The Arctic tundra has extremely cold winter temperatures and short winter days. In contrast, summer days are long and moderately warm. Small cushion plants, blueberries, birch, and willow, which grow in a thin layer of soil atop permanently frozen soils, form the base of the food chain. Lichens are also abundant on the tundra. The plants and lichens are eaten by caribou, pika, moose, and grizzly bear. Grizzly bears also eat the caribou, pika, and moose. Which items are part of the Arctic tundra ecological community

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.