Question

Explain."some of the life forms are poisoned by oxygen"

Answer 1

Oxygen makes up 21% of the Earth’s atmosphere, and we need it to breathe. But early organisms would have found this environment toxic. Ancient bacteria evolved protective enzymes that prevented oxygen from damaging their DNA, but what evolutionary incentive did they have to do this? Researchers have discovered that ultraviolet light hitting the surface of glacial ice can release molecular oxygen. Bacteria colonies living near this ice would have needed to evolve this protective defense. They were then well equipped to handle the growth of atmospheric oxygen produced by other bacteria that would normally be toxic.

Answer 2

some of life forms:Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where theoxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where theoxygen concentration is lowest.