He has a deep interest in teratology.

I am majoring in embryology at university.

He is an expert in embryology, studying the developmental processes of many kinds of organisms.

He is an expert in statistics.

He is an expert in geography.

He is majoring in botany at university.

He is studying ballistics as a part of physics.

He is majoring in psychology.

He is known as an expert in oncology.

Genetics is a branch of biology that studies the function of genes and the laws of inheritance.