According to scientific evidence, earth’s earliest atmosphere lacked oxygen. over time, oxygen was added to the atmosphere. which statements explain how this change occurred and how it affected life on earth? choose all answers that are correct.
a. the addition of oxygen to the earth's atmosphere make possible the development of eukaryotic organisms, which need oxygen to carry out many of their life processes.

*will mark brainliest to first correct answer* photosynthesis led to increasing levels during the later proterozoic eon? a. oxygen b. water c. carbon dioxide d. none of the above

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

Which of the following is a macronutrient? carbohydrates lipids amino acids all of the above