Question

Two issues associated with the evolution of vertebrate circulatory systems has been separation of oxygen-rich blood from oxygen-poor blood and maintaining pressure levels while delivering oxygen-rich blood to the body systems. Which of the following vertebrate groups achieves good separation of oxygen-rich blood from oxygen-poor blood and delivers blood to the body systems under high pressure owing to its double-loop system and four-chambered heart?

	A.	birds
	B.	amphibians
	C.	reptiles
	D.	fish
	E.	None of the above.

A nerve impulse moves along a neuron as

	A.	sodium moves into the cell and potassium moves out of the cell.
	B.	sodium binds to potassium.
	C.	sodium and potassium are pulled apart.
	D.	acetylcholine moves along the nerve fiber.
	E.	calcium exits the dendrites.

All of the choices below are examples of mechanoreceptors (reception based on movement of something) EXCEPT?

	A.	hearing with the human ear
	B.	touch as sensed via pressure receptors in human skin
	C.	determination of scent with olfactory cells
	D.	angular acceleration as sensed via cells in the semicircular canals
	E.	All of these are examples of mechanoreception.

Answer 1

1) Four chambered heart is present in

A. Birds

Fishes have two chambered heart.

Amphibians have three chambered heart.

Most reptiles have three chambered heart (except for crocodile).

So the correct answer will be birds.

2) For a nerve impulse to move along a neuron

A. sodium moves into the cell and potassium moves out of the cell.

A sodium potassium pump maintain electric gradient across the plasma membrane of neuron. An unstimulated neuron is in polarized state. When there is stimulation, the cell depolarises as sodium moves into the cell and potassium moves out. This creates an action potential which travel to next neuron for stimulation.

The other options given donot help in transmission of nerve impulse so others options are incorrect.

3) Not a mechanoreceptor

C. Determination of smell with olfactory cells.

It is not a mechanoreceptor since the reception is based on chemical stimuli not based on any movements.

Mechanoreceptors are those stimulus based on movement of something. Stimulus such as touch, pressure, vibrations and sound from external or internal environment.

All the other options above - Hearing, touch receptor, angular acceleration detection by the semicircular canals are mechanoreceptor as it is based on movement of something ( eardrum, hair cells, physical interaction of pressure or vibrations).

So the correct answer will be C. Olfactory cells