heterogamy and oogamy.
Isogamy(1) - a form of sexual reproduction in which gametes (conditionally female and conditionally male) are mobile and have the same morphology and size.
Heterogamy(2) - a form of sexual reproduction in which female and male gametes are motile, but female gametes are larger than male ones and less mobile.
Oogamy(3) - a form of sexual reproduction in which female gametes are immobile and larger than male gametes. In this case, female gametes are called eggs, male gametes, if they have flagella, - spermatozoa, if they don’t have, - sperm.
Oogamy is characteristic of most species of animals and plants. Isogamy and heterogamy occur in some primitive organisms (algae). In addition to the above, some algae and fungi have forms of reproduction in which sex cells are not formed: hologamy and conjugation. At hologamia single-celled haploid organisms merge with each other, which in this case act as gametes. The resulting diploid zygote then divides by meiosis to produce four haploid organisms. At conjugation(4) the contents of individual haploid cells of filamentous thalli merge. Through specially formed channels, the contents of one cell flow into another, a diploid zygote is formed, which usually, after a period of rest, also divides by meiosis.
In eukaryotes, the sexual process is associated with the formation of germ cells - GAMETE. Male gametes are sperm, female gametes are eggs. A new organism arises as a result of fertilization, FUSION OF EGG NUCLEI AND SPERM. Formed ZYGOTE.
It is obvious that gametes must have half the number of chromosomes than somatic cells, since otherwise the number of chromosomes in each subsequent generation would have to double. This does not happen due to a special type of cell division MEIOSIS.
Sexual reproduction creates higher genetic variability within a population. As a result of a number of processes, genes that were originally carried by the parents end up in a new combination in the offspring. It is thanks to recombination within the litter that numerous genetic differences are discovered, which increases the adaptive potential of the population and the species as a whole.
23 .Gametogenesis (spermatogenesis and oogenesis).
1.1. Gametogenesis or pre-embryonic development is the process of maturation of germ cells, or gametes. Since during gametogenesis the specialization of eggs and sperm occurs in different directions, oogenesis and spermatogenesis are usually distinguished, respectively. Gametogenesis is naturally present in life cycle a number of protozoa, algae, fungi, spores and gymnosperms, as well as multicellular animals. In some groups, gametes are secondarily reduced (marsupial and basidiomycetes, flowering plants). The processes of gametogenesis have been studied in most detail in multicellular animals.
Reproduction - adaptation of organisms to continued life. Reproduction is associated at the molecular level with DNA replication. There are sexual and asexual reproduction. In asexual reproduction, a new organism arises from somatic cells. In case of sexual intercourse, it is made from special germ cells. Asexual - vegetative is more common in low-organized organisms. New individuals exactly repeat the parent individual (genetic copying of the parent individual). Genetically identical individuals in animals and humans are a rather rare phenomenon. Sexual reproduction is based on a mechanism aimed at preventing the copying of genetic information. More evolutionarily younger organisms reproduce sexually.
Benefits of Sexual Reproduction
1. The ability of a population to change more quickly.
2. Facilitation of speciation.
3. Greater genetic diversity in the offspring facilitates adaptation to unpredictable environmental conditions.
Mature germ cells contain a haploid set of chromosomes. When they mature, they are diploid. They have a nucleus, cytoplasm, and cellular organelles. Despite this, the structure of male and female reproductive cells is not the same. This is explained various functions. Functions sperm – fertilization (stimulation further development eggs), providing genetic information to the male body. All sperm have flagella, are motile, and small in size (50-90 µm in humans). Consist of a head, neck, middle part and tail. Head -5 microns, neck - 5. The head of the sperm is almost completely occupied by the nucleus, there is little cytoplasm, it is in a liquid crystalline state (protection from harmful phenomena - ionizing radiation). Located on the periphery of the nucleus. At the end of the head is an acrosome with a modified Golgi complex. Enzymes: hyaluronidase, mucinase. In the plasma membrane there is proacrosin, which is converted into acrosin, passing through the female genital tract (the inhibitor is cleaved off). The function of acrosin is the detachment of follicular cells, the detachment of the zona pellucida.
The neck contains a pair of centrioles. The microtubules of one of them lengthen, forming the main thread of the tail. The neck contains many mitochondria arranged in a spiral.
The organelles of movement are flagella, capable of beating only when mixed with secretion. Prostate gland during ejaculation. If the functions of the prostate gland are impaired - male sterility.
Egg.
Functions: transfers half of its future to the embryo chromosome set; during fertilization, the egg brings much more cytoplasm; the egg supplies the embryo with food reserves before its own nutrition begins.
The size of eggs is much larger than the size of sperm (130-150 microns in humans). The mature egg stores all the materials that provide the initial stages of embryo development. If the sperm, when maturing, tries to get rid of the cytoplasm, the egg, on the contrary, strives to increase its quantity. There are ribosomes, r-RNA, t-RNA, morphogenetic factors. Many proteins are synthesized in the liver, fat body, and then transported to the egg. The egg cell has a plasma membrane. During fertilization, the plasma membrane controls the entry of many ions (such as sodium). Adjacent to it is the vitelline membrane (glycoproteins - the specific attachment of a sperm of its species to the corresponding egg), often transparent, the egg is surrounded by a layer of cells of the radiate egg - follicular feeding cells. For fertilization, the sperm must pass through all membranes.
Hereditary material, brought by the egg and sperm are the same in size.
The process of formation of eggs in the ovaries is oogenesis, oogenesis. Spermatozoa are formed in the testes, a process called spermatogenesis. Both cells are formed differently, but there are some common features.
Spermatogenesis. Morphologically, the testis consists of many seminiferous tubules. Lobed structure. Between the seminiferous tubules, Leiding cells (begin to work at 12-14 years of age) synthesize testosterone - the development of secondary sexual characteristics. The testis very early becomes an endocrine organ; under the influence of androgens, the formation of male genital organs occurs. The seminiferous tubule has zones:
Reproduction,
Maturation and formation.
There are periods of growth of the same name. The reproduction zone is in the outer part of the testis. The cells are round, there is a lot of cytoplasm, the nucleus is large - spermatogonia. They multiply by mitosis, and the testis increases in size until puberty, after which only stem cells divide. The supply of cells does not decrease and the testis does not decrease either. In the breeding zone 2n2c. the next phase is growth. The size of the nucleus and cytoplasm increases, DNA replication occurs (interphase 1), the cells are first-order spermatocytes 2n4c. These cells enter the zone of formation and maturation at the seminiferous tubules. Meiosis consists of 2 mitotic divisions, after the first division n2c, after the second - nc.
Oogenesis (ovaries). The gonads are formed in the 2nd month of embryonic development. In humans, the yolk sac is formed very early (the function of forming primary germ cells, providing nutrients). Germ cells (primary) migrate into the developing gonad, and the yolk sac degenerates. During embryogenesis, the ovaries are not active. The formation of female germ cells is passive. Primary germ cells are oogonia, they divide. First order oocytes are formed. The division period ends by the 7th month of embryogenesis - 7,000,000 primary cells. 400-500 mature during life, the rest are unclaimed. The development of eggs in humans is blocked in the prophase of the first meiotic division (at the diplotene stage). With the onset of puberty, the oocyte increases in size, and the size of the yolk also increases. Pigments accumulate, biochemical and morphological changes occur. Each oocyte is surrounded by small follicular cells that mature in the follicle. The egg, maturing, approaches the periphery. Follicular fluid surrounds it at all stages. The follicle ruptures. The egg enters the abdominal cavity. Then into the oviduct funnel. Continuation of meiosis in 2/3 of the oviduct as a result of contact of the egg with the sperm.
During meiosis, chromosomes are distributed. The result is 4 cores. Chromosome conjugation occurs (due to highly repetitive DNA sequences in 1 gene). During gametogenesis, each of the 4 nuclei receives only 1 chromatid from a pair. As a result of meiosis during spermatogenesis, from each first-order spermocyte, 4 chromatids are obtained and 4 sperm are formed. From one first-order oocyte, 2 nuclei with a haploid set of chromosomes are formed. One of them is with a large amount of cytoplasm (since during cytokinesis the division is uneven) and the other is a reduction (directing) body. Subsequent division produces an egg and a guide body. During oogenesis, 1 egg and 3 guiding bodies are formed from each oocyte, which degenerate and disappear. The egg contains all the necessary reserves of nutrients.
Meiosis– a method of distribution of chromosomes and genes, ensuring their independent and random recombination. During oogenesis, it serves to redistribute cytoplasm between cells. Crossing over is a method that brings together and redistributes the genes of individual homologous chromosomes.
Phases of meiosis
Meiosis consists of 2 consecutive divisions with a short interphase between them.
· Prophase I- prophase of the first division is very complex and consists of 5 stages:
· Leptotene or leptonema- packaging of chromosomes, condensation of DNA with the formation of chromosomes in the form of thin threads (chromosomes are shortened).
· Zygotene or zygonema- conjugation occurs - the connection of homologous chromosomes with the formation of structures consisting of two connected chromosomes, called tetrads or bivalents and their further compaction.
· Pachytena or pachynema- (the longest stage) - in some places, homologous chromosomes are tightly connected, forming chiasmata. Crossing over occurs in them - the exchange of sections between homologous chromosomes.
· Diplotena or diplonema- partial decondensation of chromosomes occurs, while part of the genome can work, the processes of transcription (RNA formation), translation (protein synthesis) occur; homologous chromosomes remain connected to each other. In some animals, the chromosomes in oocytes at this stage of meiotic prophase acquire the characteristic lampbrush chromosome shape.
· Diakinesis- DNA condenses to the maximum again, synthetic processes stop, the nuclear membrane dissolves; Centrioles diverge towards the poles; homologous chromosomes remain connected to each other.
By the end of Prophase I, centrioles migrate to the cell poles, spindle filaments are formed, the nuclear membrane and nucleoli are destroyed
· Metaphase I- bivalent chromosomes line up along the equator of the cell.
· Anaphase I- microtubules contract, bivalents divide, and chromosomes move toward the poles. It is important to note that, due to the conjugation of chromosomes in zygotene, entire chromosomes, consisting of two chromatids each, diverge to the poles, and not individual chromatids, as in mitosis.
· Telophase I
The second division of meiosis follows immediately after the first, without a pronounced interphase: there is no S period, since DNA replication does not occur before the second division.
· Prophase II- condensation of chromosomes occurs, the cell center divides and the products of its division diverge to the poles of the nucleus, the nuclear membrane is destroyed, and a fission spindle is formed, perpendicular to the first spindle.
· Metaphase II- univalent chromosomes (consisting of two chromatids each) are located at the “equator” (at an equal distance from the “poles” of the nucleus) in the same plane, forming the so-called metaphase plate.
· Anaphase II- univalents divide and chromatids move towards the poles.
· Telophase II- chromosomes despiral and a nuclear envelope appears.
As a result, four haploid cells are formed from one diploid cell. In cases where meiosis is associated with gametogenesis (for example, in multicellular animals), during the development of eggs, the first and second divisions of meiosis are sharply uneven. As a result, one haploid egg and three so-called reduction bodies (abortive derivatives of the first and second divisions) are formed.
Reproduction- the ability of living organisms to reproduce their own kind. There are two main reproduction method- asexual and sexual.
Asexual reproduction occurs 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 mother’s body, in other species - in specialized organs. The following are distinguished: methods of asexual reproduction: division, budding, fragmentation, polyembryony, sporulation, vegetative propagation.
Division- a method of asexual reproduction characteristic of unicellular organisms, in which the mother 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 the paramecium (1), the micronucleus is divided by mitosis, the macronucleus by amitosis. During schizogony (2), the nucleus is first divided repeatedly 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), or 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 maternal individual breaks up (anneli, 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 (monozygotic twins).
Vegetative propagation- 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.) specifically designed for this form of reproduction. Vegetative propagation is typical for many groups of plants and is used in gardening, vegetable gardening, and plant breeding (artificial vegetative propagation).
| Vegetative organ | Method of vegetative propagation | Examples |
|---|---|---|
| Root | Root cuttings | Rosehip, raspberry, aspen, willow, dandelion |
| Root suckers | Cherry, plum, sow thistle, thistle, lilac | |
| Aboveground parts of shoots | Dividing bushes | Phlox, daisy, primrose, rhubarb |
| Stem cuttings | Grapes, currants, gooseberries | |
| Layerings | Gooseberries, grapes, bird cherry | |
| Underground parts of shoots | Rhizome | Asparagus, bamboo, iris, lily of the valley |
| Tuber | Potatoes, sunflower, 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 they 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 collection of cells or individuals descended from a common ancestor through asexual reproduction. The basis for obtaining a clone is mitosis (in bacteria - simple division).
Sexual reproduction is carried out with the participation of two parent individuals (male and female), in which specialized cells are formed in special organs - gametes. The process of gamete formation is called gametogenesis, the main stage of gametogenesis is meiosis. The daughter generation develops from zygotes- a cell formed as a result of the fusion of male and female gametes. The process of fusion of male and female gametes is called fertilization. An obligatory consequence of sexual reproduction is the recombination of genetic material in the daughter generation.
Depending on the structural features of the gametes, the following can be distinguished: forms of sexual reproduction: isogamy, heterogamy and oogamy.
Isogamy(1) - a form of sexual reproduction in which gametes (conditionally female and conditionally male) are mobile and have the same morphology and size.
Heterogamy(2) - a form of sexual reproduction in which female and male gametes are motile, but female gametes are larger than male ones and less mobile.
Oogamy(3) - a form of sexual reproduction in which female gametes are immobile and larger than male gametes. In this case, female gametes are called eggs, male gametes, if they have flagella, - spermatozoa, if they don’t have it, - sperm.
Oogamy is characteristic of most species of animals and plants. Isogamy and heterogamy occur in some primitive organisms (algae). In addition to the above, some algae and fungi have forms of reproduction in which sex cells are not formed: hologamy and conjugation. At hologamia single-celled haploid organisms merge with each other, which in this case act as gametes. The resulting diploid zygote then divides by meiosis to produce four haploid organisms. At conjugation(4) the contents of individual haploid cells of filamentous thalli merge. Through specially formed channels, the contents of one cell flow into another, a diploid zygote is formed, which usually, after a period of rest, also divides by meiosis.
Go to lectures No. 13"Methods of division eukaryotic cells: mitosis, meiosis, amitosis"
Go to lectures No. 15"Sexual reproduction in angiosperms"
Reproduction- the ability of living organisms to reproduce their own kind. There are two main reproduction method- asexual and sexual.
Asexual reproduction occurs 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 mother’s body, in other species - in specialized organs. The following are distinguished: methods of asexual reproduction: division, budding, fragmentation, polyembryony, sporulation, vegetative propagation.
Division- a method of asexual reproduction characteristic of unicellular organisms, in which the mother 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 the paramecium (1), the micronucleus is divided by mitosis, the macronucleus by amitosis. During schizogony (2), the nucleus is first divided repeatedly 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), or 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 maternal individual breaks up (anneli, 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 (monozygotic twins).
Vegetative propagation- 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.) specifically designed for this form of reproduction. Vegetative propagation is typical for many groups of plants and is used in gardening, vegetable gardening, and plant breeding (artificial vegetative propagation).
| Vegetative organ | Method of vegetative propagation | Examples |
|---|---|---|
| Root | Root cuttings | Rosehip, raspberry, aspen, willow, dandelion |
| Root suckers | Cherry, plum, sow thistle, thistle, lilac | |
| Aboveground parts of shoots | Dividing bushes | Phlox, daisy, primrose, rhubarb |
| Stem cuttings | Grapes, currants, gooseberries | |
| Layerings | Gooseberries, grapes, bird cherry | |
| Underground parts of shoots | Rhizome | Asparagus, bamboo, iris, lily of the valley |
| Tuber | Potatoes, sunflower, 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 they 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 collection of cells or individuals descended from a common ancestor through asexual reproduction. The basis for obtaining a clone is mitosis (in bacteria - simple division).
Sexual reproduction is carried out with the participation of two parent individuals (male and female), in which specialized cells are formed in special organs - gametes. The process of gamete formation is called gametogenesis, the main stage of gametogenesis is meiosis. The daughter generation develops from zygotes- a cell formed as a result of the fusion of male and female gametes. The process of fusion of male and female gametes is called fertilization. An obligatory consequence of sexual reproduction is the recombination of genetic material in the daughter generation.
Depending on the structural features of the gametes, the following can be distinguished: forms of sexual reproduction: isogamy, heterogamy and oogamy.
Isogamy(1) - a form of sexual reproduction in which gametes (conditionally female and conditionally male) are mobile and have the same morphology and size.
Heterogamy(2) - a form of sexual reproduction in which female and male gametes are motile, but female gametes are larger than male ones and less mobile.
Oogamy(3) - a form of sexual reproduction in which female gametes are immobile and larger than male gametes. In this case, female gametes are called eggs, male gametes, if they have flagella, - spermatozoa, if they don’t have it, - sperm.
Oogamy is characteristic of most species of animals and plants. Isogamy and heterogamy occur in some primitive organisms (algae). In addition to the above, some algae and fungi have forms of reproduction in which sex cells are not formed: hologamy and conjugation. At hologamia single-celled haploid organisms merge with each other, which in this case act as gametes. The resulting diploid zygote then divides by meiosis to produce four haploid organisms. At conjugation(4) the contents of individual haploid cells of filamentous thalli merge. Through specially formed channels, the contents of one cell flow into another, a diploid zygote is formed, which usually, after a period of rest, also divides by meiosis.
Go to lectures No. 13“Methods of division of eukaryotic cells: mitosis, meiosis, amitosis”
Go to lectures No. 15"Sexual reproduction in angiosperms"