Biology 3 Nov/Dec 2011 - Candidates Weakness

Biology Paper 3,Nov/Dec 2011

Questions:		1	2	4		Main

General Comments
Weakness/Remedies
Strength

Question 1
(a) (i) Identify the process represented in the diagrams ---------------------------------------------------------------------------------------------------------------- (ii) Name the parts labeled I,II,III,IV,V and VI I. ------------------------------------------------------ IV. ---------------------------------------------------- II. ----------------------------------------------------- V. ----------------------------------------------------- III. ----------------------------------------------------- VI. ----------------------------------------------------- (iii) State one function each of the parts labeled I and VI. I. ------------------------------------------------------------------------------------------------------------------- VI. ------------------------------------------------------------------------------------------------------------------ [ 2 marks ] (b) (i) Name each stage of the process indicated in diagrams A to E A. ------------------------------------------- -- D. ---------------------------------------------- B. ---------------------------------------------- E. ……………………………………………………….. C. ----------------------------------------------- [ 5 marks ] (ii) Arrange the stages in the correct order -------------------------------------------------------------------------------------------------------------------- [ 3 marks ] (c)(i) Describe briefly the process taking place in A ---------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------- [ 4 marks ] (ii) In a tabular form, state three differences between stages C and D Differences between C and D C D ------------------------------------------- ---------------------------------------------- ------------------------------------------- ---------------------------------------------- ------------------------------------------ ---------------------------------------------- [ 3 marks ] (d) Name two organs each: (i) in plants; (ii) in animals; in which the process illustrated in the diagrams occurs. Plants:……………………………………………………………………………………………………………………………… ------------------------------------------------------------------------------------------------------------------- Animals: ………………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………………………… [ 4 marks ]
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OBSERVATION
The performance of candidates on this question was fair. Many candidates could identify X and Y as Oxygen and gas bubbles respectively and could state the aim of the experiment as an experiment to show that oxygen is released during the process of photosynthesis. Some candidates however said it was an experiment to demonstrate the process of transpiration and so lost marks on many of the sub items. Most candidates could say why a glass funnel was used for the experiment and could describe a simple test to identify X /oxygen but many candidates wrote insert a glowing splinter instead of a glowing splint. Some candidates however could not state why the funnel was placed on plasticine, why sodium bicarbonate was added to the water and why the setup was placed in sunlight. Expected answer include - Funnel was raised to allow free movement of water. - Sodium bicarbonate was added to provide (sufficient) carbon-dioxide; for the water plant to photosynthesize. - The set-up was placed in the sunlight to provide sunlight/light/solar energy; which is used for photosynthesis/the light stage of photosynthesis. Many candidates could not describe what happened in the time interval between diagrams A and B, neither could they write a balanced chemical equation for the process nor state five ways in which the process is important. Expected answers include Description of what happened between diagrams A and B. Sunlight energy is absorbed by the plant; Carbon dioxide produced by the bicarbonate and water are used for photosynthesis; Bubbles of gas/oxygen are released into the funnel; And accumulate in the test tube; Which displaces water/water level falls in the test tube. …/3 Balanced Chemical equation Chemical Equation 6H2O + 6CO2 light C6H12O6 + 6O2 Chlorophyll Many candidates wrote Co2 instead of CO2. Importance of the process The Oxygen is released into the environment during the process; It reduces CO2 concentration in the atmosphere/it reduces the greenhouse effect; Conversion of solar energy to chemical energy; Production of food/carbohydrates/fats protein for herbivores/carnivores/animals. Source of energy for all life processes.