Thousands of years ago many newly formed post-glacial lakes were initially colonized by a small number of a single species of

Question

Thousands of years ago many newly formed post-glacial lakes were initially colonized by a small number of a single species of three-spined sticklebacks (originating in the ocean). Today these lakes contain freshwater-adapted sticklebacks that lack the bony armor and spines found in the marine environment. What is the most plausible way in which this morphological change came about? 
Disruptive selection associated with habitat choice within each lake. 
The environment induced the desired genetic changes. 
Selection for alleles resulting in the deactivation of key homeotic genes associated with armor. 
Selection for increased protection from larger fish predators present in the brand-new freshwater environment. 
Inheritance of traits acquired by the sticklebacks during their lifetimes.

Kunduz · Accepted Answer

Click to see the answer