Answer: Fossil data acquired by the the chemical study of oxygen isotopes ratio i.e ¹⁶O and ¹⁸O, in the shells of foraminifera, helps in indicating the palaeoclimatic condition as well as the type of food habitat.
Foraminiferas are unicellular organisms that are comprised of a hard shell which was made of chitin (a fibrous like substance). They are very prone to frequent environmental changes.
Scientist use this organism's hard shell to study about the climatic condition during their time of existence by comparing this oxygen isotopes.