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Vestigial Organs – Definition, Features, Importance, List of Vestigial Organs

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Vestigial Organs are one of the most prominent pieces of evidence of the evolutionary process. They are the remnants of the evolutionary past. The presence of vestigial organs shows that evolution may result in loss of function of certain organs. Vestigial organs are proof of the redundancy of certain anatomical structures in the process of adaptation of an organism to changing environmental conditions.

Vestigial organs in humans are the appendix and coccyx which in due course of time and the evolution of human anatomy have become non-functional yet present in the body. Other vestigial organs examples are sinuses, eye membranes, tonsils, etc.

What are Vestigial Organs?

Vestigial Organs are parts of the body or cells that have stopped working during evolution but are still present in modern creatures. In the human body, certain organs that were once useful to our ancestral species are no longer needed by current species. However, this phenomenon is not exclusive to humans but is seen in many other organisms. Such organs that fail to develop and evolve during the evolution of the organism resulting in their loss of function are considered as vestigial organs.

Key Features of Vestigial Structures

Some of the key features of Vestigial Organs are:

  • These organs have either very insignificant or no function as compared to their ancestral counterparts.
  • Vestigial organs usually fail to evolve as they are not found to be necessary with changing environmental conditions that lead to evolution.
  • Their presence acts as remnants of their ancestral form which gives a huge amount of information about how the evolution took place.
  • They provide significant insights into how the organism might have evolved in response to possible environmental changes.
  • These vestigial organs may be found in multiple species which is proof of shared ancestry and evolutionary relationship.
  • Comparative anatomy of such vestigial organs helps scientists to determine an evolutionary tree or phylogenetic tree.
  • The Vestigial Organs of one species may be a functional organ of another species based on the evolutionary pathway both organisms took.

Vestigial Organs Evolution

Evolution is a continuous and dynamic process based on the natural selection of characters and random mutations of genes. This process is dependent on nature’s choice of the most suitable gene for an organism based on the changes in the environmental conditions. However, there are certain exceptions in the process of evolution i.e. it is not every time the development of organs or parts of a species to adapt to the changes in the environmental conditions.

Sometimes, old Organs become non-functional as the organism evolves. These Organs are either lost from the body or remain in the body as an extra appendage also called the Vestigial Organs or parts. With the gradual evolution taking place over thousands or millions of years, such Vestigial Organs keep on regressing in structure.

Vestigial Structures Examples

Vestigial structures as evidence of evolution are found in plants, humans, and other animals. We have provided the list of vestigial organs examples below:

Vestigial Structures Examples in Humans

Some of the most common Vestigial Organs that are found in humans are:

Eye Membrane

Certain organisms have a third eye membrane called the nictitating membrane that helps them to keep their eyes moisturized. However, humans don’t need these membranes so they are replaced by Plica semilunaries, a small fold or Vestigial structure in the inner corner of the eye.

Appendix

The small finger-like projection called the appendix in the human’s large intestine was once a crucial organ aiding the digestion of food in our ancestors. However, with the discovery of fire and cooking this organ became a Vestigial Organs.

Also Read: Difference Between Small Intestine And Large Intestine

Sinuses Bones

They are usually known as the sinuses. They are bones located behind the forehead of humans. They are air-filled bones. Generally, they don’t have any uses. Scientists believe that they are Vestigial Organs. But sometimes due to bacterial infection, a person may suffer from sinusitis.

Vestigial Structure Coccyx Bone

Ancestor of humans possess a tail. But with time, they stop using their tail due to bipedalism. That is why the tail becomes the Vestigial Organs. In the newborn baby, the coccyx may be in a functional form. But with time, it gets reduced as the Vestigial Organs.

Vestigial Structure Wisdom Teeth

This is the third set of molars found in humans. Sometimes, in humans, wisdom teeth can be found. Mostly, this can be found in children. Scientists believe that this tooth was important when the human ancestors used to take raw food. They use this tooth to intake raw and solid food. This tooth helps them to chew the food in a good manner.

External Ear

The external ear in humans is a Vestigial Organ. Earlier, ancestors of humans could move their ears toward the source of the soundwave, like cats and dogs. But with time, the muscles in the external ear or helix did not evolve. That is why it is considered the Vestigial Organs.

Tonsil

The tonsil is the little muscular projection found in the mouth of humans. This is also a type of Vestigial Organs. As this piece of muscle doesn’t have any specific function to perform. It is just like the appendix in the human body. It just acts to protect from microbes into the human body through the nose & mouth.

Also Read: List of Five Sense Organs and Their Functions

Behavioural

Even though no Organs are listed as behavioural type, goosebumps can be considered a Vestigial movement. Scientists, classify goosebumps as a behavioural feature rooted in the ancestral ability of humans to raise their body hairs in response to various emotions or warmth just like cats do. As in due course of time humans have lost a significant amount of body hair this ability is also lost and remains just as a Vestigial trait of goosebumps.

Vestigial Organs

Vestigial Organs In Animals

Some of the most common vestigial organs in different animals are;

Legs In Snake

Scientists believe that snakes evolved from lizards, but they don’t have legs. However, in some species of snakes there is evidence that at some point in time, they have legs. In Boa & Python, they have a rear leg-like structure in their body. The leg acts as the Vestigial Organs in those species.

Eyes Of Salamander

Salamanders have eyes but they don’t use them. As they live in the cave most of the time. Scientists believe that due to the immense low use of the eyes, those become the Vestigial Organs of the Salamander.

Teeth Of Whale Shark

Whale Shark is a type of shark which uses its gills to feed. They use the Gill as the filter & incur the food to its body. But still, they have teeth. Though, those teeth can’t do their work. This means they are the Vestigial Organ of Whale Sharks.

Wings Of Flightless Bird

There are many species of flightless birds like ostriches, kiwis, penguins, and cormorants that have reduced wings that can not be used for flying. These wings are considered to be Vestigial Organs developed as a result of environmental conditions.

Vestigial Organs in Plants

Some of the most common Vestigial Organs in plants are:

Reduced Leaves in Dodder (Cuscuta spp.)

This plant species lacks the photosynthetic pigment called chlorophyll. Because of this, they adapted to a parasitic lifestyle and their leaves became reduced.

Reduced Leaves in Indian Pipe (Monotropa uniflora)

This plant species also lacks the photosynthetic pigment called chlorophyll as they rely on mycorrhizal for nutrients. Because of this, they adapted to have reduced leaves.

Tendrils of Pea Plant (Pisum sativum)

The ancestors of modern pea varieties used to climb with the help of tendrils. Currently, these tendrils are non-functional and are found in certain varieties as Vestigial Organs.

Importance Of Vestigial Organs

Some importances of Vestigial Organs are:

  1. They are functionless but hold significance in studying the evolutionary process.
  2. They help to link the evolutionary linkage between different species.
  3. They help to determine the common ancestor of different species.
  4. They may be functional in certain species making them a great source of genetic and evolutionary data.
  5. Vestigial structures help to study the biodiversity and adaptative variations among different species.

Conclusion – Vestigial Organs

The vestigial organs are one of the most prominent pieces of evidence of the evolutionary process. Vestigial structures humans include are coccyx, wisdom teeth, appendix, etc. These organs have either very insignificant or no function as compared to their ancestral counterparts. Vestigial organs examples are found in plants, animals, and humans.

Also Read:

FAQs – Vestigial Organs

What are Vestigial Organs meaning in Biology?

In biological studies Vestigial Organs are defined as those organs which are once functional in our ancestors but due to evolutionary changes currently became non-functional, yet present in the body.

What are the 4 Vestigial Structure in Humans?

Four Vestigial structures in the human that are present in the body but are non-functional; pilica semilunaries, tonsils, wisdom teeth, and appendix

Why are Goosebumps Vestigial?

Human ancestors could raise their body hairs for warmth or to display emotions, but in due course of time due to evolution its functionality is lost, yet the mechanism remains that is currently called goosebumps.

How many Organs are Vestigial?

Vestigial Organs lose their functions but remain in the body until they degenerate and disappear in the process of evolution. As per scientists, there are around 180 Vestigial Organs in the human body.

Is Body Hair Vestigial?

Body hairs are not completely Vestigial, but have very less to negligible function in the majority of the human population.

What is a Vestigial Reflex?

A vestigial reflex is an instinctive response or behavior that was functional in ancestors but serves no purpose in the current species, often considered a leftover trait from evolutionary history.

What is the Difference Between Vestigial and Rudimentary Organs?

Vestigial organs are remnants of ancestral structures with reduced function, while rudimentary organs are underdeveloped structures with little or no function.

How many Vestigial Organs are there in Human Body?

There are 180 vestigial organs in the human body.



Last Updated : 21 Feb, 2024
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