preferential type of “handedness” is common for one species, but both right- and
left-handed helical structures are known and found for all these asymmetric species.
Several fossil molluscs demonstrate the evolutionary potential of asymmetric structures, for example, ammonites and the Nautilus pompilius (L.) shell are the most
prominent examples for asymmetric natural shapes in pre-historical time, where
links have been revealed between ammonites and the present cephalopodae, while
Nautilus represents one of those rare examples that survived and almost exactly
exhibit their former shape (living fossils). Certain asymmetric helical structures can
also be found for humans, for example, the umbilical cord of the newborn child
shows a clear helical structure. Cords were found to be winded left- and righthanded. The reason why a certain direction is preferred is still under discussion
(Fletcher 1993).
Another type of non-helical asymmetry is being represented by a passerine bird
species which can be found in both North America and Middle Europe, a bird
species called cross bill (Loxia curvirostra L.). The bird’s upper and lower beaks
crossover each other, where two ways are possible, to the left- or the right-hand side
of each other. These two ways represent two mirror image-like procedures. Interestingly enough, the upper bill of the American population crosses to the left-hand
side of the bird, whereas the opposite can be observed for the European birds.
An unusual type of asymmetric shape occurs in the marine flatfish family
(Pleuronectiformes), for example, halibut (Hippoglossus hippoglossus L.), sole
(Glyptocephalus cynoglossus L.) and flounder (Pleuronectes platessa L.) belong to
this group of marine fish species (Suzuki and Kurokawa 2000; Falk-Petersen 2005).
During embryo development, one eye slowly migrates to the other side of the
organism. As an adult animal, the flatfish lies on the ground with one side and
both eyes upwards, hunting small crustaceans and fish. The side which is preferentially directed upwards differs from one species to the other; however, this side is
characteristic of one species. “Left- and right-sided” individuals are known for
several species (e.g. soles ¼ Limanda limanda).
In general, it can be assumed for plants and animals that a radial or bilateral
symmetry is coupled with small asymmetric structures (Gardner 1990). During the
evolution of the present plants and animals, particularly bilateral structures have
proven to be important for survival strategies. Nevertheless, there cannot be any
doubt that for certain purposes, asymmetric structures have shown to be better
adapted than bilateral symmetric shapes.
1.4 Chirality in Chemistry
The first to discover the principle of asymmetry from a chemical point of view was
Louis Pasteur who succeeded in separating two types of sodium ammonium tartrate
crystals in 1848 (Pasteur 1848). He showed that separate solutions of those two types
of crystals are able to rotate the plane of linearly polarised light in different
directions, to the right- and left-hand side, respectively. Depending on this
4
1 Introduction
left-handed helical structures are known and found for all these asymmetric species.
Several fossil molluscs demonstrate the evolutionary potential of asymmetric structures, for example, ammonites and the Nautilus pompilius (L.) shell are the most
prominent examples for asymmetric natural shapes in pre-historical time, where
links have been revealed between ammonites and the present cephalopodae, while
Nautilus represents one of those rare examples that survived and almost exactly
exhibit their former shape (living fossils). Certain asymmetric helical structures can
also be found for humans, for example, the umbilical cord of the newborn child
shows a clear helical structure. Cords were found to be winded left- and righthanded. The reason why a certain direction is preferred is still under discussion
(Fletcher 1993).
Another type of non-helical asymmetry is being represented by a passerine bird
species which can be found in both North America and Middle Europe, a bird
species called cross bill (Loxia curvirostra L.). The bird’s upper and lower beaks
crossover each other, where two ways are possible, to the left- or the right-hand side
of each other. These two ways represent two mirror image-like procedures. Interestingly enough, the upper bill of the American population crosses to the left-hand
side of the bird, whereas the opposite can be observed for the European birds.
An unusual type of asymmetric shape occurs in the marine flatfish family
(Pleuronectiformes), for example, halibut (Hippoglossus hippoglossus L.), sole
(Glyptocephalus cynoglossus L.) and flounder (Pleuronectes platessa L.) belong to
this group of marine fish species (Suzuki and Kurokawa 2000; Falk-Petersen 2005).
During embryo development, one eye slowly migrates to the other side of the
organism. As an adult animal, the flatfish lies on the ground with one side and
both eyes upwards, hunting small crustaceans and fish. The side which is preferentially directed upwards differs from one species to the other; however, this side is
characteristic of one species. “Left- and right-sided” individuals are known for
several species (e.g. soles ¼ Limanda limanda).
In general, it can be assumed for plants and animals that a radial or bilateral
symmetry is coupled with small asymmetric structures (Gardner 1990). During the
evolution of the present plants and animals, particularly bilateral structures have
proven to be important for survival strategies. Nevertheless, there cannot be any
doubt that for certain purposes, asymmetric structures have shown to be better
adapted than bilateral symmetric shapes.
1.4 Chirality in Chemistry
The first to discover the principle of asymmetry from a chemical point of view was
Louis Pasteur who succeeded in separating two types of sodium ammonium tartrate
crystals in 1848 (Pasteur 1848). He showed that separate solutions of those two types
of crystals are able to rotate the plane of linearly polarised light in different
directions, to the right- and left-hand side, respectively. Depending on this
4
1 Introduction