There is quite a bit of confusion in the industry. In computer science, most people loosely consider 1 Gb as 2^30=1073741824 bytes, while the prefix Giga actually means 10^9, or 1,000,000,000.
When we buy a hard disk, we are told (correctly) that it holds 1 Gb. Manufacturers base it on the mathematical definition of Giga and give you 10^9 bytes (less than 1073741824=1Gibibyte, or 1 GiB). This is standard practice in the disk drive industry. For example, a Windows 7 will show a 3 tera byte external disk as having 2.72 TB, or 3,000,557,891 byes, in which case it is actually assuming a TB to mean 2^40 byes (instead of TiB). That's where confusion lies.
Can something be done about it? Yes, it has been done since 2007. The less well-known, but official quantity for 1073741824 bytes is one GiB, proposed by the International Electrotechnical Commission (IEC), adopted by IEEE, EU, and NIST. Similarly, 1 TiB means 2^40=1,099,511,627,776 bytes. The prefixes have been replaced by bi (for binary), so Kibibyte, Mebibyte, Gibibyte, Tebibyte, etc.are used to represent 2^10, 2^20, 2^30, 2^40 bytes. Unfortunately I have yet to see this widely being used, or even known!
<u>Answer</u>: option B they have a random gene mutation that affects their fur colour.
<u>Explanation</u> :-
<em>Variation</em> is the phenomena which occurs in all populations.
These variations result in slight differences in the phenotypes of individuals .
These variations only arise due to <em>random mutations </em>that arise in the individuals’ genome and then can be inherited by their offspring.
There is always a probability of one particular trait to make the individuals survive better in the environment as compared to other trait.
The individuals having the trait that helps them to survive better in the environment tend to survive more and leave more progeny. This is termed as <em>survival of the fittest</em>.
Thus, according to the question it can be inferred that the dark fur colour arose due to a <em>random mutation </em>since it is the only source of variation. Since, in the given environmental conditions the mice having the dark fur colour were less susceptible to the predators they are better fitted to survive.
The dark brown fur coat mice, survive better, leave more progeny and hence, increase their population with time. However, the orginal source of origin of this trait was a random mutation. Had this mutation not occured, the dark coloured fur mice would not have been there.
So, a <em>random gene mutation affecting the fur colour made the dark coloured mice first appear in the population.</em>
Geographic isolation can be described as a term that describes the model of speciation in which a biological population becomes isolated from other members of the population and can no longer have gene flow with them.
The same scenario of gene isolation is occurring in the species of taods which live at the top of the mountains in southern Arizona. This population has become reproductively isolated fro all other species of toads within the mountain range.
