Vestigial organs or parts of the body
are those that has lost its function in the course of evolution. These organs
or parts have degenerated or atrophied. It can appear as remaining small or
imperfectly developed. An example is the tiny eyes on an insect living in a
lightless cave.
Technically you are able to argue both ends. Biotic factors are living things while abiotic factors are no living things. since the plant was once living, you can argue that it is a biotic factor, however, I would say the dead plant decay would be abiotic because it is not living anymore. I hope that helped!
