Random changes are things like mutations that don't confer a benefit to the individual. For example, Down's syndrome is a random mutation where the individual has three copies of chromosome 21. This is being filtered out by natural selection because these individuals have a decreased life expectancy and are going to have a shorter time period in which to reproduce and pass on their genes. Therefore, they will comprise an increasingly smaller part of the population (assuming this was a strictly random mutation and not influenced by age). So use this info to think up some other examples you may have learned in class and then give your opinion about whether you agree with all of evolutionary theory. You just need to justify your choice.