Why have biologists hypothesized that the first land plants had a low, sprawling growth habit?

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 of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

Nh3 +02-no + h20 is unbalanced what is the balanced equation