Ariver separates two groups of mice, one black and the other all white. a beaver dam allows the mice to cross the river. over time, many gray mice are born. the river is lined with light stones. gray mice are most visible to hawks that fly overhead and feed on mice. although many gray mice are born, not many live long enough to reproduce. what is this an example of?

Disruptive selection

Explanation:

Disruptive selection is a type of natural selection that occurs when the extreme phenotypes have increased survival fitness that the phenotypes with the intermediate trait. The disruptive selection favors the extreme phenotypes at the expanse of the intermediate phenotype.

In the given example, the intermediate phenotype (the gray mice) have lesser survival fitness as they are visible to predators. The disruptive selection does not favor gray mice and leads to the evolution of populations of black and white mice.  

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

when it is at an intermediate population density