Disappearance of META Widget and Share Buttons in Twenty Eleven Theme V 1.5

I changed the theme of my site from twenty ten to twenty eleven version 1.5. After changing it, I noticed that the Facebook,twitter and other share buttons displayed below every post have disappeared. I had used one of these buttons,Facebook button, sharing my latest post to my Facebook account many times.Now I cannot do it by just clicking the button because it is not there anymore. So I have do it by copying the link of the post’s page, and post it in Facebook or Twitter manually. However it is much better when the share buttons are available so it is easy for the readers to share posts to their social media accounts if they like them. Other than that, I have noticed that the META widget which contains WordPress.com, Log In/Out, Admin Site, and others have also disappeared.
Soliciting your opinions on how to retrieve those things in my twenty eleven theme is highly appreciated. Many thanks in advance!