Question -
Answer -
The birds are adopted for flying by reducing the weight and other modifications which are as follows :
(i) The fore limb modified into wings to assist in flight.
(ii) Left ovary absent or reduced
(iii) Presence of pneumatic or hollow bones for making a light weight skeleton.
(iv) Aerodynamic body helps in flying.
(v) Excretion of urine and faeces occurs through single opening.