What on Earth Evolved? by Christopher Lloyd
There's an SF story in which aliens study Earth and decide what's really in charge there: grass.
In fact, poa pratensis and its cousins comes in only at number 24 in this addictive guide to the 100 species that have had the greatest impact on the planet over its evolutionary history.
Stretching via bite-sized essays up a chain of being from Anthrax to Rabbit, Herpes to Whale, the book finds a bewitchingly fresh way to present the greatest show on earth. Given all his variables, you can argue with Lloyd's order. But here's (most of) his Top Ten: 10/ Penicillium; 9/ Influenza; 8/ Yeast; 7/ Stony Coral; 6/ Homo sapiens (well done us!); 5/ Lactobacillus; 4/ Rhizobia... for the rest, use those over-developed brains, or buy a copy yourself.