This document defines key terms related to homologous and analogous structures in biology. It explains that homologous structures share an ancestral structure, but may not have the same function, while analogous structures between species have similar functions but different underlying structures. Examples are given of homologous limb bones in vertebrates and vestigial structures providing evidence of evolution from common ancestors. References are also provided.

1. IB Biology Grade 11
Clarissa Nitihardjo & Stella Sunarja

2. A body part with a same structure between some
groups of organisms due to inheritance from a
same ancestor
 Though not necessarily sharing the same function

3.  Havinghomologous structure does not always
have analogous structure
 Analogous structure: different species with
similar features in function but not
necessarily in structure

4.  To provide a track of evolutionary paths
 Diverges between species and sub-species
 Helps recognizing the same behavioral
characteristics which are modified in different
subspecies by their environments

6.  Penta=five
 Dactyl=digits
 Bones of limbs of vertebrates are very similar
 The functions of each forelimb are different
http://carrier.pbworks.com/Evolution-Fourth-Hour

7.  Structures
or organs that are not very
useful—vestigal
 Humans have tail bones
 Some snakes have limb bones
 Some salamanders have eyes (although they are
blind)
 Vestigal organs usually are useful in other
species
 It can be viewed as an evidence of evolution:
share common ancestors

8. http://www.talkorigins.org/faqs/comdesc/section1.html.
 Reptile: the stapes contacts the
quadrate, which in turn contacts the
articular
 Mammal: the stapes contacts the
incus, which in turn contacts the malleus

9.  1. Analogous Structures. Biology Online. [Online] [Cited: September
20, 2010.] http://www.biology-
online.org/dictionary/Analogous_Structures.
 2. 29+ Evidences for Macroevolution. Talk Origins. [Online] [Cited:
September 20, 2010.]
http://www.talkorigins.org/faqs/comdesc/section1.html.
 3. iscid. Homologous Structure. [Online] 2005. [Cited: September
18, 2010.] http://www.iscid.org/encyclopedia/Homologous_Structure.
 4. unknown. Evolution. [Online] [Cited: September 18, 2010.]
http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html.
 5. Allott, Andrew. Evidence for Evolution. Biology. New York : Oxford
University Press, 2007, p. 37.
 6. ExamplesOF. Example of Homolgous Structure. [Online] 2010. [Cited:
September 18, 2010.]
http://www.examplesof.com/language/homologous_structure.html.
 7. Taylor, Stephen. Evolution. Science Video Recources. [Online] 2010.
[Cited: September 18, 2010.] http://sciencevideos.wordpress.com/bis-
ib-diploma-programme-biology/05-ecology-and-evolution/evolution/.