HTML Anchor and Input Button Font Difference

Anyone knows why the font of this elements are not the same?

Using Anchor Element

<a style="font-weight: bold; ">bold</a>

Us开发者_StackOverflowing Input Button

<input type="submit" value="bold" 
style="font-weight:bold; border: none; background-color: transparent" />

That's because the font-family and font-size are different too:

see
http://jsfiddle.net/RQBr3/

vs
http://jsfiddle.net/RQBr3/1/
with font-size and font-family added.