Given marks for having been observant (7)

I believe the answer is:

spotted

I'm a little stuck... Click here to teach me more about this clue!

'given marks' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps you can see a link between them that I don't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for spotted that I've seen before include "As Dick may be" , "Observed" , "Dappled - saw" , "Noticed" , "Saw; mottled" .)

I've seen this clue in The Irish Independent and The Globe and Mail.

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