I have muddled about with the topic for a long time:
from my freshman class in Philosophy, 58 years ago. (from memory)

"Evolution is the integration of matter and the concomitant dissipation of motion, during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, and during which the retained motion undergoes a parallel transformation."

...Herbert Spencer

We had to memorize that: I never did understand what it meant or why it was included in a basic class... except that the old man who taught it also taught religion courses, and it was perhaps a way to avoid Darwin.   

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Pete... "... changes within the organism . they call it evolution. then they talk about pond scum to people , and call that evolution, as though it were the same thing.

Well... there are changes "within the organism" that affect YOU, you highly developed bit of pond scum! We all get common colds because the virus changes so fast.... it evolves quickly.... as does the flu virus. Some diseases can be prevented by vaccination, because the relevant organism does NOT evolve rapidly.

I'm not sure why I neglected to mention this before as an example of evolution in a short time scale.

As to pond scum..(or teeny little whatevers). The evidence is there, whether you choose to accept it or not, that all life began in some primordial bubbling. It is fascinating to follow the attempts to find as many links & details as possible, even knowing we can NEVER assemble all the stages.

You might be interested to know that the guy who found the Burgess shale *(Walcott )and its weird Cambrian fossils was a very religious Presbyterian who had no problem with the 'idea' of evolution, but made some scientific errors in analysis, partly because of his religious training and preconceptions. He believed that God "revealed Himself" thru evolution, but assumed a more regular, simple progression than what we actually see.