Main article: Asexual reproduction
Asexual reproduction is a form of reproduction that is not associated with the exchange of genetic information between individuals - the sexual process.
Asexual reproduction is the oldest and simplest method of reproduction and is widespread in unicellular organisms (bacteria, blue-green algae, chlorella, amoebas, ciliates). This method has its advantages: there is no need to find a partner, and beneficial hereditary changes are preserved almost forever. However, with this method of reproduction, the variability necessary for natural selection is achieved only through random mutations and therefore occurs very slowly. However, it should be noted that the ability of a species to reproduce asexually does not exclude the ability to undergo the sexual process, but then these events are separated in time.
The most common method of reproduction single-celled organisms- division into two parts, with the formation of two separate individuals.
Among multicellular organisms, almost all plants and fungi have the ability to reproduce asexually - the exception is, for example, Welwitschia. Asexual reproduction of these organisms occurs vegetatively or by spores.
Among animals, the ability to reproduce asexually is more common in lower forms, but is absent in more developed ones. The only way asexual reproduction in animals - vegetative.
There is a widespread misconception that individuals resulting from asexual reproduction are always genetically identical to the parent organism (if mutations are not taken into account). The most striking counterexample is reproduction by spores in plants, since during sporulation a reductional division of cells occurs, as a result of which the spores contain only half of the genetic information available in the sporophyte cells (see Life cycle of plants).
Sexual reproduction
Sexual reproduction is associated with the sexual process (cell fusion), and also, in the canonical case, with the fact of the existence of two complementary sexual categories (male organisms and female organisms).
During sexual reproduction, gametes, or sex cells, are formed. These cells have a haploid (single) set of chromosomes. Animals are characterized by a double set of chromosomes in ordinary (somatic) cells, therefore gamete formation in animals occurs during the process of meiosis. Many algae and all higher plants Gametes develop in a gametophyte, which already has a single set of chromosomes, and are obtained by simple mitotic division.
Based on the similarities and differences between the resulting gametes, several types of gamete formation are distinguished:
isogamy - gametes of the same size and structure, with flagella
anisogamy - gametes of different sizes, but similar structure, with flagella
oogamy - gametes of different sizes and structures.
Small male gametes with flagella are called sperm, and large female gametes without flagella are called eggs.
When two gametes merge (in the case of oogamy, the fusion of gametes of different types is required), a zygote is formed, which now has a diploid (double) set of chromosomes. From the zygote, a daughter organism develops, the cells of which contain genetic information from both parents.
Forms of animal reproduction
Definition 1 Reproduction – vital important process
By reproducing my own kind, I ensure the continuity and heredity of life.
There are two main forms of reproduction: sexual and asexual. Each animal on Earth has its own form of reproduction. For example, amoebas reproduce only asexually, vertebrates only sexually. In some types of animals, alternating forms of reproduction are observed. For example, in foraminifera and some coelenterates, alternation of generations is necessary for reproduction, but in hydra and ciliates, which are characterized by alternation of generations, it is not always necessary for reproduction.
Types of asexual reproduction in animals
Definition 2 Asexual reproduction
In asexual reproduction, all offspring of one individual are genetically identical to each other and to the mother. This form of reproduction is characteristic of unicellular animals. There are some types of asexual reproduction: fission and vegetative reproduction. Division. Mitotic division is characteristic of unicellular organisms. There are binary fission and schizogony. Binary - from one mother cell two daughter cells are formed, from which the new organism. Schizogony - several daughter cells are formed from one individual. Vegetative propagation. Characteristic of multicellular organisms. There are two types of this type: budding and fragmentation. Budding is the formation of an outgrowth on the mother’s body, and its further development and transformation into an adult. Fragmentation is the separation of a section of the body, with further regeneration of the remaining parts of the body, to form a new organism.
Types of sexual reproduction in animals
Definition 3
Sexual reproduction– reproduction with the participation of gametes.
Note 1
A gamete is a cell with a haploid set of chromosomes. Zygote is the fusion of gametes to form a diploid set of chromosomes. Gametogenesis is a process with meiosis in which the genetic material is reduced by half.
There are male and female gametes. Thus, when non-identical gametes merge, non-similar copies are formed, that is, variability in phenotypes and genotypes occurs in the offspring. An organism is called hermaphrodite if it produces both types of gametes. A dioecious organism produces one of the types of gametes.
Definition 4
Isogamy is a type of reproduction in which male and female gametes are identical.
Definition 5
Anisogamy is a type of reproduction in which male and female gametes are different in behavior and morphology.
Definition 6
Oogamy is a type of reproduction in which the female gamete is large and immobile, and the male gamete is small and mobile.
Definition 8
Neoteny is a type of reproduction in which larvae reproduce sexually.
Alternation of forms of reproduction
The process of meiosis and fertilization in living organisms is called a change in nuclear phases, and a qualitative and quantitative change in the genetic material occurs. Some species of animals that reproduce sexually and asexually are characterized by a change of generations.
So, for example, the slipper ciliate is characterized by a change in sexual and asexual reproduction. After multiple divisions, the two shoes come closer and conjugate. After which they disperse and begin to divide again. It turns out that at first there was asexual, then sexual and again asexual reproduction.
Sexual reproduction can also alternate with vegetative reproduction. For example, in sponges, coelenterates and hydra. During the summer, hydra undergoes vegetative asexual reproduction through budding, and in the fall sexual reproduction is observed. During sexual reproduction, hydra produces a sperm and an egg in one organism. In spring, the development of the embryo ends with the formation of a formed hydra.
Asexual reproduction.
In the animal world, there are a number of methods of reproduction, for example, direct fission or budding, characteristic of lower invertebrates, as well as parthenogenesis, observed even in higher vertebrates. It is quite obvious that asexual reproduction is the simplest and least energy-intensive way to increase the number of individuals. However, for some reason, in the process of evolution a complex process of sexual reproduction arose, associated with many problems and conventions.
Sexual reproduction.
1. Conjugation. Sexual reproduction appears in animals already at the lowest levels of the evolutionary ladder. Thus, already in the simplest unicellular microorganisms - ciliates, which reproduce by direct division, so-called conjugation is observed, which is a kind of analogue of the sexual process. In the process of conjugation, two ciliates seem to grow together, for the time during which they exchange hereditary information. The ciliates then separate and then each continues to divide on its own.
2. Parthenogenesis. A number of invertebrates, as well as many vertebrates, exhibit a phenomenon called parthenogenesis, in which females lay eggs or give birth to live young without the participation of males. Hatch from these eggs or are born In a similar way only females, and it is interesting that in nature there are entire local populations of similar species. A similar population of rock lizards was discovered in Armenia. In other places of its habitat, this one is very normal look, reproduces in the usual way.
Parthenogenesis under experimental conditions is possible even in mammals. To do this, it is necessary to somehow stimulate the unfertilized egg to divide, which can be done in different ways, for example, simply by injecting it with a microneedle.
3. Hermaphroditism. A number of invertebrate animals exhibit hermaphroditism, in which each individual has both male and female gonads. Among the most famous animals that are hermaphrodites are, for example, earthworms, leeches and many types of snails. However, despite the fact that in such animals each individual produces both eggs and sperm, they mate with each other, producing a mutual exchange of sex cells. In large, shellless mollusks, Aplysia or sea hares, living in coastal zone sea, up to 10-12 individuals can simultaneously take part in the fertilization process, playing both the roles of males and the roles of females.
However, despite the presence of both types of germ cells in hermaphrodite animals, they extremely rarely resort to self-fertilization, and on the contrary, they usually strive to mate with other, preferably unrelated, individuals.
4. Gender change. Some animals, including a number of fish species, change sex with age. Thus, among swordtail fish, well known to aquarists, it is quite common for middle-aged females to transform into males. At the same time, they grow a xiphoid process on their tail, which is found only in males, and they begin to exhibit typical sexual behavior, successfully fertilizing females. A similar phenomenon is observed in small sea cadet fish that live in the coastal zone of the Black Sea. In some species of fish, the reverse process is also observed: the transformation of males into females.
5. Alternation of sexual and asexual types of reproduction. In invertebrates such as coelenterates, worms different types, echinoderms, there are both sexual and asexual reproduction in parallel. Many invertebrates are characterized by alternating sexual and asexual generations. For example, coral polyps, which grow very actively due to vegetative reproduction, periodically produce great amount motile male and female reproductive cells. Fertilization occurs in the water column. From the resulting zygotes, mobile larvae develop, which settle on a suitable substrate and give rise to new colonies of corals. All attached forms reproduce in a similar way: sponges, bryozoans, hydroid polyps, etc.
In some species, parthenogenesis alternates with normal sexual reproduction. For example, aphids reproduce throughout the summer by viviparity, in which unfertilized females give birth to females only. Young female aphids begin giving birth to subsequent females when they are just a few hours old.
Thus, during the summer, a huge series of asexual generations passes. Zoologists have calculated that if all the offspring of one aphid survived, then in one summer it could cover the entire Earth. Fortunately, since many other animals feed on aphids, this does not happen. It would seem that, this method Aphid breeding is very successful and does not require anything better. However, in the fall, many aphids lay eggs, from which males hatch, which fertilize relatively quickly. a large number of females
While in the fall most aphids, having finished their life cycle, dies, fertilized females successfully survive the winter and lay eggs in the spring. Winged aphids hatch from the eggs, they fly away in different directions, and, having settled on suitable food plants, they lose their wings and begin to reproduce by parthenogenesis. It is obvious that for successful survival in continental climates, aphids need an expansion of the range of variability in the genome, provided by sexual reproduction.
Thus, the main significance of sexual reproduction is not simply to increase the number of individuals, but to expand the gene pool, which further contributes to natural selection.
Features of the animal reproduction process
The role of sexual reproduction in evolution
Types marital relations in animals
Communication in sexual behavior, ritualization
Animal marriage ceremonies
Methods of birth in animals
Caring for the offspring of animals, invertebrates, and reptiles
Peculiarities of reproduction of birds and mammals
Juvenile, early postnatal period
Features of ontogenesis of different taxonomic groups, its periodization
Animal learning in the process of ontogenesis
Leontiev-Fabry concept
Elementary sensory psyche, evolution
Reproduction is the ability of living organisms to reproduce similar individuals.
Animals reproduce asexually and sexually. Definition 2 characteristic primarily of lower animals. During asexual reproduction, part of its body is separated from the mother individual or the entire individual is divided into two or larger number parts, each of which develops into an independent animal.
There are several methods of asexual reproduction of animals: division, budding, schizogony (Fig. 23).
23. Asexual reproduction of protozoa:
/-division of amoeba;
2 -
budding of ciliates (suvoika); 3
Schizogony of Plasmodium falciparum
24. Forms of sperm:
/ - ram; 2 - cancer; 3 - roundworm; 4
Division consists of constricting the mother individual into two more or less equal parts, each of which becomes a new organism.
Budding is asexual reproduction when an outgrowth (bud) is formed on the body of the mother, which gradually takes on the shape and structure of an adult animal.
After separation (budding) from the mother’s body, the new individual begins to lead an independent life.
Sexual reproduction common to all types of animals.
During sexual reproduction, a new organism develops from a zygote resulting from the fertilization of an egg by a sperm.
Women's sex cell- an egg (ovum) usually has a round or oval shape and consists of cytoplasm and a nucleus. The cytoplasm contains one or another amount of nutrients. The egg, as a rule, is covered with shells of various structures.
Male reproductive cells - spermatozoa - have a variety of shapes (Fig.
24), but usually consist of a head, a connecting part and a tail, which serves for movement in a liquid medium.
Definition 1
Most of the head is occupied by the nucleus.
In some multicellular animals (usually living in water), external fertilization is observed: both eggs and sperm are released into the water, where they fuse. Other animals are characterized by internal fertilization: the sperm is introduced into the female’s genital tract, and there the act of fertilizing the egg with the sperm takes place. Sometimes an animal develops from an unfertilized egg; Such reproduction is called virgin - partiogenetic.
Reproduction of multicellular animals
Animals, like plants, reproduce asexually and sexually. The reproductive characteristics of multicellular animals are largely determined by their living conditions.
Definition 2
Asexual reproduction is characteristic of the most simply structured animals, for example, hydra.
Reproduction methods
In summer, under favorable conditions, it reproduces by budding. A protrusion of the body wall is formed on the body of the hydra - a nochule, which grows, forming a mouth and the rudiments of tentacles at the top. The bud at the base unlaces, falls to the bottom and begins independent life. Sometimes budding proceeds so vigorously that even before the first bud breaks off, 2-3 others manage to form on the hydra.
Sexual reproduction
Many animals, including hydra, reproduce sexually before the onset of cold weather.
This process begins with the formation of germ cells - gametes. Male reproductive cells of animals are sperm. They are small and mobile, unlike sperm.
Sperm are formed in males in the male gonads - the testes. Female reproductive cells, eggs, are immobile and have large stock nutrients. They are formed in females in the female gonads - the ovaries. During sexual reproduction, the fusion of two sex cells occurs - the egg and the sperm. This process is called fertilization. From the resulting cell, the zygote, a new organism is formed, combining the characteristics of both parents.
The advantage of sexual reproduction over asexual reproduction is that the offspring are similar to their parents and at the same time differ slightly from them and from each other.
This allows organisms of the same species to better adapt to changing environmental conditions.
In most fish and amphibians (frogs, toads, newts), eggs are fertilized by sperm in the aquatic environment surrounding them.
This type of fertilization is called external. If cell fertilization occurs inside the female's body, it is called internal. Internal fertilization is typical for insects, reptiles, birds, and mammals.
Development of a new organism
The development of a new organism can occur during external environment or inside the mother's body.
Many animals lay eggs in places where there are conditions for their development. Insects - where there is food for the larva emerging from the egg (on leaves, in flower buds, next to fruits).
Reptiles usually place eggs in sand, soil or rotting leaves. Under the influence of temperature environment or as a result of the release of heat from rotting plant debris, embryos develop in the eggs.
Lizards, turtles, crocodiles, and birds lay fertilized eggs with a large supply of nutrients.
The eggs of lizards and pits are covered on the outside with a leathery shell, while the eggs of crocodiles, turtles and birds have a calcareous shell.
All these animals are called oviparous. In mammals, the embryo develops from the zygote into special body females - to the uterus. This development is called intrauterine. The embryo is well protected from adverse environmental influences. This ensures high survival rate of mammalian offspring. Fully formed cubs are born.
Such animals are called viviparous.
Of course, in in this case it represents the basic form of self-reproduction. Indirect evidence of this is the fact that modern prokaryotic organisms (bacteria) reproduce exclusively asexually - by dividing the mother cell-organism in two.
This method is also characteristic of many single-celled eukaryotic organisms - algae, fungi, protozoa. Moreover, for some of them (for example, in amoebas) it is the only one. The division of the body of the mother cell is preceded by mitotic division of the nucleus - two daughter nuclei are formed, identical both to each other and to the mother. Following this, the cytoplasm divides and two daughter cells are formed.
In some unicellular organisms (for example, flagellates), reproduction occurs by budding.
In this case, in parallel with the mitotic division of the nucleus, a small protrusion of the cytoplasm is formed in the mother cell, where one of the daughter nuclei moves. Then this fragment buds off and a small daughter individual is formed. For some time it grows and develops, then reaching the size of the mother’s body.
A special form of asexual reproduction of unicellular organisms is schizogony - multiple division (for example, in fungi, protozoa): in the cell of the mother organism the volume of the cytoplasm increases, and the nucleus is repeatedly mitotically divided.
At a certain moment, the mother cell divides, simultaneously giving rise to many daughter individuals, the number of which corresponds to the number of nuclei formed.
At the stage of their appearance, the single-celled organism is inactive - it does not feed, does not move, etc. When the spore gets into favorable conditions, its shell is destroyed and the released organism begins to behave actively.
The formation of spores is often combined with asexual reproduction of a unicellular organism, either through multiple division or in two.
Asexual reproduction in multicellular organisms.
Many multicellular organisms are characterized by such forms of asexual reproduction as vegetative reproduction and sporulation.
During vegetative propagation, the daughter organism is formed at the expense of a body part, vegetative organ or group of somatic cells of the mother organism. Such reproduction is especially widespread in plants and fungi, as well as in different groups invertebrate animals. In higher plants, vegetative propagation is carried out using various vegetative organs: rhizomes (lily of the valley, wheatgrass, iris), creeping shoots (strawberries, cranberries), tubers (potatoes), bulbs (onion, garlic, tulip), root suckers (raspberries, sow thistle, fireweed), leaves (begonia, bryophyllum) (rice.
1). U lower plants, fungi and invertebrate animals, vegetative reproduction occurs by division or fragmentation of the body of the mother organism (thallus in multicellular algae, the body of sponges, coelenterates, worms, echinoderms).
Rice. 1. Vegetative propagation: 1 - brood buds (on the Marchantia moss thallus); 2 - accessory buds (bryonia leaf); 3 - adventitious buds (on the root system of field thistle); 4 - creeping stems (strawberries)
A special form of vegetative propagation is budding, which occurs in some invertebrate animals.
The formed daughter individual separates from the mother and begins an independent existence (for example, in hydra; Fig. 2). If the individuals formed by budding do not separate from the mother, maintaining a close connection throughout life, a colony of organisms is formed (as, for example, in sponges, corals, ascidians).
Rice. 2.
10 examples of reproduction without males from nature
Hydras: 1 - budding; 2 - with eggs
In addition to vegetative propagation, many species of fungi and plants are characterized by sporulation. It assumes that in special bodies multicellular organism(sporangia) single-celled spores are formed, and when one of them germinates, a whole organism develops (for example, daughter mycelium in fungi).
The spores of many fungi and plants are covered with a dense shell and are resistant to external influences, are motionless and dissipate passively. Algal zoospores equipped with flagella actively swim in the aquatic environment.
A unique form of asexual reproduction is polyembryony (the development of several embryos from a zygote), which is directly related to sexual reproduction. Several embryos develop during zygote cleavage due to the division of embryonic cellular material (blastomere mass) into several parts.
As a result of the development of these embryos, animals are born identical twins with the same genotypes. In many plants (for example, water lilies, tulips) and animals (for example, equestrians, armadillos), the phenomenon of polyembryony is natural.
However, it can also occur in species that are not characteristic of it in principle, for example in humans (twins are born once per thousand singleton births).
Biological role of asexual reproduction
Maintaining the greatest fitness in slightly changing environmental conditions. It reinforces the significance of stabilizing natural selection; ensures rapid reproduction rates; used in practical selection. Asexual reproduction occurs in both unicellular and multicellular organisms.
U unicellular eukaryotes asexual reproduction is mitotic division, in prokaryotes - nucleoid division, in multicellular forms - vegetative reproduction.
Krasnodembsky E. G. “General biology: A manual for high school students and applicants to universities”
N. S. Kurbatova, E. A. Kozlova “Lecture notes on general biology”
Reproduction is the power of living organisms to create similar ones, which is based on the transmission of genetic information from parents to offspring. There are two ways of creating new organisms: without state and by reproduction.
Reproduction state – type of reproduction for which specialized state cells (gametes) are created and the state process is carried out.
The state of reproduction of power to representatives of all types of creatures and plants. In addition to somatic cells of the body, state cells (gametes), have a hapoid (single) set of chromosomes. When two state cells merge, a diploid (subdivision) set of chromosomes is created.
In general, two organisms share their fate, which coincides with the appearance of new individuals that diversify from Father’s. Forms of statistic reproduction: – copulation – conjugation – parthenogenesis – statistic reproduction from fertilization
Equal characteristics of forms of state reproduction
| FORMI | CHARACTERISTIC | PUT IT ON | |
| Single-celled organisms | Conjugation (lat. conjugatio – connection) |
The cells melt for a period of time (the cytoplasmic reservoir is created), at the hour of such a stink, parts of the nuclear apparatus and cytoplasm are exchanged | In the simplest (infusoria) |
| Single-celled organisms | Copulation (lat. copulatio – union) | Two individuals awaken to the power of the state’s cells and get angry, creating a zygote | In the simplest (polistomeli, polytomi) |
| Rich cell organisms | Parthenogenesis (Greek) parthenos – unborrowed + genesis – walk) |
Development of an organism from an unfertilized egg. There are obligate (eggs are hatched before development without sealing) and facultative parthenogenesis (eggs are developed through parthenogenesis and as a result of sealing) | In Roslins, spineless creatures (Bjoli, Daphnia, Coloverts, Popelica), Caucasian rock lizard |
| Rich cell organisms | Statement of reproduction from fertilization | Formation of two types of specialized cells - gametes (human and female), which lead to the formation of the zygote, from which the organism develops | In plants, animals and mushrooms |
Type of state reproduction - Isogamy.
Human and female gametes are created until the end and have the same shape and size. – Anisogamy. The human and female gametes are large, they have a similar shape, but are of different sizes (the females are larger in size).
Login form
- Oogamy. Human and female gametes have different shapes and sizes. Until the end of the century, only human gametes were created. In case of statistic propagation, condensation occurs (in addition to parthenogenesis). Implantation is the process of uniting a female cell (ovum) with a human cell (sperm or sperm).
When fertilized, the diploid set of chromosomes is renewed, which results in the formation of a zygote, from which a new organism develops.
Biological significance of state reproduction
The biological significance of statistic reproduction lies in the fact that the shells significantly renew sedimentary material, they have a great ability to survive until the middle of life, compared to organisms that have been lost during statless reproduction, if the landings practically do not rise up from the heads behind their recession signs.
The state of reproduction is to work with organisms that are resistant to weak and unfriendly minds in an excessively middle way, which promotes their life.
Whom appreciates the diversity of offspring, which is the result of the combined decline of two organisms.
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All animals reproduce differently. Only a very few species (about 3%) give birth to live young. As a rule, these are animals that live on land. Whales and some fish also give birth to live young.
Most animals lay eggs, from which offspring appear after a certain period of time.
The majority of animals reproduce sexually, that is, by combining male and female reproductive cells, resulting in the birth of a new individual containing the characteristics of both parents. But there are animals, for example sea sponges, which can also reproduce asexually (vegetatively), in which case the offspring are born from only one parent.
Mass Fertilization
Coral reefs are collections of millions of tiny animals called polyps.
To procreate, polyps secrete sex cells - sperm and eggs, which float up and connect with each other. From fertilized eggs, larvae develop, swimming in the sea until they find a place where they attach and turn into polyps.
Many types of coral polyps can also reproduce asexually.
Nest in an earthen hole
Grape snails dig holes in soft damp soil and lay eggs there.
Definition 1
They cover the hole with earth so that predators do not get to the eggs until the babies hatch. After a few weeks, small but fully formed snails crawl out of the ground.
Live birth
The Arabian oryx lives in the Arabian deserts. Like almost all mammals, these antelopes give birth to live young. Usually only one calf is born. Within a few minutes after birth, the baby stands on its feet, and a few hours later it runs along with the rest of the herd.
Definition 2
Until the 19th century, sea sponges were thought to be plants.
Currently, biologists classify them as animals. Many species of sponges reproduce sexually, while others reproduce asexually, called budding. At the same time from adult some part of it separates, giving rise to a new sponge.
Last moult
Cicada nymphs (larvae) live underground for several years and molt five times before adult insects emerge.
Development outside the mother's body
The female cat shark attaches the egg and embryo it contains to an underwater plant, where it remains for six to eight months.
summary of other presentations“How animals reproduce” - Sex cells fuse outside the body. How many parents do these animals have? Flounder. How animals reproduce. Reproduction and development river perch. Guess the riddles. Frog. Sex cells. Sexual reproduction. Goose. Concepts about forms of animal reproduction. Hermaphroditism. Forms of asexual reproduction. Animal reproduction. Reproduction method. Asexual reproduction. Fertilized egg. Amoeba division.
“Methods of animal reproduction” - The process of fusion of an egg with a sperm. Asexual reproduction. Graphic organizer. Asexual reproduction occurs in protozoa and lower multicellular organisms. The fertilized egg forms a dense membrane. Fusion of germ cells. Division process. Methods of reproduction of protozoa. During asexual reproduction, sex cells are not produced. Larvae develop from fertilized eggs. Reproduction of mollusks.
“Reproduction of the animal world” - Change of generations. The beginning of bird breeding. Hydroid. Chordata. Cat. Fertilization. Oviparous. Primal beasts. Low animals. Hermaphrodites. Dioecious. The process of intrauterine gestation. Flatworms. Insects. Higher beasts. Birds. Sexual dimorphism. Shellfish. Insects with incomplete transformation. Reptiles. Ovaries. Roundworms. Amphibians. Scyphoid. Dimensions. Lizards and snakes lay eggs.
“Reproduction of animals in nature” - Testes. Two parents. One reproductive system. Reproductive system. Reproduction. Prolongation of the family. Sexual reproduction. Asexual reproduction. Conclusion on evolution. Evolution of reproductive organs in animals. The existence of sexual and asexual reproduction in nature. Evolution of animal reproductive organs. Uterus. Reproductive organs. Continuity of life. Development of the embryo. Nature. The ability of living organisms to reproduce their own kind.
“Artificial insemination of animals” - With insufficient pressure, ejaculation occurs sluggishly. To obtain sperm, an artificial vagina is used: When obtaining sperm, the temperature of the vagina should be within 40-42 "C. A decrease in temperature disrupts the dynamics of ejaculation. Diluents: GF - glucose phosphate diluent, gelatinized, glucose-yolk media. Types of media for sperm. Artificial insemination with /x animals (I. o. s. zh.) - the main method of reproduction of agricultural animals.
“Features of animal reproduction” - Radiosensitivity of the ovaries. Stages of ontogenesis. Pre-fetal period. The influence of AI on the reproductive qualities of animals. Morphology and physiology of animal reproduction. Cow. Internal exposure. Fertile period. Timing of manifestation of changes. The structure of the reproductive organs of females. General pattern. Radiosensitivity of the embryo. The influence of AI on the endocrine glands. Diagnostic exposures. Irradiation with sublethal doses before implantation.
Reproduction of organisms is the reproductive reproduction of similar individuals with the participation of both partners, so by default it is considered sexual. This is a characteristic distinguishing feature of all life on Earth. This is all clear. Now let's find out what kind of reproduction is called asexual, and in what ways it occurs.
Before formulating this concept, we note that the form is common in both multicellular and unicellular organisms. For those not in the know, let us explain that the former include plants and fungi, and the latter include the simplest living organisms (for example, amoebas). The name of this method of reproduction speaks for itself - without the participation of germ cells. This is how amoebas, slipper ciliates and other protozoa reproduce. Note that this reduces the variability of the body to nothing. The only "loophole" in the natural selection of single-celled organisms is just random mutations.
So, reproduction in plants and animals that occurs asexually is the reproduction of their own kind, not associated with the exchange of genetic information between two individuals.
Methods of asexual reproduction
After we have figured out what kind of reproduction is called asexual, it would not be amiss to mention its methods, of which there are quite a few. The first is division. From one individual, for example, an amoeba, two others are formed - daughter ones. The nucleus begins to divide, and the cytoplasm begins to split into two parts.
The second method is reproduction by spores or sporulation. It requires spores such as plants or fungi. Important! Bacterial spores do not participate in reproduction, since one bacterium can form only one spore.
The next method is budding. This is how, for example, the coelenterate protozoan, Hydra, reproduces. Daughter individuals are formed from the “mother’s” body. By the way, budding and division refer to special way asexual reproduction - vegetative. We will talk about this in more detail below.
For example, they have a fragmented method of asexual reproduction. It happens like this: the “mother’s” body begins to divide into parts. Each of them becomes a daughter organism.
A special way of asexual and lower animals is vegetative. Reproduction occurs through vegetative organs such as roots, leaves or For example, raspberries reproduce by roots (see figure), violets by leaves, and so on. By the way, this method of reproduction is most popular among wild plants.
From a biological point of view, this process of reproduction is explained by the plant’s desire to restore its lost parts. Vegetative propagation can occur both naturally and artificially, for example, with the help of humans. Many plants that can reproduce sexually also have this method of reproduction. In animals, division or budding is carried out vegetatively.
So, quite a large number of reproductive methods on own examples show us what kind of reproduction is called asexual.
