What characterizes the tundra biome?

The tundra biome is distinctly characterized by its cold climate, which has very low temperatures for most of the year. It features treeless plains that are typically covered with snow for a significant portion of the year. The ground in this biome is also notable for being permanently frozen at lower layers, a condition known as permafrost. This frozen ground significantly impacts the types of vegetation and animal life that can thrive there, leading to a landscape dominated by mosses, lichens, and other hardy, low-lying plants that are adapted to short growing seasons.

The other options do not accurately represent the tundra. Dense forests are more characteristic of warmer temperate regions or tropical biomes, not the tundra. A hot climate and rich biodiversity are typical of tropical regions, which contrasts sharply with the tundra's harsh, cold conditions and limited species presence. Additionally, wetlands and aquatic plants are more representative of different ecosystems, such as marshes or swamps, rather than the cold, dry characteristics of the tundra.