The dog family can be used as a good example. The Great Dane is an ext- remely large dog weighing more than one hundred pounds, while the Chihauhau is the smallest of dog species and may weigh between one and six pounds. There is tremendous variation in size between these two, but they are both dogs. This is exactly what is seen in the geologic record. There is a variability about a mean within a particular kind of species but distinct separation between types.
Birds always remain in the bird family and lizards are always in the lizard family.
The fossil record also shows an amazing amount of stability for some particular species. This has baffled evolutionary scientists because it is contrary to the prediction of constant change and increasing complexity as time progresses. Some species have died out and become extinct, while others have appeared suddenly only to disappear again. There are other branches of science which also support the creation model. The age of the earth is also highly debated.