Q23 of 805 Page 169

Water hyacinth float on water surface. Explain.

Water hyacinth float on water surface because of buoyancy provided by aerenchym tissue present in its spongy or swollen petiole. Aerenchym is a modified parenchyma plant tissue which contains airspaces. These spaces trap the air and thus help hyacinth to float.


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If a person takes concentrated solution of salt. After sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.

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Differentiate the following activities on the basis of voluntary or involuntary muscles.

(a) Jumping of frog


(b) Pumping of the heart


(c) Writing with hand


(d) Movement of chocolate in your intestine

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Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?

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Give reasons for

(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole.


(b) Intercellular spaces are absent in sclerenchymatous tissues.


(c) We get a crunchy and granular feeling, when we chew pear fruit.


(d) Branches of a tree move and bend freely in high wind velocity.