When many scientists reach the same conclusion the conclusion can be called?
A theory. It's not "popular" -_-
When scientists are doing research to determine how the environment affects a life form it often takes many years to reach a conclusion why do you think that is the case?
There are many environmental factors that can affect a life form, and changes occur over time, usually. Scientists must figure out which environmental factors affect a life form and observe the effects over time before any conclusions can be reached. Also, the environment is a complex interaction of many factors, so more than one single factor may interact to affect a life form.
There are many different types of scientists because one person could not handle all the information of geology, astrology, and other types of science. Since there are numerous types of sciences, there has to be many different types of scientists, so there are many different scientists because there are many different sciences.