Biology question: How are phylogenetic trees arranged?

[imabrat]

I'm blanking out on this one, and the book doesn't explain it very well. Can someone explain to me how a phylogenetic tree is arranged?

 

[crazytp93]

I'll try. lol.

It shows the evolutionary relationships b/t a common ancestor.

So humans, for example, come off the same branch as, say a gorilla and a chimp, because we share a common ancestor with them.

The type of graph it is determines how fast it evolves. Curved lines mean it slowly changes over time, but at a steady rate. The lines that look like forks (best visual I could come up w/, sorry =P) mean that its changing but in times where it can not evolve at all, and then a change in line movement would signal evolution.

Sorry if its so vague, I have a hard time explaining it over the computer.