There are two ways to look at the “gaps” in evolution, and these blind spots are innumerable. Just a few examples of the top of my head, 1) how did membrane-covered eggs laid in water evolve into hard-shelled eggs laid on land, 2) where did lungs come from?, and 3) why did eye lenses develop?
One way to look at these unknowns is to say that they show that the theory of evolution is not consistent, therefore it is not true. This sort of view usually comes from someone with a different agenda (creationism) who is determined to make this theory appear to be false. Yet these gaps actually show that what we lack is the data to fill them. THe reason is that 99% of the species that have occupied the earth over the history of life have disappeared and we have none of their fossil records to bring them “back to life” (metaphorically). In fact one of the essential ingredients of understanding the theory is to look at the whole evolutionary picture with all of the innumerable gaps completely visible. Anyone who can stand back and look at “all of life” will naturally understand that the blind spots must be there because we simply lack those essential bits of evidence. Yet those gaps in no way lessen the veracity of the theory.
The other way to look at the gaps is to imagine how they might be filled. This use of the human imagination is essential to hypothesizing about alternative explanations for the existing forms. The egg dilemma is very easily “imagined away” - (laying eggs in marshes and peat beds will change the environmental conditions from eggs laid in water, certain types will be better suited to survive, same goes for the membrane coverings, etc., until we eventually see the emergence of bird-like eggs). The appearance of lungs is largely taken up by the lives of amphibians and the explanation for the emergence of complex eyes can also be imagined by looking closely at the genetics and the stages of development in gestation . . . plus imagination. This ability to use your imagination to hypothetically “fill in the gaps” goes a long way to showing that the gaps are indeed only a lack of physical evidence (and nothing else). Of course the imagined fillings could be completely incorrect, but they give us a probable scenario and when the final data is discovered and analysed, it’s not unusual to think “I’d never have imagined such a scenario.”
Finally, pecking little holes in the theory here and there and then saying that it doesn’t hold up is quite ludicrous when everyone knows that at the level of individual creatures, the theory is obviously (and naturally) full of holes. One MUST be able to see the big picture when making the assessment as to the credibility of the theory of evolution. One must take into account that these changes take place over billions of years. One must know that there is no goal in the process, that every living phenomenon along the way, including all those that presently inhabit this planet are “in the process” of evolving (as species in the big picture of life). Evolving does not happen at the level of individual creatures. At this particular level it is the mechanisms that are at play, mutations, selections, survival, etc., but the theory of evolution is about the macro level of life over great expanses of time and space that is the only way to understand it.