a moment to the organelles which operate inside the
cell. The mitochondria transform food -- glucose, fat, proteins -- into
the chemical substance adrenosin-triphosphate, ATP for short, which all
animal cells utilise as fuel. It is the only type of fuel used throughout
the animal kingdom to provide the necessary energy for muscle cells,
nerve cells and so on; and there is only this one type of organelle
throughout the animal kingdom which produces it. The mitochondria have
been called 'the power plants of all life on earth'. Moreover, each
mitochondrion carries not only its set of instructions how to make ATP,
but also its own hereditary blueprint, which enables it to reproduce
itself independently from the reproduction of the cell as a whole.
Until a few years ago, it was thought that the only carriers of heredity
were the chromosomes in the nucleus of the cell. At present we know that
the mitochondria, and also some other organelles located in the cytoplasm
(the fluid surrounding the nucleus) are equipped with their own genetic
apparatus, which enables them to reproduce independently. In view of this,
it has been suggested that these organelles may have evolved independently
from each other at the dawn of life on this planet, but at a later stage
had entered into a kind of symbiosis.
This plausible hypothesis sounds like another illustration of the
watchmakers' parable; we may regard the stepwise building up of complex
hierarchies out of simpler holons as a basic manifestation of the
integrative tendency of living matter. It seems indeed very likely
that the single cell, once considered the atom of life, originated in
the coming together of molecular structures which were the primitive
forerunners of the organelles, and which had come into existence
independently, each endowed with a different characteristic property
of life -- such as self-replication, metabolism, motility. When they
entered into symbiotic partnership, the emergent whole -- perhaps some
ancestral form of amoeba -- proved to be an incomparably more stable,
versatile and adaptable entity than a mere summation of the parts would
imply. To quote Ruth Sager:
Life began, I would speculate, with the emergence of a stabilised
tri-partite system: nucleic acids for replication, a photosynthetic
or chemosynthetic system for energy conversion, and protein enzymes
to catalyse the two processes. Such a tripartite system could have
been the ancestor of chloroplasts and mitochondria and perhaps of
the cell itself. In the course of evolution, these primitive systems
might have coalesced into the larger framework of the cell. . . . [2]
The hypothesis is in keeping with all we know about that ubiquitous
manifestation of the integrative tendency: symbiosis, the varied forms of
parmership between organisms. It ranges from the mutually indispensable
association of algae and fungi in lichens, to the less intimate but no
less vital inter-dependence of animals, plants and bacteria in ecological
communities ("biocoenosis"). Where different species are involved, the
partnership may take the form of 'commensualism' -- barnacles travelling
on the sides of the whale; or of 'mutualism', as between flowering plant
and pollinating insects, or between ants and aphides -- a kind of insect
'cattle' which the ants protect and 'milk' for their secretions in
return. Equally varied are the forms of co-operation within the same
species, from colonial animals upward. The Portuguese man-of-war is
a colony of polyps, each specialised for a particular function; but to
decide whether its tentacles, floats and reproductive units are individual
animals, or mere organs, is a matter of semantics; every polyp is a holon,
combining the characteristics of independent wholes and dependent parts.
The same dilemma confronts us, on a higher turn of the spiral, in the
insect societies of ants, bees, termites. Social insects are physically
separate entities, but none can survive if separated from its
Kōbō Abe
Clarence Lusane
Kerry Greenwood
Christina Lee
Andrew Young
Ingrid Reinke
C.J. Werleman
Gregory J. Downs
Framed in Lace
Claudia Hall Christian