A person who studies inland waters (running and standing waters, both fresh and saline), including lakes, is called a Limnologist.
The Person Who studies about mamals , he is called mamalogist....
A person who studies volcanoes is called a volcanologist.
A person who studies the grass and soil, etc. is called a Agrostologist
A person who studies or writes history is called a historian.
A person who studies geology is a geologist.
A person who studies culture is called an anthropologist.
a person that studies gems is called a gemologist.
A person who studies bees is called an apiologist.
A person who studies the grass and soil, etc. is called a Agrostologist
A person that studies animals is called a Zoologist.
A person who studies audiology would be called an audiologist.
A person who studies birds is called an ornithologist.