PLEASE I NEEED THE ANSWERS

it would lead to upper respiratory infections and pneumonia.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.