Although they were once classed together, archaea and bacteria have now been separated into two different domains. why was this change necessary?

a. the archaea only have cell membranes and the bacteria only have cell walls.
b. the two groups are composed of species with different cell sizes.
c. the archaea have nuclei and the bacteria do not.
d. the two groups replicate their dna in different ways.

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?

Asolution of an enzyme and a substrate was placed in a water bath and the temperature of the reaction was raised gradually. the graph shown was plotted at the end of the experiment. what can be concluded from the graph? a) temperature has no effect on the activity of the enzyme. b) the effect of temperature on the enzyme is unpredictable. c) the enzyme shows increased activity up to a certain temperature. d) the activity of the enzyme is inversely proportional to the temperature.

Describe the function of the endomembrane system? what organelles are involved?