Question

Which of the following statements is correct about the process of breathing in the MAMMALIAN Respiratory System?

		Strong contraction of the Diaphragm exerts a positive force on the Trachea and Bronchioles, which pushes air into the lungs through positive pressure.
		Breathing with Lungs must be more efficient than breathing with Gills, since atmospheric air has less oxygen available, when compared to the amount of oxygen dissolved in water.
		During Inhalation, contraction of the Rib Muscles and Diaphragm increases the volume of the Thoracic Cavity, which forms negative pressure that pulls air into the Lungs.
		The exchange of O2 and CO2 during Inhalation and Exhalation, respectively, depends on the property of gasses diffusing from areas of low partial pressure to high partial pressure.
		None of the above.

Echnioderms (e.g. starfish) are members of the Bilateria Clade, which llater “re-acquired” radial symmetry through evolution. Thus, within the Enchinodermata Clade the trait of radial symmetry would be considered a(n):

		vestigial characteristic
		ancestral characteristic
		homologous characteristic
		derived characteristic
		redundant characteristic

Answer 1

Breathing involves inhalation of oxygen rich air and exhalation of CO2 rich air. This movement of air is dependent on the pressure difference between lungs and external atmosphere.

Air enters lungs when lungs are at lower pressure than external environment. This is negative lung pressure and is created by increasing volume of thoracic cavity (remember that pressure and volume are inversely proportional at a given temperature) . Thoracic cavity's volume is increased when ribs and diaphragm contract.

Conversely, air exits lungs when lungs are at higher pressure (positive lung pressure) relative to external atmosphere. This happens when ribs and diaphragm relax.

Thus, the correct choice should be:

During Inhalation, contraction of the Rib Muscles and Diaphragm increases the volume of the Thoracic Cavity, which forms negative pressure that pulls air into the Lungs.

Traits which re-appear in evolution are redundant traits, such as the reappearance of radial symmetry in starfish.

Ancient characters are those which are retained in the original ancestral form without much changes. Vestigial traits are those inherited traits which do not perform any function presently in a given organism, and are in reduced form. Homologous traits are those traits which have similar basic structural design but perform different function.

Hence, the correct choice should be:

redundant characteristic

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