An intervening variable facilitates a better understanding of the relationship between the independent and dependent variables when the variables appear to not have a definite connection. They are studied by means of operational definitions and have no existence apart.
Macroevolution is the process that takes place over several thousands of years and describes how humans have evolved from primates and how reptiles turned into birds. Microevolution leads to small changes in the same species whereas macroevolution leads to the creation of a new species from parent species.
Micro lenders operate in the same way banks do. They get people to invest with them and pay them interest, while lending out that money to people who ask for loans and charging interest on those loans. The difference between micro lenders and banks is that banks have a ceiling on the amount of interest they can charge, which is stipulated in the Usury Act.