Heredity and Evolution — Science STD 10 — Question

Define hydrotropism. Give one example of hydrotropism. State whether this example is of positive hydrotropism or negative hydrotropism. Illustrate your answer with the help of labelled diagram.

Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.

With the help of a labelled diagram, illustrate the pathway of response when someone pricks in your hand with a pin.

A scientist removed some cells from the growing point of a plant and placed it in a suitable medium leading to the formation of a shapeless lump of mass X. X is then transferred to another medium which stimulates it to develop roots. When X with developed roots is placed in a yet another medium, then it develops shoots to form tiny plantlets. These plantlets can then be transplanted in pots or soil where they can grow to form mature plants.

1. What is the shapeless lump of mass X known as?
2. What name is given to this method of producing new plants?
3. The growth medium used in this method contains plant nutrients in the form of a 'jelly'. Name this jelly.
4. What is the general name of chemicals used to stimulate the growth of plant cells and development of roots and shoots?
5. Name any two plants which are produced by this method.
6. State any two advantages of this method of producing plants.
7. What is the other name of this method [other then that given in (b) above]?

1. A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
2. We see advertisements for eye donation on television or in newspapers. Write the importance of such advertisements.

1. Draw a ray diagram to show the formation of image by a convex lens when an object is placed in front of the lens between its optical centre and principal focus.
2. In the above ray diagram mark the object-distance (u) and the image-distance (v) with their proper signs (+ve or – ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.
3. Find the power of a convex lens which forms a real, and inverted image of magnification -1 of an object placed at a distance of 20cm from its optical centre.

A, B and C are three living organisms. The organism A is a unicellullar fungus which can live without air. It is used in the commercial production of an organic compound P from molasses. The organism B is a unicellular animal which lives in water and feeds and moves by using pseudopodia. It breathes through an organelle Q. The organism C is a tiny animal which acts as a carrier of malarial parasite. It breathes and respires through a kind of tiny holes R and air - tubes S in its body.

1. What are organisms A, B and C?
2. Name P, Q, R and S.
3. Which organism/ organisms undergo aerobic respiration?
4. Which organism/ organisms undergo anaerobic respiration?

Water and dissolved minerals get into the root hair of a plant by a process called A and enter the conducting tissue B. The process C helps the water and dissolved minerals to move up through the tissue B in roots and stem, and reach the leaves of a plant. In the leaves food is made by a process D. This food is then transported to all the parts of a plant through tissue E. The process of distributing food made in the leaves to all the parts of the plants is called F.

1. What are (i) A, (ii) B, (iii) C, (iv) D, (v) E, and (vi) F?
2. Which tissue is made up of living cells: B or E?
3. Which tissue, B or E, contains sieve tubes?
4. Which tissue, B or E, contains tracheids?

Draw the ray diagram in each case to show the position and nature of the image formed when the object is placed:

1. At the centre of curvature of a concave mirror.
2. Between the pole P and focus F of a concave mirror.
3. In front of a convex mirror.
4. At 2f of a convex lens.
5. In front of a concave lens.