Answer:
(i) In a vasectomy, a small portion of the sperm duct (or vas deferens) is removed by surgical operation and both the cut ends are tied properly.
It prevents the sperms from passing to the urethra and hence it is not released in the vagina of the female during mating.
(ii) In tubectomy, a small portion of the oviducts is removed by surgical operation and the cut ends are tied.
It prevents the ovum from travelling to the fallopian tube and hence, prevents its fertilisation by sperm.