Do I have to get permission from my son's biological father for him (my son) to be adopted by his stepfather?

My son's biological father is not very involved in his life, pays no child support, and didn't even sign the birth certificate. Can the adoption go on without his involvement? What kind of "rights" does he have? My son will be 12 years old in February.

The bio dad's parental rights have to be severed before your son can be adopted by his stepfather.

why would he have to be adopted anyway. 90% of stepfathers don't adopt their stepson, it is understood.

if he didnt sign the birth certificate then no

Yes, you need his consent, or you will run into bigger problems later on. We did this too. But you can get him to agree easier if you have something on him. Court and child support to start.

Unless the biological parent specifically signed away his parental rights when your son was born, he does have do it now in order for your husband to adopt him.

A failure to sign the birth certificate is not the same as signing away his parental rights and failing to pay child support has no bearing whatsoever on biological birth rights.
It is unlikely that a biological parent would be compelled by the court to sign away his parental rights. However, you can file for child support. If your son's father doesn't want to pay child support, he may be willing to allow your husband to adopt your son because that will legally excuse him from owing child support from this point further.
Contact an adoption attorney.

You don't say where you live. It depends a lot on which legal jurisdiction you're in.
In some jurisdictions a father of child born out of marriage has no rights whatsoever, especially if he has not recognised paternity (ie not named on the birth certificate).
Be sure that the person you want to adopt the child is a responsible parent and that the child agrees.

The biological father has the same rights and access to his child as the mother.

The ONLY way the child can be adopted by a step-father is if the REAL father files papers in a court of law to terminate his parental rights.

You cannot do that....only the father can.