How does the Respiratory system fight off pneumonia

What is the ecological role of food chains and food webs

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?

Make a claim about the factors that cause inherited genetic variations within populations. also make a claim about the effects of mutations.