you will not get ripped through weightless exercise pooky, i'm sorry to break it to you. if you want to maintain health it's fine but you need weights.
agreed
but there are types of push ups and pull ups you can do to give you a bit more muscle definition
do push ups with your feet raised (on a chair or something) for the top of your pecs (the part that chicks will see when you're wearing a v-neck shirt)
doing push ups on your knees ("girls push ups") really works your biceps depending on how close you keep your arms together.
you can do overhand pull ups, it'll help most of your arm and by raising your chin to your right hand, then to your left and continuously alternating where you pull up to you can work your back
there are probably a whole lot more but those are the ones I've tried and show results though nothing great like weights