UNIT
5
The origin of life and evolution
HOMOLOGOUS, ANALOGOUS
AND VESTIGIAL ORGANS
Biology and Geology 4. Secondary Education
UNIT
UNIT
5
3
Homologous, 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:
Homologous
organs
Analogous
organs
Click on each organ to find out more.
Biology and Geology 4. Secondary Education
Vestigial
organs
UNIT
UNIT
5
3
Homologous, analogous and vestigial organs
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.
Dog
Dolphin
Horse
Bat wing
Human
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Biology and Geology 4. Secondary Education
Basic structure
present in a
common ancestor
UNIT
UNIT
5
3
Homologous, 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
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Biology and Geology 4. Secondary Education
Insect wing
UNIT
UNIT
5
3
Homologous, 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.
Coccyx
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Biology and Geology 4. Secondary Education