
EnvironmentSeptember 1, 1970
The Oxygen Cycle
The oxygen in the atmosphere was originally put there by plants. Hence the early plants made possible the evolution of the higher plants and animals that require free oxygen for their metabolism

The Oxygen Cycle
The oxygen in the atmosphere was originally put there by plants. Hence the early plants made possible the evolution of the higher plants and animals that require free oxygen for their metabolism

Acetabularia: A Useful Giant Cell
This marine alga grows to a length of an inch but has only one cell and one nucleus. It is therefore almost ideal for studying the relations between the nucleus and other parts of the cell