removing blanks and duplicates in drop down list (with attached workbook)

Please view attached workbook.

Each cell in column B has a drop down menu. This drop down menu shows duplicates and blanks.
I know very little about excel, but the A column will have hundreds of animals and I need to tag each animal with its family without using a predetermined list. Imagine it was a test where the student had to correctly input the family of the animal (not multiple choice but he has to come up with the answers himself but he would like the list to grow as he progresses so he doesn't have to retype the same thing repeatedly) but did not want to have duplicates or blanks in the drop down list. Thanks.


I have also posted on another website in hopes of getting an quick answer.

http://www.mrexcel.com/forum/excel-q...down-list.html