[jQuery] combining results

What is the easiest way to combine the results from multiple jquery
objects.
for instance if i want to do an operation with each span and div tag
x = $('span');
y = $('div');
x.each(function(){alert('yo');})
y.each(function(){alert('yo');})
is there a way that i can combine x and y in z so that i can just call
the following once instead of multiple times?
z.each(function(){alert('yo');})