Observational Science
What is the definition of "science"? There are many different explanations, but most include words like "observation" and "experiment". One definition of science is, "the systematic study of the nature and behaviour of the material and physical universe, based on observation, experiment, and measurement, and the formulation of laws to describe these facts in general terms", (Collins English Dictionary).
The evolution of one kind of animal to a completely different kind (such as fish to land animal, reptile to bird or dolphin to cow ...) has not been observed, nor demonstrated by experiment. For that kind of evolution to happen, there must be an increase in genetic information, and yet this has never been observed, even in fruit flies that have been extensively investigated and used in genetic experimentation.
What does observational science point to? The answer is Natural Selection and animals reproducing after their "kind" (like begats like ).
Science is limited - it can take evidence and analyse it, then answer the 'what', 'how' and 'when' questions (although 'when' is often controversial ), but not the 'why' questions - these are philosophical questions, not scientific.
"Perhaps a simple illustration will help convince us that science is limited. Let us imagine that my Aunt Matilda had baked a beautiful cake and we take it along to be analysed by a group of the world's top scientists. I, as master of ceremonies, ask them for an explanation of the cake and they go to work. The nutrition scientists will tell us about the number of calories in the cake and its nutritional effect; the biochemists will inform us about the structure of the proteins, fats etc. in the cake; the chemists, about the elements involved and their bonding; the physicists will be able to analyse the cake in terms of fundamental particles; and the mathematicians will no doubt offer us a set of elegant equations to describe the behaviour of those particles.
Now that these experts, each in terms of his or her scientific discipline have given us an exhaustive description of the cake, can we say that the cake is completely explained? We have certainly been given a description of how the cake was made and how its various constituent elements relate to each other, but suppose I now ask the assembled group of experts a final question:
Why was the cake made? The grin on Aunt Matilda's face shows she knows the answer, for she made the cake, and she made it for a purpose. But all the nutrition scientists, biochemists, chemists, physicists and mathematicians in the world will not be able to answer the question - and it is no insult to their disciplines to state their incapacity to answer it. Their disciplines, which can cope with questions about the nature and structure of the cake, that is, answering the 'how' questions, cannot answer the 'why' questions connected with the purpose for which the cake was made. In fact, the only way we shall ever get an answer is if Aunt Matilda reveals it to us. But if she does not disclose the answer to us, the plain fact is that no amount of scientific analysis will enlighten us."
(From John Lennox, God's Undertaker - Has Science Buried God? - p. 40,41)