a tree is a kind of plant & an example of observing things is taking a picture ->  taking a picture of the tree can be used to observe the tree  taking a picture of the tree can be used to observe the tree & taking pictures is similar to recording images ->  recording images of the tree can be used to observe the tree  recording images of the tree can be used to observe the tree & a camera is used for recording images -> a camera can be used to record images of the tree for observation