Ontogenesis is called the set of processes occurring in the body, from the moment of the formation of the zygote to death.

It is divided into two stages: embryonic and postembryonic.

The embryonic period The embryonic period is considered the period of embryonic development from the moment the zygote is formed to the release of the egg membranes or birth; in the process of embryonic development, the embryo goes through the stages of cleavage, gastrulation, primary organogenesis and further differentiation of organs and tissues. Crushed . Crushing is the process of formation of a multicellular single-layer embryo - blastula. Cleavage is characterized by: 1) cell division by mitosis with preservation of the diploid set of chromosomes; 2) a 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 and smaller; 5) the cytoplasm of the zygote does not mix and does not move.

Development stages of the embryo.

1. The period of the unicellular embryo, or zygote, is short-term, flowing from the moment of fertilization to the beginning of egg cleavage. 2. Period of crushing. During this period, the cells multiply, the cells obtained during cleavage are called blastomeres. First, a bunch of blastomeres is formed, resembling a raspberry berry in shape - a morula, then a spherical single-layered blastula; blastula wall - blastoderm, cavity - blastocele. 3. Gastrulation. A single-layer embryo turns into a two-layer one - a gastrula, consisting of an external germ layer - an ectoderm and an internal one - an endoderm. In vertebrates, already in the course of gastrulation, a third germ layer, the mesoderm, arises. In the course of evolution in chordates, the process of gastrulation was complicated by the emergence of an axial complex of primordia (anlage of the nervous system, axial skeleton, and musculature) on the dorsal side of the embryo. 4. The period of isolation of the main rudiments of organs and tissues and their further development. Simultaneously with these processes, the unification of the parts into a single developing whole is intensified. From the ectoderm, the epithelium of the skin, the nervous system and partially the organs of the senses are formed, from the endoderm - the epithelium of the alimentary canal and its gland; from the mesoderm - muscles, epithelium of the genitourinary system and serous membranes, from the mesenchyme - connective, cartilaginous and bone tissues, the vascular system and blood.

Consequences of the influence of alcohol, nicotine, narcotic substances on the human embryo.

The 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 lag in length and body weight, poorly developing physically, predisposed to the development of any diseases. The stronger the narcotic substance used by the parents, the more serious the changes in the children's body can be. The use of these substances by women is especially dangerous.

2. Struggle for existence. The premise of 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 the main reason for the struggle for existence. The struggle for existence is of three types:

Intraspecific

Interspecific

Fight against abiotic factors

Question 1. What is called the individual development of the organism?

The entire set of transformations of an individual from emergence to the end of life is called the individual development of an organism or ontogenesis. In the cell, from which ontogenesis begins, the program for the development of the organism is laid. It is realized through the interaction of the nucleus (genetic information) and the cytoplasm of each cell, as well as cells and tissues with each other.

In bacteria and unicellular eukaryotes, ontogenesis begins at the moment of the formation of a new cell as a result of division and ends with death or new division.

In multicellular organisms that reproduce asexually, ontogenesis begins from the moment of isolation of a cell or a group of cells of the mother's body.

In organisms that reproduce sexually, ontogenesis begins from the moment of fertilization and the appearance of a zygote.

Question 2. List the periods of ontogenesis.

Question 3. What development is called embryonic, and what is postembryonic?

Ontogenesis is subdivided into two periods. The first of them - the embryonic period (embryogenesis) lasts from the moment of fertilization until the release of the egg or birth. Let us describe its stages using the example of a lancelet.

Fragmentation: the egg cell divides repeatedly and quickly by mitosis, the 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; early gastrula is a two-layered embryo; its outer layer (germ layer) is called the ectoderm, the inner layer is the endoderm; the gastrula cavity is the future intestinal cavity of the body; late gastrula is a three-layered embryo: it is formed in all organisms (except for coelenterates and sponges) when the third germ layer is laid, 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 post-embryonic period. It lasts from the moment of leaving the egg (or birth) and until death.

Question 4. What are the types of postembryonic development of the body? 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 not at all like an adult organism. After some time, she undergoes metamorphosis - transformation into an adult form. Indirect development is inherent in amphibians, insects and many other organisms.

Direct development. With this type of development, the born calf looks like an adult. Direct development is ovipositor and intrauterine. During ovipositor 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, young birds, reptiles and oviparous mammals develop. During intrauterine development, the growth of the embryo takes place inside the mother's body. All vital functions (nutrition, respiration, excretion, etc.) are carried out by 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 adults are sedentary (for example, many marine mollusks, 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, all (except for coelenterates and sponges) develop a third germ layer - the mesoderm, which is located between the ectoderm and endoderm. Further, 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 external epithelium are formed from the ectoderm. From endoderm - tissues lining the intestines and respiratory tract, lungs, liver, pancreas. Muscles, cartilaginous and bone skeletons, organs of the excretory, endocrine, reproductive and circulatory systems are formed from the mesoderm.

Question 7. What is cell differentiation? How is it carried out in the process of embryonic development?Material from the site

Differentiation is the process of transformation of non-specialized germ cells into various cells of the body that differ in structure and perform certain functions. Differentiation does not begin immediately, but at a certain stage of development and is carried out through the interaction of the germ layers (at an early stage) and organ rudiments (at a later stage).

Some cells, even in an adult organism, remain incompletely 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 for the treatment of many diseases, restoration of organs after injuries, etc. is being actively investigated.

Question 8. Describe the concept of "growth". What is certain growth? Uncertain growth?

The growth of an organism is an increase in its size and mass. With the type of growth, which is called certain, the organism, having reached a certain level of maturity, ceases to grow in size. This type of growth is typical for most animals. If an organism grows all its life, then one speaks of an indefinite type of growth. It is characteristic of plants, fish, molluscs, and amphibians.

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On this page material on topics:

• biogenetic law in brief
• intrauterine ovipositor
• what is called the individual development of the body
• in organisms developing without transformation, baby
• ovipositor stage of ontogenesis

Ontogenesis- the individual development of the organism from fertilization (during sexual reproduction) or from the moment of separation from the mother (during asexual reproduction) to death.

In fact, ontogeny is the body's path from conception to death.

The term "ontogeny" was introduced Ernst Haeckel in 1866

Individual development (ontogeny) is always under control.

In the process of ontogenesis, the genetic information received from the parents is realized.

All cells in one organism potentially carry the same genetic program, but as the organism develops, different cells use different parts of this program. The nature of the work of genes is greatly influenced by environmental conditions.

Ontogenesis stages

Formed gastrula... The embryo becomes two- or three-layer (depending on the complexity of the organism), these layers in the future will form organs.

Organogenesis. Formation of organs and organ systems.

Interestingly, the first to be laid are:

• neural tube - the future central nervous system (central nervous system),
• notochord - future spine and
• the intestinal tube is the future digestive system.

Formed.

These are the most basic systems of any organism and, as you can see, they are laid even when the embryo and organs still do not ...

Postembryonic stage of ontogenesis

The development of the body after birth is direct and indirect.

Direct development - typical for,. A small organism differs from an adult only in size and puberty.

Indirect development- development from metamorphoses(with transformations).

2. Embryonic development of the embryo in animals:

a) crushing; types of crushing;

b) gastrulation; methods of gastrulation;

c) primary organogenesis (laying of the axial complex of organs);

d) embryonic induction.

3. Postembryonic development:

a) types of postembryonic development;

b) direct development - non-larval and intrauterine;

c) indirect development - with complete and incomplete metamorphosis.

4. The influence of environmental factors on the individual development of the organism.

1. Ontogenesis. Types of ontogenesis. Periodization of ontogenesis.

Ontogenesis - the process of individual development of an individual, that is, the entire set of transformations from the moment of the formation of the zygote to the death of the organism.

In species that reproduce asexually, ontogenesis begins with the isolation of one or a group of cells of the maternal organism. In species with sexual reproduction, it begins with the fertilization of the egg. In prokaryotes and unicellular eukaryotic organisms, ontogeny is, in fact, a cell cycle, usually ending with cell division or death.

In the course of individual development, multicellular organisms undergo a number of regular processes:

Formation of morphological and functional traits inherent in a particular biological species;

Implementation of specific functions;

Reaching puberty;

Reproduction;

Aging;

All these processes, as components of ontogeny, proceed on the basis of hereditary information received by descendants from parents. This information is a kind of instruction about the time, place and nature of the individual developmental mechanisms of the individual. Therefore, ontogeny can be defined as the process of realization of genetic information received from parents in certain environmental conditions.

There are the following types of ontogenesis: direct and indirect. Indirect development occurs in larval form, and direct development- in non-larval and intrauterine (rice ...)

TYPES OF ONTOGENESIS

Direct development Indirect development

(with metamorphosis)

Non-large type with incomplete metamorphosis:

(oviposition with a lot of yolk) egg - larva - adult - individual

Intrauterine with complete metamorphosis

Egg - Larva - Pupa - Adult - Individual

Ontogenesis is a continuous process of development of an individual. However, its stages differ in the content and mechanisms of the processes taking place. For this reason, the ontogenesis of multicellular organisms is divided into periods: embryonic- from the moment of fertilization of the egg and until the release of the egg membranes or the birth of birth and postembryonic- from release from egg membranes or birth to death. For placental animals and humans, the division into prenatal (before birth) and postnatal (after birth) periods is accepted. Often, the pro-embryonic, or prezygous, period is also distinguished, which includes the processes of formation of germ cells (spermato- and ovogenesis).

1. Embryonic development in animals.

Embryonic (embryogenesis) development begins from the moment the zygote is formed and is a process of transformation of the latter into a multicellular organism.

Embryonic development consists of the following main stages:

splitting up, as a result of which a multicellular embryo is formed;

gastrulation, in the process of which the first tissues appear - ectoderm, endoderm and mesoderm, and the embryo becomes two- or three-layer;

primary organogenesis - the formation of a complex of axial organs of the embryo (neural tube, chord, intestinal tube);

exit from the egg or embryonic membranes (with larval and non-larval types of development) or by birth (with intrauterine development).

Splitting up - the process of multiple, rapidly replacing each other mitotic divisions of the zygote, leading to the formation of a multicellular embryo. Divisions of cleavage, in contrast to ordinary cell divisions, take place without a postmitotic period, the resulting cells ( blastomeres) do not grow. In the process of crushing, the total volume of the embryo does not change, but

the sizes of its constituent cells decrease, i.e. the embryo splits.

The type of cleavage of a fertilized egg depends on the amount of yolk and the nature of its distribution in the cytoplasm of the egg, that is, on the type of egg. In this regard, crushing is distinguished complete when the whole egg is cleaved, and incomplete, when part of it is crushed. This is due, in turn, to the fact that the yolk prevents the formation of constrictions during cell division.

Complete crushing happens uniform if the cells formed as a result of division are approximately the same in size, and uneven if they differ in size.

Incomplete crushing can be partial superficial, or discoidal.

Crushing happens synchronous(simultaneous division of all cells) and asynchronous(non-simultaneous cell division).

Isolecital Moderate Lecithal Telolecital Alecital

Complete, Complete, Incomplete, Complete,

Uniform Uneven Discoidal Uniform

(lancelet) (frog) (birds) asynchronous

(Human)

Complete uniform crushing .

In the ovum of the lancelet, the yolk is small and it is evenly distributed in the cytoplasm, therefore, the cleavage of the fertilized egg is complete and even.

I - zygote; II - stages 2, 4 and 32 blastomeres; III - blastula; IV - gastrula; V - bookmark of the axial complex of organs (1 - neural tube; 2 - chord; 3 - ectoderm; 4 - intestinal tube).

The 1st furrow runs in the meridional plane in the direction from the animal pole to the vegetative one; the zygote is divided into two equal cells - blastomeres.

The 2nd groove runs perpendicular to the first, also in the meridian plane; 4 blastomeres are formed.

The third groove is latitudinal - it runs slightly above the equator and immediately divides 4 blastomeres into 8 cells.

Further, the meridional and latitudinal furrows alternate correctly. As the number of cells increases, division becomes asynchronous. At the stage of 32 blastomeres, the embryo looks like a raspberry berry and is called morula. Blastomeres diverge further and further, forming a cavity at the stage of 64 blastomeres - blastocoel and the embryo takes the form of a bubble with a wall formed by one layer of cells closely adjacent to each other, inside which there is primary body cavity, i.e., blastula (celloblastula).

Complete uneven crushing.

Typical for moderately telolecital eggs. The egg cell of the frog contains more yolk than that of the lancelet, and it is concentrated mainly at the vegetative pole.

The first two meridional furrows divide the egg into 4 identical blastomeres.

3rd - the latitudinal furrow is strongly displaced towards the animal pole, where the yolk is less. As a result, 4 micro- and 4 macroblastomeres are formed, sharply differing in size.

As a result of the continuing fragmentation, the cells of the animal pole, less overloaded with yolk, divide more often and are smaller in size than the cells of the vegetative pole. Blastula has a wall formed by several rows of cells; the blastocoel is small and displaced to the animal pole ( amphiblastula).

Incomplete discoidal cleavage.

Typical for telolecital eggs of reptiles and birds, heavily overloaded with yolk. The yolk-free cytoplasm is about 1% of the volume. The yolk prevents cleavage and therefore only a narrow strip of cytoplasm at the animal pole is crushed. As a result, germinal disc (discoblastula).

Regardless of the characteristics of the cleavage of fertilized eggs in different animals, due to differences in the number and nature of the distribution of yolk in the cytoplasm, cleavage, as a period of embryonic development, is characterized by the following features:

As a result of cleavage, a multicellular embryo - blastula is formed (blastulation) and cellular material accumulates for further development.

All cells in the blastula have a diploid set of chromosomes (2n), are identical in structure and differ from each other, mainly in the amount of yolk, i.e., blastula cells are not differentiated.

A characteristic feature of cleavage is a very short mitotic cycle compared to its duration in adult animals.

During the cleavage period, DNA and proteins are intensively synthesized, there is no RNA synthesis. The genetic information contained in the nuclei of blastomeres is not used.

During cleavage, the cytoplasm does not move.

Gastrulation - this is the process of formation of a two- or three-layer embryo - gastrula, which is based on complex and varied movements of cell masses and cell differentiation. The layers that form are called germ layers. They are layers of cells with a similar structure, occupying a certain position in the embryo and giving rise to certain organs and organ systems.

Distinguish external - ectoderm- and internal - endoderm- sheets, between which in three-layer animals is located mesoderm.

During gastrulation, cell division is either poorly expressed or absent - the embryo does not grow.

1 - invagination; 2 - epiboly; 3 - immigration; 4 - delamination.

Depending on the type of blastula, there are four main ways of gastrulation:

- intussusception- the formation of a two-layer embryo by invading the wall of the blastula into the cavity of the blastocoel (lancelet);

- epiboly- the formation of a two-layer embryo as a result of the crawling of small cells of the animal pole onto the vegetative one, the cells of the animal pole overgrow it and it turns out to be inside the embryo (amphibian);

- immigration- penetration by immersion of a part of the blastula cells into the blastocoel (coelenterates);

- delamination- as a result of cell division, the embryonic disc, as it were, splits into two layers (reptiles and birds).

However, in their pure form, the listed methods of gastrulation are almost never found in nature, which gives reason to single out the fifth method - mixed, or combined.

Gastrula is a two-layer sac, the cavity of which (gastrocoel) communicates with the external environment through an opening - blastopore(primary mouth). The outer layer of the gastrula is the ectoderm, the inner layer is the endoderm. The structure of the gastrula depends on the type of egg and the way of life of the embryo at this stage. So, in coelenterates, gastrula is a free-living larva - planula, in other types of gastrula it develops in egg membranes or in the mother's body.

In some animals (sponges, coelenterates), the gastrulation process ends with the formation of two germ layers - ecto- and endoderm. For other representatives of the animal world, the stage of formation of the third germ layer, the mesoderm, is characteristic. The establishment and formation of the mesoderm is carried out in two ways: teloblastic and enterocoelous... With the teloblastic method of anlage in the region of the blastopore lips, 2 large cells are subdivided ( teloblasts); multiplying, they give rise to two mesodermal stripes, from which (with the appearance inside the cavity) coelomic vesicles are formed. With the enterocoelic method of laying, the primary intestine forms symmetrical protrusions into the blastocoel, which then detach and turn into coelomic vesicles. In both cases, the vesicles expand and fill the primary body cavity. The layer of mesoderm adjacent to the ectoderm is called parietal, or parietal leaf, and adjacent to the endoderm - gut, or visceral leaf... The cavity formed in the mesodermic vesicles and replacing the primary one is called secondary body cavity, or coelom. With the teloblastic method of laying the mesoderm, the blastopore turns into the mouth of an adult animal ( protostomes). With the enterocoele method, the blastopore is closed, and the mouth of an adult is formed a second time ( deuterostomes).

The formation of germ layers is the result of differentiation of similar relatively homogeneous blastula cells.

Differentiation - This is the process of the appearance and growth of morphological and functional differences between individual cells and parts of the embryo.

Morphological differentiation manifests itself in the formation of several hundred types of cells with a specific structure.

Biochemical differentiation- specialization of cells in the synthesis of specific proteins characteristic only of this type of cells. Keratin is synthesized in the epidermis, insulin is synthesized in the islet tissue of the pancreas, etc. The biochemical specialization of cells is ensured by the differential activity of genes, that is, different genes begin to function in different rudiments. Genetic information is realized through the synthesis of i-RNA at the stage of gastrula, which sharply increases during the period of laying the axial complex of organs.

With further differentiation of the germ layer cells in the process of histo- and organogenesis, the same tissues and organs are formed in different animal species, which means that the germ layers are homologous. The homology of the germ layers of the overwhelming majority of animals is one of the proofs of the unity of the animal world.

Histo- and organogenesis.

After the completion of gastrulation, a complex of axial organs is formed in the embryo: the neural tube, chord and intestinal tube. Consider this process using the example of a lancelet

The ectoderm, located on the dorsal side of the embryo, bends along the midline, forming a longitudinal groove. The areas of the ectoderm located to the right and left of the groove begin to grow on its edges. The groove - the rudiment of the nervous system - plunges under the ectoderm and its edges are closed (the process is called neurulation, and the stage of development is neurula). A neural tube is formed. The rest of the ectoderm is the rudiments of the skin epithelium, the sense organs ..

The dorsal part of the endoderm, located under the neural tube, gradually separates (separates) from the rest of the endoderm and folds into a dense elastic cord - chord... From the rest of the endoderm, the intestinal epithelium, digestive glands, and respiratory organs develop.

Further differentiation of the embryonic cells leads to the emergence of numerous derivatives of the germ layers - organs and tissues.

Embryonic induction.

The process of cell differentiation is largely due to the influence of parts of the developing embryo on each other. Observing the development of a fertilized frog egg cell makes it possible to trace the path of development of cells in different parts of the embryo. It turns out that strictly defined cells occupying a strictly defined place in the blastula give rise to strictly defined organ rudiments. With the onset of gastrulation, cell movement begins. If at this moment (at the stage of early gastrula) part of the cells on the dorsal side - the rudiment of the axial complex are cut out and transplanted under the cutaneous ectoderm of another embryo on the abdominal side, then it is possible to obtain the development of an additional complex of axial organs in the second embryo. In this case, the embryo that has lost its organizing cells dies. Consequently, in the process of development, one rudiment affects the other, determining the path of its development. This phenomenon is called embryonic induction, and the parts of the embryo that direct the development of the structures associated with them are called inductors(or organizational centers). The phenomenon of induction is also observed when other organs arise: contact of the protrusion of the neural tube - the eye bladder - with the ectoderm leads to the development of the lens of the eye; the lens, in turn, induces the transformation of the ectoderm into the cornea.

A huge influence on the development of the embryo is exerted by unfavorable factors of the external environment in which the future organism is formed (temperature, light, humidity, alcohol, nicotine, pesticides, a number of drugs, drugs, etc.). They can disrupt the normal course of embryogenesis and lead to the formation of various deformities or a complete stop of development.

Derivatives of germ layers

EKTODERM	ENTODERM	Mesoderm
The neural plate, which gives rise to the central and peripheral nervous system; The ganglion plate, from which the ganglia of the autonomic nervous system, cells of the adrenal medulla, pigment cells are formed; Components of the organs of sight, hearing, smell; Skin epidermis, hair, nails, sweat, sebaceous and mammary glands; Enamel of teeth; Epithelium of the oral cavity and rectum.	Epithelium of the intestinal tube (midgut); Liver, pancreas; Lungs; Epithelium of the gills.	All types of connective tissue (bones, cartilage, tendons, dermis); Skeletal muscle; Circulatory system; Excretory system; The reproductive system.

The 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 common scientific name is ontogenesis. Its main task is to observe, identify the main stages and features of each period, identify patterns, as well as analyze changes and identify factors that these changes can cause.

It is inherent not only in humans, but also in all living beings and plants. The main ones are:

We will not consider the individual development of the plant organism in this short article, but dwell on the development of representatives of the animal world that is closer to man. 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 - spermatozoa) and oogenesis (maturation of female germ cells - eggs). Fertilization is possible only under the condition of mature sex cells in the male and female individuals. When pathologies occur in fertilization, organisms can form - chimeras, some of which are quite viable.

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 is formed, genetic or other pathologies can manifest themselves.

The individual development of the organism consists in the further development of organs, an increase in size and mass, the acquisition of new mental functions, a change 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 the characteristics due to 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, come with completed gametogenesis.

Aging of the body is the stage of wilting, depletion of all the resources of the body. Irreversible disturbances in nerve cells occur, the quality of vision and hearing decreases, vital organs "wear out", the skin changes, the function of reproduction is lost and tissue regeneration sharply slows down, etc.