The Role of Biology in System of Medical Education

The biology as a natural science about the life. The biology - is a science, which studies life as a special form of matter being having its own laws of existence and development. The subject of biology study is live organisms and their natural communities. Biology is a natural science as astronomy, physics, chemistry, geology and other sciences are.

It is a complex science. It includes more than 50 disciplines. There are following among them:
- Morphological disciplines (anatomy, histology) describing organism structure.
- Physiological disciplines (cell physiology, plant physiology, animal physiology).
- General biological disciplines (cytology, genetics, evolution etc.).
- Ecological disciplines (biogeography, parasitology).
- Bordering disciplines (biochemistry, biophysics, anthropology, molecular biology, space biology etc.).

Biology is a leading natural science. The high level of biological research is necessary condition for modem medicine progress.

The essence of life. The life organization levels. What is a life? Many scientists have tried to answer this question. And it is still an aim of contemporary biology. Many hypothesis and thesis were generated to give an appropriate answer. However, everyone needs to have in mind that each theory, each hypothesis is a reflection of life position of definite scientist. For example, Karl Linney (1707-1778) suggested many new principles in biology (new biology nomenclature which is in use until now), but being a very faithful he accepted the world creation by god.

The contemporary view on life suggests that life substrate is a complex of substances. These substances are from two biopolymer classes: proteins and nucleic acids. There were several efforts to determine life based on this statement. One of most successful was given by J. Bemar: “Life is a function of proteins and nucleic acids interaction on Earth”.

All modern views on a life origination based on two following statements: 1) Life weren’t brought to Earth from outspace; 2) The living organisms weren’t self originated.

In 1924 A.I. Oparin was first to consider all theoretical points about life origination. In his book “The origin of life”, he presented the main principles about life origin on Earth, about its evolutionary development. These principles were proved in following years. The process of life origination has three stages:

1) chemical - primary formation of simple organic substances on Earth.
2) prebiological - abiological synthesis of main organic substances.
3) biological - origination and evolution of simple biological systems.

The main feature of life is reproduction and renewing of protein bodies. It is based on DNA self replication and transmitting genetic information to a new cell. V.M. Goldansky (born in 1923) suggested following definition of life: “The life is a form of polymer bodies (systems) being which are able to self replication in conditions of constant exchange of energy and substance with environment”.

The others fundamental features of life are: self-renewing on a base of substance and energy exchange, self-reproduction providing relations between generations, selfregulation based on information, energy and substance flow. These features provide main signs of live, which can be described in following.

Discretion and integrity. The organic world is integral and discrete in a same time. It is integral because it is a system of related units. It is a discrete because it consists of separated units - organisms. Each organism consists of cells, they in turn consist of organelles, but all of them work together as integral system.

Structural organisation. Life mater is built out of same substances as inorganic matter. However, molecules of life matter are more complex. It is because of special order on a molecular level. The structural organization is a proper feature of life on an all level of its organization. The hereditary information is encoded by genes, but none gene act successfully outside of genotype. The integrity of proteins and nucleic acids provides life being on Earth.

Substance and energy exchange. The main property of life is metabolic exchange. Each organism can be presented as an open system supporting constant substance and energy exchange with environment. In life organisms, substance exchange leads to repairing lost parts. The structure of life matter reproduces itself with help of DNA information. Life organisms are in integrity with environment, whereas all physical, chemical and biological properties of environment provide conditions for all life processes.

Reproduction. It provides life being. Each species consist of individuals having their own life span. With help of reproduction, life span of species is much longer than life span of individual. The reproduction of species provides biosphere being.

Heredity and diversity. They are the important features of life connected with traits inheriting and ability of these traits to be changed in different environmental conditions. The heredity provides material succession between generations. Traits, which are inherited, provide adaptation to environment. The storage and transmitting hereditary information is a function of nucleic acids.

The diversity is a feature opposite to heredity. It provides origination of new traits which were absent in parents. If structure of nucleic acid have been changed, the new traits appeared from that can lead to organism die or to better adaptation to environmental conditions. The diversity gives matter for new species formation and evolution.

Growth and development. It is a property of organism to grow and develop on a base of cell divisions and differentiation. An organism grows and develops puberty, which allows it reproducing. The organisms inherit only possibility to develop trait. This possibility is realized during individual development (ontogenesis).

Irritability. It is a property of life, which provides contacts of organism with environment and surrounding organisms. In monocellular organisms, it is presented by taxises, in plants - by tropisms, in higher animals - by reflexes. With help of this, organisms selectively react on stimuli; they can get from environment necessary substances. Consequently, the metabolic exchange is closely related with it. The irritability is connected with chemical nature of life substrate.

Internal regulation and homeostasis. Each organism, being an open system, keeps main parameters of internal environment on a same level. It keeps homeostasis. Homeostasis is supported with help neurohumoral regulation. The self-regulation in biological systems is based on negative feedback. Thus, such processes as inheritance, metabolism, reproduction and so on are regulated.

Modem biology study life processes on different levels. These levels are called life organization levels. There is a list of them.

Molecular-genetic level. Elementary structures of this level are central regulating systems - codes of hereditary information, transmitted from generation to generation. Elementary events are codon reproducing and protein synthesis on a gene matrix. DNA reduplication preserves genetic information, placed in genes, for next generation.

Cellular level. Elementary structure of this level is a cell. Elementary event is cell division and cell development. On this level all organisms look kind of similar. The genetic information is realized in particular proteins on this level too. Protists cellular level coincides with organism level. This level dominated in Archey Era.

Ontogenetic level. Elementary structures are organisms. Elementary events are ontogenesis, differentiation and still unknown mechanism that direct all that processes. On this level, there is variety of life forms. Earth is inhabited by more than 3 millions species. Each species consist of organisms. Each organism presents elementary life unit. Nervous and humoral regulation provides constant state of internal environment and homeostasis. There is no life outside of organism.

Population level. Elementary structures are populations of any life species. Elementary event is directed changes in their genofond. Such changes lead to formation of new adaptation to changing nature. Accumulated adaptations and adjustments result in new species formation on a base of natural selection. Population is open genetic system because of possibilities of interpopulation breading. The elementary evolutionary factors act on population genofond, which results in evolutionary significant changes in genofond, which are elementary events on this level.

Biospheral level. Elementary units on this level are biogeocenosis, whereas elementary evens are biogeocenosis upgrade to next level, to next well-balanced state. Biogeocenos is open system for energy flow and substance flow, as well. All biogeocenosis even different in structure are united to one complex - called biosphere. Biosphere is a perpetually-sealed envelope, so that faces us a problem of environment protection.