Looks Like?

Seem is usually used when there is no direct observation.

She seems to be happy. (I listened to her talk highly of her son's exam performance.)

Here, we don't know if she is really happy.

And, as for "look like", we usually use it when we sense some cues about what we understand.

I am seeing a lot of people at the exhibition. It looks like there are at least 500 people here now.

So, when it comes to your sentence, we can use look like when speaker has first hand cues of the situation. Seem can be used when he or she has got the information from others or read about it somewhere.

kumenglishIt looks like more than 100 people turned up at the business event.

It seems that more than 100 people turned up at the business event.

Correct, as shown above.

kumenglish

It looks like more than 100 people turn up at the business event.

Semantically, it doesn't make sense as written. If the event already had taken place, then you need past tense "turned out", or showed up", so "turn up" is in correct. My suggestion: It looked like more than 10,000 people turned out at the convention. With this statement, you felt 10,000 people showed up but you weren't positive. So "looked like..." is correct.

It seems that more than 100 people turn up at the business event.

Same goes for # 2

Do they give the same meaning? He seemed nervous = He looked /appeared to be nervous.

anonymousso "turn up" is in correct.

Thank you, anon.

I was wrong here. It should be turned out or showed up, as you have suggested.

Suresh

"Turn up" is less common than showed up, but still correct.