IGCSE Biology Paper-2: Specimen Questions with Answers 134 - 135 of 203

Question 134

MCQ▾

Whale respires through

Whales and dolphins are mammals and breathe air into their lungs, just like we do. They cannot breathe underwater like fish can, as they do not have gills. They breathe through nostrils, called a blowhole, located right on top of their heads. This allows them to take breaths by exposing just the top of their heads to the air while they are swimming or resting under the water.
After each breath, strong muscles that surround it, so that water cannot get into the whale or dolphin’s lungs, seal the blowhole tightly. Large whales have two blowholes (with the exception of the sperm whale) whereas dolphins have just one.

MCQ▾

Which row shows the chambers of the heart, from those with the thickest walls to those with the thinnest walls?

Choice (4)
a.	Atria, Left ventricle, Right, Ventricle
b.	Atria, Right ventricle, Left ventricle
c.	Left ventricle, Right ventricle, Atria
d.	Right ventricle, Left, ventricle, Atria

Ventricles:

The right and left ventricles are demarcated by an interventricular septum, which is obliquely curved towards right, so that the left ventricle is larger than right one. However, the cavity of left ventricle is relatively smaller and nearly circular because the myocardium of left ventricle is 3 times thicker than right ventricle whose cavity is larger and somewhat crescentic.
The walls of the ventricles are internally raised into a number of thick, muscular, column shaped projections called columnae carnage or trabecular carnae; and a few large muscular elevations called papillary muscles or musculli papillae’s which are 3 in right ventricle and 2 in left ventricle. These muscles act as anchors for chordae tendinae.