Ontogenesis of animals

Comparison of vertebrate embryos at different stages of embryonic development. The sadly famous illustration of the work of Ernst Geckel, on which the differences between embryos are artificially understated, for the sake of greater compliance of the theory of recapitulation (repetition of phylogenesis in ontogenesis). It should be noted that the falsification of this illustration does not cancel the fact that embryos are usually indeed more similar to each other than adult organisms, which was noted by embryologists even before the emergence of the theory of evolution.

Ontogenesis is divided into two periods:

1. embryonic - from the formation of zygotes before birth or exit from egg shells;
2. post-emptil - from the exit from egg shells or birth to the death of the body.

Embryonic period

In the embryonic period, three main stages are distinguished: crushing, gastration and primary organogenesis. Embryonic, Or the embryonic, the period of ontogenesis begins from the moment of fertilization and continues until the release of the embryo from the egg shells. In most vertebrates, it includes stages (phases) crushing, gastralization, histo and organogenesis.

Splitting up

Crushing - a number of consecutive mitotic divisions of fertilized or initiated to the development of an egg. Crushing is 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 Blastula (Single-layer embryo). At the same time, the mass of the embryo and its volume does not change, that is, they remain the same as the zygota, and the egg is divided into more and more small cells - Blastomers. After each division of crushing, the nucleus becomes becoming more small, then nuclear plasma relations change: the kernel remains the same, and the volume of cytoplasm decreases. The process proceeds until these indicators reach the values \u200b\u200bcharacteristic of somatic cells. The type of crushing depends on the amount of yolk and its location in the egg. If the yolk is small and it is evenly distributed in the cytoplasm (olecital eggs: iglojee, flat worms, mammals), then crushing proceeds by type full uniform: Blastomers are the same in size, the whole egg is crushed. If the yolk is unevenly distributed (telolecital eggs: amphibians), then crushing proceeds by type full uneven: Blastomers - different quantities, those that contain yolks are larger, the egg is crushed entirely. In case of incomplete crushing of the yolk in the eggs, so many that crushing grooves cannot divide it entirely. Crushing the egg, which is crushed only concentrated on the animal pole "cap" of cytoplasm, where the zygota core is called incomplete discoomal (Telolecital eggs: reptiles, birds). For incomplete surface fraction In the depths of the yolk, the first synchronous nuclear fissionnot accompanied by the formation of intercellular boundaries. The kernels surrounded by a small amount of cytoplasm are evenly distributed in the yolk. When they become quite a lot, they migrate to the cytoplasm, where, then, after the formation of intercellular boundaries, blastoderma arises (centolecital eggs: insects).

Gastral

One of the mechanisms of gastroaction is invagination (prying part of the wall of Blastuly inside the embryo) 1 - Blastuly, 2 - Gastraul.

Primary organogenesis

Primary organogenesis is the process of forming a complex of axial organs. In different groups of animals, this process is characterized by its peculiarities. For example, at the chord, at this stage there is a laying of a nervous tube, chords and an intestinal tube.

In the course further development The formation of the embryo is carried out at the expense of growth processes, differentiation and morphogenesis. Growth ensures the accumulation of the cell mass of the embryo. During the differentiation process, various specialized cells arise, forming various fabrics and organs. The morphogenesis process ensures the acquisition of a prophetic form.

Post-emptilic development

Slock

Wikimedia Foundation. 2010.

Watch what is a "embryonic period" in other dictionaries:

embryonic period - Embryology of the animal embryonic period, the germ period - a period in which the embryo turns into a fruit. From the fertilized egg, an organism arises, which has primitive bookmarks of various organs and systems. Form and occupy their ... General Embryology: Terminology Dictionary

Embryonic period - (Embryonic Period). The second period of prenatal development, which continues from the end of the 2nd week to the end of the 2nd month of pregnancy (counting from the moment of conception). All major structures and individuals of the individual are formed during this period ... Psychology of development. Dictionary on the book

Embryonic, embryonic, embryonic (book.). arr. To embryo, which is an embryo, germ. Embryonic development. || Occurred during the development of the embryo, successful. Embryonic period. Dictionary Ushakov. D.N. Ushakov ... Explanatory Dictionary Ushakov

Embryonic stage - in plants that breed seeds, the period of formation of the embryo and seed, from the fertilization of the egg and before the start of the germination of the seed; In vegetatively breeding plants, the period of the formation of the kidneys in the organs of vegetative reproduction, from ... ... Dictionary of Botanical Terms

Male Pubertat (increasing hair cover) Pouring period of puberty. It is individual and can vary in some limits, depending on racial, geographical and other conditions. Conditionally, it is considered to be age from ... ... Wikipedia

"Introduction to general biology and ecology. Grade 9. "A.A. Kamensky (GDZ)

Embryonic and post-brand periods of development of the body. Biogenetic law

Question 1. What starts and how does the embryonic development period ends?
Embryonic period (Greek. Embryon - Germ) begins with fertilization and education of zygota. The end of this period with different types of ontogenesis is associated with different points of development.
The embryonic period is divided into the following stages:
1) fertilization - the education of the zygota;
2) crushing - the formation of Blastuly;
3) gastrules - the formation of germinal sheets;
4) histo and organogenesis - the formation of organs and tissues of the embryo.
In the larval form of ontogenesis, the embryonic period begins with the formation of zygotes and ends with an outlet of the egg shells.
With the non-sinic form of ontogenesis, the embryonic period begins with the formation of zygotes and ends with an output of germinal shells.
With the intrauterine form of ontogenesis, the embryonic period begins with the formation of zygotes and lasts before birth.

Question 2. What starts and how does the post-emptil development period ends?Post-Imbrium period Begins birth (for example, in mammals) or the exit of the organism from egg shells (for example, in reptiles, birds) and lasts until the end of his life. From the moment of the birth of the body or the exit of the body from the egg shell, the period of post-mixed development occurs. Post-emptilic development can be direct when a creature similar to adults (reptiles, birds, mammals) appears from the egg or the mother's body, when the larva formed in the embryonic period is easier than an adult organism, and differs from it in power supply, movement et al. (Intestine, flat and killed worms, crustaceans, insects, amphibians).
Post-emptilic development of animals is divided into three periods:
Growth and formation period (expensive). This period is characterized by a continuation of the organogenesis that began in the embryonic life and an increase in body sizes. By the beginning of this period, all organs achieve the degree of differentiation, in which the young animal can exist and develop outside the organism of the mother or outside the egg shells. From this point on, the digestive tract, respiratory organs and the senses organs begin to function. Nervous, blood and excretory systems begin their function still in the embryo. During the growth period and formation, the species and individual characteristics of the body are finalized, and the individual reaches characteristic of the size of the sizes. Later, the field system is differentiated by other organs. When its formation ends, the second stage of post-emptilic development comes.
The period of maturity (reproductive). During this period of maturity, reproduction occurs. The duration of this period in various animal species is different. In some species (rods, a taled silkworm), it lasts only a few days, from others - for many years.
Old age period (postproindulative). It is characterized by a decrease in the intensity of metabolism and the involution of the organs. Aging leads to natural death.

Question 3. What bodies are formed from ectoderma; Entoderm; Mesoderm?
At the end of the crushing period, the embryos of all multicellular animals enter into the formation of germinal layers (leaflets). This stage is called gastralization.
In the process of gastralization distinguish two stages. First, an early gastrol is formed, having two germinal leaf: external - ectoderm and internal - Entoderm. Then the late gastrol occurs when the average germinal sheet is formed - Mesoderma, the third layer of cells appears at this stage, which is laid between the ecto and entoderma. Initially, it has the form of two pockets, whose cavities are called the secondary cavity of the body. In the embryo, the chordovyov comes after this stage of neurules - an axial complex is formed, consisting of chords and nervous records located in parallel to each other. The chord arises from the Entoderma (more precisely from the chordomezodermic), and the nervous plate is from Etoderma. In the future, cell differentiation is underway: coating epithelium, enamel of teeth are formed from the ectoderm nervous system, senses. From Entoderma - intestinal epithelium, digestive glands, lungs. Mesoderma is a skeleton, muscles, a blood system, excretory organs, a genital system. All animals and a person have the same germinal sheets of the same organs and fabrics. This is just indicating that germinal sheets are homologous and have a single origin in evolution.

Question 4. Give examples of animals with direct and indirect development.
Post-emptilic development can be direct when a creature similar to adults (reptiles, birds, mammals) appears from the egg or the mother's body, when the larva formed in the embryonic period is easier than an adult organism, and differs from it in power supply, movement et al. (Eastern, flat and ringed worms, crustaceans, insects, amphibians).

Question 5. What is the importance of a biogenetic law?
Biogenetic lawF. Muller and E. Hekkel, formulated by F. Muller and E. Geckel, allows you to use these embryology to recreate the stroke of the historical development of the form.

The projectal period preceding the education of the zygota is associated with the formation of Games. Otherwise, it is Gametogenesis (Ovogenesis and Spermatogenesis).

The processes characterizing the ovogenesis lead to the formation of a haploid set of chromosomes and the formation of complex structures in the cytoplasm. RNNA and I-RNA accumulates in the egg, yolk accumulation is accumulated . The type of development of ontogenesis depends on the amount of yolk and its distributions.

Depending on the amount of yolk, 4 types of egg cells are distinguished:

1) polyletcital (Many yolk; lecitos - gr. Yolk);

2) Mesolecital (average yolk);

3) oligolecital (small yolk quantity);

4) Alecital (Yolk is almost absent).

Fig. 1. Types of eggs for the distribution of yolk: a - alecital, b - isolecital, in - telolecital, g - centolecital.

By the nature of the distribution of the yolk eggs are divided into 3 types:

1) isolecital or gomolecital (With a uniform distribution of yolk on an egg), in the number of yolk, they are more often oligo or sharp. Examples: Eggs of oskulkin, lower chord, mammals.

2) telolecital (yolk focuses on the vegetative pole; Greek. End); In the content of yolk, these eggs are most often poly- or meslecital. Examples: Mollusks, fish, amphibians, reptiles, birds.

3) centolecital (Yolk focuses in the center of the cell, and cytoplasma on the periphery and inside the kernel). Examples: Eggs of insects, in the content of the yolk, is most often oligo or meslecital eggs.

1.5. Embryonic period

The embryonic period (Greek. Embryon - the embryo) begins with fertilization and education of the zygota. The end of this period with different types of ontogenesis is associated with different points of development.

Embryonic period It is divided into the following stages:

1) fertilization - the education of the zygota;

2) crushing - the formation of Blastuly;

3) gastrules - the formation of germinal sheets;

4) histo and organogenesis- formation of organs and tissues of the embryo.

In the larval form of ontogenesis, the embryonic period begins with the formation of zygotes and ends with an outlet of the egg shells.

With the non-sinic form of ontogenesis, the embryonic period begins with the formation of zygotes and ends with an output of germinal shells.

With the intrauterine form of ontogenesis, the embryonic period begins with the formation of zygotes and lasts before birth.

1.5.1. Zygote.

The zygota- single-cell stage of development of the new organism. In the zygote allocate the stage of two pronuclei and the stage of Sinkarion. The stage of two pronuclei precedes the stage of Sinkarion. The spermatozoa penetrates the egg, but the core of the spermatozoa and the eggs have not yet merged. The Stage of Sinkarion is characterized by the merger of the nuclei. As a result of synicoogamia, the diploid set of chromosomes is restored. After the formation of Sinkarion, the zygota embarks on crushing.

Fig.2. Fertilization in mammals. A - spermatozoa penetrates the egg; B - The core was formed from the sperm head, and from the neck - Centriol. 1- Egg core, 2 - spermatozoa, 3 - perceiving tuberculosis, 4 - centriole, 5 - spermatozooid core.

1. Where does the embryo grow mammals?

The fertilized egg falls into the uterus, where it is the process of its consolidation and development.

2. What is zygote?

The zygote is a single-cell stage of the development of the body, which arises as a result of the merger of the sperm and egg.

Questions

1. What starts and how does the embryonic development period ends?

The embryonic period (embryogenesis) begins at the time of the formation of the zygote and ends with birth (for example, in mammals) or exit from egg shells (for example, birds).

2. What starts and how does the post-brand development period ends?

The post-embryonic period begins from the moment of birth or the exit of the body of the egg shells and lasts until the end of the life of the individual.

3. What development is called direct? Give examples of animals with direct development.

Post-emptilic development is called direct when a creature similar to adults (reptiles, birds, mammals) appears from the egg or organism of the mother.

4. What development is indirect? Give examples of animals with indirect development.

Post-emptilic development is called indirect when the larva formed in the embryonic period is easier than an adult organism, and differs from it in power supply, movement, etc. (intestine, flat and ringed worms, crustaceans, insects, amphibians).

5. What is the biogenetic law of Muller-Geckel?

Individual development of individuals (ontogenesis) to a certain extent repeats historical development species (phylogenesis), to which this particular belongs.

6. What is the importance of a biogenetic law?

Biogenetic law is very important because it testifies to the general ancestors of animals belonging to various systematic groups. It allows you to use embryology data to recreate philogenesis.

Tasks

1. Using knowledge obtained in the study of the "Animals" section, provide examples of post-computer development related to lifestyle variation, habitat.

A frog, for example, develops a larva (tadpole) from eggs, which differs from adult animals in structure, lifestyle and habitat. Upbeat, like fish, there are gills, side line, tail, two-chamber heart, one circle circulation. The larva is powered, grows and over time turns into a frog.

The presence of a larval stage in the development of amphibians and many other animals provides them with the opportunity to live in different environments and use different sources of food. So, the headastrum lives in water and eats vegetable food, and the frog leads mainly ground lifestyle and feeds on animal food.

Change of habitat and, as a result, changing the lifestyle of the animal when it moves from the larvae to an adult organism reduces intraspecific competition. In addition, some sedentary or attached animals ( coral polyps, Oysters, Mussels, etc.) Free-peeling larva contributes to the settlement of the species, expanding its range. This avoids overpopulation, which would lead to increased competition for food and other resources that threaten the survival of the species.

2. B. early period Development The heart of the human embryo consists of one atrium and one ventricle. Relying on the provisions of the biogenetic law, comment on this fact.

The human embryo in the process of individual development repeats the accuracy of the evolution (two-chamber heart - a sign of fish).

During the classes

1. Organizational moment.

2. Check d / s:

a) give the definition of words: mitosis, meyosis, gamets, zygota, gametogenesis, ovogenesis, spermatogenesis;

b) the story of students about the bunch of reproduction;

c) Student story about sexual reproduction.

3. Message Themes and objectives of the lesson: "Individual development of the body."

Teacher's word:

So, with sexual reproduction, the beginning of the whole organism gives one cell - the zygote, with a bunch of reproduction - one or several cells of the parent individual.

But in any case, so that a small number of cells turns into a full-fledged organism, a number of complex transformations are needed.

4. Work on new material.

Ontogenesis ( individual development The organism) is the period of development of the body from the origin and education of the zygota to the end of the life of the individual.

Ontogenesis is divided into 2 periods: embryonic and post-emptilic development.

5. Embryonic development (embryogenesis, on the example of the lancing).

Embrygenesis is the development of the body since the formation of the zygota before the birth or exit from egg shells.

Stages of embryogenesis:

a) Blastuly (crushing) - during which the zygota is divided by mitosis, and cells formed during crushing, less zygota.

Crushing ends with the formation of Blastuly - hollow ball or bubble; Blastuly cells - blastomeres (located on the surface).

The Blastuly cavity is called Blastocel, and the process of the formation of a single-layer embryo - blasting.

b) gastrol (gastruption) - the formation of a two-layer embryo, and a two-layer ball - gastrol.

The outer layer of cells (or germs) is called Entoderma.

The cavity inside the gastrul is the primary intestine, and the opening leading to the primary intestine is a primary mouth (they are formed by fusing or moving cells).

c) Neurula - the formation of the third germinal sheet - Mesoderm. The peculiarity of the stage is that the formation of tissues and organs of the future organism begins (organogenesis).

Derivatives of embryonic leaves.

6. Post-empty development.

This is the development of the body from the moment of birth and lasts until the end of the life of the individual (exit from egg shells).

Post-emptilic development is divided into 3 periods:

1. Effective - the growth of the body, development and puberty.

2. Reproductive - active functioning of an adult organism, reproduction.

3. Pospertivative - aging, gradual fussing of life processes.

Types of development:

a) direct,

b) indirect (with metamorphosis):

1) Complete transformation (except for the larva stage there is a pupae stage - butterflies, beetles),

2) incomplete transformation (there is a larva, but no dolls - grasshoppers, thaws).

7. Biogenetic law (embryo comparison).

K. Baer formulated the law of germinal similarity: "within the type of embryos, starting from the most early stages, reveal the well-known common resemblance. "

Muller and Geckel formed a biogenetic law: "ontogenesis is a brief repeating phylogenesis."

The value of the biogenetic law - it indicates the general ancestors of animals belonging to various systematic groups.

8. "The story has not born baby. Abortion."

Fragment of the film: "Development of a human embryo on weeks" (Discussion of the act of failed mom and harm abortion).

9. Sorry (consolidation).

10. Summing up.

1) What starts and how does the embryonic development period ends?

2) What starts and how does the post-brand development period ends?

3) What bodies are formed from ectoderma? Entoderm? Mesoderm?

4) Give examples of animals with direct and indirect development.

5) What is the significance of a biogenetic law?