Nyrath (now I can read the posts) is reminding us of green metallic. To recapitulate: metal-poor stars give off more UV-C (100-280 nm). About the same UV-B (315-400 nm) as the metal-rich stars, but the UV-C swamps it. UV-C upon a high-oxygen planet creates ozone, which not only absorbs that wavelength / frequency by that very creation, but the ozone will go on to block UV-B.
Anyway here's my followup question, which I hadn't considered in April. Say we got a F or (pushing it) A star, as will likely die before its planets spawn sentient life (F0: 2700-My lifespan). Its habitable zone is accordingly further-out, starting at like 1.3 AU (but much wider!). A F will shift to more UV-C baseline on account such're higher-energy. The Fs we see around us will be secondarily-generated so mostly high metallic - and will just get more metallic as they age. That's a problem for UV-C!
Let's also allow for a smaller world with higher-escape velocity. Introduce chlorophyll-bearing plants to the oceans.
Now it's 2.7 billion years from planetary-formation; this planet - yeah, it's orbiting a midrange F - has finally embarked upon what on Earth would be boring-billion. The star is already showing its age. How long before sufficient oxygen is converted to ozone, that life on the surface is untenable?
... As We Know It. Or can animal life evolve as can process ozone instead of oxygen? Oxygen-efficient life is dinosaur life; we mammal synapsids are inefficient!
As ozone-processing reaches an equilibrium (the high atmosphere is still able to block the UV-B) would this inefficient (but smarter?) life be able to live alongside birdbrained animal life as can process plain oxygen?
This life would have to have formed in an earlier generation of F star-systems. So their remains will be destroyed already, by the time palaeontologists start roaming the stars.
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