Ngram ecological terms

The recent availability of google ngram data is a great source of data on language use. Here are some terms from ecology from 1890 to 2000 (from here: http://ngrams.googlelabs.com/). Note that the word "ecology" doesn't appear at all until about 1890.

Notice the close alignment of "ecology" and "ecosystem", while "predation" and "facilitation" put in somewhat equal showings. "Parasitism" is almost constant through time, while "mutualism" falls way below predation and facilitation and parasitism. 

Google Ngram plot of six ecological terms + environmentalism for giggles