Study of fossils is an important aspect of study of evolution.

Explanation

i. Fossils are remnants and impressions of organisms that remain preserved underground.
ii. Carbon consumption of animals and plants stops after death and only the decaying processes of C-14 takes place continously.
iii. The ratio of C-14 to C-12 changes constantly with time as C-12 is non radioactive in dead plants and animals.
iv. The time passed since the death of a plant or animal can be calculated by carbon dating i.e. by measuring the radioactivity of C-14 and ratio of C-14 to C-12 present in the remains of the dead organism.
v. The oldest fossils are buried deep in the Earth's crust, while the younger ones occupy the upper surfaces. Hence, fossils of invertebrates are found buried deep as they are very old and belong to the Palaeozoic era. The fossils of Pisces, Ambhibians and Reptiles were obtained in the consecutive layers. The Mesozoic era was dominated by reptiles, while the Cenozoic era showed presence of mammals and brids.
vi. Thus, study of fossils is an important aspect of evolution since it can be used in the paleotology and anthropology for determining age of the fossils and deducing information about their ancestors.