Het geval van de ontwikkeling van het oog is een klassieker in de wetenschap
van de evolutie. Hier het geval van de weekdieren:
Bronnen bij Evolutie versus ID, de kansberekening: natuur
The Evolution of the Mollusc Eye
Stages in the evolution of eyes among molluscs.
Source: Wikipedia. a: Flat eye; b: cup eye; c: pinhole eye;
d: vesicular eye; e: lens eye.
The example of the molluscs offers a good opportunity to observe the
evolution of light sense organs in the animal kingdom. Among the numerous and
various groups of molluscs there are primordial and advanced, movable and
In the most primitive form light perception happens by single sense cells
located somewhere in the body. Singular light sense cells dispersed over the
body surface, as on snails and segmented worms, can tell the difference between
light and dark, so the animal may benefit from a shadow reflex to protect itself
against predators. They are, however, not a sense organ in the common sense of
speaking: A sense organ is a complete organ, not just singular cells,
specialized in a defined sensory performance. The first light sense organ is a
specialized field of light sense cells and pigment cells for
lateral isolation. It is called a flat eye. It enables its possessor to
differentiate between light and dark, but only basically makes it possible to
tell where the light comes from.
Flat eyes today can still be found in primitive groups of invertebrates, such
as jellyfish (Coelenterata). It may also be assumed that the molluscs'
ancestors, primitive, worm-like ground-living creatures, also possessed such
A primitive flat eye may be of valuable use to an animal either sessile or
moving passively. The directed movement of more highly developed molluscs
required the formation of more advanced light sense organs. In the consequence
the light-sensitive epithelium of the flat eye caved in to form a pit. So the
light sense cells on facing sides of the eye can tell apart light and shade.
That makes it possible to determine where the light comes from. Pit shaped eyes
can be found in sessile and slow moving invertebrates. ...
While a pit eye may be able to differentiate between light and shade, it is
not capable of producing pictures. Especially for predatory molluscs, having to
observe and to follow their prey, an improvement of the eye's picture projection
capability was necessary: The eye opening narrowed, and in consequence the
picture projected on the retina became more focused. So the pigmented cup eye
came into existence. Today, in its primitive state, this type of eye can be
found among certain
bivalves and turbellarian worms.
Pigmented cup eyes can also be found among primitive, mainly sessile,
gastropods, such as
(Patellidae) and ormers (Haliotidae).
In the further course of evolution, the eye opening reduced in size and as a
result the eye achieved abilities comparable to a so-called pinhole camera: A
focused, but low-light picture can be projected to the retina. Among the
molluscs, pinhole eyes can be found among primitive cephalopods, such as
Nautilus. Nautilus is a living fossil, a remnant from the Mesozoic. It is
also assumed, that fossil cephalopods, such as the giant endocerate
Cameraceras from the Ordovician had comparable eyes. ...
Red.: Kortom: het ontstaan van het oog is zo logisch als het
maar kan, als je het maar ziet in zijn juiste tussenstappen. Hier geldt een
adagium van Vance: "Mysterie is een niet-opgelost raadsel - los het raadsel
op, en weg is het mysterie"
Naar Religie en ratio, kansen
Religie en ratio
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