Important Questions (1 Mark): Life Processes - SSS 1 MCQ

The form of veins that transfer oxygenated blood from the lungs to the heart is the pulmonary veins. The four major pulmonary veins, two from each of the lungs that flow into the left atrium of the heart, are the largest pulmonary veins. 

• When a pair of guard cells surrounding a stoma receives the signal to open the stomatal pore, it is filled with water, thus changing the cell's shape and opening the pore.
• When guard cells receive a signal to close the stoma, this initiates a loss of water and causes them to shrink and the pore closes.

Thus, option C is correct.

2. Peristalsis.

Explanation: The movement of food through the esophagus is primarily due to a process called peristalsis. Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract, including the esophagus, which is a part of the alimentary canal. While lubrication by saliva helps in swallowing, the actual movement of food down the esophagus is due to the coordinated contractions of the muscles in the walls of the alimentary canal.

Photosynthetic oxygen evolution occurs via the light-dependent oxidation of water. Free oxygen is generated as a by-product of this reaction and is released into the atmosphere.

• During heavy exercise, the demand for energy is high but the supply of oxygen to produce energy is limited. Therefore, anaerobic respiration takes place in the muscle cells to fulfil the demand for energy.
• This anaerobic breakdown of glucose leads to the formation of lactic acid in muscles.
• The accumulation of lactic acid in muscles leads to muscle cramps.

Thus option A is correct.

Nephrons are the basic filtering units of a kidney each kidney poses a large number of nephrons approximately 1-1.5 million.

The main functions of a nephron are:
(i) Filtration
(ii) Ultrafiltration
(iii) Absorption
(iv) Reabsorption

Aerobic respiration first occurs in the cytoplasm and then in mitochondria, whereas Anaerobic respiration occurs in the cytoplasm itself.

The air we exhale contains CO₂. When carbon dioxide is passed through lime water or Ca(OH)₂ then it form calcium carbonate which is white in colour.

Salivary amylase, present in saliva, is the first digestive enzyme that gets mixed with food in the oral cavity during the process of mastication and bolus formation. The digestive enzyme salivary amylase hydrolyzes starch into maltose, malto-triose, dextrin and a small amount of glucose.
Thus, Option C is correct

The small intestine is made up of duodenum, jejunum, and ileum. It receives the bile from the liver which helps in the breakdown of fats.