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 diagram of stomata of Rheo leaf and write any two functions of stomata.

Stomata are abundant on the lower surfaces but fewer from the upper ones. The upper surfaces are present a small intercellular space. Stomata are present in tetracyclic, oval in outline. The guard cells are reniform with abundant chloroplast. Functions: Stomata help the exchange of gases (CO 2 and O 2 ) in the atmosphere. The evaporation of water from the leaf surface occurs through the stomata. Thus, the stomata help in the transpiration process.