Question

Attempt either (a) or (b): **(a)** (i) What are the limitations of electrical impulses in multicellular organisms? (ii) (I) In a 'Touch-me-not' plant, movement is seen on touch. Compare it with that of animals. (II) Name the type of movement shown by the growth of pollen tube towards an ovule. **OR** **(b)** (i) Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough. Draw a flowchart showing the path of a reflex arc. (ii) Identify the part of the brain i

Accepted Answer

0. **Part (a):** (i) Electrical impulses reach only cells connected by nervous tissue, and once an impulse is transmitted, a cell takes time to reset before generating a new impulse. (ii) (I) 'Touch-me-not' plant movement is nastic (non-directional) involving changes in cell turgor pressure without specialized nervous tissue, unlike animals which use nervous/muscular system. (II) Chemotropism. **Part (b):** (i) Receptor $\rightarrow$ Sensory Neuron $\rightarrow$ Spinal Cord (Relay Neuron) $\rightarrow$ Motor Neuron $\rightarrow$ Effector Muscle. (ii) (I) Cerebellum, (II) Cerebellum, (III) Medulla (Hindbrain).

Nervous System and Plant Movements

Explanation

Practise this under board exam conditions