searching polygons

What query would i have to use to search for an item using a polygon as a
parameter? (i.e a very large polygon that would identify smaller polygons
within it) ideally i would like to give postgresq a series of co-ordinates
and then have it return all those results whose polygons fall into that set
of co-ordinates, is this possible?

at the moment all i can think of is


select * from species where location between '(0,0)' and  '(1000,0)' and
'(0, 1000)' and '(1000; 1000)';

I think im way off, any suggestions?

Cheers Dave