Final answer:
The selva is a part of the Amazon rainforest with immense biodiversity and is considered one of the richest biological resources. It isn't the largest rainforest alone but forms a large part of the extensive Amazon rainforest and covers a significant area of Brazil.
Step-by-step explanation:
The rainforest referred to as the selva is indeed one of the richest biological resources in the world because of its immense biodiversity. Tropical rainforests, like the Amazon, which includes the selva, play a crucial role as nature's pharmacy due to the multitude of plant species that have the potential for new drug discovery.
Yet, these rainforests are under significant threat from deforestation caused by logging, cattle production, plantation agriculture, and slash-and-burn farming practices. While the selva within the Amazon rainforest is not the largest rainforest in the world by itself, the Amazon as a whole fulfills that criterion. Lastly, the selva does cover a substantial part of Brazil, contributing significantly to the country's natural landscape.