Which biome is characterized by very low temperatures and permafrost?

The tundra biome is characterized by extremely low temperatures, which often remain below freezing for much of the year. One of the defining features of the tundra is the presence of permafrost, a thick layer of permanently frozen soil found beneath the surface. This permafrost limits the types of vegetation that can grow, as only plants with shallow root systems can survive in the harsh conditions. The growing season is short, and the harsh climate creates a unique ecosystem with adapted flora and fauna.

In contrast, deserts are defined by minimal precipitation, rainforests are known for high rainfall and biodiversity, and tropical savannas are characterized by a mix of grassland and scattered trees, with a warm climate that does not support the extreme cold and permafrost found in the tundra. Therefore, the tundra is the ideal answer, as it uniquely encompasses both the low temperatures and the permafrost conditions described in the question.