There is a very interesting article by the biologist J.B.S Haldane on the sizes of various animals and how it affects the way they live , the things they have to care about etc . It is called ” On being the right size”.
Great article ! a must read !
Take the force of gravity . It is helluva important to large animals
like man . Take a guy to first floor and drop him . Will break his bones .
But take a fly to the 7th floor and drop her . Nothing happens to Miss Fly .
Now take the force of Surface Tension ( The force exerted by
the surface of liquids ) . We dont bother about it . We can go into a
swimming pool and come out with 1/15 inch of water on our body . But a
fly once wet may have to carry 2 times its own weight of water film .
It is in a very serious position indeed !! Die Fly !
Now consider the problem of flight . Principles of Aeronautics
say that a plane which has 4 times the linear dimentions of another
plane must fly 2 times as fast to keep airborne. That is why most birds
are of small sizes . Large size birds have to float . And even a limit
to the size that can soar is soon reached .
The eye can only be an efficient instrument if it is large . It must
have a lots of rods and cones to see anything properly . 2 objects can be
seperated only if their images fall on seperate rods/cones . Therefore
small animals have big eyes( compared to their bodies ) .
Small mammals cannot live in extreme cold . The surface area of
their bodies is large but they have small weights . They cant eat too much
but they need lots and lots of food to keep them warm ( many times their
body weight ) . The smallest mammal above the arctic circle is the fox !!
So friends look around u . If something is teeny weeny it may
have a good reason to be teeny weeny