We already know that different species cannot interbreed – have fertile offspring-, so gene flow is stopped. Why does that happen?
This is due to the prezygotic and postzygotic reproductive isolation. These are barriers which prevent interbreed happening. They avoid it either before fertilization, in prezygotic ones; or after fertilization has occurred, postzygotic.
The prezygotic reproductive isolation mechanisms are :
- Habitat: living beings from different areas cannot mate as they cannot possibly meet either.
- Behavioural: during the selection of a possible mate, individuals from different species may discard each other as they don’t have the same mating rituals.
- Temporal: individuals from different species may be in season at different times in the year so they won’t be interested in copulating at the same time.
- Mechanical: different species may have different sex organs which aren’t compatible. It just won’t fit.
- Gametic: for fertilisation to occur, the sperm must reach the ovum. For this to happen they usually attract each other through chemical means, but the chemicals might vary from one specie to another. In this case gametes won’t recognise each other and fertilization won’t take place.
The postzygotic reproductive isolation mechnisms are the following:
- Hybrid viability: sometimes the hybrid dies prematurely.
- Hybrid fertility: even if an offspring is produced from the mating of different species usually they are infertile as they generally have a random mixed number of chromosomes (so it’s not the same even between hybrids).
- Hybrid breakdown: if the hybrid results to be fertile, the hybrid population might dissappear along time as from one generation to the next they may result weaker, less fertile, etc.
The sources of information are these videos:
March 1, 2012 at 13:33
branson missouri
Wow! I love this very nice Article
branson mo
March 17, 2012 at 00:48
Thank you it was explained very easy.
January 3, 2013 at 20:42
awesome biology revision
April 8, 2013 at 14:38
Excellent! Thank you! 🙂
April 9, 2013 at 09:38
Beautiful explanation
December 4, 2013 at 00:44
Great explanation
January 24, 2014 at 16:51
awesome
July 4, 2014 at 05:37
what’s your last name angela?
July 31, 2014 at 21:32
Really helpful!
January 22, 2015 at 06:16
AMAZING! Very well explained and easy to understand. Thank you so much!
February 22, 2015 at 10:44
This just helped me in my finals, thanks alot
January 20, 2016 at 17:33
Cooolll Dudeeeeee
April 1, 2016 at 01:26
thnx a lot 4 helping
November 6, 2016 at 15:18
awesome..
November 18, 2016 at 03:48
It is goog but very short.
December 6, 2016 at 00:31
Awesome
December 18, 2016 at 10:30
[…] Hybrids are infertile […]
August 5, 2017 at 19:52
I saw yet another thing concerning this on another blog. Youve obviously spent some time on this. Well done!
September 12, 2017 at 22:45
If some one wishes expert view regarding blogging after that i advise him/her to pay a
quick visit this webpage, Keep up the good work.
October 10, 2017 at 19:53
[…] https://bio4esobil2009.wordpress.com/2010/04/28/prezygotic-and-postzygotic-reproductive-isolation/ […]
August 19, 2018 at 21:47
thanks for helping people