Biology 3 Nov/Dec 2010

Biology Paper 3,Nov/Dec 2010

Questions:		1	2	3	4	Main

General Comments
Weakness/Remedies
Strength

Question 4
Study the diagrams below on a water culture experiment using young maize plants and use it to answer questions 4(a) to 4(e). Diagram (a) (i) Name the parts labelled I to VI in diagram B I. .............................................................. IV. ........................................................... II. ............................................................. V. ........................................................... III. ............................................................ VI. .............................................................[3 marks] (ii) What is the function of the part labelled IV? ..................................................................................................................................................... ........................................................................................................................................[2 marks] (iii) What is the importance of pumping air into the part labelled VI? ..................................................................................................................................................... ........................................................................................................................................[2 marks] (b) (i) Name four major inorganic ions that will be contained in the part labelled VI in diagram B. ..................................................................................................................................................... .................................................................................................................................................. ..................................................................................................................................................... ........................................................................................................................................[4 marks] (ii) Outline the process by which the effect of one of the major inorganic ions named in 4(b)(i) above on the maize plant can be investigated . ..................................................................................................................................................... .................................................................................................................................................. ..................................................................................................................................................... ........................................................................................................................................[5 marks] (c) (i) State two observable differences between the plants in diagrams A and B. ..................................................................................................................................................... ........................................................................................................................................[2 marks] (ii) State two reasons for the differences observed in 4( c )(i) above . ..................................................................................................................................................... ........................................................................................................................................[2 marks] (d) (i) State the function of the part labelled II in diagram B. ........................................................................................................................................[1 mark] (ii) State one reason why the part labelled II in diagram B should be kept dry. ........................................................................................................................................[1 mark] (iii) State three factors that should be kept constant in the environment for the experiment to be successful. ..................................................................................................................................................... .................................................................................................................................................... ........................................................................................................................................[3 marks] (e) (i) State the class of the plant in diagram B. ........................................................................................................................................[1 mark] (ii) Give four reasons for placing the plant in the class stated in 4(e)(i) above ..................................................................................................................................................... .................................................................................................................................................... ........................................................................................................................................[4 marks]
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OBSERVATION
This question was on water culture and the candidates' performance was generally poor. Most candidates could not correctly name the labeled parts and could not state the function of the part labelled IVrrhe black paper/cover. They could state the importance of pumping air into the culture solution as well as major inorganic ions likely to be present in the solution and observable differences between the two plants but could not outline the process for investigating the ions as well as the reasons for the observed differences between the plants. Expected answers include: Name of parts I - Leaf II - Cotton wool; III - Stopper; Rubber bung/cork; IV - Black paper cover; V - Glass jar; VI - Culture solution Function of IV/black cover - to prevent light entering the culture solution/VI; - to prevent growth of algae which will alter the composition of the solution. Investigating a major ion Prepare a complete culture solution, containing all the major and minor ions needed by the plant; pour it into a glass jar; prepare another solution containing all the mineral ions except the one under investigation, select two plant seedlings of the same age and size; wash their roots with distilled water and place in the glass jars suspended with dry cotton wool; cover the jars with black paper; and place where there is enough sunlight; observe each plant and note the differences; the one with the element under investigation will show weak/growth; the one with all the elements/ions will show healthy growth. Reasons for differences between plants Plant B is placed in complete culture solution/solution containing all the essential mineral ions for the healthy growth. While plant A is place in an incomplete culture solution/distilled was hence the stunted growth/poor root/shoot development. Most candidates could not state the function of II1the cotton wool and could not classify the plant with reasons. They were however able to state three factors that should be kept constant in the environment for the experiment to be successful. Expected answers include Class of plant Monocotyledonae Reasons - parallel venation - presence of leaf sheaths - felonious roots - narrow leaf blade