p203 of the 5e PHB indicates that
A character can use a component pouch or spell casting focus in place of the components specified for a spell. But if a cost is indicated for a component, a character must have that specific component before he or she can cast the spell...
So, if I'm starting out as a Knowledge Domain cleric, I get Identify as a level 1 Domain spell - normally this requires "A pearl worth at least 100 gp and an owl feather."
I'm assuming that a holy symbol would stand in in place of the feather, but I still need the pearl to cast?