Great Danes stretch more than a meter from paw to shoulder and can easily weigh more than 90 kilograms. A Chihuahua fits snugly inside a purse. Domestic dog breeds are more varied in body size and shape -- not to mention coat color and fur length -- than any other land-based mammal. Yet, according to a new study, a mere two to six regions in doggy DNA account for most of this diversity.

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Like an engineer accounting for a skyscraper swaying in the wind, Madagascar's Darwin's bark spider (Caerostris darwini) spins enormous, river-spanning webs that stretch and contract as the trees to which they're anchored bend this way and that. A new study finds that this spider's silk is the toughest biomaterial yet discovered.

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