I'm not sure how to classify this question so I'll just put it under Biology

Why would a biologist be interested in sedimentary rocks?

Paleontology is a part of biology and fossils can be found in sedimentary rocks.

Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in four main ways: by the deposition of the weathered remains of other rocks (known as clastic sedimentary rocks); by the accumulation and the consolidation of sediments; by the deposition of the results of biogenic activity; and by preipation from solution.