INSTRUCTIONS
- Candidates answer all questions in the spaces provided
- Candidates should answer all the the questions in English.
- You are provided with iodine solution, visking tubing, a beaker and solution labeled X.
Tie one end of the tubing provided with a thread tightly. Measure 5ml of solution X, pour 5ml of solution X into the visking tubing.
Tie the end of the tubing tightly. Ensure there is no leakage. Rinse the outside of the tubing with distilled water and immerse its contents in a beaker containing iodine solution. Allow it to stand for 20 minutes.-
- Record your observation at the beginning and end of experiment. Record your results in the table below
Experiment set up Solution X inside the tubing Iodine solution outside the tubing Beginning of experiment End of experiment - What was the identity of solution X? (1mk)
- State the property of visking tubing. (1mk)
- Account for the results obtained in (a)(i) above (4mks)
- Record your observation at the beginning and end of experiment. Record your results in the table below
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- Which physiological process was being investigated in this experiment? (1mk)
- State three factors which affects the process the process being investigated. (3mks)
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- The picture below shows series of beaks in birds.
- Using observable features in the photograph, place with reason, the class to which the above pictures belong
- Class…………………………………………(1mk)
Reason……………………………………… (1mk) - State the type of evolution that may have led to the emergence of the different beaks shown on the pictures above…………………………………………………(1mk)
- Name the type of evolution structure represented by the beaks shown on the pictures above. (1mk)
- Observe the pictures carefully. From your observations, what features are responsible for the different types of beaks?………………………………………………………………… (3mks)
- Class…………………………………………(1mk)
- Below are pictures from two different animals
- What is the specific function of the two structures shown in the picture (1mk)
- Name the class to which each image belongs
- X……………………………………………………………………………………………………….. (1mk)
- Y………………………………………………………………………………………………………. (1mk)
- What type of evolutionary structures is represented in the above pictures (1mk)
- Name two economic importance of animal X (2mks)
- Using observable features in the photograph, place with reason, the class to which the above pictures belong
- The photographs below show three bean seedlings that are of the same age but were grown under different environmental conditions.
- Based on the external appearance of the seedlings, suggest the condition under which each of them was grown.
- Q
- R
- S
- State two observable differences between seedling Rand S
- State the term that is used to describe the phenomenon exhibited by specimen S and state its significance. (2mks)
Term –
Significance – - Name the response exhibited by seedling Q and explain how it occurs
Name – (1mk)
Explanation - (3mks) - State the type of germination that occurs in the three seedlings and give a reason. (2mks)
Name –
Reason -
- Based on the external appearance of the seedlings, suggest the condition under which each of them was grown.
MARKING SCHEME
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Experiment set up Solution X inside the tubing Iodine solution outside the tubing Beginning of experiment White/ cream rej.yellow Yellow/brown colour of iodine retained End of experiment Solution turns blue black/black No colour change /brown/yellow colour iodine
remains - Starch
- Semi – permeable
- Iodine (molecules) moved into starch solution / solution X across the tubing through diffusion, turning it blue black; starch (molecules) were too large such that they could not move across the tubing into the iodine solution.
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- Diffusion/ selective diffusion
- Size of diffusing molecules, solubility, thickness of the medium/tubing/membrane/permeability of medium/tubing
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- class – Aves
Reason – presence of beaks and feathers - divergent evolution / adaptive radiation
- homologous structures
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- length
- shape
- size
- class – Aves
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- flight
- X – Insecta
Y- mammalian - Analogous structures
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- Pollination
- production of honey used as food
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- Q – unidirectional light
- R – Sufficient / adequate light
- S – in the dark.
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Seedling R Seedling S Short stem Longer stem Large leaves Small leaves Green leaves Yellow leaves Green stem Light yellow stem Thick stem Thinner stem - Term – Etiolation
Significance – the seedling is elongating / growing fast to reach light - Name – positive phototropism; reject phototropism alone
Explanation – exposure to unidirectional light causes auxins to migrate to the shaded side. This stimulates faster elongation of cells in the shaded side relative to lighted side resulting in faster growth on that side causing the seedling to bend to the light side. - Name – Epigeal
Reason – cotyledons are brought above the ground
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