Does AutoCad LT include such objects at trees, plants, cars, etc.. in the software? If not how do I import such files? 

Hello brennanpeck, you can try and found what is loaded in your C disk with a search in C:\Program Files\AutoCAD ( probably in a directory named : templates but you can find what you want right here in the site in the CAD Blocks directory ( take a look on the top left corner ).
Launch a search with the word tree and you will find a lot of trees, lauch a search with the word car and you will find also a lot of cars...

Thanks for the information! Whats the best way to download them to Autocad, so they can be used? I download a block and when i input the block all the objects are inputted to the drawing. I'm not able to pick one object at a time. Thanks! 

You can use the DesignCenter function (Ctrl+2) to use (drag) blocks from other DWG files. Or you can download hundreds of cars and trees from the CAD block library on this web site - see the "CAD Blocks" section in the left menu.