Which describes a difference between birds and mammals? Birds protect and feed their young.
Birds have nearly hollow bones.
Birds undergo internal fertilization.
Birds efficiently transport oxygen to cells.

What is the function of nucleic acids

Why is the theory of evolution important? it disproves all other theories about how life began. it provides a topic for debate. it is a unifying concept in biology. it explains how life began. i know for sure, it is not "it is a unifying concept in biology."

When is your breathing likely to speed up? a. when your white blood cells increase b. when your cells need more energy c. when your heart cells need more carbon dioxide d. when your blood cells have too much oxygen