Life Processes

Living things must carry out certain maintenance processes all the time, even when they appear to be at rest, to repair and maintain their bodies. These life processes include nutrition, respiration, transportation and excretion. In this chapter you will study autotrophic nutrition in plants, where photosynthesis uses carbon dioxide, water, sunlight and chlorophyll to make carbohydrates, and heterotrophic nutrition, from Amoeba engulfing food to digestion in the human alimentary canal with the help of enzymes such as salivary amylase, pepsin, trypsin and lipase, and absorption by the villi of the small intestine. You will learn how glucose is broken down to release energy as ATP, aerobically in mitochondria or anaerobically in yeast and muscle cells, and how the human respiratory system exchanges gases in the alveoli. You will study the human heart, double circulation, blood vessels, blood and lymph, and transport of water and food through xylem and phloem in plants. Finally, you will learn how the kidneys and nephrons filter blood to form urine, and how plants get rid of wastes.

Detailed Worksheet: Life Processes Section A - Definitions (10 marks) 1. What are life processes? Name four basic life processes. (2 marks) 2. Define autotrophic and heterotrophic nutrition with one example of each. (2 marks) 3. Distinguish between aerobic and anaerobic respiration with respect to the site and the products formed. (2 marks) 4. What is double circulation? Why is it necessary in mammals and birds? (2 marks) 5. What is a nephron? Name its two main parts involved in filtration. (2 marks) Section B - Calculations and Applications (15 marks) 6. Write the balanced chemical equation for photosynthesis. State the three events that occur during the process and name the raw materials and the source of energy. (3 marks) 7. In a student's experiment with an aquatic plant (Hydrilla), the number of oxygen bubbles released per minute was counted at different distances from a lamp: 10 cm: 40 bubbles, 20 cm: 22 bubbles, 30 cm: 12 bubbles, 40 cm: 6 bubbles. What conclusion can be drawn? Calculate the percentage decrease in bubble rate from 10 cm to 40 cm. (3 marks) 8. An adult at rest breathes about 15 times a minute, taking in about 500 mL of air with each breath. Calculate the volume of air breathed in per minute and per hour in litres. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms? (3 marks) 9. The kidneys filter about 180 litres of fluid from the blood every day, but only about 1.5 litres is excreted as urine. Calculate the volume reabsorbed and the percentage reabsorbed. Name the part of the nephron where reabsorption takes place. (3 marks) 10. The heart of a person beats 72 times per minute. Calculate the number of beats in a day. If a heart pumps about 70 mL of blood per beat, how many litres of blood does it pump in one minute? (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of the human alimentary canal showing the mouth, oesophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine and anus. (4 marks) 12. Draw a labelled diagram of a sectional view of the human heart showing the four chambers, the vena cava, aorta, pulmonary artery and pulmonary veins. (3 marks) 13. Draw a labelled diagram of a nephron showing the Bowman's capsule, glomerulus, tubule and collecting duct. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Why is the small intestine very long in herbivores and shorter in carnivores? Explain how the inner lining of the small intestine is adapted for absorption, and describe the roles of bile juice and pancreatic juice in digestion. (5 marks) 15. During a race, a sprinter's leg muscles begin to cramp. Explain the cause using the pathway of glucose breakdown in muscle cells, compare it with anaerobic respiration in yeast, and write the word equations for both. Why does a sprinter breathe heavily even after the race? (5 marks) 16. Explain how water and minerals move up a tall tree from the roots to the leaves without a pump, using the ideas of root pressure and transpiration pull. How is the transport of food in phloem different from the transport of water in xylem? (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every part. Write equations wherever asked.