Will jaw bone deteriorate if you extract 2nd bottom molar?

Yes, bone resorption: When a tooth is extracted, the bone that surround the tooth (alveolar bone) slowly disappears because there is no reason for the bone to be there. Any bone in your body needs constant tension and stress to keep them healthy and strong. That's why weight bearing exercises increase bone mass.

Loss of teeth: Tends to cause loss of surrounding bone over time. The extent and rate varies greatly from individual to individual and also depends upon the location. That's just one of the reasons why it's generally very important to replace missing teeth. Some teeth are more important to replace than others. Discuss this issue with your own dentist.