Initiation and conduction of heart beat:
(i) Human heart is myogenic in nature.
(ii) Contraction is initiated by a specialised portion of the heart muscle, the sino-atrial (SA) node which is situated in the wall of the right atrium near the opening of the superior vena cava.
(iii) The Sino-atrial node acts as the 'pacemaker' of the heart because it is capable of initiating impulse which can stimulate the heart muscles to contract.
(iv) This impulse is spread by the contraction of right and the left atrial walls pushing the blood into the ventricles.
(v) The wave of contraction from SA node reaches the (AV) atrio ventricular node which is stimulated to emit an impulse of contraction spreading to the ventricular muscle through the atrioventricular bundle and the purkinje fibres.
(vi) In an healthy adult during normal resting condition systolic and diastolic blood pressure is expressed as 120mm / 80mm Hg.

Definition: Transpiration is the evaporation of water from the aerial parts of the plant especially through stomata in the leaves.
Importance of Transpiration:
(i) Creates transpirational pull for transport of water.
(ii) Supplies water for photosynthesis.
(iii) Transports minerals from soil to all parts of the plant.
(iv) Cools the surface of the leaves by evaporation.
(v) Keeps the cells turgid; hence, maintains their shape.

(i) During transpiration, water is lost from leaves.
(ii) Still transpiration is essential for the movement of water and minerals from the root to the healthy parts of the plant.
(iii) But excess transpiration may result in drying up of the leaves or wilting and loss of soil water.
(iv) Hence it is termed as a necessary evil.

(i) A stethoscope is used to detect the sound produced by the internal organs of human body.
(ii) It is a useful diagnostic tool to identify and localize health problems and diagnose disease.

Imbibition:
(i) Imbibition is a type of diffusion in which a solid absorbs water and gets swelled up.
(ii) Eg: Absorption of water by seeds and dry grapes.