Help!

I need some advice on my singing,
cuz we need to play for our practical exam in my music subject and i was assignedt to do vocals for our band
the thing is, uhmm so i recorded myself with my phone,

http://boomp3.com/m/6109f3f06d3d


i think i sound bad, my father and lil sis do too,
how can/will i improve?, what key do i sing and what songs can you recommend for my voice?
lastly, do you think my voice will improve if i was using a mic?
here's another one..

i tried to do some screaming on this one..

http://boomp3.com/m/be8e75751628

There's no music.. I know that I can never sing very well without the music to accompany me. And yes, it's practise.. I find that if I sing close enough to something solid (like my computer monitor) the sound bounces off it and back into my ears better and I can hear whether I am off pitch or not... You only have to listen to a handful of really famous singers to know that they all can't sing like Celine Dion. The most obvious example of this is Bob Dylan, he has.. let's say.. a unique voice. ;)

A microphone won't make you sing better, it will just let you hear yourself (eg. through headphones) much easier and be able to much more easily hear yourself going off key etc