As per your concern I will get the list of subject which come under the Indian Forest Services exam along with the syllabus so that you can check it easily.

In Indian Forest Services you have to choose tow optional subject selected from the following subjects, the paper will be divided into two parts, viz. Part A and Part B, each part containing four questions. Out of eight questions, five questions are to be attempted.


Here is the syllabus

General English Syllabus
The English paper would consist of an essay and passages to write summary.
The standard level of papers in General English and General Knowledge are designed for a Science or Engineering graduate of an Indian University.
Other questions are designed to test general understanding of English and everyday use of words.

General Knowledge
Current Event of National and International importance.
History of India and Indian National Movement
Indian and world Geography
Indian polity and Governance
Economic and social Development
General Science

Optional subjects
Agriculture
Agricultural Engineering
Animal Husbandary & Veterinary Science
Botany
Chemistry
Chemical Engineering
Civil Engineering
Forestry
Geology
Mathematics
Mechanical Engineering
Physics
Statistics
Zoology