When kingdoms were the highest classification, plants, animals, and fungus were in completely different groups. The differences between them could be seen as equal to the differences between those three and bacteria. Now that Domains exist, that has changed, and the relationships between plants, animals and fungus can be shown more clearly.
So basically, Domains show that some kingdoms are more closely related to each other than others, and kingdoms that are related are put in the same domain.
You need to describe how using Domains changed the way people looked at relationships between kingdoms. Then give 3 pieces of information to show why scientists chose to start using Domains. You can use examples of the body structure, types of molecules inside organisms, or differences in DNA as your answer.
The last part of the question asks you to use the way organisms are put in Domains to describe four characteristics that the first life form would have had - would the first cell have had a nucleus? would it have been multicellular? Would it have highly developed organelles?
I hope that helps you out! Good luck!