Question

The amphibians as frog differ from humans in possessing
A. Nucleated red blood cells
B. Thyroid as well as parathyroid
C. Paired cerebral hemispheres
D. Only hepatic portal system

Answer 1

Hint: Humans through the course of time have evolved to perform multiple functions and therefore require much more oxygen when compared to other organisms such as frogs. As the oxygen is primarily carried out by the RBC in the blood, humans have evolved an enucleate RBC which ensures large oxygen-carrying capacity.

Complete answer: Humans and other mammals have evolved into complex organisms when compared to the other cousins of the vertebrate family such as fishes, amphibians, birds, and reptiles. This complex build is seen in the oxygen-carrying capabilities. Mammals have evolved an enucleate RBC.
Enucleate stands for without nucleus. Mammalian RBC is one of the most prominent peculiarities in cell biology where a cell is capable of functioning without a nucleus. Mammals have evolved such a trait to aid oxygen-carrying capacity.

Oxygen is primarily transported via the RBC to other portions of the body. As we know the haemoglobin along with other proteins allows us to carry oxygen. Thus, in order to carry more oxygen, the RBCs in humans have evolved an enucleated cell. This however is not the case for the other members of the Animalia family. Frogs are sedentary organisms, which can easily respire through their skin and do have a high oxygen demand. Therefore, their cells are nucleated.
Therefore, the correct option is A.

Note: The function of the RBC nucleus diminishes as the organism complexity increases. For example, the frog’s RBC has a functioning nucleus whereas that of a fish or a bird is non-functioning and that of mammals are enucleated. Frogs have functioning hepatic portal systems, a functioning bilobed brain, and a thyroid organ situated near the spinal column. Therefore, they are not the answers.