Ask A Scientist© Zoology Archive

name         Robert
status       student
age          10

Question -   How do cat's make their pupils smaller?


Hi Robert.
That is a question i answer with great pleasure
since a am a cat lover, see?.
.Look, the cats are naturally nocturnal animals...
Their retina is extra sensible to light, this is due to a
layer of guanine, (a colourless, crystalline substance)
  that causes the eyes to shine at
night when are focused by a strong light. The eyes
are large and, as you noticed, the pupils expand or
contract to mere slits according to the density
of light. That is, the pupils react to the quantity
of light, if it is great they get smaller so the quantity
of light that enters and hit the retina is small.
At night when it gets dark, the pupils become
larger allowing all the local light to enter it.
That is also why people says that cats see
in the dark...All that happens due to adaptation
to the environment.
Thanks for asking NEWTON!
Mabel
(Dr. Mabel Rodrigues)
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