book

Appendix 1

List of genetic markers of E. coli (After Taylor, 1970).

incorporation in the course of evolution remains unsolved. Decoding this
key problem would provide the answer to some aspects of the origin of
life and its further development.
Multicellular organisms have emerged from the integration of single
cells, their interactions, and the formation of pores, channels and
cytoplasmic bridges among them. Besides somatic reproduction at the
initial stages of their development, sex reproduction appears and
gradually gets consolidated. It provides much greater opportunities for
genetic combinations and recombinations, the latter strongly increasing
living organism diversity.
At present the problem of the regeneration of multicellular
organisms from single somatic cells known as cloning is of exceptionally
great interest. In the animals it is accomplished by transplanting a
nucleus of a given somatic cell line into an enucleated unfertilized egg. It
is quite logical that this could also be achieved through somatic
embryogenesis which is a routine method in plant growing. This shows
that multicellular organisms are a product of cell integration. The degree
to which these independently existing before that cells are able to
preserve their autonomy and their relationships and interactions in the
framework of the multicellular systems built by them is one of the
numerous unclear problems of cell biology.
Discovered more than three centuries ago, the cell is still
inadequately elucidated by man. Such it will be in the hands of the
researchers at the beginning of the third millennium.

CONCLUSION

The planet Earth represents a unique combination of favourable conditions
for the origination and development of life. As a result of the abiogenic
chemical evolution based on hydrocarbon compounds formed from the
methane (CH₄), ammonia (NH₃), molecular hydrogen (H₂) and water
vapours (H₂O) available in the primitive atmosphere on the Earth, under the
action of Sun’s ultraviolet irradiation, the various space and radioactive
emissions, the electric discharges, favourable temperature, etc., living
matter emerges. Cell structures have arisen from it with their immanent
properties to exchanges with the surroundings and to reproduce. Most
probably, the Earth is not the only planet in the Universe where life exists,
but up to now there are no concrete and reliable proof of that.
The cell as a generalized notion, becomes the basic structural and
functional biological system. Under the influence of environmental factors
and regular internal biochemical and genetic processes, it is subjected to a
permanent evolution. The metabolic changes lead to differences both in
structural and functional organization. Together with the primary autotrophic
cells, heterotrophic ones arise, satisfying their life needs by the use of
ready-made synthesized substances. Depending on the energy sourse
used in the biochemical processes, these are divided into phototrophic and
heterotrophic ones. If metabolic processes take part without oxygen
consumption the cells are anaerobic, while if they use oxygen — they are
aerobic. Some of them are obligatory anaerobic and aerobic respectively,
others are facultatively because of their ability to exist both in the absence
of oxygen as well as in the presence of it. All that is in favour of the concept
of earth origin of life, respectively the cell.
The emergence of photosynthesis lays the foundations not only of a
more effective biosynthesis, but also for the enlargement of the diversity of
living forms. It is the basic and most powerful mechanism for incorporating
the energy of the Sun in the synthesis of organic compounds and the
release of molecular oxygen (O₂) in the atmosphere, which introduces
radical changes in the metabolism of the living organisms. Besides
photosynthesis, hemosynthesis and nitrogen fixation take place in a much
more limited scale. These facts indicate the great biological capacities of
the cells and their adaptive ability to the conditions of existence.
In the course of evolution, except the mechanisms of metabolism, cells
have built many others — protection from the various harmful factors of the
environment, mutations and reparations, modes and types of cell division,
relationships and interactions with cell organelles, etc. The cell underlies as
well the two of the most important biological phenomena concerning
directly the human — senescence and neoplasms resulting from cell
specialization, differentiation and dedifferentiation.
The main compounds building materials of the cells are proteins
(polypeptides), nucleic acids (polynucleotides) and carbohydrates
(polysaccharides). Some authors are inclined to add lipids as well. The
problem of the sequence of their arising and the stages of their

continue to exist, and a part of them develop into higher organisms,
including man. The key of this process lie in the cell specialization and
differentiation.
The second problem is related with the cloning. Until recently, only
sexual cells were considered capable to reproduce multicellular
organism. Using the cloning methods proved that individual somatic cells
can regenerate a whole multicellular organism. This shows, that these
cells contain hereditary information not only about their individual
development and reproduction, but also the information acquired in the
course of evolution, i.e. about the organism as a whole. Although cloning
is not yet realized in all kinds of multicellular organisms (mainly animal),
undoubtedly this circle will extend. It will be the next great discovery in
biology — when it will be proven that it is a norm, not exception. Then
biology will be even more advanced science and will answer many
questions.

All stated in this Chapter shed light on two very important general
biology problems. They are presented in Figure 4–6.

The first problem is relevant to the formation and development of
multicellular organisms in evolutionary aspect. From the brief survey the
logical conclusion follows, that multicellular organisms are a product of
association (integration) of single cells, existed before as independently
organisms. In the course of evolution they form coenobial and colonial
forms, encircled by a common mucous cover. On this cover there are
pores connected with channels through which the connection with
surroundings, taking and excretion of substances are realized, and in the
interior the cells are connected with cytoplasmic fibres. Gradually, the
integrated cells specialize and differentiate by forming different tissues
and organs performing specific functions. In the beginning the coenobial
and colonial forms reproduce asexually or by budding, and then the
sexual reproduction arises where two types of cells strictly differentiate
— vegetative (somatic) and reproductive (sexual). Undoubtedly, the
process of forming multicellular organisms possesses polyphylic
character. Some of the lines disappear, other come to a “dead-end” and