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What is a dinosaur? & when did they live??

What is a dinosaur? & when did they live??

Saturday, 4 June 2011

Tundra
Tundra is the cold, treeless region around the poles that has permafrost as one of its defining features. Even at the height of summer, the soil a few centimetres under the surface remains frozen. The tundra therefore lacks animals that dig deep burrows and plants that require deep root systems. The permafrost, plus the short summer and seasonal waterlogging, also explains why trees don't grow here.

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