Spiked and studded dog-collars derive from the days of the Ancient Greeks, who would give their sheep-dogs sharply spiked collars to protect their necks from wolves whilst they watched over a Sheppard's flock at night.

Some sharks remain on the move for their entire lives. This forces water over their gills, delivering oxygen to the blood stream. If the shark stops moving then it will suffocate and die.

Micro-organisms have been brought back to life after being frozen in perma-frost for three million years.

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