Answer: The hilum is the point at which arteries carrying nutrients and lymphocytes enter the lymph node and veins leave it. Afferent lymphatic vessels enter the lymph node through the capsule peripherally and efferent lymphatic vessels leave the node via the hilum.
The answer is the forcing mechanism. It is the process that would alter the balance of the climate system that includes solar irradiance,the volcanic eruptions as well as the enhancement of the greenhouse effect through emission of the carbon dioxide.
Bats are very unique and interesting organisms, as they live all there life away from sunlight, they are considered to be the most advance of all the predators just because of having a sonar system inbuilt in there body system. While, they feast on there food outside the place where the remain most of the time and those places are caves.
Now, caves are more then just we exactly know, caves comprises of the different level of organisms and they play a very vital role in the over all balancing of the ecological system.
As, there are some insecticides, and other large organisms which then feast upon the bodies of bats corpses or when they are injured due to some reason. So, they play a vital role in the over all ecological food system inside the caves as well.