(i) Transport of respiratory gases (Oxygen and CO₂).
(ii) Transport of digested food materials to the different body cells.
(iii) Transport of hormones.
(iv) Transport of nitrogenous excretory products like ammonia, urea, and uric acid.
(v) It is involved in protection of the body and defense against diseases.
(vi) It acts as buffer and also helps in regulation of pH and body temperature.
(vii) It maintains proper water balance in the body.

WBC's are colourless and nucleated cells. Granulocytes contain granules in their cytoplasm. Agranulocytes do not contain granules in their cytoplasm, So they are classified as Granulocytes and Agranulocytes.
Granulocytes: Granulocytes contain granules in their cytoplasm. They are of three types.
(i) Neutrophils:
i) They are large in size and have a 2-7 lobed nucleus.
ii) These corpuscles form 60% - 65% of the total leucocytes.
iii) Their number are increased during infection and inflammation.
(ii) Eosinophils:
i) Eosinophils has a bilobed nucleus and constitute 2% - 3% of the total leucocytes.
ii) Their number increases during conditions of allergy and parasitic infections.
iii) It brings about detoxification of toxins.
(iii) Basophils:
i) Basophils have lobed nucleus.
ii) They form 0.5% - 1.0 % of the total leucocytes. 
iii) They release chemicals during the process of inflammation.
(iv) Agranulocytes:
i) Granules are found in the cytoplasm of these cells.
ii) The Agranulocytes are of two types:
(i) Lymphocytes:
i) These are about 20 - 25% of the total leucocytes.
ii) They produce antibodies during bacterial and viral infections.
(ii) Monocytes:
i) They are the largest of the leucocytes and are amoeboid in shape.
ii) These cells form 5 - 6% of the total leucocytes.
iii) They are phagocytic and can engulf bacteria.

(i) There are millions of root hairs on the tip of the root which absorb water and minerals by diffusion
(ii) Root hairs are thin walled, slender extension of epidermal cell that increase the surface area of absorption.
Pathway of water absorbed by roots:
(i) Once the water enters the root hairs, the concentration of water molecules in the root hair cells become more than that of the cortex.
(ii) Thus, water from the root hair moves to the cortical cells by osmosis and then reaches the xylem.
(iii) From there, the water is transported to the stem and leaves.

The walls of the left ventricle is thicker than the other chambers of the heart because, the ventricles have to pump out blood with force away from the heart.