Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.
any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights. There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms. Isotopes of a single element possess almost identical properties.
The doctor has used INDUCTIVE REASONING. Inductive reasoning refers to a logical process in which multiple premises are combined to obtain a specific conclusion. The doctor used inductive reasoning to obtain the facts about the patient's symptoms.
The most logical answer that I can think from Darwin's Theory of Evolution is that that species had been isolated from other possible panthers to mate with. So after generations of that isolated group of panthers their offspring would eventually become increasingly similar.
