Triathlon - Base building, one by one or all at once?

I've been off running and physical activity for two years. I've just started riding again with my kid in the Burley. I figure it's been about six weeks of riding and three with a HRM. My question is are all bases the same? I run about 40 minutes twice a week and go at about 6mph. I currently ride about 1:15 five times a week at 70-80%, which with a kid and a mountain bike averages about 12mph. Not like all that has anything to do with my question but, do I have to build my base one at a time or is a base a base no matter what sport you're in?

from the reading that I've done, I would have to say that they have some specificity to them. That being said, as you gain a base in one it may not take as long to get a good base in another. I would say if you feel ready test the waters and see what happens. If it takes a long time to recover from the higher effort stuff then you need to back off some more, otherwise keep at it.

There is cross over in aerobic base. It is easier on the body to do large volumes of cycling. You can shift your focus from one week to another if you want. Just be careful of total volume.