Sight and Colour

One of the primary ways in which the beauty of the world is experienced is visually. Colour is intrinsically important to this. The world would be dull and drab without colour. Imagine being a crocodile and just seeing colours as varying shades of grey! Beautiful, brilliant colours are, in the world of nature, linked with sexual reproduction. The bright colours of flowers help to make them more visible to insects and animals to assist in the spread of pollen and seeds.

The perception of colour by humans is a complicated process of interaction involving the physical qualities of the object, the intensity of the light, the perceiving subject, and the cultural context of the perceiving subject.

The wavelength of light determines colour. If sunlight is passed through a prism, as Sir Isaac Newton first did in the late 1600s and early 1700s, all the rainbow colours of the spectrum are revealed. What appears to be ‘white light’ is actually a combination of light of red, orange, yellow, green, blue, indigo, and violet. Objects appear to be different colours because they absorb some wavelengths and reflect others. A green flower absorbs all coloured light wavelengths except for green which it reflects.

Photoreception is the general scientific term used to describe the biological responses of organisms to light. Photosynthesis is the specific method by which green plants utilise light energy to transform water and carbon dioxide into their necessary carbohydrate sustenance.

In animals rods and cones are the names given to the two different types of photoreceptor cells in the retina which affect visual perception. Rods primarily influence visual perception when the light intensity is low or dim. Cones are responsible for the differentiation of colour in many animals in conditions of greater light intensity.

Many insects have good colour vision whereas dogs and other mammals have limited colour vision and probably see in yellows and blues. Many insects can see into the ultraviolet spectrum which the unaided human eye can not. Many flowers emit patterns of ultraviolet light which are visible to insects but not to humans. Flowers which are pollinated by insects tend to have flowers with white, yellow, orange or blue flowers. Butterflies are probably the only insects which can detect red as a colour. Many fish which swim near the surface have colour vision while those in the ocean deep where it is dark do not. Most primate species, except for those which are primarily nocturnal, also have colour vision as do many birds. Because birds are descended from dinosaurs it is thought that dinosaurs may also have had colour vision.

Colour is strongly associated with different emotional states though this can vary from culture to culture. For example, ‘green with envy’, ‘blue’ or ‘the baby blues’, and ‘yellow’ for being afraid. Red is ambiguous as a colour symbol. It can signify a warning through such things as a ‘Stop!’ sign or sexual attractiveness through the usage of rouge and lipstick. In Western cultures black is the colour of mourning but in other cultures white, purple or gold can signify mourning. In Western cultures ‘white’ has traditionally signified purity while for the Chinese it is a colour associated with mourning. In Ancient Egypt black was the colour symbolizing fertility because of its associations with the colour of the alluvial plains surrounding the Nile after the annual flooding. Interestingly, the Inuit have about seventeen words to describe the whiteness of snow depending on its condition. This kind of fine discrimination was undoubtedly necessary for survival in the harsh arctic environment. All human languages have words for some colours but not all colours. All languages have words for ‘black’ and ‘white’. ‘Red’ is the next most common colour which is identified by a specific colour word.

In the natural world colour has strong communicative and adaptive properties which help the particular species to survive. Colour conveys information. Many plants need insects or animals to help them either be pollinated or to spread their seeds. Therefore they need ways in which they can be noticed-brilliant flowers and brightly coloured fruits, often red, which will strongly contrast with the green of the leaves being two of the most common.

Chlorophyll causes the green of the leaves. The two pigments mainly responsible for the colour in flowers are flavonoids and carotenoids both singly and in mixtures. The flavonoids tend to give us the blues and bluish reds while the carotenoids tend to give us reds, yellows, and orange colourings. The more genetically complex plants tend to have more colours. The male part of the plant, the stamen, is often the most colourful.

Different types of adaptive use of colour are:

1)advertising coloration such as when male birds are often brilliantly coloured in order to attract females;

2)disruptive coloration as when the outline of the animal/fish is broken up through the use of spots, stripes and patches of color;

3)Protective coloration as when an animal or insect has the same color as its background in order to blend in and not be seen by predators.

4)Protective warning coloration as when an animal/insect is either poisonous or looks like something its predators would not like to eat such as viscount butterflies which resemble the bitter tasting monarchs.

5)Protective resemblance as when an insect/animal has the same shape/colour as its surroundings such as the stick insect which resembles twigs


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