Individual development of organisms - ontogenesis. Individual development of the body. Features of the process Individual development of the body definition

Animal ontogeny

Comparison of vertebrate embryos at different stages of embryonic development. An infamous illustration from the work of Ernst Haeckel, in which the differences between embryos are artificially reduced in order to be more consistent with the theory of recapitulation (repetition of phylogeny in ontogeny). It should be noted that the falsification of this illustration does not negate the fact that embryos usually do appear to be more similar to each other than adult organisms, which was noted by embryologists even before the theory of evolution.

Ontogenesis is divided into two periods:

embryonic - from the formation of the zygote to birth or exit from the egg membranes;
postembryonic - from exit from the egg membranes or birth to the death of the organism.

Embryonic period

There are three main stages in the embryonic period: cleavage, gastrulation and primary organogenesis. Embryonic, or embryonic, the period of ontogenesis begins from the moment of fertilization and continues until the embryo emerges from the egg membranes. In most vertebrates it includes stages (phases) fragmentation, gastrulation, histo- and organogenesis.

Splitting up

Cleavage is a series of successive mitotic divisions of a fertilized or initiated egg. Cleavage represents the first period of embryonic development, which is present in the ontogenesis of all multicellular animals and leads to the formation of an embryo called a blastula (single-layer embryo). At the same time, the mass of the embryo and its volume do not change, that is, they remain the same as that of the zygote, and the egg is divided into smaller and smaller cells - blastomeres. After each cleavage division, the cells of the embryo become smaller and smaller, that is, the nuclear-plasma relationship changes: the nucleus remains the same, but the volume of the cytoplasm decreases. The process continues until these indicators reach values characteristic of somatic cells. The type of crushing depends on the amount of yolk and its location in the egg. If there is little yolk and it is evenly distributed in the cytoplasm (isolecithal eggs: echinoderms, flatworms, mammals), then crushing proceeds according to the type full uniform: blastomeres are identical in size, the entire egg is crushed. If the yolk is distributed unevenly (telolecithal eggs: amphibians), then crushing proceeds according to the type completely uneven: blastomeres are of different sizes, those containing the yolk are larger, the egg is crushed entirely. With incomplete crushing, there is so much yolk in the eggs that the crushing furrows cannot separate it entirely. The crushing of an egg, in which only the “cap” of cytoplasm concentrated at the animal pole, where the zygote nucleus is located, is crushed, is called incomplete discoidal(telolecithal eggs: reptiles, birds). At incomplete surface crushing in the depths of the yolk, the first synchronous nuclear divisions occur, not accompanied by the formation of intercellular boundaries. The nuclei, surrounded by a small amount of cytoplasm, are evenly distributed in the yolk. When there are enough of them, they migrate into the cytoplasm, where then, after the formation of intercellular boundaries, the blastoderm (centrolecithal eggs: insects) appears.

Gastrulation

One of the mechanisms of gastrulation is invagination (invagination of part of the blastula wall into the embryo) 1 - blastula, 2 - gastrula.

Primary organogenesis

Primary organogenesis is the process of formation of a complex of axial organs. In different groups of animals this process is characterized by its own characteristics. For example, in chordates, at this stage the formation of the neural tube, notochord and intestinal tube occurs.

During further development, the formation of the embryo is carried out through the processes of growth, differentiation and morphogenesis. Growth ensures the accumulation of cell mass of the embryo. During the process of differentiation, variously specialized cells arise that form various tissues and organs. The process of morphogenesis ensures that the embryo acquires a specific shape.

Postembryonic development

Links

Embryogenesis
Biology Embryology Developmental biology
Stages, processes/ result	Egg cleavage/Zygote, Morula Blastulation/Blastula, Blastocyst Gastrulation (intussusception, epiboly)/Gastrula Neurulation/Neurula Organogenesis/Embryo
Germinal leaflets	Ectoderm Endoderm Mesoderm
Differentiation cells	Blastomer Embryoblast Trophoblast Epiblast Hypoblast

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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 - a 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 the main reason for the struggle for existence. The struggle for existence is of three types:

Intraspecific

Interspecific

Combating abiotic factors

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 aerodynamic body - 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.

The first cleavage furrow runs in the meridional bone, connecting both poles - vegetative and aimal - and divides the zygote into two identical cells. This is the stage of two blastomeres. The second groove is also meridional, but perpendicular to the first. It divides both blastomeres, which arose as a result of the first division, in two - four similar blastomeres are formed. The next, third, crushing furrow is latitudinal. It lies slightly above the equator and divides all four blastomeres into eight cells at once. Subsequently, the crushing furrows alternate. As the number of cells increases, their division becomes non-simultaneous. The blastomeres move further and further from the center of the embryo, forming a cavity. At the end of cleavage, the embryo takes the form of a vesicle with a wall formed by one layer of cells closely adjacent to each other. The internal cavity of the embryo, which initially communicated with the external environment through the gaps between the blastomeres, becomes completely isolated as a result of their tight closure. This cavity is called the primary body cavity - blastocoel. Fragmentation ends with the formation of a single-layer multicellular embryo - blastula

The fragmentation of a fertilized egg can occur in different ways. The lancelet egg is completely crushed and has blastomeres of equal size. This type of crushing is called full, even. In fish, amphibians and some other animals, fragmentation is also complete, but uneven: blastomeres at the vegetative pole (where the yolk is concentrated) are larger than at the opposite animal pole (where the nucleus is located surrounded by cytoplasm)

The third type of fragmentation is characteristic of the eggs of birds and reptiles, which have a lot of yolk, and is called discoidal. Here, only the nucleus and a thin section of the cytoplasm are involved in crushing, resulting in the formation of a germinal disc (the yolk of the egg is not crushed). In arthropod eggs (the yolk is concentrated in the center of the egg), crushing superficial - blastomeres are located along the periphery of the egg, where the cytoplasm covering the yolk lies in a narrow strip.

With complete fragmentation (for example, in a lancelet at the stage of 32 blastomeres), the embryo has the appearance of a mulberry and is called Morula. At approximately the stage of 64 blastomeres, a cavity is formed in it, and the blastomeres are arranged in one layer, forming the wall of the embryo. This stage of the embryo is called blastula . Soon the process of the emergence of a two-layer embryo begins - gastrulation. The embryo at this stage consists of clearly separated layers of cells, the so-called germ layers: external, or ectoderm, and internal, or endoderm. Gastrulation is characterized by: 1) movement of cell masses; 2) the beginning of the use of the hereditary material of the embryonic cells and the appearance of the first signs of cell differentiation; 3) cell division is weakly expressed; 4) the appearance of the first tissues

There are several ways of gastrulation. First -immigration - observed in coelenterates: after the formation of the blastula, some cells of the body wall of the embryo immigrate deep into the cavity and gradually fill it. Then it is adjacent to the outer layer of cells from the inside and a two-layered structure appears. embryo-gastrula. Gastrulation in the lancelet and some other animals occurs by intussusception. Following the formation of the blastula, the entire vegetative pole is invaginated inward, adjacent to the animal pole, and the embryo becomes two-layered: the outer germ layer is called ectoderm, internal - endoderm. This stage of the embryo has a primary mouth - a blastopore, leading into the primary gut. Two-layer animals - sponges and coelenterates - complete their embryonic development here. Subsequently, the cells of their ectoderm and endoderm differentiate and several cell types arise.

In amphibians, the gastrula is formed differently: smaller blastomeres from the side of the animal pole creep over the large blastomeres of the vegetative pole, so that a two-layer embryo is obtained by fouling small blastomeres of large ones. In arthropods, during cleavage, blastomeres separate daughter cells from themselves into the cavity, where they form the second layer of the embryo - the endoderm. This method of gastrula formation is called splitting. Different ways of forming a two-layer embryo in different animal species are determined by the amount and nature of the distribution of the yolk in the egg. However, strictly separate types of gastrulation are not observed; their division is conditional.

Primary organogenesis. After completion of gastrulation, the embryo forms a complex of axial organs: neural tube, notochord, and intestinal tube. Starting with flatworms, a major complication occurred in the evolution of the animal world: the third germ layer is laid in the embryo - mesoderm. In chordates, this occurs by detachment from the endoderm of mesodermal pockets, which grow between the first and second germ layers, forming a secondary body cavity.

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

Differentiation ordifferentiation - this is the process of the emergence and growth of structural and functional differences between individual cells and parts of the embryo. From a morphological point of view, differentiation is expressed in the formation of several hundred types of cells of a specific structure that differ from each other. From a biochemical point of view, cell specialization consists in the synthesis of certain proteins characteristic only of a given cell type. Biochemical specialization of cells is ensured differential activity new, that is, in the cells of different germ layers - the rudiments of certain organs in systems - different groups of genes begin to function. With further differentiation ke cells included part germ layers from ectoderm are formed: nervous system, sensory organs, skin epithelium, tooth enamel; from endoderm - epithelium of the midgut, digestive glands - liver and pancreas, epithelium of the gills and lungs; from mesoderm- muscle tissue, connective tissue, circulatory system, kidneys, gonads, etc. In different species of animals, the same germ layers give rise to the same organs and tissues. This means that they homologous.

In chordates, soon after gastrulation, a small section of the dorsal ectoderm in the form of a plate plunges deep into the embryo, bends and forms a neural tube with a cavity inside filled with fluid. The skin with its derivatives (hair, nails, feathers, hooves) and sensory organs develop from ectoderm cells. The notochord is formed from the upper part of the endoderm, and the epithelium lining the middle sections of the intestine, digestive glands and respiratory organs is formed from the lower part. The neural tube develops from the ectoderm located above the notochord. From the mesoderm, muscles, skeleton, circulatory system, gonads, excretory organs and the skin itself - the dermis - are formed.

The embryonic development of animals occurs either in the maternal body or in the external environment.

The homology of the germ layers of the vast majority of animals is one of the proofs of the unity of the animal world.

Embryonic induction. Embryonic induction can be defined as a phenomenon in which, during embryogenesis, one rudiment influences another, determining the path of its development, and, in addition, is itself subject to inducing influence from the first rudiment.

Germ layers, their derivatives (T.A. Kozlova, V.S. Kuchmenko. Biology in tables. M., 2000)

embryonic development (T.A. Kozlova, V.S. Kuchmenko. Biology in tables. M., 2000)

Postembryonic period of development

At the moment of birth or the release of the organism from the egg membranes, the embryonic stage ends and the postembryonic period of development. Postembryonic development may be direct sumindirect and be accompanied transformation (metamorphosis). During direct development, an organism of small size emerges from the egg membranes or from the mother’s body, but it contains all the main organs characteristic of an adult animal (reptiles, birds, mammals). Postembryonic development in these animals is reduced mainly to growth and puberty - pre-reproductive period; reproduction - reproductive period and aging - post-reproductive period.

In organisms with a low yolk content in the egg, indirect development is accompanied by the formation of the larval stage. A larva emerges from the egg, usually simpler in structure than an adult animal, with special larval organs that are absent in the adult state. The larva feeds, grows, and, over time, the larval organs are replaced by organs characteristic of adult animals. At incomplete metamorphosis replacement of larval organs occurs gradually, without stopping active feeding and movement of the organism (locusts, amphibians). Complete metamorphosis includes the pupal stage, in which the larva transforms into an adult animal - an adult (butterfly).

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DEPARTMENT OF EDUCATION AND SCIENCES OF KEMEROVSK REGION

State educational institution

secondary vocational education

Tom-Usinsk Energy Transport College

in the discipline ODB.07: Biology

Topic: “Individual development of the body”

Completed:

student of group TRUC-1-14

Zhuleva Daria

Checked:

biology teacher

Chudinova L.E.

Introduction

1. Embryonic period

1.1 Crushing

1.2 Gastrlation

1.3 Organogenesis

2. Postembryonic development

Bibliography

Introduction

The individual development of an organism, or ontogenesis, is a set of successive morphological, physiological and biochemical transformations undergone by the organism from the moment of its inception to death. During ontogenesis, the implementation of hereditary information received by the body from its parents occurs.

There are two main periods in ontogenesis - embryonic and postembryonic. In the embryonic stage, an embryo is formed in animals, in which the main organ systems are formed. In the postembryonic period, the developmental processes are completed, puberty, reproduction, aging and death occur.

1. Embryonic period

The embryonic period begins with the formation of a zygote and ends with the birth or emergence from the egg or embryonic membranes of a young individual. It consists of three stages: cleavage, gastrulation and organogenesis.

1.1 Crushing

The initial stage of development of a fertilized egg is called cleavage. A few minutes or a few hours (different species vary) after the sperm is introduced into the egg, the resulting zygote begins to divide by mitosis into cells called blastomeres. This process is called cleavage, since during it the number of blastomeres increases exponentially, but they do not grow to the size of the original cell, but become smaller with each division. Blastomers formed during cleavage are early germ cells. During cleavage, mitoses follow one after another, and by the end of the period the entire embryo is not much larger than the zygote.

The type of egg crushing depends on the amount of yolk and the nature of its distribution. A distinction is made between complete and incomplete crushing. In yolk-poor eggs, uniform crushing is observed. Lancelet and mammal zygotes undergo complete crushing, since they contain little yolk and it is distributed relatively evenly.

In eggs rich in yolk, crushing can be complete (uniform and uneven) and incomplete. Due to the abundance of yolk, the blastomeres of one pole always lag behind the blastomeres of the other pole in the rate of fragmentation. Complete but uneven fragmentation is characteristic of amphibians. In fish and birds, only the part of the egg located at one of the poles is crushed; incomplete occurs. splitting up. Part of the yolk remains outside the blastomeres, which are located on the yolk in the form of a disk.

Let us consider in more detail the fragmentation of the lancelet zygote. Cleavage covers the entire zygote. The furrows of the first and second cleavage pass through the poles of the zygote in mutually perpendicular directions, resulting in the formation of an embryo consisting of four blastomeres.

Subsequent crushing takes place alternately in the longitudinal and transverse directions. At the stage of 32 blastomeres, the embryo resembles a mulberry or raspberry. It's called moru-loy. With further fragmentation (at approximately the stage of 128 blastomeres), the embryo expands and the cells, arranged in a single layer, form a hollow ball. This stage is called blastula. The wall of a single-layer embryo is called blastoderm, and the cavity inside is called blastocoel (primary body cavity). ontogeny embryonic gastrulation organogenesis

1.2 Gastrulation

The next stage of embryonic development is the formation of a two-layer embryo - gastrulation. After the lancelet blastula has fully formed, further cell fragmentation occurs especially intensively at one of the poles. As a result, they seem to be drawn in (bulge) inward. As a result, a two-layer embryo is formed. At this stage, the embryo is cup-shaped and is called a gastrula. The outer layer of gastrula cells is called the ectoderm or outer germ layer, and the inner layer lining the gastrula cavity - the gastric cavity (the cavity of the primary intestine) is called the endoderm or inner germ layer. The gastrula cavity, or primary intestine, turns into the digestive tract in most animals at further stages of development and opens outwards into the primary mouth, or blastopore. In worms, mollusks and arthropods, the blastonore develops into the mouth of an adult organism. That's why they are called protostomes. In echinoderms and chordates, the mouth breaks through on the opposite side, and the blastonore turns into an anus. They are called deuterostomes.

At the stage of two germ layers, the development of sponges and coelenterates ends. In all other animals, a third is formed - the middle germ layer, located between the ectoderm and endoderm. It's called mesoderm.

1.3 Organogenesis

After gastrulation, the next stage in the development of the embryo begins - differentiation of the germ layers and the laying of organs (organogenesis). First, the formation of axial organs occurs - the nervous system, notochord and digestive tube. The stage at which the formation of axial organs occurs is called neirula.

The nervous system in vertebrates is formed from the ectoderm in the form of a neural tube. In chordates, it initially looks like a neural plate. This plate grows more intensively than all other parts of the ectoderm and then bends, forming a groove. The edges of the groove close, a neural tube appears, which stretches from the anterior end to the posterior. The brain then forms at the anterior end of the tube. Simultaneously with the formation of the neural tube, the formation of the notochord occurs. The notochordal material of the endoderm bends, so that the notochord is separated from the common plate and turns into a separate cord in the form of a solid cylinder. The neural tube, intestine and notochord form a complex of axial organs of the embryo, which determines the bilateral symmetry of the body. Subsequently, the notochord in vertebrates is replaced by the spine, and only in some lower vertebrates its remains are preserved between the vertebrae even in adulthood.

Simultaneously with the formation of the notochord, the third germ layer, the mesoderm, is separated. There are several ways to form mesoderm. In the lancelet, for example, the mesoderm, like all major organs, is formed as a result of increased cell division on both sides of the primary gut. As a result, two endodermal pockets are formed. These pockets enlarge, filling the primary body cavity; their edges break away from the endoderm and close together, forming two tubes consisting of separate segments, or somites. This is the third germ layer - the mesoderm. In the middle of the tubes is the secondary body cavity, or coelom.

Further differentiation of the cells of each germ layer leads to the formation of tissues (histogenesis) and the formation of organs (organogenesis). In addition to the nervous system, the outer covering of the skin develops from the ectoderm - the epidermis and its derivatives (nails, hair, sebaceous and sweat glands), the epithelium of the mouth, nose, anus, lining of the rectum, tooth enamel, sensory cells of the organs of hearing, smell, vision etc.

From the endoderm develop epithelial tissues lining the esophagus, stomach, intestines, respiratory tract, lungs or gills, liver, pancreas, epithelium of the gall and bladder, urethra, thyroid and parathyroid glands.

2. Postembryonic development

Postembryonic development can be direct or indirect.

Direct development is development in which the emerging organism is identical in structure to the adult organism, but is smaller in size and does not have sexual maturity. Further development is associated with an increase in size and the acquisition of sexual maturity. For example: the development of reptiles, birds, mammals.

Indirect development (larval development, development with metamorphosis) - the emerging organism differs in structure from the adult organism, is usually simpler in structure, may have specific organs, such an embryo is called a larva. The larva feeds, grows, and over time the larval organs are replaced by organs characteristic of the adult organism (imago). For example: the development of a frog, some insects, worms.

Postembryonic development is accompanied by growth

Bibliography

1. Azimov A. Brief history of biology. M., 1997.

2. Kemp P., Arms K. Introduction to biology. M., 2000.

3. Libbert E. General biology. M., 1978 Llozzi M. History of physics. M., 2001.

4. Nebel B. Environmental Science. How the world works. M., 1993.

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