Question 11
Describe double circulation of blood in human beings. Why is it necessary?
Double circulation is a process during which blood passes twice through the heart during one complete cycle through the human body. First, the deoxygenated blood is send to lungs and oxygenated blood from lungs reaches heart. This circulation is known as pulmonary circulation. Oxygenated blood that reaches the heart is send to whole body and the deoxygenated blood from different body parts is again brought to heart. This is known as systemic circulation.
Human beings constantly use energy to maintain their body temperature. Therefore, they need a highly efficient supply of oxygen to the body. The mixing of oxygenated and deoxygenated blood lowers the efficiency to supply oxygen. Therefore, it is necessary to separate oxygenated and deoxygenated blood
Chapter 5: Life Processes — Quick Revision Guide
Introduction
Life processes are the basic functions performed by all living organisms to sustain life. This chapter covers nutrition (autotrophic and heterotrophic), respiration, transportation, and excretion in plants and animals.
Key Points at a Glance
- Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 (in chloroplasts using chlorophyll and sunlight)
- Stomata: tiny pores for gas exchange and transpiration; guard cells control opening/closing
- Human digestive system: mouth (salivary amylase) → stomach (HCl, pepsin) → small intestine (bile, trypsin, lipase; absorption by villi) → large intestine → anus
- Aerobic respiration (mitochondria): glucose + O2 → CO2 + H2O + 38 ATP
- Anaerobic: in yeast → ethanol + CO2; in muscles → lactic acid; both yield 2 ATP
- Xylem: transports water upward (dead cells, transpiration pull); Phloem: transports food bidirectionally (living cells, uses ATP)
- Heart: 4 chambers, double circulation (pulmonary + systemic); septum prevents mixing
- Blood: plasma + RBCs (O2 via haemoglobin) + WBCs (immunity) + platelets (clotting)
- Nephron: Bowman's capsule + glomerulus → filtration → reabsorption → urine; dialysis for kidney failure
- Plant excretion: transpiration, leaf fall, stored in vacuoles, resins/gums
Real-World Connections
Photosynthesis is the basis of all food chains; fermentation used in bread and alcohol production; blood donation saves lives; dialysis machines sustain patients with kidney failure.
Quick Self-Test (5 Questions)
- What is the most important concept you learned from this chapter?
- Can you write three key equations/formulae from this chapter from memory?
- Draw a labelled diagram relevant to this chapter without looking at your notes.
- Explain one real-world application of a concept from this chapter.
- What is one common mistake students make in this chapter, and how can you avoid it?
Further Study
- NCERT Textbook Chapter 5
- NCERT Exemplar Problems
- Bright Tutorials Detailed Notes: ch05-life-processes.html
- Bright Tutorials Practice Questions: ch05-life-processes.html
- Previous Year CBSE Board Papers