The process by which molecules of a solvent tend to pass through a semipermeable membrane from the low-level of concentrated solution into a high-level of concentrated one is called osmosis.

Why formation of urine and its elimination is necessary in humans?

The purpose of making urine is to filter out waste products from the blood. Just as Carbon dioxide is removed from the blood in the lungs, nitrogenous waste such as urea or uric acid are removed from blood in the kidneys. It is then no surprise that the basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate. Each kidney has large numbers of these filtration units called nephrons packed close together. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra. This process helps to maintain homeostasis in the body.

Draw a well-labelled diagram of a longitudinal section (LS) of the human heart.

The heart is a complex muscle that pumps blood through the three divisions of the circulatory system: the coronary (vessels that serve the heart), pulmonary (heart and lungs), and systemic (systems of the body). Coronary circulation intrinsic to the heart takes blood directly from the main artery (aorta) coming from the heart. For pulmonary and systemic circulation, the heart has to pump blood to the lungs or the rest of the body, respectively.

Draw a well-labelled diagram of the human digestive system.

Human Digestive system: The human digestive system consists of the alimentary canal and its associated glands. The various organs of the human digestive system in the sequence include the mouth, oesophagus, stomach, small intestine and large intestine.

Define photosynthesis and write the chemical equation of this process.

Photosynthesis is the process by which green plants, autotrophs, green algae, etc. produce food substances such as glucose and starch. Chlorophyll a pigment absorbs the sunlight and convert it into energy. The carbon dioxide and water use light energy to produce starch. Plants release oxygen as a by product during photosynthesis. The balanced equation is 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2 .

Write the function of HCl secreted in the stomach.

The function of HCl secreted in the stomach is as follows: It maintains low pH to promote the growth of microorganisms (bacteria, fungi, etc). It facilitates absorption. It maintains low pH to activate pepsinogen to form pepsin. It dissolves enzymes secreted in the stomach.