Answer:
Unique physical appearance, behaviour and intelligent mind.
Step-by-step explanation:
Humans are significant in the vast universe because of their unique physical appearance, behaviour and mind. Humans are the most powerful social animals on the planet of earth due to their intelligent minds which able them to formed certain technologies which help them to find out the life on other planets which is farther about millions of kilometers from the earth. There is no life on other planets except planet earth so that's why humans are significant in the vast universe.