Answer all questions in this section
3. Two equal strips “P” and “S” were cut from a raw potato tuber when cell sap was 28.5% sugar. The strips were placed in sugar solutions of different concentrations as follows: P=10% and S=35%
(a) What changes would you expect in strips P and S?
(b) Name and define the scientific process that took place in strips P and S.
(c) Account for the changes observed in 3(a) above.
(d) State any two ways by which the process mentioned in 3 (b) occurs in our daily life.
4. The figure below is a diagrammatic representation of the breathing apparatus of a man. Study the figure carefully and answer the questions that follow.
(a) The following parts of the diagram represent which structures in the human body?
(i) Glass tube
(ii) Bell jar
(iii) Balloons
(iv) Rubber sheet
(b) How does the apparatus fail to give an accurate representation of the breathing mechanism in man?
(c) Explain what will happen if the rubber sheet is pulled down.
5. (a) State two importance of evolution.
(b) Evolution is the gradual change and development of organisms from a simple form to a more complex form over a long duration. Give four points to justify this statement.
6. (a) Earthworms are said to be the farmer's friend. Justify this statement with three reasons.
(b) Why are earthworms said to be hermaphrodites?
(c) What features make arthropods the most successful group of organisms on the earth’s surface? (Give three points).
7. (a) If the pancreas were mistakenly completely removed during surgery from a patient, describe four problems the patient would get.
(b) Give biological reasons for the following facts:
(i) Plants do not have a well-elaborated excretory system like animals do.
(ii) The wall of the left ventricle of the mammalian heart is thicker than the wall of the right ventricle.
(iii) The rate of breathing increases quickly during physical exercise.
(iv) Camels can survive in the desert for a long time without drinking water.
(v) Humans are the most intelligent animals.
8. In an experiment, a variety of garden peas having a smooth seed coat was crossed with a variety having a wrinkled seed coat. All the seeds obtained in the F1 had a smooth seed coat. The F1 generation was selfed. The total number of F2 was 7324. Let the gene for smooth seed coat be S.
(a) Work out the genotypes for the F1.
(b) Work out the genotype and phenotype ratio of F2.
(c) Calculate the number of the
(i) Wrinkled seeds in F2
(ii) Smooth seeds in F2
SECTION C (30 MARKS)
Answer two questions from this section.
9. Mzee Mafuru, a famous farmer in Mkonza village, is facing a problem associated with having no knowledge of balanced diets to the extent that his family is suffering a lot due to that. As a biologist, help Mzee Mafuru to understand that the suffering of his family will end if he decides to allow the knowledge of a balanced diet into his family by explaining to him the meaning of a balanced diet, two components of a balanced diet and their sources, two importance of a balanced diet, and two factors that may lead someone not to have a balanced diet.
10. Between the months of June and October, most plants undergo wilting due to excessive water loss to the atmosphere brought on by the intense sunlight.
(a) Name and define the process by which the plant leaves lose water to the atmosphere during the day.
(b) Outline and explain three environmental factors that affect the rate of the process mentioned in (a) above.
(c) Explain three advantages of the process named in (a).
11. When the time reaches 10:20 am, Collins rings the bell, and students leave their classrooms for a short break every day. Explain the mechanism by which students hear when Collins rings the bell.
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