Forests and other green plants uses carbon dioxide in photosynthesis thus lowering its amount in the atmosphere. In assumption, we can claim that in the ice ages, the low level temperatures may have caused the carbon dioxide levels to neutralize over these phenomenons, also to note that there were less oxygen-breathing organisms and higher carbon-dioxide dependent performing photosynthesis.
Immune system that is the answer to you question I think
To be malnourished means to lack proper nutrients that keep you healthy say a person likes fast food and eats only fries for a long period of time they will lack nutrients and get sick which is the bodies way of saying you need to eat a variety of food.
When that bacteria changes in some way that reduces or eliminates the use of the drug.
