Install [Better Exposed Filters][1] module. Under advanced portion of view choose following

    **Exposed form**
    Exposed form in block: Yes
    Exposed form style: Better Exposed Filters | BEF Settings

Then Choose autosubmit in BEF Settings as shown below

![enter image description here][2]

This will hide Aply button and the select list to work directly on selecting an item, instead of clicking on Apply button.

  [1]: http://drupal.org/project/better_exposed_filters
  [2]: https://i.sstatic.net/5QW2P.png