Question
i. List three points of difference between nervous and hormonal mechanisms for control and coordination in animals.
ii. How are auxins related with the bending of plant shoot towards unidirectional light? Explain.

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The descriptions of five kinds of images are given below:
  1. Diminished and virtual.
  2. Enlarged and real.
  3. Enlarged and erect.
  4. Real and inverted.
  5. Virtual and the same size.
Which one of these describes the image formed:
  1. On the retina of the eye?
  2. By a magnifying glass?
  3. By a convex driving mirror on a car?
  4. By a plane mirror?
  5. on the screen of a slide projector?
Can the following groups of elements be classified as Dobereiner's triads?
  1. Na, Si, Cl.
  2. Be, Mg, Ca.
Give reason for your answer.

(Atomic masses: Be 9; Na 23; Mg 24; Si 28; Cl 35. 5; Ca 40)
  1. Draw a diagram of human alimentary canal and label - gall bladder, pancreas, liver and small intestine on it.
  2. Give two reasons to explain why absorption of digested food occurs mainly in the small intestine.
Describe the structure of diamond. Draw a simple diagram to show the arrangement of carbon atoms in diamond.
State and explain the various methods for preventing or retarding rancidity of food.
A unicellular animal P having no fixed shape ingests a food particle by forming temporary finger-like projections Q. The food particle is engulfed with a little surrounding water to form a temporary stomach R inside it. The chemicals S from surrounding cytoplasm enter into R and break down food into small and soluble molecules by chemical reactions. The digested food is absorbed directly into cytoplasm by the process T. The undigested food is thrown out of the body by the rupture of a cell organelle U in a process called V.
  1. Name the unicellular animal P.
  2. What are (i) Q, and (ii) R?
  3. Name (i) chemical S, and (ii) process T.
  4. Name (i) organelle U, and (ii) process V.
Draw a neat labelled diagram of the human excretory system.
Explain tissue culture technique. In which area this technique is finding its application?
A cylindrical structure P in our body begins in continuation with medulla and extends downwards. It is enclosed in a bony cage Q and surrounded by membranes R. As many as x pairs of nerves arise from the structure P. The structure P is involved in the reflex actions of our body and conduction of nerve impulses to and from another organ S of our body with which it forms CNS.
  1. Name the structure P.
  2. Name (i) bony cage Q, and (ii) membranes R.
  3. How much is x?
  4. Name the organs S.
  5. What are the reflexes involving structure P only known as?
$i.$ Draw a labelled ray diagram to show the path of a ray of light incident obliquely on one face of a glass slab.
$ii. $Calculate the refractive index of the material of a glass slab. Given that the speed of light through the glass slab is $2 \times 10^8 m / s$ and in air is $3 \times 10^8 m / s$.
$iii.$ Calculate the focal length of a lens, if its power is $- 2.5 D.$