These (first five parts) are external to us - in comparison to the last three parts of Ashtanga Yoga, but they are internal compared to the external world and worldly objects.
Sadhaka does not make the Samaadhi happen. He waits for it. He is not in a hurry for it. Samaadhi is the result of all the seven earlier limbs of Ashtanga Yoga.
Some people can be seen to be doing aasana and pranayama without yama and niyama. This is possible. Teaching in some modern Yoga schools is focused on pranayama and different aasanas to the exclusion of other parts of yoga