Hydra removes undigested food by

Which structure is the glomerulus?

Free nitrogen is released to the atmosphere by

The part labelled 3 is the

If the blood is too concentrated, more water is absorbed from

In a reflex action, impulse flows from

Physiological adaptation to very dry condition in animals is called

All the cell bodies in the spinal cord are found in

Viruses are considered to be living organisms because they