Genetic drift is one mechanism of evolutionary change. Which of the following best describes an example of genetic drift?

A.
A small population of frogs, which used to be brown and green, is now all green due to chance.
B.
Gazelles, which are preyed on by cheetahs, have gotten faster and more agile over time.
C.
The genetic variation between two populations of gorillas decreases due to interbreeding.
D.
Over time, birds acquired stronger beaks by opening and eating tougher nuts and seeds.

B) Random fluctuations in the gene frequencies within a population

Explanation:

Genetic Drift Examples. Genetic drift is a change in the frequency of an allele within a population over time. This change in the frequency of the allele or gene variation must occur randomly in order for genetic drift to occur. ... Examples of genetic drift are more evident in smaller populations of organisms.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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