Vestigial organs mean the organs which were useful for our anscestors but not for us and human being consists 180 vestgial organs      EX- APPENDIX ,nails,hairetc

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during the course of evolution some organs remains is organisms.we have studied about appendix in the digestive human beings it has no role to play in the process of digestion.but in herbivores like rabbit appendix plays an important role.such type of organs which are not useful in animals are called vestigial organs.
there are nearly 180 vestigial organs in human beings. for example pinna,hair on skin, mammary glands in men,etc. that's why human beings are said to be moving museum of vestigial organs.