Biology question

[Corky Cacas]

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a sever winter storm kills many chickadees. An investigation comparing the body size of dead birds with that of survivors reveals that the dead birds included mainly the largest and smallest members of the population. This winter storm exemplifies:

a. kin selection
b. stabilizing selection
c. directional selection
d. balancing selection
e. disruptive selection

i believe the answer is c. but it says that the correct answer is B. anyone knows?

 

[sajjy]

a sever winter storm kills many chickadees. An investigation comparing the body size of dead birds with that of survivors reveals that the dead birds included mainly the largest and smallest members of the population. This winter storm exemplifies:

a. kin selection
b. stabilizing selection
c. directional selection
d. balancing selection
e. disruptive selection

i believe the answer is c. but it says that the correct answer is B. anyone knows?

the extremes are killed so the bell graph will be steeper but lesser in thickness.
so it is Stabilizing.

 

[Corky Cacas]

the extremes are killed so the bell graph will be steeper but lesser in thickness.
so it is Stabilizing.

why it is not directional? how do you decide what extreme?

 

[sajjy]

why it is not directional? how do you decide what extreme?

http://en.wikipedia.org/wiki/Image:Selection_Chart.PNG

The first chart shows that shortest and longest lizards are eliminated. and the medium size are the survivors.

Directional,in your questions, would take place if
(1) largest and medium are killed OR
(2) smallest and medium are killed.

in the website, small and medium trunk are killed and so it is directional.

 

[bruinshockey12]

You're killing off the smallest and largest of the species. If you think of the species on a bell curb (the average size chick as the peak in the center) you would be killing off the large and small pop. or lowering their frequency on both ends of the bell curb, thus raising the frequency of the medium size chicks.


I believe an example for directional stabilization is if one killed off only the small chicks it would shift the bell curve towards the right, favoring a directional change towards the larger members of the species

 

[Corky Cacas]

http://en.wikipedia.org/wiki/Image:Selection_Chart.PNG

The first chart shows that shortest and longest lizards are eliminated. and the medium size are the survivors.

Directional,in your questions, would take place if
(1) largest and medium are killed OR
(2) smallest and medium are killed.

in the website, small and medium trunk are killed and so it is directional.

thanks.