Ecological Implications of Human Alterations to the Nitrogen Cycle Many human activities have ... increases in nitrogen can often lead to anoxia (no oxygen) or hypoxia (low oxygen), altered ...

This daily feast-and-famine cycle in oxygen availability created an intense physiological challenge for early animals, ...

Carbon dioxide (CO₂) pollution drives climate change, warming the planet and threatening human survival. Plants naturally ...

We report the first evidence that oxygen tension ... activity in human fibroblasts. Sparse cultures of embryonic fibroblasts were synchronized in the G 0 portion of the cell cycle by serum ...

If you were in the bloodstream, you would follow the steps below one by one. Oxygen-poor blood (shown in blue) flows from the body into the right atrium. Blood flows through the right atrium into ...