Question 2
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
The movement of leaves of the sensitive plant occurs due to electrical-chemical impulse that helps to convey information from cell to cell in plants. This is a rapid movement that happens by changing the amount of water in plant cells resulting in swelling or shrinking. It is not a growth movement instead it is a defensive mechanism of the plant. This phenomenon is called thigmonasty.
In contrast, the movement of a shoot towards light is a slower growth oriented movement in plants. This phenomenon is called phototropism. Plant hormone auxin plays a key role in phototropism. When light strikes one side of the shoot, the auxin moves to the shaded side, causing cells on that side to elongate. This differential growth results in the bending of the shoot towards the light source.
Chapter 6: Control and Coordination — Quick Revision Guide
Introduction
Control and coordination in organisms is achieved through the nervous system (fast, electrical signals) and the endocrine system (slow, chemical hormones). Plants coordinate using phytohormones.
Key Points at a Glance
- Neuron: cell body + dendrites (receive) + axon (transmit) + synapse (chemical transmission between neurons)
- Reflex arc: receptor → sensory nerve → spinal cord → motor nerve → effector; involuntary, fast
- Brain: cerebrum (thinking, memory), cerebellum (balance), medulla (involuntary actions); protected by skull + CSF
- Plant tropisms: phototropism (light), geotropism (gravity), hydrotropism (water), chemotropism (chemicals), thigmotropism (touch)
- Nastic movements: non-directional; Mimosa pudica folds on touch (thigmonasty)
- Plant hormones: auxin (elongation), gibberellin (stem growth), cytokinin (cell division), abscisic acid (growth inhibitor), ethylene (ripening)
- Animal hormones: GH (growth), thyroxine (metabolism, needs iodine), adrenaline (fight-or-flight), insulin (lowers blood sugar), testosterone/estrogen (sexual characters)
- Feedback mechanism: blood sugar regulated by insulin (lowers) and glucagon (raises); homeostasis
Real-World Connections
Reflexes protect us from burns and injury; diabetes is managed with insulin injections; iodised salt prevents goitre; artificial ripening of fruits uses ethylene gas.
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 6
- NCERT Exemplar Problems
- Bright Tutorials Detailed Notes: ch06-control-coordination.html
- Bright Tutorials Practice Questions: ch06-control-coordination.html
- Previous Year CBSE Board Papers