Technically, the black widow spider is the deadliest spider despite it's size, due to it's overwhelmingly potent venom, which can and will kill a human if no medical attention is sought out for the person bit.
Ozone is the pollutant that forms when automobile emissions react with oxygen gas and ultraviolet light.
Answer: If the global warming trend continues and permafrost under the tundra melts, the biome that would you predict would replace it is:
Boreal Forest
Explanation: A boreal forest is a vegetation composed primarily of cone-bearing needle-leaved or scale-leaved evergreen trees, found in northern circumpolar forested regions characterized by long winters and moderate to high annual precipitation.