immuno=genetics<ecology
*While genetics in important on the DAT, your intro bio classes should pretty much cover the material (hardy-weinberg, punnett squares, linked, unlinked, codominance, etc...) if you don't know this stuff than definitely take the genetics course. Ecology can be random and not covered by intro bio classes so thats why I am saying ecology.
But, I bet the order reverses in terms of which class looks better on applications