Stages of individual development of organisms. Individual development of the body - Knowledge Hypermarket What is the process of individual development of the body called?
Individual development of a person, like any other organism, is ontogenesis with a phylogenetic program embedded in it; its periodization inevitably rests on the identification of a number of universal age-related processes (growth, maturation, development, aging), during which the corresponding age-related properties (differences) are formed. Both are generalized in the concept of age stages (phases, stages, periods) or stages of development (childhood, adolescence, maturity, old age, etc.). Age-related processes imply the question of how age-related properties are formed and in what way (gradually or abruptly, spasmodically) the transition from one age stage to another occurs.
IN modern science There are three main terms to describe individual development as a whole - life time, life cycle, And life path. Although they are often used as synonyms, they are significantly different in content. Lifetime, its length or space, refers to the time interval between birth and death. Life expectancy has important social and psychological consequences. It largely determines, for example, the duration of the existence of generations and the duration of the primary socialization of children. The concept of life cycle is more specific and meaningful. It assumes that the course of life is subject to a certain pattern, and its stages (“ages of life” or “seasons of life”, similar to the seasons) represent a constant cycle. The idea of a cyclical cycle of life, similar to the cyclicity of natural processes (alternation of day and night, change of seasons, etc.). Many biological and social age-related processes are indeed cyclical. The body normally goes through the phases of birth, growth, maturation, aging and death. The personality assimilates, then carries out and, finally, gradually leaves a certain set social roles(labor, family, parental), after which the same cycle is repeated by her descendants. Cyclicality also characterizes the change of generations in society, where the younger ones (children) first learn from the older ones, then actively act alongside them, and then, in turn, socialize the younger ones. The concept of a life path differs from the “life cycle” primarily in its multidimensionality, in that it involves many different trends and lines of development within the same biography, and these lines are both autonomous and interconnected. Its periodization is based on non-linear, once and for all defined phases, but on specific life events. The timing, sequence and manner in which any life event occurs, be it marriage or retirement, is no less important than the fact that the event took place. This requires a combination of sociological, psychological and historical analysis. Thus, a meaningful description of the processes, properties and stages of individual development is possible either in the ontogeny system, or in the life cycle system, or in the life course system. However, these systems are not side by side: the life path of an individual includes the life cycle of the individual, and this in turn includes ontogenesis.
Growth of development of the human body
The processes of growth and development are influenced by a large number of diverse endo- and exogenous factors. “Growth” and “development” are usually used as identical concepts, inextricably linked. Meanwhile, the biological nature of these processes is different, their mechanisms and consequences differ.
Growth is a quantitative increase in the biomass of an organism due to the geometric dimensions and mass of individual cells.
Development is a qualitative transformation in a multicellular organism due to differentiated processes (increasing diversity a lot cellular structures), which lead to qualitative and quantitative changes in body functions.
The process of growth and development is characterized by the following patterns:
1. Differentiation and integration of parts and functions, autonomy of development, increasing during phyloontogenesis.
2. Dialectical unity of continuous and discontinuous; gradualism and cyclicality. On the human growth curve, three main cycles in postnatal development can be noted:
a) from birth to 10-13 years with a constant decrease in speed;
b) pubertal spurt;
c) a drop in speed below the level before puberty and cessation of growth.
A combination of periods of accelerated development and relative stabilization can be detected even during short periods of ontogenesis. For example, with long-term observation at weekly intervals of children from birth to 2 years. Non-linearity of growth (mini-spurts) is observed in approximately 70% of children and adolescents when assessed weekly for 6-10 months.
3. Heterochrony (different times) in the maturation of different body systems (or tissues) and different characteristics within one system. According to the concept of systemogenesis by P.K. Anokhin, vital functions mature at a determining pace, ensuring the primary formation of complex adaptive reactions specific to each specific stage of the body’s relationship with the external environment.
4. Significant individual diversity in age dynamics at individual stages of ontogenesis, depending on the genetic program.
Topic 11. Periodization of individual development (ontogenesis)
Ontogenesis is a complex of successive transformations of the body, starting from the stage of fertilization of the egg and until the end of the life cycle.
Pythagoras (VI century BC) distinguished 4 periods human life: spring (up to 20 years), summer (20-40 years), autumn (40-60 years) and winter (60-80 years), which corresponded to formation, youth, prime of life and decline.
Hippocrates divided the entire postnatal ontogenesis into ten seven-year cycles.
Ontogenesis is divided into 2 periods: embryonic and fetal (fetal). During the first period, which lasts 8 weeks, the formation of organs and body parts characteristic of an adult occurs. During the fetal period, the size increases and organ formation is completed. The growth rate of the fetus increases up to 4-5 months. After 6 months, the growth rate of linear dimensions decreases.
At the VII All-Union Conference on Age-Related Morphology, Physiology and Biochemistry, held in 1965 in Moscow, the following scheme for the age periodization of human ontogenesis was adopted. This scheme has found wide application in anthropology, pediatrics, and pedagogy.
Scheme of age periodization of human ontogenesis
Newborns |
|
Infancy |
10 days--1 year |
Early childhood |
|
First childhood |
|
Second childhood |
8-12 years old (boys) 8-11 years old (girls) |
Adolescence |
13-16 years old (boys) 12-15 years old (girls) |
Adolescence |
17-21 years old (boys) 16-20 years old (girls) |
Mature age (1st period) |
22-35 years old (men) 21-35 years old (women) |
Mature age (2nd period) |
36-60 years (men) 36-55 years (women) |
Elderly age |
61-74 years (men) 56-74 years (women) |
Senile age |
|
Centenarians |
90 years and above |
From the moment of birth, the neonatal period begins. At this time, the baby is fed colostrum for 8-10 days. The next period - infancy - lasts up to 1 year. Its beginning is associated with the transition to feeding on “ripe milk”. Body length increases from birth to one year by about 1.5 times, and weight triples. From the age of 6 months, milk teeth begin to erupt, and at 2-3 years of life, the eruption of milk teeth ends. During first childhood, starting at age 6, the first permanent teeth appear. During the period of second childhood, gender differences in body size and shape are revealed, and increased growth in length begins. On average, by the age of 12-13, boys and girls finish changing their teeth. Secondary sexual characteristics begin to develop. The next period - adolescence - is called the period of puberty, or puberty, by the end of which the body size reaches 90-97% of its final size, and the main functional characteristics of adolescents approach those of an adult body. During adolescence, the process of growth and formation of the body ends, all the main dimensional characteristics reach a definitive (final) value. In adulthood, the shape and structure of the body changes little. Between 30 and 45-50 years, body length remains constant, and then begins to decrease. In old and senile age, involutive changes in the body occur.
Topic 12. Pubertal growth spurt
An important event of the puberty period is spurt - an abrupt increase in height, observed on average in boys at 13-15 years old, and in girls at 11-13 years old. During this time, the absolute growth rate is not constant and gradually decreases: for boys - from 12 to 7 cm / year, for girls - from 11 to 6 cm / year.
Many factors are involved in the growth spurt, primarily sex hormones and growth hormone - STH, which exerts its effect through somatomedins - peptides synthesized in the liver. In addition to these hormones, the universal anabolic hormone insulin and the thyroid hormones - thyroxine and triiodothyronine - are essential in this period. Insulin regulates protein and fat metabolism, and thyroxine and triiodothyronine affect the growth and differentiation of tissues, increasing the intensity of basal metabolism and heat production. The maturation of reproductive function is completed by 18-20 years.
Morphological maturation of the frontal cortex is achieved only by 12 years, and the final formation of the telencephalon hemispheres is achieved at 20-22 years. Characteristics of the puberty period are considered to be: increased subcortical influences and weakened activity of the cerebral cortex, disruption of the vegetative sphere, increased emotionality, especially in girls.
The process of individual development of any organism is called ontogenesis. The concept of ontogeny was introduced into biology by Ernst Haeckel in 1866. According to modern concepts, ontogeny (Greek ontos - being, individual, genesis - development) is a complete cycle of individual development of each individual, which is based on the implementation of hereditary information at all stages of existence in certain environmental conditions; it starts with education zygotes(during sexual reproduction) and ends in death. The biological species Homo sapiens is characterized by direct intrauterine development.
Depending on the environment in which the human body develops, ontogenesis is divided into two large periods, separated from each other by the moment of birth:
- Intrauterine(prenatal, or antenatal), when the newly born organism develops in the womb; this period lasts from conception to birth.
- Extrauterine (postnatal), when a new individual continues its development outside the mother’s body; this period lasts from birth to death.
IN Lately it is also proposed to highlight prezygotic the period preceding the formation of the zygote.
Prezygotic period
Prezygotic period development is associated with the formation of gametes (gametogenesis). The formation of eggs begins in women even before their birth and is completed for each given egg only after its fertilization. By the time of birth, a female fetus in the ovaries contains about two million first-order oocytes (these are still diploid cells), and only 350 - 450 of them will reach the stage of second-order oocytes (haploid cells), turning into eggs (one at a time during one menstrual cycle ). Unlike women, sex cells in the testes (testes) in men begin to form only with the onset of puberty. The duration of sperm formation is approximately 70 days; per gram of testicle weight, the number of sperm is about 100 million per day.
Fertilization is the process of fusion of an egg and a sperm, leading to the formation of a zygote. Fertilization of the egg occurs in the initial section of the fallopian tube, where only about a hundred sperm penetrate. The ability of sperm to fertilize in the female genital tract persists for two days. The sperm has an acrosome in its head, which contains an enzyme to dissolve the membrane of the egg. When the sperm and egg come together, the acrosome ruptures, and the released enzymes dissolve the shell of the female gamete. The sperm penetrates the egg, after which it is covered with a dense membrane that prevents the penetration of other male gametes. As a result of fertilization, the diploid set of chromosomes is restored. The resulting single-celled embryo is a zygote. In it, complex movements of individual sections of the cytoplasm and its organelles occur throughout the day.
Prenatal period Human development lasts 280 days and is divided into:
- initial period(the first week after fertilization, during which the zygote fragments, the formation of a blastula and its implantation into the uterine wall);
- embryonic period(the first two months), when the initial development of the embryo (embryo) occurs and when the main formation of tissues and organs occurs;
- fertile period(3-9 months), when the growth of parts formed in the embryonic stage and the further formation of organs and systems continues. From the third month, the human embryo is called a fetus.
Initial period
Initial period. Splitting up- This is the initial stage of development of a fertilized egg (zygote). In humans, it lasts 3-4 days (the zygote is fragmented through a series of successive mitoses, but without the growth of daughter cells to the size of the zygote). In humans, the fragmentation of the zygote is full and uneven. Cells formed as a result of fragmentation are called blastomeres. The result of the fragmentation stage is the formation of a multicellular embryo - morulas. Crushing and formation of the morula occurs as the embryo moves along the fallopian tube. The morula enters the uterus, where the process takes place blastulation. The blastomeres in the morula repel each other, shift to the periphery and line up in one layer, and by the 6th day a single-layer embryo in the form of a vesicle is formed. Different blastomeres divide at different rates. Some of them (lighter) are located on the periphery, others (darker) are located in the center.
The surrounding embryo is formed from light cells trophoblast, the cells of which play an auxiliary role and do not directly participate in the formation of the embryo body. Trophoblast cells are able to dissolve tissue, due to which the embryo is implanted ( implanted) into the wall of the uterus. Next, the trophoblast cells peel off from the cells of the embryo, forming a vesicle around it. The trophoblast cavity is filled with fluid diffusing into it from the uterine tissue. Formed from dark cells embryoblast, having the appearance of a nodule. As a result of further fragmentation of the embryoblast, the embryo takes the form of a disk, spread out on the inner surface of the trophoblast. This stage of embryonic development, when the trophoblast and embryoblast are distinguished, is called blastocyst. The blastocyst, once in the uterine cavity, implanted, receiving nutrients from the uterine wall. Trophoblast cells differentiate into two layers. From the cells of the outer layer of trophoblast are formed trophoblast villi, which grow into the epithelium of the uterus. This layer with villi forms the outermost membrane of the embryo - chorion. The chorion plays an important role in the nutrition of the developing embryo and the removal of its final metabolic products. At later stages this function is performed by placenta. Two cavities form in the inner layer of trophoblast cells; the walls of these cavities give rise to two more embryonic membranes - amnion and yolk sac. Amnion is a thin shell that covers the embryo and performs protective functions; its cells secrete amniotic fluid, filling the amniotic cavity located between the amnion and the embryo. As the embryo grows, the amnion expands so that it is always pressed against the wall of the uterus. Amniotic fluid supports the embryo and protects it from mechanical damage. The yolk sac in the human embryo does not play a significant role; it is a kind of rudiment (the yolk sac is especially developed in reptiles and birds; it absorbs the nutrients stored in the yolk and transfers them to the midgut of the embryo). In humans, the yolk sac contains practically no yolk; its main function is hematopoiesis. In addition, primary germ cells are formed in its wall, then migrating into the primordia of the gonads.
Embryonic period
Embryonic period lies in the flow gastrulation and education three germ layers, histogenesis (tissue formation) and organogenesis (organ formation).
Gastrulation is the process of formation of germ layers. The disc-shaped embryoblast is called germinal disc. An embryo develops from it. The cells of this disc at an early stage, when its diameter does not reach 2 mm, differentiate into two germ layers (leaves) - ectoderm and endoderm. At a later stage it is formed mesoderm. These three germ layers give rise to all the tissues of the developing embryo. At the end of gastrulation in the 4th week, primordia are formed neural plate And chords.
In the early stages of development, the exchange between the embryo and the maternal organism occurs due to the trophoblast villi, and then the fourth shell develops - allantois. The allantois grows outward until it comes into contact with the chorion, forming a structure rich in blood vessels that participates in the formation of the placenta.
Placenta has the form of a disc fixed in the uterine mucosa, and from the 12th week of development it completely ensures the exchange between the fetus and the mother. By the end of the eighth week, all internal organs are formed. In the placenta, the blood of mother and fetus does not mix. Between the body of the fetus and the placenta is formed umbilical cord, in which two umbilical arteries, carrying venous blood from the embryo, and one umbilical vein, carrying arterial blood from the placenta to the embryo. Tissues are formed and differentiated from the cellular material of embryonic rudiments. This ends the embryonic period. An eight-week embryo is 3-3.5 cm long and weighs about 4 grams. His neck is separated, facial features are outlined, limbs and external genitalia are formed.
Fetal period begins from the 9th week of intrauterine life with a predominance of growth processes and final tissue differentiation. By the end of 3 months, the fruit weighs about 40 grams, its length reaches 8-9 cm. Ossification nuclei appear in almost all bones. In the 4th month, individual facial features are formed. At the 5th month, the skin becomes covered with fluff, and the movements of the fetus are felt by the mother. The fetal heartbeat is heard, which is faster than that of the mother. At 6 months, the embryo is 30 cm long and weighs 650-700 g. In the case of premature birth at 7 - 8 months, the fetus is viable, but needs the conditions of intrauterine life. By the end of the 9th month, the fuzz on the skin is lost, but a layer of cheese-like lubricant remains, the nails protrude above the fingertips, the arms are longer than the legs, and in boys the testicles descend into the scrotum. The weight of the fruit is about 3.5 kg and the length is 50 cm.
Fetal development ends childbirth(expulsion of the fetus and placenta from the uterus). The onset of labor is associated with the release of a hormone from the pituitary gland oxytocin, causing strong contractions of the muscles of the uterus and abdominal muscles. The baby is pushed into the pelvis and is born. The first sign of pulmonary respiration is a cry. After 15-20 minutes, the placenta and amniotic membrane are separated from the uterine wall and pushed out.
During the process of embryogenesis, various factors (poisons, radiation, vitamin deficiencies, oxygen starvation, etc.) can affect the developing organism and cause developmental deviations in the form of anomalies and deformities. Violation of living conditions is especially dangerous if it coincides with periods of increased sensitivity of the embryo, the so-called critical periods of embryogenesis.
In humans, the 7th day, 7th week and childbirth are considered critical periods. Therefore, a pregnant woman must be protected from any adverse effects from the very first days of pregnancy.
Extrauterine (postembryonic) period.
Lasts from birth to death extrauterine (postembryonic, postnatal) development.
Its following periods are distinguished (the periodization of ages was adopted at the VII International Symposium on Problems of Age-Related Morphology, Physiology and Biochemistry in 1965):
- newborn(first 1 - 10 days after birth),
- chest(from 10 days to 12 months),
- early childhood(from 1 to 3 years),
- first childhood(from 4 to 7 years old),
- second childhood(from 8 to 12 years old),
- adolescence(from 13 to 16 years old),
- adolescence(from 17 years old to 21 years old),
- period of maturity(from 22 years to 55 -60 years),
- elderly age(from 56-61 years to 74 years),
- old age(75 – 90 years)
- centenarians ( over 90 years).
The most intensive growth and development of a child is observed in the first year of life and during puberty. During the process of growth and development, the proportions of the body change. For example, the ratio of head to body size in a newborn is 1:4, while in an adult it is 1:8.
The main features of humans in comparison with animals are the presence of thinking, speech and motor activity, which is closely related to work activity. For the development of these functions, proper upbringing of children aged 2 to 4 years is very important. The period of time from 7 to 18 years of age is a decisive period for the physical, mental and moral development of a person.
Return to Human Development
Development of the human body. Individual human development (ontogenesis) begins from the moment of fertilization, when the fusion of female (egg) and male (sperm) germ cells occurs. The initial stages of development occur in the woman’s genital tract, so all ontogenesis is usually divided into prenatal and postnatal (from the Latin natus - childbirth) periods, i.e. prenatal and postnatal.
In the prenatal (intrauterine) period of ontogenesis, in turn, the germinal (embryonic) and fetal (fetal) periods are distinguished. The first lasts 2 months, the second - from the 3rd to the 9th inclusive.
From the moment of birth, the process of independent life of the individual and his adaptation to the environment begins. Newly acquired characteristics are layered on those inherited, as a result of which complex transformations occur in the body.
The physical development of an individual is characterized by weight, height and size of individual parts of the body.
These indicators change unevenly throughout life.
Accelerated growth is observed during early childhood (from 1 to 3 years), at the ages of 5 to 7 years and during puberty (from 11-12 to 15-16 years), while the basic proportions of the body also change. In parallel with growth, age-related changes are observed in all organs and systems. Around the age of 20-25, a person’s growth stops and a relatively stable period of existence begins - adulthood. After 55-60 years, a person begins to gradually age, and sclerotic changes occur in a number of organs. This in turn causes a decrease in various body functions.
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Development of the human body. Individual human development (ontogenesis) begins from the moment of fertilization, when the fusion of female (egg) and male (sperm) germ cells occurs. The initial stages of development occur in the woman’s genital tract, so all ontogenesis is usually divided into prenatal and postnatal (from the Latin natus - childbirth) periods, i.e. prenatal and postnatal.
In the prenatal (intrauterine) period of ontogenesis, in turn, the germinal (embryonic) and fetal (fetal) periods are distinguished. The first lasts 2 months, the second - from the 3rd to the 9th inclusive.
In the embryonic period, there is an increase in the number of cells, which gradually differentiate into the rudiments of all types of tissues (histogenesis). During the second month of intrauterine development, organs are formed (organogenesis); The main parts of the body are formed: head, neck, torso and limbs. From the 3rd month, intensive growth and development of the fetal body begins, which continues after the birth of the child.
From the moment of birth, the process of independent life of the individual and his adaptation to the environment begins. Newly acquired characteristics are layered on those inherited, as a result of which complex transformations occur in the body. The physical development of an individual is characterized by weight, height and size of individual parts of the body.
These indicators change unevenly throughout life.
Accelerated growth is observed during early childhood (from 1 to 3 years), at the ages of 5 to 7 years and during puberty (from 11-12 to 15-16 years), while the basic proportions of the body also change. In parallel with growth, age-related changes are observed in all organs and systems. Around the age of 20-25, a person’s growth stops and a relatively stable period of existence begins - adulthood. After 55-60 years, a person begins to gradually age, and sclerotic changes occur in a number of organs. This in turn causes a decrease in various body functions.
From the moment of birth, the process of independent life of the individual and his adaptation to the environment begins. Newly acquired characteristics are layered on those inherited, as a result of which complex transformations occur in the body. The physical development of an individual is characterized by weight, height and size of individual parts of the body. These indicators change unevenly throughout life.
Accelerated growth is observed during early childhood (from 1 to 3 years), at the ages of 5 to 7 years and during puberty (from 11-12 to 15-16 years), while the basic proportions of the body also change. In parallel with growth, age-related changes are observed in all organs and systems. Around the age of 20-25, a person’s growth stops and a relatively stable period of existence begins - adulthood. After 55-60 years, a person begins to gradually age, and sclerotic changes occur in a number of organs. This in turn causes a decrease in various body functions.
In the process of development and growth of the body and the formation of its nervous system, the nature and level of human needs changes. A newborn is dominated by vital needs associated with the implementation of vital functions: nutrition, breathing, sleep, etc. Various physiological needs are gradually formed and intensively developed associated with movement in space, with the absorption of various nutrients, growth and development, as well as independent performance and voluntary regulation of physiological functions. Relatively early, already in the first year of life, cognitive needs begin to form, especially during early childhood (1-3 years) and later during the preschool and school periods of the child’s development. The formation of social and communicative needs takes a rather long period of ontogenesis, including the mature life of an individual.
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Lesson development
in general biology
on the topic “Stages of individual development of organisms”
Performed:teacherbiology Skryabina Anna Yaroslavovna
Feodosia 2016
General biology lesson
Subject. “Stages of individual development of organisms”
Target : create conditions for the perception, comprehension and primary consolidation of students’ knowledge about the characteristics of the individual development of organisms;give the concept of ontogenesis and consider in more detail the embryonic and postembryonic period of development of organisms.
Educational goals : to update students’ personal meaning in studying this topic and to ensure the further development of students’ reflective skills, to develop students’ creative and analytical abilities.
Lesson objectives:
characterize the content of the stages of ontogenesis: embryonic and postembryonic periods;
expand ideas about the postembryonic period of individual development, about the ways of its passage (direct and indirect);
reveal the dependence of ontogenesis on environmental conditions.
Equipment and materials: multimedia board, computer, educational presentation, textbooks, and task cards.
Basic concepts and terms: ontogenesis, embryonic period, embryo, postembryonic period, cleavage, blastula, gastula, blastomeres, morula, invagination, ectoderm, endoderm, mesoderm, germ layers.
Lesson concept : talk about ontogenesis, drawing attention to the fact that ontogenesis is extremely diverse and proceeds differently in different organisms, then dwell on the embryonic development of multicellular animals and show how the laying of germ layers occurs, prepare students to understand the processes of organogenesis.
Lesson type: lesson on learning new material.
Lesson timing:
Update background knowledge and motivation for learning activities……5 min.
Studying new material………………………………………………………30 min.
Generalization, systematization and control of students’ knowledge and skills…..8 min.
Homework…………………………………………………………..2 minutes.
Structure and content of the lesson.
1.Updating basic knowledge and motivating learning activities.
Questions for students:
1. WhatWhat is individual development?
2. How does the development of plants differ from the development of animals?
3. What stages of individual development do you know in plants and animals?
4. What is the embryonic and post-embryonic development of organisms?
5.What phases does the cell cycle consist of?
2. Studying new material.
Plan :
The concept of ontogenesis.
Historical information.
Embryonic period.
Impact of environmental factors on embryo development.
Postembryonic period.
Lesson summary.
Ontogenesis is a long and complex process of the formation of organisms from the moment of formation of germ cells and fertilization (with sexual reproduction) or individual groups of cells (with asexual reproduction) until the end of life.
(Slide - 1)
From the Greek “ontos” - existing and genesis - emergence. Ontogenesis is a chain of strictly defined complex processes at all levels of the body, as a result of which the structural features, life processes, and ability to reproduce that are inherent only to individuals of a given species are formed. Ontogenesis ends with processes that naturally lead to aging and death.
(Slide – 2)
With the genes of its parents, the new individual receives a kind of instructions about when and what changes should occur in the body so that it can successfully go through its entire life course. Thus, ontogeny represents the implementation of hereditary information.
(watching an educational film about ontogenesis – 9 minutes)
Historical information.
The process of the appearance and development of living organisms has interested people for a long time, but embryological knowledge accumulated gradually and slowly.
The true creator of embryology as a science is the Russian scientist Karl Baer (1792-1876), a native of the Estonian province. He was the first to prove that during the development of all vertebrate animals, the embryo is first formed from two primary cell layers, or layers. Baer saw, described, and then demonstrated at a congress of naturalists a mammalian egg cell from a dog he had opened. He discovered a method for the development of the axial skeleton in vertebrates (from the so-called dorsal chordae). Baer was the first to establish that the development of any animal is a process of unfolding something previous, or, as they would now say, gradual differentiation of more and more complex formations from simpler ones - rudiments (law of differentiation). Finally, Baer was the first to appreciate the importance of embryology as a science and based it on the classification of the animal kingdom.
(Slide – 3)
Individual development of unicellular organisms.
In the simplest organisms, whose body consists of one cell, ontogenesis coincides with the cell cycle, i.e. from the moment of appearance, through the division of the mother cell, until the next division or death.
The ontogeny of unicellular organisms consists of two periods:
Maturation (synthesis of cellular structures, growth)
Maturity (preparation for division), and the division process itself.
Individual development of multicellular organisms.
Ontogenesis is much more complicated in multicellular organisms.
For example, in various divisions of the plant kingdom, ontogenesis is represented by complex development cycles with alternation of sexual and asexual generations.
In multicellular animals, ontogeny is also a very complex process and much more interesting than in plants.
In animals, there are three types of ontogenesis: larval, oviparous and intrauterine. The larval type of development is found, for example, in insects, fish, and amphibians. There is little yolk in their eggs, and the zygote quickly develops into a larva, which feeds and grows independently. Then, after some time, metamorphosis occurs - the transformation of the larva into an adult. In some species, there is even a whole chain of transformations from one larva to another and only then to an adult. The reason for the existence of larvae may lie in the fact that they feed on different foods than adults, and thus the food base of the species expands. Compare, for example, the nutrition of caterpillars (leaves) and butterflies (nectar), or tadpoles (zooplankton) and frogs (insects). In addition, during the larval stage, many species actively colonize new territories. For example, the larvae of bivalve mollusks are capable of swimming, while adults are practically motionless. The oviparous type of ontogenesis is observed in reptiles, birds and oviparous mammals, whose eggs are rich in yolk. The embryo of such species develops inside the egg; there is no larval stage. The intrauterine type of ontogenesis is observed in most mammals, including humans. In this case, the developing embryo is retained in the mother’s body, a temporary organ is formed - the placenta, through which the mother’s body provides all the needs of the growing embryo: breathing, nutrition, excretion, etc. Intrauterine development ends with the process of childbirth.
Embryonic period.
The individual development of multicellular organisms can be divided into two stages:
embryonic period.
postembryonic period.
(Slide -4)
The embryonic or embryonic period of the individual development of a multicellular organism covers the processes occurring in the zygote from the moment of the first division until exit from the egg or birth.
The science that studies the laws of individual development of organisms at the embryonic stage is called embryology (from the Greek embryo - embryo).
Embryonic development can occur in two ways: in utero and ending with birth (in most mammals), as well as outside the mother’s body and ending with the release of the egg membranes (in birds, fish, reptiles, amphibians, echinoderms, mollusks and some mammals)
Multicellular animals have varying levels of organizational complexity; can develop in the womb and outside the mother’s body, but for the vast majority, the embryonic period proceeds in a similar way and consists of three periods: cleavage, gastrulation and organogenesis.
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The impact of environmental factors on the developing embryo.
(Slide -6)
A developing embryo (especially a human embryo) has periods called critical periods, when it is most sensitive to the damaging effects of environmental factors. This is the implantation period on days 6-7 after fertilization, the placentation period - the end of the second week and the period of childbirth. During these periods, restructuring occurs in all body systems.
Postembryonic period.
The development of an organism from the moment of its birth or emergence from the egg shells until death is called the postembryonic period. In different organisms it has different duration: from several hours (in bacteria) to 5000 years (in sequoia).
There are two main types of postembryonic development: direct and indirect.
Direct development, in which an individual emerges from the mother’s body or egg shells, differing from the adult organism only in smaller size (birds, mammals). There are: non-larval (oviparous) type, in which the embryo develops inside the egg (fish, birds), and intrauterine type, in which the embryo develops inside the mother’s body - and is connected to it through the placenta (placental mammals).
With transformation (metamorphosis), in which a larva emerges from the egg, which is simpler in structure than an adult animal (sometimes very different from it); as a rule, it has special larval organs that are absent in an adult animal, and is not capable of reproduction; often the larva leads a different lifestyle than the adult animal (insects, amphibians). Of interest are the facts of the transformation of a neotenic axolotl larva into an ambistoma, and the transformation of tadpoles into frogs under the influence of thyroid hormone.
The duration of the postembryonic period varies among different multicellular organisms.
For example:
Turtles - 100-150 years,
Elephant - 77 years old,
Man - 70 years old,
Monkey - 35-40 years old,
Leo - 35 years old,
Mouse - 3-4 years.
Generalization, systematization and control of students' knowledge and skills.
Independent work on task cards.
Option 1.
What is ontogeny?
What period of ontogenesis is called embryonic?
What is the advantage of indirect development?
(Slide – 7)
Option – 2.
What stages are distinguished in the ontogenesis of all organisms?
What characterizes the postembryonic period of ontogenesis?
What factors influence ontogenesis?
(Slide – 8)
Homework
(Slide – 9)
Individual development of organisms or ontogenesis is a long and complex process of formation of organisms from the moment of formation of germ cells and fertilization (with sexual reproduction) or individual groups of cells (with asexual reproduction) until the end of life.
From the Greek “ontos” - existing and genesis - emergence. Ontogenesis is a chain of strictly defined complex processes at all levels of the body, as a result of which the structural features, life processes, and ability to reproduce that are inherent only to individuals of a given species are formed. Ontogenesis ends with processes that naturally lead to aging and death.
With the genes of its parents, the new individual receives a kind of instructions about when and what changes should occur in the body so that it can successfully go through its entire life course. Thus, ontogeny represents the implementation of hereditary information.
Historical reference
The process of the appearance and development of living organisms has interested people for a long time, but embryological knowledge accumulated gradually and slowly. The great Aristotle, observing the development of a chicken, suggested that the embryo is formed as a result of the mixing of fluids belonging to both parents. This opinion lasted for 200 years. In the 17th century, the English physician and biologist W. Harvey carried out some experiments to test Aristotle's theory. As court physician to Charles I, Harvey received permission to use deer living on royal lands for experiments. Harvey studied 12 female deer that died at different times after mating.
The first embryo, removed from a female deer a few weeks after mating, was very small and did not look at all like an adult animal. In deer that died in more than late dates, the embryos were larger, they had a great resemblance to small, newly born fawns. This is how knowledge in embryology accumulated.
The following scientists made significant contributions to embryology.
· Anthony van Leeuwenhoek (1632–1723) discovered sperm in 1677 and was the first to study parthenogenesis in aphids.
· Jan Swammerdam (1637–1680) pioneered the study of insect metamorphosis.
· Marcello Malpighi (1628–1694) made the first studies on the microscopic anatomy of the development of organs in the chicken embryo.
· Kaspar Wolf (1734–1794) is considered the founder of modern embryology; more precisely and in more detail than all his predecessors, he studied the development of a chicken in an egg.
· The true creator of embryology as a science is the Russian scientist Karl Baer (1792–1876), a native of the Estonian province. He was the first to prove that during the development of all vertebrate animals, the embryo is first formed from two primary cell layers, or layers. Baer saw, described, and then demonstrated at a congress of naturalists a mammalian egg cell from a dog he had opened. He discovered a method for the development of the axial skeleton in vertebrates (from the so-called dorsal chordae). Baer was the first to establish that the development of any animal is a process of unfolding something preceding, or, as they would now say, the gradual differentiation of increasingly complex formations from simpler rudiments (the law of differentiation). Finally, Baer was the first to appreciate the importance of embryology as a science and based it on the classification of the animal kingdom.
· A.O. Kovalevsky (1840–1901) is famous for his famous work"History of the development of the lancelet." Of particular interest are his works on the development of ascidians, ctenophores and holothurians, on the postembryonic development of insects, etc. By studying the development of the lancelet and extending the data obtained to vertebrates, Kovalevsky once again confirmed the correctness of the idea of the unity of development throughout the animal kingdom.
· I.I. Mechnikov (1845–1916) gained particular fame for his studies of sponges and jellyfish, i.e. lower multicellular organisms. Mechnikov's prominent idea was his theory of the origin of multicellular organisms.
· A.N. Severtsov (1866–1936) is the largest of modern embryologists and comparative anatomists, the creator of the theory of phylembryogenesis.
Individual development of single-celled organisms
In the simplest organisms, whose body consists of one cell, ontogenesis coincides with the cell cycle, i.e. from the moment of appearance, through the division of the mother cell, until the next division or death.
The ontogeny of unicellular organisms consists of two periods:
– maturation (synthesis of cellular structures, growth).
– maturity (preparation for division).
– the process of division itself.
Ontogenesis is much more complicated in multicellular organisms.
For example, in various divisions of the plant kingdom, ontogenesis is represented by complex development cycles with alternation of sexual and asexual generations.
In multicellular animals, ontogeny is also a very complex process and much more interesting than in plants.
In animals, there are three types of ontogenesis: larval, oviparous and intrauterine. The larval type of development is found, for example, in insects, fish, and amphibians. There is little yolk in their eggs, and the zygote quickly develops into a larva, which feeds and grows independently. Then, after some time, metamorphosis occurs - the transformation of the larva into an adult. In some species, there is even a whole chain of transformations from one larva to another and only then to an adult. The reason for the existence of larvae may lie in the fact that they feed on different foods than adults, and thus the food base of the species expands. Compare, for example, the nutrition of caterpillars (leaves) and butterflies (nectar), or tadpoles (zooplankton) and frogs (insects). In addition, during the larval stage, many species actively colonize new territories. For example, the larvae of bivalve mollusks are capable of swimming, while adults are practically motionless. The oviparous type of ontogenesis is observed in reptiles, birds and oviparous mammals, whose eggs are rich in yolk. The embryo of such species develops inside the egg; there is no larval stage. The intrauterine type of ontogenesis is observed in most mammals, including humans. In this case, the developing embryo is retained in the mother’s body, a temporary organ is formed - the placenta, through which the mother’s body provides all the needs of the growing embryo: breathing, nutrition, excretion, etc. Intrauterine development ends with the process of childbirth.
Direct development , in which an individual emerges from the mother’s body or egg shells, differing from the adult organism only in smaller size (birds, mammals). There are: non-larval (oviparous) type, in which the embryo develops inside the egg (fish, birds), and intrauterine type, in which the embryo develops inside the mother’s body - and is connected to it through the placenta (placental mammals).
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 its 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 for different types of ontogenesis is associated with different 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, inner layer- endoderm; the gastrula cavity represents the future intestinal cavity of the body; late gastrula - a three-layer embryo: 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 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. 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. At 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 metamorphosis?
Metamorphosis allows individuals of different ages don't 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 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 ectoderm forms nervous system, skin glands, tooth enamel, hair, nails, outer epithelium. 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 explored.
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 amount of growth is characteristic of organisms that grow only for a limited period of time, 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, stops increasing 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.
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