Here's a recent article published in the journal Genetics. It neither cites Mendel nor Hunt Morgan, Fisher, Muller, Wright, Watson & Crick or any other founder of that science. Yet it fluently speaks of genes, mutations and all that. Take any other article that is not concerned with the history of genetics, that is not a review with a particularly long reach backwards, and is not dealing with a topic that has been particularly reticent at being solved and understood either, and you will find the same pattern. DNA, gene, mutation, likage disequilibrium, drift, epistasis etc. etc. are simply taken for granted as the basic vocabulary which a fluent researcher knows how to use properly. Using these terms and concepts does not require references to the original historical records.
This is not plagiarism but simply communicating in the specialized language of a discipline. It is taking for granted that any researcher, in the currently ruling paradigm, will know these things and that they are not new coinages but belong to the heritage of the discipline. Although it is hard to imagine that the currently ruling paradigm of genetics will ever be completely overturned and superseded, let us imagine just that, in order to illustrate a difference between communication and plagiarism.
Some readers of this imagined future would deplore the poor referencing of current researchers, because they no longer know our current meaning of terms like gene or mutation. That's what makes the job of a historian so difficult. They'd have to decode our current language first, which to them is foreign. Some future readers would even jump to the conclusion that the now living geneticists were plagiarists, because they did not, according to their future standards, properly cite the original sources. But we know from our actual experience that this future judgement would not be true. Someone who uses the term double-helix, today, without giving Watson & Crick (1953) as a reference, is simply using common knowledge that does not need special reference. On the contrary, if current authors attempted to reference each and every snippet and term they used, this would make their article completely illegible.
Back from the future into the past, there must likewise have been items of common knowledge in the past, say the pre-Darwinian time, that required no special reference. If we look at literature from that period, we find that Cuvier, Buffon and many other have often not been cited, where we would wish for such a citation. Have they therefore been plagiarists?
Academic articles are special in that they aim to give proper references for every bit of information that cannot be taken for granted as common knowledge among the peers. Such standards of citation would shred daily communication such as a talk in a cafe or pub into an incomprehensible staccato. Even those visitors that do talk science there do not constantly interrupt their communication by parenthetical ellipses giving references to their statements. Only a small number of publications will be mentioned explicitly.
That does not hinder an idea from an unmentioned publication transpiring and inspiring a researcher. However, (s)he will not know the ultimate source of the idea. (S)he might sleuth it up in a literature recherche or not, if (s)he belives it to be originally hers/his.
The conversationalists, who contribute in such an informal manner, habitually get a general thanks for help/discussions/feedback/comments in the acknowledgements but usually not a specific thanks for a specific idea or inspiration. Again, that is not plagiarism but simply what happens when scientists communicate informally.