Seven Deadly Colours

With vivid and fascinating examples of how colour has affected animals in different environments across the globe, Seven Deadly Colours not only shows the endless wonder of the natural world but also extends our understanding of evolution itself.The second volume of Parker's trilogy on the topic, this one shows how colour perception - or lack of it - has guided the track of natural selection. There are many hidden facets to vision and perception. We tend to think we can see everything, but in fact, our visual acuity has serious limitations. Other creatures, such as bees, see in the ultraviolet range. Many ocean fish have colour limitations due to their habitat, particularly those in deep water. Parker describes how these abilities evolved by using seven - well, eight, actually - commonly detected colours. Parker explains how eyes are structured. Certain types have differing colour detection abilities. Within the eye are organelles known as "rods" and "cones". The rods are the light intensity detectors, while the cones are colour selectors. As he explains, light is meaningless until the signals reach the brain where they are decoded. Eye and brain are thus closely linked, the arrangement having evolved with each species over time. Changes in habitat are reflected in changes in visual abilities. Some colours seem straightforward and unambiguous, like leaves or fruit. Others, however, are generated by pattern or movement. Moth and bird wings have delicate shifts of colour from rest state to flapping, for example. Birds and many insects have evolved superior colour perception as a result.Not all colour is simply variations of reflectivity. Some creatures produce light. Parker's chapter on "Blue" takes us through the realm of "bioluminscence".