Read the following statements and find out the incorrect statements. a. Heart is situated in the thoracic cavity, is between the two lungs, slightly tilted to the right. b. Heart has the size of a clenched fist. c. Heart is protected by double walled membranous bag, pericardium, enclosed the pericardial fluid. d. Human heart has four chambers, two relatively larger upper chambers called atria and two smaller lower chambers called ventricles. e. A thick muscular wall called the inter - atrial septum separates the left atria, whereas a thinwalled , the inter- ventricular septum, separates the left and right ventricles.

Read the following statements carefully and select the appropriate option given below. (i) In prokaryotes a special membranous structure is the mesosome which is formed by the extensions of plasma membrane into the cell. (ii) Several ribosomes attach to a single rRNA and form a chain called polyribosomes or polysome. (iii) In human beings, the membrane of the erythrocyte has approximately 52 per cent lipids and 40 per cent proteins. (iv) Algae have cell wall, made of cellulose, galactans, mannans and minerals like calcium carbonate. (v) In the absence of ribosomes, ER appear smooth and are called smooth endoplasmic reticulum (SER).

The heart chamber having the thickest muscular wall named