There are lots of fossils in the fossil record that show a gradual change like land mammals to whales. There's also lots of gaps. The conditions necessary for fossilization aren't common. You'll never see a transition of a bird to a dog, because that's not what happened. This [url=https://www.google.com/url?sa=t&source=web&rct=j&ei=47wIVaBA0a2iBMnzgrAH&url=http://m.youtube.com/watch%3Fv%3DhOfRN0KihOU&ved=0CBwQtwIwAA&usg=AFQjCNG_qpy50i9dm1TMb5m72aP2UdZARg&sig2=h1gy8Q1HaDfooD1qwDmlxA]video[/url] is the best one I've found for explaining it simply.