The members of the council of ministers are appointed by the President on the advice of the Prime Minister. The minister can be members of either house. The Prime Minister and the other minister can remain in power as long as they have the support of the Lok Sabha.
The Prime Minister along with his council of ministers is directly responsible to the Lok Sabha for all acts of commission and omission. A note of no confidence against even one member can bring down the whole government. The Prime Minister and his council of minister thus sink and swim together. They are collectively responsible to the Lok Sabha. This is known as the Principle of Collectively Responsibility.