Answer: Vestigial organ
Explanation:
Vestigial organs are those organs which were functional in ancestral organisms belonging to the same species but due to the course of evolution of body forms they become non-functional. They can be found in the body either in the same form as used to appear in the ancestors or in rudimentary or degenerated forms.
The human appendix is one of the examples of vestigial organs. It looks like a narrow tube which forms a link with a colon of the large intestine. It was functional in human herbivorous ancestors as it used to help in digestion of variety of vegetables and other plant products. The change of diet along with due course of evolution caused the appendix to become useless. But the appendix physical form remained the same in humans.
Explanation:
In thermoplastics, the arrangement of monomeric units is linear and in thermosetting plastics, it is cross-linked. Thermoplastics are usually soft, weak and less brittle, so can get soften on heating and stiffen on cooling. They can be melted, remoulded and recycled easily.
