Lens for Nikon D 5100 camera?

I have just bought a Nikon D 5100 camera. I'm now looking to buy a telephoto lens for the same. I wanted to know which would be the ideal lens for taking wildlife photographs and photographs of my children.
Do i need to buy Nikor lenses only or do other lenses work OK?
How important is the auto-focus being inbuilt in the lens. As my camera does not have a AF motor on the camera, it needs to be on the lens. So is an AF motor necessary on the lens?

Minolta to nikon lens adapter?

I have some old manual focus lenses from my minolta x-700 that i want to use on my nikon f-mount camera, i have read some forums and they say its impossible to focus correctly, but the 'Zykkor Minolta MD Lens to Nikon Body Adapter' claims to be able to focus to infinity without any glass components. What should i believe?

How to take pictures like this?

I have a Canon PowerShot S70 but I think I need something like an SLR camera to take pictures like the one above

I was also going to buy this. Do you think it's a good deal? And will it allow me to take photos like the one in the link?

http://www.gumtree.com/p/for-sale/nikon-film-slr-with-35-70mm-lens/77177625

Thanks a lot for the help in advance, I really appreciate it

Added (1). Do you know how good mine is? I feel like because it's not an slr I need to get rid of it. I was thinking of selling it for around 100 pounds.

How to take pictures like this? - 1

I have a Canon PowerShot S70 but I think I need something like an SLR camera to take pictures like the one above

I was also going to buy this. Do you think it's a good deal? And will it allow me to take photos like the one in the link?

http://www.gumtree.com/p/for-sale/nikon-film-slr-with-35-70mm-lens/77177625

Thanks a lot for the help in advance, I really appreciate it…

Good camera under £160 for wildlife photography?

I have looked at Fuji s1730 and Nikon L110 and would like some suggestions like these 'bridge' cameras. Ideally 11MP + and 720p recording. Thanks. If not bridge a digital camera thats fits these capabilities would be fine. Also having panorama feature would be good.

Can you use Nikon lens on another dSLR?

Does it matter what type of lens you use? I really wanna get a Lumix GF2, but I have Nikon lens… Would that work or should I just get Panasonic Lens?

I'm getting the nikon 300d but I don't know what lens to buy?

I like to take detailed photos of animals and people

Need a lens for my nikon f60?

I just bought a Nikon F60 body and I don't think it's autofocus will work with any new autofocus lenses… What kind of lens should I look for if i want it to be compatible with my f60?

Are film SLR camera lenses universal?

Basically I broke the lens on the Pentax p5 I have, and i was wondering if all the lenses for pentax (that are usually put onto the digital slr's) will fit onto mine?
and do they make like, adaptors? (because all my other lenses are nikon) So that i could put my nikon lenses to my pentax?

Added (1). And is it worth it just buying a new camera because i only paid like £10 for it in a charity shop?

How much do professional (not just like digital) cameras cost?

I'm 15 years old, and really like photography. However All i have is a battery-operated digital point and shoot camera. I'd like one of those nice black ones with a big lens, like Nikon or whatever. I'm new to the fancy camera world- where can i get a cheap one? Any recommendations?