The hollow bones of birds, which keep lightweight for flying is an example of a(

Why are adults bigger than they were as children biology

The oxidizing agent our bodies use to obtain energy from food is oxygen (from the air). if you breathe 15 times a minute (at rest), taking in and exhaling 0.5 l of air with each breath, what volume of air do you breathe each day? air is 21% oxygen by volume. what volume of oxygen do you breathe each day?

Which is an example of a population?