Botanists
Grass and Leaves are parts of plants, and would be the area of study for a Botanist (sometimes known as a plant biologist).
A mineralogist studies minerals.
An ecologist studies pollution
The kind of scientist who studies Urology would be a Biologist, since Urology concerns a biological function (urination). If you mean the kind of doctor who studies Urology, that would be a Urologist.
meteoroligists
Audiologist
An Ichthyologist.
Botanist
cosmologists
seismologist
a biologist
Mathmaticion