Life Processes

Step 1: Digestion makes food simple. Step 2: Respiration releases energy and transport carries materials to correct places. Step 3: Excretion removes wastes, so all these processes work together to maintain life.

Step 1: Carbon dioxide is necessary for photosynthesis. Step 2: It mainly enters the leaf through stomata. Step 3: If stomata remain closed gas entry decreases and food formation can reduce.

Step 1: Open stomata help carbon dioxide enter. Step 2: Water vapour also leaves through open stomata. Step 3: Thus stomata balance food formation and water conservation.

Step 1: Sunlight is the source of energy in photosynthesis. Step 2: The green pigment helps capture this energy. Step 3: Without it food formation can become slow.

Step 1: Food is mainly made in leaves. Step 2: Roots also need food for growth and respiration. Step 3: Phloem carries food from leaves to parts that need it.

Step 1: Water vapour leaves from leaves. Step 2: This creates an upward pull in xylem. Step 3: This pull helps move water from roots to leaves.

Step 1: Autotrophs make food from simple substances. Step 2: Carbon dioxide and water are used in the presence of light. Step 3: Glucose like food is formed and oxygen is released.

Step 1: Amoeba is a unicellular organism. Step 2: It forms pseudopodia to surround the food particle. Step 3: The food then enters the cell in a food vacuole.

Step 1: Food must move forward from the mouth through the alimentary canal. Step 2: Muscles of the tube contract and relax rhythmically. Step 3: This peristaltic movement pushes food forward.

Step 1: Saliva contains an enzyme that breaks starch. Step 2: The stomach medium is acidic. Step 3: In acidic medium the action of salivary enzyme decreases.

Step 1: Acid helps pepsin action and germ control. Step 2: The same acid can harm the stomach wall. Step 3: Mucus protects the wall and maintains this balance.

Step 1: Fat does not mix easily with water. Step 2: Bile breaks fat into small droplets. Step 3: This makes enzyme action on fat more effective.

Step 1: Juices like bile and pancreatic juice enter the small intestine. Step 2: Much digestion is completed here. Step 3: Villi absorb digested substances into blood.

Step 1: Villi increase surface area for absorption of digested food. Step 2: Alveoli increase surface area for gas exchange. Step 3: Both structures make exchange more effective.

Step 1: Most digestion occurs in the small intestine. Step 2: Remaining material reaches the large intestine. Step 3: It absorbs water and helps make faeces solid.

Step 1: In breathing air moves in and out. Step 2: Cellular respiration breaks food in cells. Step 3: This breakdown releases energy for cells.

Step 1: Oxygen is available in aerobic respiration. Step 2: Oxygen helps complete breakdown of glucose. Step 3: Complete breakdown releases more energy.

Step 1: Energy demand increases during heavy exercise. Step 2: Enough oxygen may not reach muscles immediately. Step 3: Anaerobic respiration can form lactic acid.

Step 1: Many alveoli provide a large surface area. Step 2: Thin walls reduce diffusion distance for gases. Step 3: This makes oxygen and carbon dioxide exchange effective.

Step 1: Haemoglobin carries oxygen in blood. Step 2: Oxygen is needed for cellular respiration. Step 3: If it is low energy release can decrease and tiredness may occur.