Tropical grasslands in Venezuela are known as "Llanos".

Explanation:

1. What are tropical grasslands?
Tropical grasslands, also known as savannas, are characterized by vast expanses of grasses with scattered trees and shrubs. They are located in tropical regions with a distinct wet and dry season. These grasslands are found in various parts of the world, including parts of Venezuela.

2. Llanos in Venezuela:
The Llanos is a vast plain region in Venezuela, covering approximately one-third of the country's land area. It is characterized by extensive grasslands with occasional patches of trees and shrubs. The Llanos experience a tropical climate with distinct wet and dry seasons. During the wet season, the Llanos get flooded, creating temporary wetlands that support a rich diversity of wildlife.

3. Biodiversity of the Llanos:
The Llanos is known for its rich biodiversity, with numerous species of mammals, birds, reptiles, and fish. It is home to iconic wildlife such as jaguars, capybaras, giant anteaters, and anacondas. The flooded wetlands during the wet season provide important breeding grounds for aquatic species and attract migratory birds.

4. Human activities in the Llanos:
The Llanos has significant economic importance for Venezuela. It is primarily used for extensive cattle ranching, with large herds of cattle grazing on the grasslands. The Llanos also have oil and gas reserves, which contribute to the country's economy. However, human activities such as ranching and oil exploration have posed challenges to the conservation of the Llanos' biodiversity.

In conclusion, the tropical grasslands in Venezuela are called "Llanos". These vast plains are home to diverse wildlife and play a crucial role in the country's economy. However, conservation efforts are necessary to protect the biodiversity of the Llanos amidst human activities.