If you're referring to Prof. Aurea Juniper's request, then yes, you can just see the Pokemon and she will give you your reward.
If you're referring about Prof. Cedric Juniper's request, then no, you have to catch every Pokemon in the national Pokedex (except event legendaries), not just see them.
You might as well catch the Pokemon; you need to do that for Prof. Cedric's request anyway.
