Life Processes

Step 1: Carbon dioxide is a raw material for photosynthesis. Step 2: Without carbon dioxide, glucose and starch will not form. Step 3: Therefore, iodine will not give a blue-black color.

Step 1: The green part appears green because of chlorophyll. Step 2: Chlorophyll traps light energy for food formation. Step 3: Therefore, starch is mainly formed in the green part.

Step 1: Water content changes the shape of guard cells. Step 2: When water decreases, they become flaccid. Step 3: This closes stomata and reduces water loss.

Step 1: Closing stomata reduces water loss. Step 2: But carbon dioxide also enters through stomata. Step 3: Therefore, food formation may decrease when stomata remain closed.

Step 1: Water is also a raw material in photosynthesis. Step 2: Water is split with the help of light. Step 3: Oxygen is released from this splitting.

Step 1: Glucose is first formed in photosynthesis. Step 2: Extra glucose can be stored as starch in plants. Step 3: Therefore, starch presence indicates food formation.

Step 1: Amoeba does not have a permanent mouth. Step 2: It forms pseudopodia to surround food. Step 3: This temporary structure helps food enter the cell.

Step 1: Saliva moistens food and contains amylase. Step 2: Amylase acts on starch. Step 3: Without it, initial digestion of starch will stop.

Step 1: After swallowing, food enters the oesophagus. Step 2: Wave-like movement of its walls pushes food forward. Step 3: So its main function is transport, not digestion.

Step 1: Pepsin needs an acidic medium in the stomach. Step 2: Hydrochloric acid provides this medium. Step 3: It also kills some harmful bacteria entering with food.

Step 1: Digestive enzymes act less effectively on large fat droplets. Step 2: Bile breaks fat into small droplets. Step 3: Increased surface area makes fat digestion easier.

Step 1: Many digestive juices reach the small intestine. Step 2: Food changes into small soluble substances. Step 3: Villi absorb these substances into blood.

Step 1: Villi increase surface area in the small intestine. Step 2: Digested food is absorbed through their surface. Step 3: Blood capillaries carry these nutrients to other body parts.

Step 1: Oxygen is present in aerobic respiration. Step 2: This allows complete breakdown of glucose. Step 3: Complete breakdown releases more energy.

Step 1: During heavy exercise, muscles need more energy. Step 2: Sometimes oxygen supply is not enough. Step 3: Then partial breakdown forms lactic acid.

Step 1: Yeast breaks sugar in the absence of oxygen. Step 2: Alcohol and carbon dioxide are produced. Step 3: Carbon dioxide bubbles make the dough rise.

Step 1: Thin walls reduce the distance for gas movement. Step 2: Large surface area helps exchange more gases. Step 3: Blood capillaries quickly carry gases to and from alveoli.

Step 1: Gas exchange in alveoli occurs through a thin surface. Step 2: Fluid accumulation creates a barrier for gases. Step 3: This can reduce oxygen entry into blood.

Step 1: Inhalation brings oxygen into alveoli. Step 2: Oxygen concentration there is higher than in blood. Step 3: So oxygen combines with haemoglobin and is carried to the body.

Step 1: Cellular respiration produces carbon dioxide. Step 2: Blood carries it to the lungs in different forms. Step 3: A major part is transported as bicarbonate.

Step 1: Humans need a high amount of energy. Step 2: Cells need more oxygen for more energy. Step 3: Four chambers reduce mixing of blood and improve oxygen supply.

Step 1: The first route sends blood from the heart to the lungs. Step 2: The second route sends blood from the heart to the body. Step 3: Therefore, blood passes through the heart twice in one full cycle.

Step 1: Arteries carry blood from the heart under high pressure. Step 2: So their walls are thick and strong. Step 3: Veins have low pressure, so valves prevent backflow.

Step 1: Tissues need oxygen and nutrients. Step 2: Thin capillary walls allow materials to move in and out. Step 3: A network increases contact area and speeds exchange.

Step 1: Platelets help in blood clot formation. Step 2: A clot stops bleeding at the injury site. Step 3: Low platelets increase the risk of excessive blood loss.