Cats are still cats, dogs still dogs, roses still roses. Large accumulated change leads to sterility. The theory of evolution is built on the assumption that the limited changes that have been observed in nature, continued for millions of years, could indeed transform primeval slime into modern people. This kind of thinking is called extrapolation. In extrapolation an observed set of data is the basis for inferring or assuming that other things not observed are also true.
Science deals with that which is observable and reproducible.
But evolution of new kinds of plants and animals is not observed and cannot be reproduced in the laboratory. The new discoveries in the four decades of molecular biology about the detailed structure of DNA molecules comprising the genes have failed so far to give evolutionary scientists a scientific theory for evolutionary change, i.e., the origination of complex new biological designs. He would not be able from the DNA to tell what the structure, functions and behavior of the organisms are. Therefore, there is no scientific theory of inheritance , for although we know much about how DNA is inherited, there is no general theory by which we can tell what structures, functions and behavior are being inherited. He would not be able from the DNA to predict what the course of development from fertilized egg to adult will be.