define vestigial and how many vestigial organs in humans beings amd and example it ??
Answers
Answer:
Vestigial organs are non-functional organs in an organism which are functional in related animals and were functional in the ancestors. There are 90 vestigial organs in the human body and mainly include coccyx (tail bone); nictitating membrane (3rd eyelid); caecum and vermiform appendix ; canines ; wisdom teeth etc.
Explanation:
Examples of Vestigial Organs
Following are a few examples of vestigial organs:
Sinuses
Human cheekbones hold the maxillary sinuses. The face consists of pockets of air called sinuses. They are lined by a thin layer of mucosa. It has no significant use but infection can lead to sinusitis.
Appendix
It is one of the most commonly known vestigial organs. This finger-like tube closed at one end arises from the vermiform process. In prime ancestors, the appendix is believed to have brought about the digestion of cellulose. Today, scientists predict that the appendix may play a role in digestion by bacteria.
Coccyx
It forms the last part of the vertebral column, the residue of the lost tail and is often termed as the tailbone. It is observed during human embryogenesis. This formed as the centrepiece of the ‘theory of recapitulation’.
Wisdom Tooth
Forms the third set of molars in our buccal cavity. They may have been significant in the past(chewing rough and raw food) but in modern times, as they are inaccessible and remote, it causes pain and infection.
External Ear
The Helix(outer rim of the ear) is known to be a vestigial structure. Underdeveloped muscles in the ear make us incapable to bring about the movement of ears. Darwin’s tubercle is a vestigial feature present on the juncture of the upper part of the ear.
Nictitating Membrane
Nictitating membrane is the third eyelid found in a few animals that protect and keep the eyes moist and also helps in vision. In humans, it is replaced by plica semilunaris.
Tonsils
The tonsils remain as vestigial organs in the human body. They act as the first line of defence and protect the body from harmful microorganisms that are either inhaled or ingested by the body.etc
Hope it helpful
Mark me as brainliest answer