If I am not wrong about this, we must use look when express a quality of person, animal or object (the verb "to look is a linking verb like others: to become, to seem, to be). On the other hand, we must use look like when there is the necessity of to do a comparisson between two people, two animals or two things, al last when we want to do a comparisson. My answers follow below:
1. What's the matter with you? You look worried.
2. Anna doesn't looks like her mother.
3. I'd like to know if he looks like us.
4. Jack looks happy. He must've seen Jane today.
5. It looks like rain.
6. This tree looks like that one over there.
7. Mary looks beautiful tonight.
8. You look younger now.