Hello,

PG means post graduate which means master level of a graduation stream. Like Btech is for graduation and Mtech is for masters which is known as PG.

You have done Bsc in Biology and you have to do MSc in biology which is PG. After masters you can do PhD. This is related to the research field and making thesis and new inventions.

As you want to be a teacher then MSc is best on to choose. You will lot of options in your domicile and you can choose anyone you will suitable for you.

After joining try to improve your work and look for government colleges or Universities and work there as a teacher which will be a boost to your career.

Hope it helps!