Instructions to Candidates
- Spend the first 15 minutes of the time allocated to read through the question paper before commencing your work
- Answer ALL the questions
- You are provided with the following materials;
- Substance labelled L
- 2cm3 Copper sulphate solution
- 2cm3 Sodium hydroxide solution
- 2cm3 DCPIP solution
- 2cm3 Benedict’s solution
- Source of heat
- 3 test tubes
- 3 droppers
You are provided with a substance labeled L. Make a solution of substance L by adding 20 ml of distilled water and stir thoroughly. Design an experiment to investigate the food materials present in L. (9 marks)
Substance Chemical test Procedure Observations Conclusion L L L - State the importance of the food substances present in L to the human body. (2 marks)
- Describe how the body deals with the substances mentioned in (a) above when they are in excess. (2 marks)
- Study the photographs below and answer the questions that follow.
-
- Identify the type of response exhibited by specimen A. (1 mark)
- What is the survival value of the response you have identified in (a)(i) above. (1 mark)
-
- Identify the phenomenon exhibited by specimen B. (1 mark)
- State the significance of the phenomenon in (b) (i) above. (1 mark)
- Explain how the response exhibited by seedlings in photograph C occurred. (3 marks)
- Study the photograph below showing a certain trait in man.
- Identify the trait exhibited in the photograph above. (1 mark)
- The trait you have identified in (d)(i) above is sex linked. In which chromosome is it contained. (1 mark)
- Name any other sex linked trait in man. (1 mark)
- The man in the photograph married a woman. Use a genetic cross to predict the offspring of the above marriage. Let YH represent the gene for the trait above. (4 marks)
- The photographs below show certain chromosomal mutations.
- Identify them
P …………………………… (1 mark)
Q …………………………… (1 mark)
- Identify them
-
- Study the photographs below and answer the questions that follow.
- Give two visible survival adaptive features for the organism in photograph X. (2 marks)
- Identify the dentitions exhibited in photograph Y and Z (2 marks)
Y
Z - Study the photographs below showing a certain type of tooth and teeth arrangement in man.
- Label any three parts of the tooth in photograph S. (3 marks)
- Give two adaptations of the tooth to its function. (2 marks)
- Write the dental formula for the teeth arrangement in photograph T. (1 mark)
CONFIDENTIAL
REQUIREMENTS
- One spatula of substance labelled L (Fortified Exe wheat flour)
- 2cm3 Copper sulphate solution
- 2cm3 Sodium hydroxide solution
- 2cm3 DCPIP solution
- 2cm3 Benedict’s solution
- Source of heat
- 3 test tubes
- 3 droppers
- 2oml of distilled water in a beaker
MARKING SCHEME
- You are provided with the following materials;
- Substance labelled L
- 2cm3 Copper sulphate solution
- 2cm3 Sodium hydroxide solution
- 2cm3 DCPIP solution
- 2cm3 Benedict’s solution
- Source of heat
- 3 test tubes
- 3 droppers
You are provided with a substance labeled L. Make a solution of substance L by adding 20 ml of distilled water and stir thoroughly. Design an experiment to investigate the food materials present in L (9mks)
Substance Chemical test Procedure Observations Conclusion L DCPIP Reject Vitamin C plus subsequent stepsPut 1cm3 of DCPIP into a test tube. Add solution L dropwise;Colour of DCPIP disappears/purple; Reject DCPIP decolourisedDCPIP present; L Benedict’s Reject Reducing sugars plus subsequentPut 1cm3 of solution L into a test tube Add 1cm3 of Benedict’s solutionBoil ;Green ; Traces /little reducing sugars present; Reject Reducing sugars aloneL Biuret’s Reject Proteins plus subsequentPut 1cm3 of solution L into a test tube Add 1cm3 of Sodium Hydroxide solutionAdd 1cm3 of Copper Sulphate solution;(Light) purple; Proteins present; - State the importance of the food substances present in L to the human body. (2mks)
- Proteins –used in formation of body tissues/enzymes/hormones
- Glucose –oxidised by cells to release energy
- Vitamin C- protection against diseases mark any 2
- Describe how the body deals with the substances mentioned in (a) above when they are in excess. (2mks)
- Proteins – excess amino acids deaminated
- Glucose – converted to glycogen and stored in liver cells
- Vitamin C - excreted (as oxalates) mark any 2
- State the importance of the food substances present in L to the human body. (2mks)
- Study the photographs below and answer the questions that follow.
-
- Identify the type of response exhibited by specimen A (1mk)
- Haptonasty
- What is the survival value of the response you have identified in (a)(i) above (1mk)
- A way of obtaining some limited mineral nutrients
- Identify the type of response exhibited by specimen A (1mk)
-
- Identify the phenomenon exhibited by specimen B (1mk)
- Etiolation
- State the significance of the phenomenon in (b) (i) above (1mk)
- To reach/search/seek/obtain light
- Identify the phenomenon exhibited by specimen B (1mk)
- Explain how the response exhibited by seedlings in photograph C occurred (3mks)
- Seedlings subjected to unilateral/ unidirectional source of light ;causing auxins to migrate / diffuse to the dark side of the shoot;/ high concentration of auxins on dark side causing faster growth; on that side than the lit side/ faster cell elongation/ faster cell enlargement/ faster cell growth on the side than the lit.
- Study the photograph below showing a certain trait in man.
- Identify the trait exhibited in the photograph above (1mk)
- Hairy pinna
- The trait you have identified in (d)(i) above is sex linked. In which chromosome is it contained (1mk)
- Y
- Name any other sex linked trait in man (1mk)
- Premature baldness
- Colourblindness
- Haemophilia
- The man in the photograph married a woman. Use a genetic cross to predict the offspring of the above marriage. Let YH represent the gene for the trait above. (4mks)
- Identify the trait exhibited in the photograph above (1mk)
- The photographs below show certain chromosomal mutations.
- Identify them
- P - Duplication
- Q - Deletion
- Identify them
-
- Study the photographs below and answer the questions that follow.
- Give two visible survival adaptive features for the organism in photograph X (2mks)
- Presence of ( large/long/curved) sharp/sharp pointed canine for piercing ;
- Camouflage/blend well with environment concealing/hiding themselves from their predators/prey ;
- Presence of fur to insulate against the low temperature
- Identify the dentitions exhibited in photograph Y and Z (2mks)
- Y - Heterodont
- Z - Homodont
- Study the photographs below showing a certain type of tooth and teeth arrangement in man.
- Label any three parts of the tooth in photograph S (3mks)
- Give two observable adaptations of the tooth to its function (2mks)
- Broad surface to increase surface area for chewing
- Cusps /ridges to increase surface area for chewing
- Write the dental formula for the teeth arrangement in photograph T (1mk)
2 1 2 3i — c - pm — m -2 1 2 3
Reject
If Commas and capital letters are used in the dental formula
If Divisional line is missing in the dental formula
- Label any three parts of the tooth in photograph S (3mks)
- Give two visible survival adaptive features for the organism in photograph X (2mks)
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