The correct answer is Option D
Reason - Since the two species live in the separate geographical area i.e different ponds they will evolve different traits and characteristics due to geographical diversity Thus any kind of isolation produced with in a species due to change in their spatial entity is called geographic isolation.
Data given
Number of electron = 108
Number of neutron = 158
Required
Mass number=?
Solution
As we know that mass number = No of proton + No of neutron
In any neutral atom the number of proton is always equal to number of electron
So number of proton will be = 108
However the atom has +1 charge which means that one proton is less than no of electron so proton number is 107.
Put values in above formula, we will get
Mass number= 107+108
= 215 Mass number
