The acorn is not a tree
The pro abortionists sometime use the analogy of an acorn not being a tree in order to demonstrate that a fetus is not human. They say that just as the acorn has the potentiality to be a tree, the fetus also has the potentiality to be a human; but since potentiality is different from actuality, it follows that, actually, the fetus is not a human, and the acorn is not, actually, a tree.
Also, let's assume for the moment that the tree in question is an oak tree and the acorn is from that an oak tree. The problem with the above argument is that the acorn is by nature oak. It is not a tree. By definition, a tree is a fully developed plant. An acorn, by definition, is an undeveloped plant. Therefore to say that an acorn is not a tree is correct. But, it is still oak by nature. This is not a correct analogy anymore than to say a baby is not an adult and therefore the baby is not human. By definition, a baby is human as is an adult. Therefore, the problem with this defense of aborting babies is that it uses an improper pair of words without dealing with the nature of what those words represent.
Let's look at it again. The oak acorn is by nature, oak since it has oak DNA. Likewise, a fully developed oak tree is also by nature oak, since it has oak DNA. The difference is that one is fully developed and the other is not. The same goes with the life in the womb of the mother as compared to a full grown adult. A baby is not an adult. But both have the nature of human. Therefore, the attempted justification of the pro-abortionist is illogical and in invalid.