Why do giraffes have purple tongues

This week for writing we were learning to use a diagram in are writing so I chose a topic and I started to write and my topic.It ended up being why do giraffes have  purple tongues  and when were finished we had to peer assess with a buddy.I found it easy to come up with a topic and brainstorm it but I found it challenging to find a diagram. This is my story and diagram I used,       

Giraffes use their tongues to eat leaves all around thorns. The giraffe's tongue wraps around the branch and the leafs stick to the giraffe's tongue and the thorns don't hurt the giraffe's tongue.Their tongue works like a squishy object and is basically imoun to the thorns.A giraffe’s tongue has a ability to to grasp which mean it can stretch 18 inches to 20 inches.Giraffes have purple tongues so they can eat leaves around thorns.