Research and identify a vestigial structure of an organism of your choosing. Why does the organism not need that structure anymore? (Think about what the structure's original purpose was.)

The one of best example would be appendix in humans.

Explanation:

In the past, the appendix may have helped in the digestion of the plants by producing mucus and prevent any type of infection. Plants with a high content of cellulose are digested with the help of the appendix as reported.

It is not a part of the human digestive system and considers as a vestigial organ. Vestigial organs are the organs that are present in an organism with no particular function and their removal will not lead to any harm. Humans do not need it because our digestive system is more efficient and works better in the first stages of digestion than they used to.

Thus, the correct answer is - appendix in humans.