Biswas studied biology in his college instead of geology as his father wished. He graduated from the University of Calcutta in 1943 and received an MSc in 1945. He received a Ph.D. in 1952 from the University of Calcutta working under J.L. Bhaduri. He was part of the Daily Mail expedition sent to look for the Yeti around Mount Everest in 1954. He was elected Corresponding Fellow of The American Ornithologists' Union in 1963. He later took charge of the Bird and Mammal Section of the Zoological Survey of India. He won Chapman Grants from the American Ornithologists' Union in 1965, 1966 and 1970, for research at the British Museum. Later, he was Joint Director of the ZSI, until he retired in 1981, and then Emeritus Scientist until 1986.