Life Processes

Kidneys maintain internal balance by filtering blood and removing nitrogenous wastes, especially urea, along with excess water and salts. If filtration becomes inadequate, these wastes are not removed at the normal rate and their concentration can rise in body fluids and blood. Hence option A is correct. Oxygen production and chlorophyll are plant-related ideas, while bile colour does not represent the result of failed kidney filtration.

Dialysis is a treatment that partly replaces the filtering work of failed kidneys. Blood is passed through a dialyser containing a selectively permeable membrane; wastes such as urea and excess salts diffuse into the dialysis fluid, while cleaned blood is returned. Thus option A correctly explains its connection with an artificial kidney. It does not make food, pump blood like the heart, or produce stomach acid.

The urinary system has two ureters, each carrying urine from one kidney to the urinary bladder. The urethra is a separate tube that carries urine from the bladder to the exterior during urination. Therefore option A states the correct difference. Food travels through the alimentary canal, air through the respiratory tract, blood is pumped by the heart, and bile is produced by the liver, so the other options are incorrect.

Excretion removes metabolic wastes produced by cellular activities, such as carbon dioxide, urea, and excess salts or water. Egestion is different: it is the elimination of undigested and unabsorbed food from the alimentary canal as faeces. Thus option A gives the correct distinction. Neither process produces oxygen, makes food, pumps blood, or opens stomata; those statements confuse unrelated functions.

Plants do not possess specialised excretory organs such as kidneys, but they can isolate, store, and remove wastes in several ways. Some wastes are stored in old leaves, bark, or other parts and are eliminated when these parts are shed; gases may also leave through stomata. Therefore option A is correct. The other choices describe animal organs or impossible routes for plant waste removal.

Diffusion is effective only over short distances and depends on a concentration gradient. A multicellular organism has many layers of cells, so inner cells are far from the external environment and may have high oxygen and nutrient demands. Diffusion alone would be too slow to supply them and remove wastes efficiently. Hence option A is correct; the other choices are false generalisations about multicellular organisms.

A unicellular organism consists of only one cell, and that cell is directly surrounded by its environment. Its large surface-area-to-volume ratio and short internal distances allow oxygen, water, nutrients, and wastes to move across the cell membrane mainly by diffusion. Therefore option A is correct. Such organisms do not require a heart, lungs, or xylem; those structures belong to specialised multicellular systems.

The governing concept is efficient transport of oxygen for aerobic respiration. Oxygenated blood carries oxygen from the lungs to body tissues, where cells use it to release energy from food. If it mixes substantially with deoxygenated blood, the oxygen concentration delivered to tissues falls and circulation becomes less efficient. Thus option A is correct. The other choices concern digestion, excretion, or photosynthesis, not blood separation.

The governing concept is the relationship between surface area and diffusion. Alveoli are numerous, thin-walled air sacs surrounded by capillaries. Their large combined surface provides more area across which oxygen diffuses into the blood and carbon dioxide diffuses out. This makes gas exchange rapid and efficient, so option A is correct. Digestion, urine formation, and bile storage occur in different organs and are not functions of alveoli.

The governing concept is enzymatic digestion of different food components. Pancreatic juice enters the small intestine and contains amylase for carbohydrates, trypsin-type proteases for proteins, and lipase for fats. These enzymes convert large molecules into smaller substances that can be absorbed. Thus option A is correct. Oxygen transport, urine formation, and clotting are functions of blood, kidneys, and clotting factors rather than pancreatic juice.

The governing concept is the division of digestive functions among accessory organs. The liver produces bile, which emulsifies fats into smaller droplets and helps lipase act more effectively; it is not itself a digestive enzyme. The pancreas releases pancreatic juice containing enzymes that digest carbohydrates, proteins, and fats. Therefore option A is correct, while the other options assign plant or unrelated circulatory and excretory functions.

The governing concept is the dual role of stomata in gas exchange and transpiration. Open stomata allow carbon dioxide to diffuse into the leaf, supporting photosynthesis during daylight. However, the same openings permit water vapour to diffuse out, increasing transpiration and possible water loss, especially in dry conditions. Therefore option A correctly states both effects; the other choices combine unrelated animal organs or unsupported plant changes.

The governing concept is cellular respiration, which supplies usable energy to cells. Glucose acts as the respiratory substrate, while oxygen enables its complete oxidation in aerobic respiration. This process releases energy that is stored mainly as ATP and used for growth, repair, movement and other cellular activities. Therefore, option A is correct; the other options describe unrelated functions.

Life processes work as an integrated system. Digestion breaks complex food into absorbable nutrients such as glucose. Respiration uses these nutrients, especially glucose, to release energy. The transport system carries nutrients and oxygen to cells and moves wastes away. Excretion removes metabolic wastes and helps maintain internal balance. Thus option A correctly describes their connection; the remaining options deny or misassign these functions.

The governing concept is photosynthesis and the role of stomata in gas exchange. Carbon dioxide, a raw material for making glucose, normally enters the leaf through stomatal pores. If the stomata remain closed, carbon-dioxide entry becomes limited, so the rate of photosynthesis and food formation generally decreases. Option A is correct; closure does not increase oxygen entry, instantly stop root absorption, or destroy chlorophyll.

Chlorophyll is the green pigment that absorbs light energy needed to drive photosynthesis. In its absence or severe deficiency, the leaf cannot efficiently convert carbon dioxide and water into glucose, so food formation is affected directly and first. Transpiration, water transport and mineral absorption may continue through other structures, although plant growth can later suffer. Therefore option A is correct.

Water used in photosynthesis is mainly absorbed from the soil by root hairs. After absorption, it moves upward through the xylem, helped by root pressure, cohesion and transpiration pull, and reaches the leaves where photosynthesis occurs. The water is a raw material in glucose formation. Thus option A is correct; plants do not normally obtain their main supply directly from air or manufacture it in flowers or stems.

The governing idea is a controlled experiment using starch as evidence of photosynthesis. After destarching a plant, part of a leaf is covered so it receives no light while the remaining part is exposed. After exposure, iodine turns the illuminated region blue-black because starch formed there, whereas the covered region does not. This comparison supports option A and controls the effect of light.

Photosynthesis initially produces glucose, a soluble sugar that can be used immediately in respiration or converted into other substances. When present in excess, plants commonly join glucose units to form starch, an insoluble storage carbohydrate. Starch can later be broken down when energy is needed. Therefore option A is correct; proteins, fatty acids and urea are not the usual direct storage form of extra glucose.

Amoeba performs nutrition by engulfing food with temporary extensions called pseudopodia. The captured food becomes enclosed in a food vacuole, where digestive enzymes break it into simpler soluble substances that can be absorbed by the cytoplasm. The vacuole therefore serves both ingestion and intracellular digestion. Option A is correct; the other choices are not functions of a food vacuole and Amoeba does not form blood.