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UNIT
5The origin of life and evolution
Biology and Geology 4. Secondary Education
HOMOLOGOUS, ANALOGOUS AND VESTIGIAL ORGANS
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UNIT
3
Biology and Geology 4. Secondary Education
UNIT
5Homologous, analogous and vestigial organs
• The theory of evolution is based on evidence from different fields, among which is comparative anatomy.
• Comparative anatomy involves studying and comparing the structure of different organs. Two organisms are related if their organs have a similar internal structure, even if they are shaped differently.
• There are:
Click on each organ to find out more.
Homologous organs
Analogous organs
Vestigial organs
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UNIT
3
Biology and Geology 4. Secondary Education
UNIT
5Homologous, analogous and vestigial organs
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Homologous organs
• Homologous organs are similar in structure and share a common origin but may be adapted to perform different functions.
• One example of homology is the case of the limbs of mammals.
Basic structure present in a common ancestor
Dolphin
Dog
Bat wing HumanHorse
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UNIT
3
Biology and Geology 4. Secondary Education
UNIT
5Homologous, analogous and vestigial organs
Analogous organs
• Analogous organs are those that have evolved separately but look alike because they are adapted to perform the same function.
• One example of analogous organs is the case of the wings of insects and birds.
Bird wing
Bat wing
Insect wingGo back to the Start menu
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UNIT
3
Biology and Geology 4. Secondary Education
UNIT
5Homologous, analogous and vestigial organs
Vestigial organs
• Vestigial organs are those organs, found in some living things, that do not perform any functions. They simply show an evolutionary relationship with other living things.
• One example of a vestigial organ is the coccyx, or tailbone, in humans. The coccyx is the remnant of a lost tail.
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Coccyx