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1. Alveoli in the mammalian lung are thin walled to allow the quick passage of gases, for example oxygen and carbon dioxide.

2. Alveoli in the mammalian lung have a large surface are...

When cells divide by cytokinesis the nucleus also has to divide so that each new cell contains a nucleus with a complete copy of all of the genetic information. DNA replication therefore needs to ensure t...

Firstly, the 'wave of excitation' is produced by the sinoatrial node (SAN) in the top of the right atrium - this is also known as the pacemaker, as this is what controls the rate of contractions. This wav...

When a neurone is stimulated an action potential is generated by a change in ion concentrations across the cell membrane. The resting membrane potential (the potential of charge across the membrane when t...

Water moves into the plant stem from the soil, and up to the leaves via the xylem. Water is taken up by the hairs on the root of the plant down the water potential gradient via osmosis, following the acti...