Individual development of organisms is a set of biological processes that determine the growth and change of cells throughout the entire period of their existence. The generally accepted scientific name is ontogeny. Its main task is observation, identification of the main stages and features of each period, identification of patterns, as well as analysis of changes and identification of factors that these changes can cause.
It is inherent not only to humans, but also to all living beings and plants. The main ones are:
In this short article we will not consider the individual development of the plant organism, but will focus on the development of representatives of the animal world that is closer to humans. The stages of development, as already mentioned, do not change in humans and correspond to those indicated above.
Gametogenesis in humans consists of two components: spermatogenesis (maturation of male germ cells - sperm) and oogenesis (maturation of female germ cells - eggs). Fertilization is possible only if the sex cells are mature in both male and female individuals. When pathologies occur during fertilization, organisms - chimeras, some of which are quite viable, can be formed.
Human embryogenesis is one of the most important stages. It is divided into the initial stage (0 - 1 week after fertilization), the actual embryonic stage (2 - 8 weeks) and the fetal or fetal stage (9 weeks - birth). It is during this period that vital organs are formed, the body takes shape, and genetic or other pathologies may manifest themselves.
The individual development of the body consists in the further development of organs, an increase in size and weight, the acquisition of new mental functions, changes in motor activity and the development of new types of it.
The postnatal period is the most important in the development of a new person. Its length is about 17 years (from newborn to adolescence). The individual development of the organism in this period is influenced not only by characteristics determined by heredity, but also by psychological and social factors. Consciousness, speech, thinking and other processes are formed. By the end of this period, new individuals, as a rule, arrive with completed gametogenesis.
Aging of the body is the stage of withering, depletion of all the body's resources. Irreversible damage occurs in nerve cells, the quality of vision and hearing decreases, vital organs “wear out,” the skin changes, the reproductive function is lost and tissue regeneration slows down sharply, etc.
Ontogenesis call the totality of processes occurring in the body from the moment of formation of the zygote until death.
It is divided into two stages: embryonic And postembryonic.
Embryonic period The embryonic period is considered to be the period of embryonic development from the moment of formation of the zygote until exit from the egg membranes or birth; in the process of embryonic development, the embryo goes through the stages of crushing, gastrulation, primary organogenesis and further differentiation of organs and tissues. Crushed . Cleavage is the process of formation of a multicellular single-layer embryo - blastula. Fragmentation is characterized by: 1) cell division by mitosis with preservation of the diploid set of chromosomes; 2) very short mitotic cycle; 3) blastomeres are not differentiated, and hereditary information is not used in them; 4) blastomeres do not grow and subsequently become smaller; 5) the cytoplasm of the zygote does not mix or move.
Stages of embryo development.
1. The period of a one-cell embryo, or zygote, is short-term, occurring from the moment of fertilization until the beginning of egg fragmentation. 2. Crushing period. During this period, cell multiplication occurs. The resulting cells are called blastomeres. First, a bunch of blastomeres is formed, resembling a raspberry in shape - a morula, then a spherical single-layer blastula; the wall of the blastula is the blastoderm, the cavity is the blastocele. 3. Gastrulation. A single-layer embryo turns into a two-layer one - gastrula, consisting of an outer germ layer - ectoderm and an inner one - endoderm. In vertebrates, already during gastrulation, the third germ layer, the mesoderm, appears. During evolution in chordates, the process of gastrulation became more complicated with the emergence of an axial complex of rudiments (the formation of the nervous system, axial skeleton and muscles) on the dorsal side of the embryo. 4. The period of separation of the main rudiments of organs and tissues and their further development. Simultaneously with these processes, the unification of parts into a single developing whole is intensifying. From the ectoderm the epithelium of the skin, the nervous system and partly the sensory organs are formed, from the endoderm - the epithelium of the digestive canal and its glands; from mesoderm - muscles, epithelium of the genitourinary system and serous membranes, from mesenchyme - connective, cartilage and bone tissue, vascular system and blood.
Consequences of the influence of alcohol, nicotine, and drugs on the human embryo.
Systematic use of drugs, which include alcohol, and even nicotine, causes damage to germ cells - sperm and eggs. A child may be born with a delay in body length and weight, poorly developing physically, and predisposed to the development of any diseases. The stronger the drug used by parents, the more serious the changes in the children’s bodies can be. The use of these substances by women is especially dangerous.
2. The struggle for existence. Prerequisite for natural selection. Forms of the struggle for existence.
Struggle for existence – complex and diverse relationships of individuals within a species, between species and with unfavorable conditions of inanimate nature. Charles Darwin points out that the discrepancy between the possibility of species for unlimited reproduction and limited resources is main reason struggle for existence. The struggle for existence is of three types:
Intraspecific
Interspecific
Combating abiotic factors
In the lesson, we talk about how we develop - unicellular and multicellular organisms, consider their individual development - ontogenesis, and learn important stages in the life of multicellular organisms.
The new cell does not yet have enough cellular structures and does not form all the proteins for its normal life. but-sti. Therefore, the cell cycle can be divided into several stages or phases (Fig. 2).
Rice. 2. Stages of development of a single-celled organism ()
The first stage is the stage of maturation. When the necessary cell structures are formed, the cell enters the next phase - maturity. In this phase, the cell performs all the functions it needs. Maturity is behind a new deed or the death of a cell.
With many-kle-to-ny-mi or-ga-niz-ma-mi si-tu-a-tion the process is much more complicated. In the life of such organizations, two important stages can be identified (Fig. 3).
Rice. 3. Ontogenesis ()
The first period is em-bri-o-nal, in the case of young people the em-bri-o-nal period is pro-is-ho -dits internal ma-te-rin-sko-go-ga-niz-ma (intra-uterine development). The second period of na-chi-na-et-sya from the moment of birth or exit from the egg shells - according to the em-bri-o-nal-development.
The em-bri-o-nal period includes 3 main stages:
1 stage of fractionation(Fig. 4): the de-le-tion of cells proceeds to the formation of bla-sto-mers.
Rice. 4. Crushing stage ()
In just 4 hours, 64 blasts are formed from one cell, but their growth does not occur. For-kan-chi-va-et-sya st-dia fraction-le-niya for-mi-ro-va-ni-em bla-stu-ly (for-ro-dy-she-vy pu-zy-rik ). It consists of one layer of cells with a cavity inside;
2 gas-stru-la-tion stage(Fig. 5) - development of the growth of leaves.
In more primitive multi-cell organs, for example, intestinal ones, they form -there are only two germinating leaves: the outer one - ek-to-der-ma - and the inner one - en-to-der-ma. Higher-co-or-ga-ni-zo-van-living for-mi-ru-et-has a third-generation drainage - me -zo-der-ma (between ek-to-der-moy and en-to-der-moy).
Rice. 5. Gastrulation ()
3 stage - or-ga-no-gen-ez(Fig. 6) - this is the period of interaction between the birth of leaves, from which everything is formed or-ga-ny and tissue or-ga-niz-ma.
Rice. 6. Organogenesis ()
In a person, the brain is the first to separate, this happens during the third week after za-cha-tiya. The size of the em-bri-o-on at this moment is only 2 mil-li-meters (Fig. 7).
Rice. 7. Organogenesis, human embryo ()
Ek-to-der-ma gives on-cha-lo to the skin of the blood, as well as to epi-te-li-al tissues (hair, glands, external its secretions, nails), the nervous system develops from the ectoderm. Me-zo-der-ma gives the basic internal organ-ga-us - you-de-li-tel-noy and po-lo-voy si-ste-me. En-to-der-ma ob-ra-zu-et or-ga-ny pi-sche-va-ri-tel-noy, respiratory-ha-tel-noy system, as well as Call for internal section.
Already from the first days of its development, the or-ga-niz-ma senses to the influence of damaging facts ditch Such facts include various personal chemical substances: al-co-gol, ni-ko-tin, medicinal drugs, salts of heavy metals and drugs. Radiation radiation and various infections are very dangerous for the development of a living organism.
The influence of these factors on the mother’s organism can lead to the fact that further development of the fetus does not occur and will lead to death, or in the birth of a child, re-ben-ka will appear due to the non-measures that biologists at- they call it ugliness.
After birth, the next period of development of a living or-ga-niz-ma - according to st-em-bree -o-nal (Fig. 8).
Rice. 8. Postembryonic development ()
Direct development- development without rotation, with gradual growth (Fig. 9).
Rice. 9. Direct development ()
The individual looks like a ro-di-tel-sky or-ga-nism. Direct development ha-rak-ter-but for fish, pre-washed, birds and mammals.
Indirect development(with meta-mor-pho-z) - the process of transformation of the or-ga-niz-ma at the li-chi-night stage into an adult individual (Fig. 10 ).
Rice. 10. Indirect development ()
It is co-pro-vozh-da-et-sya ana-to-mi-che-ski-mi and fi-zio-lo-gi-che-ski-mi per-re-stroy-ka-mi or-ga- bottom-ma. This is a way of developing ha-rak-te-ren for the earth and the earth.
Do they ever complete meta-morphosis And incomplete meta-morphosis. With complete meta-mor-pho-ze, or-ga-ism goes through a series of stages, sharply separated from each other in the form of life and ha-rak-te-rom pi-ta-niya (Fig. 11).
Rice. 11. Complete metamorphosis ()
These are the stages of egg, li-chin-ki, ku-kol-ki, adult individual (imago). This development is ha-rak-ter-but for ba-bo-chek (che-shue-winged) and beetles (hard-to-winged).
With incomplete meta-mor-pho-ze (Fig. 12), the stage of ku-kol-ki is absent, and the li-chin-ka is little different from an adult. This can be seen at Kuz-ne-chi-kov and sa-ran-chi.
Rice. 12. Incomplete metamorphosis ()
Regardless of the type of development, all living organisms have three stages: youth, maturity and old age . Each of the stadiyas ha-rak-te-ri-zu-et-sya determines-de-len-ny-mi fi-zio-lo-gi-che-ski-mi from-me-ne-ni- I-mi.
In-di-vi-du-al-noe development is one of the most in-te-res-s processes that take place in a living or-ga-niz-me, when a complex living or-ga-ism arises from a single cell and in the process of life-not-de-i- tel-no-sti pre-ter-pe-va-et a number of-me-nots. Each or-ga-nism fulfills its main function - to leave offspring, the life of the or-ga-nism is behind it natural death.
References
- Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - Bustard, 2009.
- Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of general biology. 9th grade: Textbook for 9th grade students educational institutions/ Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.
- Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology: Textbook for grade 9, 3rd ed., stereotype. - M.: Bustard, 2002.
- Blgy.ru ().
- Sbio.info().
- Estnauki.ru ().
Homework
- What is ontogenesis and what stages does it consist of in multicellular organisms?
- What are the stages of embryonic development?
- Name the stages of development of the postembryonic period.
Question 1. What is called the individual development of an organism?
Individual development of an organism or ontogenesis refers to the entire set of transformations of an individual from origin to the end of life. The cell with which ontogenesis begins contains the program for the development of the organism. It is realized through the interaction of the nucleus (genetic information) and cytoplasm of each cell, as well as cells and tissues with each other.
In bacteria and unicellular eukaryotes, ontogenesis begins at the moment of formation of a new cell as a result of division and ends with death or a new division.
In multicellular organisms that reproduce asexually, ontogenesis begins from the moment of separation of a cell or group of cells of the mother organism.
In organisms that reproduce sexually, ontogenesis begins from the moment of fertilization and the formation of the zygote.
Question 2. List the periods of ontogenesis.
Periods of ontogenesis:
In ontogenesis there are 3 periods: proembryonic, embryonic And postembryonic. For higher animals and humans, the division into prenatal (before birth), intranatal (birth) and postnatal (after birth) periods of development is accepted.
Proembryonic period
. Proembryonic period, preceding the formation of the zygote, is associated with the formation of gametes. Otherwise, this is gametogenesis (ovogenesis and spermatogenesis).
Embryonic period
. Embryonic period(Greek embryon - embryo) begins with fertilization and the formation of a zygote. The end of this period is different types Ontogenesis is associated with various moments of development. The embryonic period is divided into the following stages:
1) fertilization - the formation of a zygote;
2) crushing – formation of a blastula;
3) gastrulation – formation of germ layers;
4) histo- and organogenesis - the formation of organs and tissues of the embryo. Postembryonic period of animal development.
Postembryonic period
The development of animals begins after their birth and is divided into three periods:
Period of growth and morphogenesis (pre-reproductive);
Period of maturity (reproductive);
The period of old age (post-reproductive).
Postembryonic period human development.
Postembryonic postnatal) period of human development, otherwise called postnatal, is also divided into three periods:
1) Juvenile (before puberty);
2) Mature (adults, sexually mature state);
3) The period of old age ending in death.
In other words, we can say that for humans it is also possible to distinguish pre-reproductive, reproductive and post-reproductive periods of post-embryonic development. It should be borne in mind that any scheme is conditional, since the actual state of two people of the same age may differ significantly.
Question 3. Which development is called embryonic and which is postembryonic?
Ontogenesis is divided into two periods. The first of these is the embryonic period (embryogenesis) lasts from the moment of fertilization until exit from the egg or birth. Let us describe its stages using the example of the lancelet.
Fragmentation: the egg is divided repeatedly and quickly by mitosis, interphases are very short;
blastula: a hollow ball is formed, consisting of a single layer of cells; at one of the poles of the ball, cells begin to divide more actively, preparing the next stage;
gastrula: formed as a result of invagination of the more actively dividing pole of the blastula; the early gastrula is a two-layer embryo; its outer layer (germ layer) is called ectoderm, the inner layer is endoderm; the gastrula cavity represents the future intestinal cavity of the body; late gastrula - a three-layer embryo: is formed in all organisms (except coelenterates and sponges) during the formation of the third germ layer - the mesoderm, which arises between the ectoderm and endoderm;
histo- and organogenesis: the development of tissues and organ systems of the embryo occurs. The second stage of ontogenesis is the postembryonic period. It lasts from the moment of exit from the egg (or birth) until death.
Question 4. What types of postembryonic development of the body are there? Give examples.
There are two types of postembryonic development.
Indirect development, or development with metamorphosis. This type of development is characterized by the fact that the born individual (larva) is often completely different from the adult organism. After some time, she undergoes metamorphosis - transformation into an adult form. Indirect development is characteristic of amphibians, insects and many other organisms.
Direct development. At this type Developmentally, the born baby is similar to an adult. Direct development is oviparous and intrauterine. During oviparous development, the embryo spends the first stage of ontogenesis in an egg, supplied with nutrients and protected by a shell (shell) from the environment. This is how, for example, the young of birds, reptiles and egg-laying mammals develop. During intrauterine development, the growth of the embryo occurs inside the mother's body. All vital functions (nutrition, breathing, excretion, etc.) are carried out through interaction with the mother through a special organ - the placenta, formed by the tissues of the uterus and the embryonic membranes of the baby. The intrauterine type of development is characteristic of all higher mammals, including humans.
Question 5. What is the biological significance of metamorphosis?
Metamorphosis makes it possible for individuals of different ages not to compete for food. For example, tadpoles and frogs, butterflies and caterpillars have different sources food. Also, the presence of a larval stage often increases the possibility of dispersal of organisms. This is especially important if the adults are sedentary (eg, many marine molluscs, worms and arthropods).
Question 6. Tell us about the germ layers.
The first two germ layers - ectoderm and endoderm - are formed at the stage of formation of the gastrula from the blastula. Later, in all (except coelenterates and sponges) the third germ layer develops - the mesoderm, which is located between the ectoderm and endoderm. Next, all organs of the embryo develop from the three germ layers. For example, in humans, the nervous system, skin glands, tooth enamel, hair, nails, and outer epithelium are formed from the ectoderm. From the endoderm - the tissues lining the intestines and respiratory tract, lungs, liver, pancreas. From the mesoderm, muscles, cartilage and bone skeleton, organs of the excretory, endocrine, reproductive and circulatory systems are formed.
Question 7. What is cell differentiation? How is it carried out during embryonic development?
Differentiation is the process of transformation of unspecialized germ cells into various cells of the body, differing in structure and performing specific functions. Differentiation does not begin immediately, but at a certain stage of development and is carried out through the interaction of germ layers (at an early stage) and organ rudiments (at a later stage).
Some cells, even in an adult organism, remain not fully differentiated. Such cells are called stem cells. In humans they are found, for example, in the red bone marrow. Currently, the possibility of using stem cells to treat many diseases, restore organs after injuries, etc. is being actively studied.
Question 8. Describe the concept of “growth”. What is a certain height? Uncertain growth?
The growth of the body is accompanied by an increase in cells and accumulation of body weight. A distinction is made between definite and indefinite growth.
Indefinite growth is characteristic of mollusks, crustaceans, fish, amphibians, reptiles and other animals that do not stop growing throughout their lives.
A certain growth is characteristic of organisms that grow only limited time life, such as insects, birds and mammals. In humans, intensive growth stops at the age of 13-15 years, corresponding to the period of puberty.
The growth and development of the organism is controlled genetically and also depends on the environmental conditions in which development occurs.
With a type of growth that is called definite, the organism, having reached a certain level of maturity, ceases to increase in size. This type of growth is characteristic of most animals. If an organism grows throughout its life, then it is called an indefinite type of growth. It is characteristic of plants, fish, mollusks, and amphibians.
Question 1. What is called the individual development of an organism?
Individual development of an organism or ontogenesis refers to the entire set of transformations of an individual from origin to the end of life. The cell with which ontogenesis begins contains a program for the development of the organism. It is realized through the interaction of the nucleus (genetic information) and cytoplasm of each cell, as well as cells and tissues with each other.
In bacteria and unicellular eukaryotes, ontogenesis begins at the moment of formation of a new cell as a result of division and ends with death or a new division.
In multicellular organisms that reproduce asexually, ontogenesis begins from the moment of separation of a cell or group of cells of the mother organism.
In organisms that reproduce sexually, ontogenesis begins from the moment of fertilization and the formation of a zygote.
Question 2. List the periods of ontogenesis.
Question 3. Which development is called embryonic and which is called postembryonic?
Ontogenesis is divided into two periods. The first of them is the embryonic period (embryogenesis) lasts from the moment of fertilization until exit from the egg or birth. Let's describe its stages using the example of the lancelet.
Crushing: the egg is divided repeatedly and quickly by mitosis, interphases are very short;
blastula: a hollow ball is formed, consisting of one layer of cells; at one of the poles of the ball, cells begin to divide more actively, preparing the next stage;
gastrula: formed as a result of invagination of the more actively dividing pole of the blastula; the early gastrula is a two-layer embryo; its outer layer (germ layer) is called ectodermis, the inner layer is endoderm; the gastrula cavity represents the future intestinal cavity of the body; late gastrula - a three-layer embryo: is formed in all organisms (except coelenterates and sponges) during the formation of the third germ layer - mesoderm, which arises between the ectoderm and endoderm;
histo- and organogenesis: the development of tissues and organ systems of the embryo occurs. The second stage of ontogenesis is the post-embryonic period. It lasts from the moment of exit from the egg (or birth) until death.
Question 4. What types of postembryonic development of the body are there? Give examples.
There are two types of postembryonic development.
Indirect development, or development with metamorphosis. This type of development is characterized by the fact that the born individual (larva) is often completely different from the adult organism. After some time, she undergoes metamorphosis - transformation into an adult form. Indirect development is inherent in amphibia, insects and many other organisms.
Direct development. With this type of development, the born baby is similar to an adult. Direct development is oviparous and intrauterine. During oviparous development, the embryo spends the first stage of ontogenesis in an egg, supplied with nutrients and protected by a shell (shell) from the environment. This is how, for example, the young of birds, reptiles and egg-laying mammals develop. During intrauterine development, the growth of the embryo occurs inside the mother's body. All vital functions (nutrition, breathing, excretion, etc.) are carried out through interaction with the mother through a special organ - the placenta, formed by the tissues of the uterus and the embryonic membranes of the baby. The intrauterine type of development is characteristic of all higher mammals, including humans.
Question 5. What is the biological significance of metamorphosis?
Metamorphosis makes it possible for individuals of different ages not to compete for food. For example, tadpoles and frogs, butterflies and caterpillars have different food sources. Also, the presence of a larval stage often increases the possibility of dispersal of organisms. This is especially important if the adults lead a sedentary lifestyle (for example, many marine molluscs, worms and arthropods).
Question 6. Tell us about the germ layers.
The first two germ layers - ectoderm and endoderm - are formed at the stage of formation of the gastrula from the blastula. Later, in all (except coelenterates and sponges) the third germ layer develops - the mesoderm, which is located between the ectoderm and endoderm. Next, all organs of the embryo develop from the three germ layers. For example, in humans, the nervous system, skin glands, tooth enamel, hair, nails, and outer epithelium are formed from the ectoderm. From the endoderm - the tissues lining the intestines and respiratory tract, lungs, liver, pancreas. From the mesoderm, muscles, cartilage and bone skeletons, organs of the excretory, endocrine, reproductive and circulatory systems are formed.
Question 7. What is cell differentiation? How is it carried out during embryonic development?Material from the site
Differentiation is the process of transformation of unspecialized germ cells into various cells of the body, differing in structure and performing specific functions. Differentiation does not begin immediately, but at a certain stage of development and is carried out through the interaction of germ layers (at an early stage) and organ rudiments (at a later stage).
Some cells, even in an adult organism, remain not fully differentiated. Such cells are called stem cells. In humans they are found, for example, in the red bone marrow. Currently, the possibility of using stem cells to treat many diseases, restore organs after injuries, etc. is being actively explored.
Question 8. Describe the concept of “growth”. What is a certain height? Uncertain growth?
The growth of an organism is an increase in its size and mass. With a type of growth that is called definite, the organism, having reached a certain level of maturity, ceases to increase in size. This type of growth is characteristic of most animals. If an organism grows throughout its life, then they speak of an indefinite type of growth. It is characteristic of plants, fish, mollusks, and amphibians.
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On this page there is material on the following topics:
- biogenetic law in brief
- intrauterine oviparity
- what is called individual development of the body
- in organisms that develop without transformation, the baby
- oviparous stage of ontogenesis
