Q27 of 30 Page 1

(a) A gas is released during photosynthesis. Name the gas and also state the way by which the gas is evolved.

(b) What are stomata? What governs the opening and closing of stomata?


OR


(a) Draw a diagram of human alimentary canal and label – gall bladder, pancreas, liver and small intestine on it.


(b) Give two reasons to explain why absorption of digested food occurs mainly in the small intestine.


(a) Oxygen gas is evolved during the process of Photosynthesis. This gas is released during the process of splitting of water in which H2O is split into H+ ions and molecular oxygen (O2).

(b) Stomata are tiny pores present on the leaf’s surface which help in the exchange of gases and in transpiration.


Opening and closing of stomata is governed by the changes in osmolarity of the Guard cells which mainly occurs due to efflux and influx of K+ ions.


OR


(a)



Human Alimentary Canal/ Digestive System


(b) The absorption of digested food occurs mainly in the small intestine because-


i. Intestinal juices secreted by the Small intestine contain several enzymes which help in the complete digestion of the food.


ii. The small intestine has many finger-like projections known as Villi which help in increasing the surface area for the absorption of digested food. Villi are not present in Large intestine.


More from this chapter

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25

Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:

(i) between optical centre and principal focus of a convex lens.


(ii) anywhere in front of a concave lens.


(iii) at 2 F of a convex lens. State the signs and values of magnifications in the above-mentioned cases (i) and (ii).


OR


An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm


(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?


(ii) Find the size of the image.


(iii) Draw a ray diagram to show the formation of image in this case.


 26

(a) What is the law of dominance of traits? Explain with an example.

(b) Why are the traits acquired during the life time of an individual not inherited? Explain.


 28

Carbon cannot reduce the oxides of sodium, magnesium and aluminium to their respective metals. Why 2 Where are these, metals placed in the reactivity series? How are these metals obtained from their ores? Take an example to explain the process of extraction along with chemical equations.

 29

The position of certain elements in the Modern Periodic Table are shown below.

Using the above table answer following questions giving reasons in each case :


(i) Which element will form only covalent compounds?


(ii) Which element is a non-metal with valency 2 ?


(iii) Which element is a metal with valency 2 ?


(iv) Out of H, C and F which has largest atomic size?


(v) To which family does H, C and F belong?


OR


Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?