Projoy - Single-celled organism? It could be.
Lib - Genus, species, commonname? No to all
Uncle Korky - Wouldn't even know where to begin with this one...! The answer is a very common phrase, which I think everyone will recognise (not least because of its use in other contexts).
Projoy - Is it connected with mutation? It might be.
Rosie - Is at least one of the words on the card Latin? No - all plain English

Rosie] To be properly pedantic, one of the words is a Latin word which is in everyday use in English.

(It's not "little green men" as all three of those words are Germanic in origin).

Projoy - Something to do with alien life? *the audience begin humming John Williams tunes* YES

Projoy - Extra Terrestrial Beings? Yes, but more specifically...
Raak - Unidentified Flying Objects? No

(or possibly just Life on Mars, I suppose.)

*Sailors fighting in the dancehall
Oh man, look at those cavemen go*
Life on Mars it is - which I thought would be got a lot sooner. Hopefully we'll grok the next one quicker...

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Huzzah! I slightly carpet-bombed my way to that one, but I was bored at work today... Had a few abstracts lately, so here's an honest-to-goodness VEGETABLE

Actually, I just thought of a better one, which is NONE OF THE ABOVE

[Raak] Newton/Apple? NO