|Great Blue Turaco|
Monday, 25 June 2012
Saturday, 16 June 2012
As you enter there is a children’s activity tent where the smaller kids can play at excavating bones and identifying the bones of a thecodontosaurus (these are resin copies with built in magnets they can affix to a board). For the older kids there is a dinosaur lab with people from the Bristol Dinosaur Project (for their website, see http://www.thebristoldinosaurproject.org.uk/ ).
We have 10 different dinosaurs in total, plus a (partly assembled) Dimetrodon to show how the mechanics work. The models move, make noises, and in some cases scare small children, but so far it seems a great success. The species we have as you progress round the zoo are these:
Saturday, 9 June 2012
|How good is his camouflage?|
First, a brief outline of how colour vision works. Vertebrates have two types of light sensitive cells in the retina of the eye. Rod cells respond to more or less all frequencies of light, and when a photoreceptor cell is struck by a photon a chemical reaction occurs which generates a nerve impulse to the visual centres of the brain. Rod cells are more sensitive, and are used for vision in low light levels. However, they cannot respond differently to different frequencies, and so enable colour vision. This is carried out by the other cells, called cone cells, which occur in several varieties each containing a receptor pigment that only responds to a specific range of frequencies, from short wavelengths (= blue or UV light) through to long wavelengths (= red or infrared light). They are not tuned to a single wavelength, but have a peak absorption in different parts of the spectrum. The brain interprets the different strength of response from different cone cells to distinguish colours.