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Vestigial organs are known as the most useless body parts. These body parts remained in our bodies through evolutions. They once represented a function that evolved out of necessity for survival. But as the homo sapiens evolved, these organs proved to be useless. Some of the vestigial organs are the appendix, plica semilunaris, wisdom teeth, extrinsic ear muscles, tonsils etc.
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Key Terms: Vestigial organs, intestine, wisdom teeth, tonsils, tailbone, appendix
Definition of vestigial organs
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Vestigial organs are defined as the part of the human, animal or plant bodies that do not have any particular function. They were inherited by their respective ancestors. These organs are proof that all living beings have evolved and adapted to the current environment. Example: The nipple in a male body is a vestigial organ.
Vestigial organs
There are a total of 180 vestigial organs in the human body. In simple words, vestigial organs mean the organ that lost their function. Vestigial organs will continue to exist before they degenerate or disappear in the process of evolution.
In the human body, the appendix is a vestigial organ but for animals, it is rather a functional organ.
NCERT Solutions: Class 11 Biology Chapter 16 Digestion and Absorption
Coming back to the evolution of these vestigial organs, before civilization the ancestors of humans used to have a tail, which helped them to walk and balance their body but after the human being evolved to have a proper functional spinal cord for balance, the tail rendered to be useless. But as a result of evolution, there is still a tailbone in our bodies which eventually will erase in the course of evolution.
However, as humans evolved, the diet has changed significantly and we no longer need the help of an appendix for digestion. Sometimes people with smaller appendices are more likely to get infected and therefore they are removed by surgery.
Read more: difference between esophagus and trachea
Plica semilunaris
It is also known as the third eyelid. It is a small fold of tissues located in the inner eye of the human body. Birds, reptiles and amphibians also have this organ which helps them to keep their eyes moist and offers protection enabling them to maintain visibility while their eyes are still open.
This organ moves vertically across the eyeballs, unlike a human's upper and lower eyelids.
Read more: dental formula
Wisdom teeth
These molars at the edges of the mouth helped the early homo sapiens in grinding the raw and hard foods. Larger jaws were required to chew the uncooked food.
However, after civilisation took place, consuming cooked food became much easier and therefore there was no need for a larger jaw and molars. Evolution has thus made the jaws of humans smaller and there is less space for the wisdom teeth to be placed correctly. This is why most people experience pain when the wisdom teeth come out and they tend to remove them surgically.
These molars sometimes do not position themselves correctly and act as a place for the cavity to thrive thus affecting the nearby healthy tooth as well.
Read More:
| Related Topics | ||
|---|---|---|
| Digestion and Absorption | Peristalsis | Absorption |
| Egestion | Gastric | Visceral Fat |
Extrinsic ear muscles
These muscles are useful for animals that cannot move or tilt their heads as they have the ability to alert them of danger. However, only a few humans have these muscles which are mostly useless because the human can capture sound effectively by moving their head.
Tonsils
The tonsil protects the body from harmful microorganisms which are either inhaled or absorbed by the body. Most of the time they are removed surgically.
Tailbone
Early homo sapiens used to have tails to support and balance their body. But as they developed a spine that provided an erect support to their body, the tail eventually became useless. As a result of evolution, a tailbone or a coccyx still exists in our bodies which is categorised as a vestigial organ.
- The Galapagos cormorants have wings but they can't fly so it is a non-functional part.
- The toe on the dog’s leg doesn't have any functions so it is a useless organ.
- The whale shark has a row of teeth that can not bite anything because the shark is a filter-feeding animal.
Read more: difference between biology and physiology
Things to Remember
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- Vestigial organs mean the organ that lost their function.
- Vestigial organs will continue to exist before they degenerate or disappear in the process of evolution.
- Vestigial organs are proof that all living beings have evolved and adapted to the current environment.
- The nipple in a male body is a vestigial organ.
- The appendix that helped in the process of digesting these raw and hard foods is now considered a vestigial organ.
- Some of the vestigial organs are the appendix, plica semilunaris, wisdom teeth, extrinsic ear muscles, tonsils, coccyx etc.
- There are a total of 90 vestigial organs in the human body.
Read More:
| Related Topics | ||
|---|---|---|
| Liver Diagram | Types of Teeth in Humans | digestive disorders |
| the small intestine | oesophagus | marasmus |
| bile | pharynx | pepsin |
Previous Year Questions
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Sample Questions
Ques. What are the vestigial organs in a python? (2 marks)
Ans. Pythons have tiny hind leg bones which are buried in the muscles towards their tail ends which are considered useless.
Ques. What are the examples of vestigial organs in a human? (2 marks)
Ans. The appendix, wisdom teeth, tail bone, goosebumps, hiccups, tonsil etc. are some of the vestigial organs found in human bodies.
Ques. How many vestigial organs do humans have? (2 marks)
Ans. Humans have 180 vestigial organs.
Ques. What are the examples of vestigial organs of animals? (2 marks)
Ans. The pelvic bone of a snake, wings of the female cockroach, wings of flightless birds, etc
Ques. What are the vestigial organs of plants? (2 marks)
Ans. In Asparagus Racemosus plants "Gynoecium" and "Staminode" are the vestigial organs. In "Septic Weed"," Androecium" is a vestigial organ.
Ques. Why do humans have tailbones? (2 marks)
Ans. The tail vanished by the time humans were born but before that the ancestors of humans have a tail so that they could walk properly and it helped them to balance their body but now the tailbone is just a useless organ.
Ques. What is vestigial structure? (2 marks)
Ans. A vestigial structure is a feature that was an adaptation for the ancestor's organs but that evolved to be non-functional because the organ's environment changed.
Ques. Why is the little toe of the human being vestigial? (2 marks)
Ans. During our ancestor's time, the little toe helped them to climb the tree properly but now humans don't need to climb in trees or live in the trees. That's why it is a vestigial organ.
Ques. What nerve opens the eyelids? (2 marks)
Ans. The Oculomotor nerve opens the eyelids.
Ques. Why vestigial organs are useless? (2 marks)
Ans. The fact that they are vestigial organs is itself the answer to this question. Vestigial organs mean those organs of the body which are of no use. In the human body, there are so many vestigial organs as well as in animal bodies or plants. These organs are only in there because the ancestors of that species have that organ and it was useful during their time but now these organs are of no use.
Ques. Give an example of characteristics being used to determine how close two species are in evolutionary terms? (2 marks)
Ans. Homologous organs, analogous organs and vestigial organs help to identify evolutionary relationships amongst the species.
Ques. Describe briefly about Vestigial Organs. (2 marks)
Ans. Vestigial organs like homologous organs provide evidence for organic evolution.
These are degenerate, non-functional and rudimentary organs to the possessor, while correspond to fully developed and functional organs of related organisms.
(a) There are about 90 vestigial organs in the human body. Some of them are tail bone (coccyx), wisdom teeth, nictitating membrane, vermiform appendix, etc.
(b) Some examples from other animals are hip girdles and bones of the hind limbs in some whales and certain snakes and wings of flightless birds.
Ques. Give some biochemical evidences of evolution. (2 marks)
Ans. Biochemical Evidences:
(a) The metabolic processes in organisms are similar to some new materials and end products. For example, the energy released by oxidation is stored in ATP which then powers the energy-requiring process.
(b) Molecular homology is the similarity among animals at the molecular level.
For example, human DNA differs in only 1.8% of its base pairs from chimpanzee DNA and there is no difference between the two in the amino acid sequence for the protein cytochrome-c.
Ques. What are Biographical evidences? (2 marks)
Ans. Biogeographical evidences are where the species restricted to a region develop unique features. Also, species present in far separated regions show similarities of ancestry.
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