生命幾何 The geometry of life
{Background music from Windows 98's media folder : Dance of the Sugar-Plum fairy.rmi}
Living things seem to be designed by a mind that could conceptualize only a few basic geometrical patterns. There are some " universal shapes " that organisms follow. Nearly every species can be mapped onto a basic structural pattern, a " biological archetype ", so to speak.
Oval shape is beautiful and inviting.
(By the way, the human hand loves to caress smooth, oval objects.)
Egg yolks are circular. Each yolk is bound by a flexible membrane, thus the yolk can alternate between circular and oval shapes, a somewhat dynamic situation.
The circular shape is applicable to red blood cells, mushrooms, jelly fishes, and many flowers.
Chrysanthemum conforms to radial symmetry.
The sea-cucumber shows penta-radial symmetry.
It is typical of the spiny-skined animals - the Echinoderms.
Many flowers also demonstrate penta-radial symmetry. The Sakura symbol shown above refers to an aerial view of the flower, with 5 overlapping petals. The photo was taken in Tokyo.
Radial symmtry is usually found in sedentary or slow-moving species. These " volcanoes " are barnacles, invertebrate filter-feeders that sift off planktons from sea water. They are members of the Phylum Arthropoda.
On the other hand, active animals usually have an anterior-posterior axis that sets the organism in bilateral symmetry. The sensory organs are concentrated at the head which is the advancing end during locomotion, this is probably adaptive to the seizing and killing of preys.
The earthworm looks like an elongaed cigar. However, the cylindrical body has a definite anterior end to which waves of muscular contraction progress. It's body is supported by a hydrostatic skeleton as a liquid (the coelomic fluid) fills up the entire body cavity (the coelom).
A common Gastropod snail found on the rocky shore of Hong Kong. The snail is characterised by a pattern of spiral growth in which the body mass (viscera) coils upon itself during development.
An uncommon hairy Begonia that shows spiral growth.
It resembles the pattern of the fossil ammonite.
Ramifying roots that climb on a stone wall. Branching roots criss-cross each other and result in a web-like pattern.
These ramifying mangrove roots appear like crawling snakes on a muddy shore surface. They contribute to maintaining support and gaseous exchange.
From a terminal circular head of a plant, hairy outgrowths branch off in an irregular pattern.
What a loose mass of interwoven yellow threads ? The unstructured shape belongs to that of a parasitic plant - Dodder. The threads twine round the host plants where they obtain nutrients and water by the use of penetrating suckers. Why are the threads yellow instead of green ? Well, they lack chlorophyll as they cannot photosynthesize.
Like the seed of dandelion, the seed of this species gives off a cluster of silvery hairs that help dispersal in air. Functionally the hairs are similar to the spokes of a parachute. The seeds simply float in air and are blown everywhere by wind, even the slightest breeze.
Leaves come in different forms. The leaves of pine are reduced to " green needles ", an adaptation to living in a dry environment because the smaller area lowers down loss of water vapour - a xerophytic adaptation. This feature is common to many Gymnosperms. The spines of cactuses are, biologically speaking, modified leaves.
Trees are always upright. The tree trunks naturally orient themselves at right angle to the ground level. And when the leaves are shed, leaving the woody branches bare, the latter look like sky-cleaning brushes. For some unknown reasons, this main tree trunk bended nearly eighty degree before nature took it back to the plumb line. Somehow, the main stem is responding to gravitational stimuli, a phenomenon Biologists call geotropism.