HOMOLOGOUS STRUCTURE

IB Biology Grade 11

Clarissa Nitihardjo & Stella Sunarja

WHAT IS HOMOLOGOUS STRUCTURE?

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

Having homologous structure does not always have analogous structure

Analogous structure: different species with similar features in function but not necessarily in structure

WHAT IS THE IMPORTANCE OF HOMOLOGOUS STRUCTURE?

To provide a track of evolutionary paths Diverges between species and sub-

speciesHelps recognizing the same behavioral

characteristics which are modified in different subspecies by their environments

WHAT ARE THE EXAMPLES OF HOMOLOGOUS

STRUCTURE?

PENTADACTYL LIMBSPenta=fiveDactyl=digits

Bones of limbs of vertebrates are very similar

The functions of each forelimb are different

http://carrier.pbworks.com/Evolution-Fourth-Hour

VESTIGAL ORGANS Structures or organs that are not very

useful—vestigal Humans have tail bonesSome snakes have limb bonesSome 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

EAR OSSICLES

Reptile: the stapes contacts the quadrate, which in turn contacts the articular

Mammal: the stapes contacts the incus, which in turn contacts the malleus

http://www.talkorigins.org/faqs/comdesc/section1.html.

BIBLIOGRAPHY 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/.