What is the meaning of not direct development?

Firstly, with indirect development, competition for food and habitat between adults and their offspring decreases. For example, a frog larva - a tadpole - feeds on plants, and an adult frog - insects. The tadpole and caterpillar differ from the adult forms in structure, appearance, lifestyle, nutrition. Secondly, in a number of species, for example corals, adult individuals lead an attached lifestyle and cannot move. But their larvae are mobile, which contributes to the spread of the species.

Duration of the postembryonic period in organisms different types different. For example, an Indian elephant lives up to 70 years, a chimpanzee - up to 40, a mouse - up to 3 years, trees can live for hundreds of years, and the mayfly insect - only a few days. May be direct or indirect(accompanied by metamorphosis (transformation)).

With direct development the newly emerged organism is similar in structure to the parent and differs from it only in size and incomplete development of organs.

Direct postembryonic development

Direct development is characteristic of humans and other mammals, birds, reptiles, and some insects.

The following periods are distinguished in human development: childhood, adolescence, adolescence, youth, maturity, old age. Each period is characterized by a number of changes in the body. Aging and death are the last stages of individual development. Aging is characterized by many morphological and physiological changes, leading to a general decline in vital processes and the stability of the body. The causes and mechanisms of aging are not fully understood. Death ends individual existence. It can be physiological, if it occurs as a result of aging, and pathological, if it is caused prematurely by some external factor (wound, illness).

Indirect postembryonic development

Metamorphosis represents a profound transformation in the structure of the body, as a result of which the larva turns into an adult insect. Depending on the nature of postembryonic development in insects, two types of metamorphosis are distinguished:

incomplete(hemimetabolism), when the development of an insect is characterized by the passage of only three stages - egg, larva and adult phase (imago);

full(holometaboly), when the transition of the larva to the adult form occurs at an intermediate stage - the pupal stage.

A chick hatched from an egg or a kitten born is similar to adult animals of the corresponding species. However, in other animals (for example, amphibians, most insects), development proceeds with sharp physiological changes and is accompanied by the formation of larval stages. In this case, all parts of the larva’s body undergo significant changes. The physiology and behavior of animals also change. The biological significance of metamorphosis is that at the larval stage the organism grows and develops not at the expense of reserve nutrients eggs, and she can feed on her own.

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. With incomplete metamorphosis, the replacement of larval organs occurs gradually, without cessation of active feeding and movement of the body. Complete metamorphosis includes the pupal stage in which the larva transforms into an adult animal.

In ascidians (type chordates, subtype larval-chordates), a larva is formed that has all the main characteristics of chordates: a notochord, a neural tube, and gill slits in the pharynx. The larva swims freely, then attaches to some solid surface on the seabed and undergoes metamorphosis: the tail disappears, the notochord, muscles, neural tube break down into individual cells most of which are phagocytosed. From nervous system In the larva, only a group of cells remains, giving rise to a nerve ganglion. The structure of an adult ascidian, leading an attached lifestyle, does not at all resemble the usual features of the organization of chordates. Only knowledge of the features of ontogenesis allows us to determine systematic position ascidian The structure of the larvae indicates their origin from chordates that led a free lifestyle. During the process of metamorphosis, ascidians switch to a sedentary lifestyle, and therefore their organization is simplified.

Periods of postembryonic development

Fast embryonic development Animal life is divided into three periods: juvenile, maturity and aging.

Juvenile period characterized by the continuation of organogenesis that began in embryonic life and an increase in body size. By the beginning of this period, all organs are developed to such an extent that the young animal can exist and develop in the environment. The nervous, circulatory and excretory systems perform their functions.

With the release of the body from the embryonic membranes, the respiratory organs begin to function, digestive system and sense organs. During the juvenile period, the species and individual characteristics of the organism are finally formed and the individual reaches the size characteristic of the species.

Later than other organs, the reproductive system develops. When its formation ends, the second stage of postembryonic development begins.

During period of maturity reproduction occurs. The duration of this period varies among different animal species. In some species it lasts only a few days, in others it lasts many years.

Aging period characterized by a slowdown in metabolism and organ degradation. Aging leads to natural death.

Direct and indirect development

The juvenile period is characterized by direct or indirect development

At direct development an individual is born that is similar to an adult, but much smaller in size. Its further development comes down mainly to growth and puberty.

Direct development is typical for animals with oviparous and intrauterine ontogenesis: mammals, birds, reptiles, some invertebrates (oligochaete worms, spiders, etc.).

At indirect development organism born larva) differs in structure and lifestyle from adult individuals. In order for a larva to become an adult, a restructuring of its body is required - transformation or metamorphosis.

Metamorphosis - a rapid change that occurs during the transition from the larval stage to the adult form.

Example:

The frog larva (tadpole) does not look like an adult amphibian, but looks like a fish (no limbs, gill breathing, lateral line, etc.). The organs of adult amphibians gradually develop.

Frog tadpoles

Indirect development of insects occurs With complete transformation (With complete metamorphosis) Andwith incomplete transformation(with incomplete metamorphosis).

During development with complete transformation, a larva appears from the egg, which feeds, grows, and then turns into a pupa. Inside the motionless pupa, a complete restructuring of all organs occurs. An adult insect (imago) emerges from the pupa.

Complete transformation is typical for Lepidoptera (butterflies), Coleoptera (beetles), Diptera (flies and mosquitoes), Hymenoptera (bees, wasps, bumblebees), etc.

Development with incomplete metamorphosis occurs when the pupal stage is missing. During the molting process, the larva gradually turns into an imago. Incomplete transformation is typical for cockroaches, hemipterans (bugs), orthoptera, and dragonflies.

Comparison of direct and indirect development

Advantages direct development of organisms:

• the development of the organism into an adult (juvenile period) usually occurs in a shorter period of time;
• There is no significant restructuring of the body and therefore less energy and nutrients are required.

Flaws direct development of organisms:

• required for embryonic development a large number of nutrients in eggs or intrauterine development of offspring;
• With overpopulation, intraspecific competition between young and mature individuals intensifies, since they need the same life resources.

Advantages indirect development of organisms:

• in many animal species, larvae and adults occupy different ecological niches- this reduces intraspecific competition;
• In sedentary or attached animals, the larvae contribute to the spread of the species and the expansion of its range.

Flaws indirect development of organisms:

• development into an adult usually takes a long period of time;
• metamorphosis requires a lot of food and energy.

In time, life is organized as a succession of generations of organisms. Organisms of each generation carry out a natural development process or life cycle. The most demonstrative life cycle is of multicellular plants and animals that reproduce sexually, which begins with one cell - the zygote. The transformations of cells formed as a result of the division of the zygote and its descendants that take place in a certain sequence* determine the growth of the organism and the release of cells in it different directions specialization and parts differing in structure and functions, and finally, achieving a state of maturity. A mature organism performs the main biological task - the reproduction of individuals of the next generation. Subsequently, the body ages, which manifests itself in a decrease in its level of vital activity. The life cycle ends with death. The life cycles of some unicellular eukaryotes and microorganisms are often exhausted by the cell cycle. Their complication is associated with the possibility of the formation of cysts or spores and the inclusion of the stage of sexual reproduction. The life cycle of some colonial protozoa, such as Volvox, serves as a transitional form between the cycles of unicellular and multicellular organisms. Unlike unicellular organisms, they have a stable selection of generative and somatic cell lines in the development, but there is no diversity of morphofunctional specializations of somatic cells. In many protozoa and lower multicellular organisms, the cycles are characterized by a high degree of complexity.

A set of interconnected and deterministic chronological events that naturally occur in the process of implementation by the body life cycle, are designated by the terms “ontogenesis” or “individual development”.

With direct development, the embryonic period ends with the birth of a young form that has overall plan structures, a set of organs and systems, characteristic of a mature state, but characterized by smaller sizes, functional and structural immaturity of organs and systems. This type of development is characteristic of animals that lay eggs with a high yolk content.

Characteristic features of the type of development placental mammals and man. It is a variant of direct development, but differs in that immediately after the end of the embryonic period after birth, the new organism is not capable of an independent lifestyle, since it needs specific nutrition - the secretion of certain glands of the mother's body (milk).

Changes in individual development manifest themselves at different levels of organization of the individual - genetic, molecular-biochemical, cellular, tissue, organ, systemic. Research on individual development is carried out with the participation of specialists from many branches of biological science - geneticists, biochemists, morphologists, embryologists, and molecular biologists. The strengthening of the role of interdisciplinary studies of ontogenesis, which emerged at the beginning of this century, led to the emergence of an independent field of science about living things - developmental biology. She studies the hereditary, molecular, structural basis, as well as the mechanisms of regulation of ontogenetic changes at all stages of the life cycle of an individual.

The basis of the process of individual development is the hereditary information received by descendants from their parents. It is enough, however, to compare, for example, a person at the initial, single-cell stage of ontogenesis and in adulthood to come to the conclusion that during development the amount of information reproduced in the structures and metabolism of the body increases. This is evidenced, in particular, by the greater variety of chemical compounds, their non-random distribution in organs, the presence of the organs themselves, and much more that we observe in an adult and are not found in the zygote. The accumulation of information during development is an important feature of ontogenesis and indicates its systemic nature. The primary hereditary information of the zygote plays the role of instructions, according to which, with the active regulatory influence of factors environment In a developing organism, molecules and structures of different levels of complexity are consistently formed and naturally interact with each other. Taking into account this remark, ontogenesis can be defined as the process of implementation by a descendant of the hereditary information of the parents under certain environmental conditions. This definition emphasizes that genetic patterns play important role in individual development, but do not exhaust its entire content.

In addition to embryonic development, growth, and aging, developmental biology also studies the molecular genetic, cellular and systemic mechanisms of regeneration - a set of processes that determine the restoration of structures worn out during the life of the body or lost due to injury.

Ontogenesis and its periodization. Ontogenesis is a continuous process of development of an individual. However, for the convenience of study, and also due to the fact that at certain stages there is a change in the prevailing molecular, cellular and systemic mechanisms and the nature of the relationship of the organism with the environment, the ontogenesis of multicellular organisms is divided into periods and stages. Several schemes for the periodization of individual development have been proposed. In accordance with one of them, which is widespread, the embryonic and postembryonic periods are distinguished. In placental animals and humans, prenatal (antenatal) and postnatal (postnatal) periods are distinguished. The first covers development before the birth of the individual and occurs under the cover of the egg membranes, and in placentals in the maternal body. During this period, environmental factors have an indirect effect on the developing organism. After birth, with the beginning of the postnatal period, the conditions of existence of the organism change fundamentally. He starts independent life, entering into direct interaction with the environment.

The named periods of ontogenesis are divided into stages that differ in the specific content of changes. In animals that reproduce sexually, the embryonic period is represented by the following stages: unicellular (zygote), cleavage (formation of a single-layer blastula embryo), gastrulation (formation of a three-layer embryo), histo- and organogenesis (formation of tissues and organs). In the first 8 weeks, the developing human body is called an embryo or fetus, which corresponds to its passage through the embryonic stage. From the 9th week the fetal stage of development begins. The body acquires characteristic external forms, and organ anlages are separated in it. At this stage it is called a fetus.

In the postnatal period, with the direct type of development, early and late postnatal ontogenesis are distinguished. At the same time, early postnatal ontogenesis includes the period of life before the acquisition of features of structural, functional and reproductive maturity, and late postnatal ontogenesis includes the period of life corresponding to the mature state and aging of the organism. The further division is carried out in more detail for humans. It is substantiated by the results of a study of age-related physiology and medicine. Thus, in early postnatal ontogenesis of a person, the periods of newbornhood, infancy, preschool and school age, and puberty (puberty) are distinguished. Isolating them helps optimal solution practical tasks of pediatrics, since early postnatal ontogenesis is characterized by a relatively rapid change in the functional indicators of various organs and systems of the body. Accordingly, the requirements for the nature of nutrition, the hygienic regime, as well as endurance in relation to temperature, physical, and emotional stress change.

The scheme of periodization of ontogenesis, which we will adhere to in the future, follows from the essence of the genetic mechanisms of individual development, which is considered as a process of implementation of hereditary information, which determines the achievement of a state of maturity and the participation of the organism in reproduction. In this scheme, reflecting general biological patterns, pre-reproductive, mature (active reproductive) and post-reproductive periods are distinguished. The first of them, starting from the moment of formation of the zygote, is limited to the achievement of puberty and can also be called the period of development of the definitive phenotype, the second - the period of stable functioning of organs and systems, the third - the period of aging of the body. One of the main criteria for identifying periods according to the given scheme is the participation of the organism in reproduction, which creates difficulties in establishing the exact boundaries of the periods. In particular, in mammals and humans, the state of sexual maturity is often achieved by the developing organism before it actually gets the opportunity to actively participate in reproduction. The reproductive and post-reproductive periods of a woman’s ontogenesis are distinguished quite clearly (menopause). An aging man retains the ability to reproduce, but his activity in this regard decreases. Accordingly, the share of participation in the formation of the gene pool of the next generation decreases. Due to its social nature, the biological criterion of maturity used in the scheme under consideration, in relation to a person, is supplemented with indicators of learning effectiveness, labor activity, creative activity of people at different age periods.

The pre-reproductive period includes embryonic development and early postnatal ontogenesis, distinguished according to the first periodization scheme. Although the act of birth fundamentally changes the nature of the relationship between the organism and external environment, in the early postnatal period in comparison with the embryonic period, the main direction of development is preserved. In particular, morphogenesis processes continue, the growth of the organism continues, changes occur in the cellular composition and intertissue relationships in various organs. However, if in the embryonic period formative processes dominate, then in early postnatal ontogenesis these processes are replaced by ordinary forms of life activity characteristic of each organ in adulthood.

IN Lately There are grounds for identifying a pre-embryonic (pre-embryonic) period in individual development, which corresponds to gametogenesis. This separation is justified by the fact that in addition to the production of nutritional material of the yolk embryo in oogenesis, some biologically important macromolecules are synthesized and stored in the cytoplasm of oocytes before the onset of development, for example, messenger RNAs that control early stages embryogenesis.

DIRECT AND INDIRECT DEVELOPMENT OF ORGANISMS

Direct development occurs without transformation. In this case, the newly born organism differs from the adult only in size, proportions and underdevelopment of some organs. This development is observed in a number of insects, fish, reptiles, birds and mammals. So, from the eggs of a fish a fry emerges, similar to an adult individual, but differing from it in size, underdevelopment of scales and fins, and a person gives birth small child who cannot walk, talk, etc.

In insects such as grasshoppers, locusts, and aphids, the egg hatches into an adult-like larva that grows, molts, and develops into an adult insect or adult.

During development and transformation from an egg, a larva appears that is completely different from the adult organism. Such development is called indirect or development with metamorphosis, i.e. the gradual transformation of the organism into an adult. The larvae grow and feed, but in most cases they are not capable of reproduction. Development with transformation is characteristic of a number of insects and amphibians. In insects, during development with complete transformation, an individual goes through several successive stages, differing from each other in their lifestyle and feeding pattern. For example, in the May beetle, a caterpillar emerges from an egg, which has a worm-like body shape. The caterpillar then, after several molts, turns into a pupa, a stationary stage. The pupa does not feed, but develops after some time into an adult insect.

The methods of obtaining food are different for a caterpillar and an adult beetle. The caterpillar feeds on underground parts of plants, and the beetle feeds on leaves. In some species, adults do not feed at all, but immediately begin to reproduce.

Among vertebrates, development with metamorphosis occurs in amphibians. A larva emerges from the egg - a tadpole. Outwardly, it resembles a fish fry, breathes through gills and moves with the help of fins. After some time, his limbs form, his lungs develop, and his tail disappears. Two months after emerging from the egg, the tadpole develops into an adult frog. However, some amphibians develop with incomplete metamorphosis, such as axolotls. Their larvae, which are quite large in size, live in water, have five-fingered limbs, breathe with gills and are capable of reproduction.

Depending on the type of reproduction, fish are divided into egg-laying, ovoviviparous, and viviparous.

Spawn-marking- the main group of fish that spawn eggs into the water column, where fertilization occurs.

Ovoviviparous– fertilization is internal, the embryo develops in the female’s body in special extensions of the oviducts, but is nourished by the nutrients of the yolk sac, and the mother’s body serves only as protection from external factors.

Viviparous– in these fish, the union of the egg and sperm occurs in the female’s genital tract, the formation of the placenta occurs, which ensures the connection of the mother’s body with the embryo and supplies nutrients.

Live birth is a rare occurrence, typical for aquarium fish(guppies, swordtails), sharks. There is no larval stage; an embryo develops in the oviducts of the female, and an already formed fry is born, which is capable of independent existence.

Features of fish reproduction

Fish are dioecious animals. Females produce eggs - eggs that develop in the ovaries and have a thin, translucent membrane for quick and easy fertilization. Moving along the oviducts, they exit through the external opening located near the anus.

Males form sperm in paired testes - milk, which is a system of tubules that flow into the excretory duct. There is an expanded part in the vas deferens - this is seminal vesicle. The laying of eggs and the release of seminal fluid occurs almost simultaneously.

Exception - rock perch, has gonads of two sexes, but they do not mature at the same time, which prevents self-fertilization.

It is typical for fish only sexual reproduction , by the fusion of male and female reproductive cells.

The process of laying eggs by females and fertilizing them with sperm from males is called spawning. During the spawning period, fish look for favorable conditions for the development of offspring, so they often leave their usual habitats. Some move from the seas to the mouths of the rivers flowing into them, while others, on the contrary, rush to the seas.

If, due to unfavorable conditions, the fish were unable to spawn, they are characterized by resorption of eggs and milt (gradual resorption of the reproductive material).

Fertilization in most cases is external; the larva develops outside the female’s body (live birth is rare).

Fish lay eggs in huge quantities (from 100 thousand to millions of eggs). Such fertility ensures the preservation of the species, because not all eggs will be fertilized, and some will die altogether.

When the eggs are spawned, sperm can enter the egg through a special hole - micropyle. After the fusion of germ cells, the egg membrane becomes more permeable (adsorbs water) and stronger.

After fertilization is complete, eggs form zygote, in which multiple divisions occur with the formation of a multicellular embryo. In the abdominal region, the remains of the yolk sac are preserved, which provides nutrition to the larva in the first days.

Larval stage begins with the rupture of the egg shells, when the formed individual comes out and begins to feed on its own (single-celled organisms, crustaceans, algae). The body shape is elongated, large eyes, and no fins.

In the first days, the larva hangs motionless, attached to some substrate, and after depleting its supply of nutrients, it begins to actively move in search of food. During this period, scales begin to form. Small fish have functioning temporary organs that are needed for survival in a new environment:

• Fin fold;
• additional external gills;
• blood vessels.

This stage is also called critical; if the larvae cannot find food, their mass death will occur.

For fry stage Characteristic is the reduction of temporary organs and the formation of a structure similar to that of adult individuals. From this stage, the fish looks like all representatives of the species, only smaller in size. The body is completely covered with scales, fins of all types are formed.

Adult fish has fully formed systems and organs, is covered with mucus and scales, has glands and sensory organs. Having reached sexual maturity, they soon begin to reproduce.

What kind of development do fish have: direct or indirect?

Indirect development occurs in larvae, which, when emerging from the egg, do not resemble the adult. Such organisms develop gradually, acquiring the characteristics of their parents through a series of successive stages, differing in their mode of nutrition and lifestyle.

After the eggs ripen, a larva emerges from it, with undeveloped fins and scales, and in appearance it is not similar to the adult. Therefore, such fish belong to organisms with an indirect type of development (mainly bony fish).

When babies are born that are similar to adult organisms, only smaller in size and with incompletely formed organs, such development is called direct. Thus, fish that are characterized by viviparity (for example, sharks) develop in a direct way.

Caring for offspring

The spawning of eggs in large quantities is due to the fact that fish do not tend to care about their offspring. The eggs left behind die from enemies, drying out, and unfavorable conditions; only a relatively small part can survive to the stage of a mature individual.

Some fish that care for their young choose spawning sites in crevices, build nests for protection, or carry eggs in their mouths. Thus, a female salmon uses her caudal fin to clear a place for laying eggs, making a depression on the sandy bottom, then covers the eggs with sand (protecting them from predators and freezing).

Parents provide constant access of oxygen to their offspring and use their fins to aerate the water. To prevent the eggs from drying out, the male waters them with water from his mouth. Manifestations of care in fish are at the instinctive level, when the larvae are able to obtain food on their own, can swim well, and their parents leave them.

The grasshopper develops

1) indirect

2) with a doll

4) with complete transformation

Explanation.

In all insects, development is indirect (with metamorphosis, with transformation). The transformation can be complete or incomplete.

Complete: egg, larva, pupa, adult insect. Characteristic of butterflies (Lepidoptera), beetles (Coleoptera), mosquitoes and flies (Diptera), bees (Hymenoptera), etc.

Incomplete: egg, larva, adult insect (no pupal stage). Characteristic of grasshoppers and locusts (Orthoptera).

So, in the grasshopper, development is indirect with incomplete transformation.

Guest 27.05.2012 00:24

THE GRASSHOPPER HAS DIRECT DEVELOPMENT WITH INCOMPLETE TRANSFORMATION, ANSWER NUMBER - 3!!! (Direct postembryonic development is when a born organism differs from an adult in its smaller size and underdevelopment of organs. In the case of direct development, a young individual is not much different from an adult organism and leads the same lifestyle as adults)

Guest, you are wrong :(

Grasshopper - insect - development is indirect, without transformation, takes place in 3 stages.

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, various worms.

Anya Plahotniuc (Comrat) 26.10.2012 00:05

The most ancient groups of insects (cockroaches, grasshoppers, dragonflies) have direct development.

In confirmation, an excerpt from the encyclopedia: “Grasshoppers are insects with direct development, which means that their larvae are similar in appearance to adults and differ only in size (in other insects the difference in the structure of the imago and larvae can be enormous) and the absence of wings.”

http://www.animalsglobe.ru/kuznechiki/

Natalia Evgenievna Bashtannik (Novocherkassk)

Anya, you can remain unconvinced, but insects have an INDIRECT type of development.

And I trust this site more than the one you indicate

http://sbio.info/page.php?id=127

Natalia Evgenievna Bashtannik (Novocherkassk)

Yes, everywhere, everywhere they write correctly:

indirect with incomplete transformation

Anastasia (Irkutsk) 20.02.2013 07:39

The grasshopper has incomplete development. To confirm my words, I would like to cite an excerpt from Green’s “Biology” (World, 1990, pp. 137-138):

"As a rule, each subsequent larva (nymph or instar) becomes more and more similar to an adult insect. This type of development is called hemimetabolic metamorphosis. It is divided into gradual metamorphosis, when nymphs and adult forms occupy the same habitats and feed on the same food as adults , and incomplete metamorphosis, when nymphs develop adaptive characteristics that allow them to develop other habitats and eat food different from that of an adult insect."

On page 142 there is a table showing the characteristics of hemimetabolic metamorphosis:

“Direct development; External rudiments of wings; Immature forms - nymphs similar to adult forms,” and examples are also given: orders Mayflies, Cockroaches, True locusts.