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Types of Asexual Animals' Reproduction

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Asexual animals reproduce, the practical value of which is small. Therefore, it was studied in animals, little. But the achievements in its study, writes O. M. Ivanova-kazas, may be key in solving the problem of aging. The summary of the accumulated data on asexual reproduction of animals is written By O. M. Ivanova-kazas. This book and the book of B. p. Tokin “Regeneration and somatic embryogenesis”, were fundamental for the formation of the following views on the formation of the processes of aging, inflammation and oncogenesis in the course of evolution.

Asexual reproduction is always associated with destruction in the body of the individual. Among modern primitive animals, the largest amount of destruction in normal ontogenesis is observed in sedentary modular animals. Probably the first Metazoa on Earth the situation was the same as them, and this destruction – evolutionary predecessors of the devastation taking place now in the unitary types in aging, inflammation and carcinogenesis. To understand why this, and not otherwise, the body is destroyed by aging, inflammation and oncogenesis, it is necessary to answer why this, and not otherwise, occur destructive processes of normal ontogenesis in sedentary modular animals. Consider the destructive processes occurring in normal ontogenesis in sedentary modular species.

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Morphogenetic adaptations of sedentary modular animals

The ability to age, undergo inflammatory processes and form a malignant tumor – the emergent properties of the individual. (An emergent property is a property of a system that is missing from its elements and is the result of its integrity.) To discuss the nature of aging, inflammation and oncogenesis, it is convenient to use the terms of the theory of functional systems [4]. According to it, the unit of activity of the body is a functional system. It is a a set of coordinated interrelated processes aimed at achieving a useful result for the body. For the emergence of a functional system requires motivational excitation. It appears because of one or another need of the body. Deployed functional system by passing through the stages of synthesis of the signals from the endo – and actication, decision-making, formation of action and evaluation of achieved results.

Along with the functional systems of normal ontogenesis there are pathological functional systems. They – the functional system of the normal ontogeny of ancestors. Motivational excitation, forming them, is aimed at meeting the needs, which the individual does not have, but which were at the passed stages of its evolution. To understand what needs of our ancestors were pathological functional systems and in this way to explain how they are regulated in the descendants, it is necessary to compare the descendants and ancestors are not separate processes, and their interrelated totality, that is, functional systems.

Individual sessile modular species-a colony. It consists of modules. There are sponges modules are called flagellated chambers, cnidarian and coral polyps with hydrants, the representatives of other groups of sessile modular types – souidania. Patterns of functioning leading attached lifestyle modular individuals with similar patterns of operation of the plant. In plants, an individual, as in sedentary modular animals, is also a set of physiologically related modules. Plant modules-shoots and leaves.

The plant and sedentary modular animal in the body there are areas of embryonic tissue, the cells of which are divided, and the ontogenesis program is carried out many times in the formation of each new module. In plants, embryonic tissue is called meristem. It is located on the tops of shoots. Its cells remain embryonic from the time of their origin from the germ meristem [63]. Unlike plants in sedentary modular animals embryonic tissue is formed each time before the act of asexual reproduction again by dedifferentiation of specialized cells. Dedifferentiated cells in sessile modular animals begin to multiply and then to differentiate in new directions in developing the child modules. This method of asexual reproduction is called somatic embryogenesis.

To update the unit composition medley sedentary individuals. Plants and sedentary modular animals adapt to changes in the environment during a favorable season with the help of a functional renewal system. Its work consists in continuous change of modular structure of an individual and in change of its form. The need to change the shape of a modular species is caused by the fact that some modules of sedentary modular animals due to changes in the flow, the growth of a number of attached sedentary modular animals or algae and because of other reasons are in a position that makes it difficult for them to collect feed, and the plant-in the shade, and photosynthesis The cost of resources for maintaining the structure and functioning of the individual cease to pay off.

These modules are individual breaks. Their destruction in sedentary modular animals is carried out by including in the modules of the mechanism of senile involution, after which the modules are resolved. In plants, shoots caught in the shade, dry up, the leaves turn yellow and fall off. Replacing the modules with others in other places facilitates the extraction of energy from the environment. Module modular sedentary individuals death. While favorable for life season iteroparity modules (that is, before you die of old age, form the intervals of time several times by asexual reproduction child modules). The functional system of updating of modular structure of an individual in different evolutionary lines of animals and plants arose independently.

Education reducing sedentary modular phone and some primitive freely motile invertebrates (turbellarians, nemertea) adapt to the action of damaging factors, which exceed their adaptive capabilities, using the functional system of reduction. The reduction consists in the transformation of modules into reduction bodies. It occurs in response to factors of physical, chemical or biological nature, as well as hunger, and is to reduce the size of the modules, they have dedifferentiation of some cells and destruction of others. The reduction bodies are similar in structure to the early embryos, are able to tolerate an unfavorable period of life and restore the former structure of the modules when the conditions improve. Plants are also capable of reduction. It can be caused by placing pieces of tissue in a nutrient solution. Thus cells dedifferentiate and become totipotent callus. The accumulation of callus cells is a structure similar to the reduction body of sedentary modular animals. The functional system of formation of reduction bodies in different phylogenetic lines of animals and plants arose independently.

Preparation for seasonal deterioration of the environment. Sedentary modular animals and plants have two programs of somatic embryogenesis. One takes place during the favorable for life season is in the formation of the active modules. Another is carried out in preparation for an unfavorable season for life and is the formation of resting modules. Resting modules of sedentary modular animals and plants are early somatic embryos. They are very different in structure and physiological properties from the early embryos of actively functioning modules. Sponges have dormant embryos called gemmule, flowing down – podiatary, bryozoans – statoblasts, vnutripolostnyh, cryogenic and colonial ascidians – resting buds. Gemmule sponges similar in structure to morulae, resting the embryos of other modular sessile species, usually with the same.

In plants, the resting germ − buds. In trees and shrubs, they are formed on the branches, in herbaceous plants – on tubers, roots and rhizomes. Onion – resting kidney. Resting embryos of plants and animals are similar structures. They are stocked with nutrients and serve for the experience of the unfavorable season, and in sedentary modular animals – and for the settlement of the species. Among the free-moving, that is, more integrated forms, somatic dormant embryos are described, as far as I know, only in the Phagocata velata Turbellaria. Primitive freely movable modular and unitary animals − the turbellarians, oligochaetes, gastrotrichs, rotifers and crustaceans and Hydra, form for the experience of adverse live season and resettlement resting early embryos, but not of somatic and zygotic, occur from the zygote, They are called latent eggs.


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