Biology Paper 3 Questions and Answers with confidential - Kassu Jet Joint Mock Exams 2023

INSTRUCTIONS

• Answer ALL the questions.
  
  

QUESTIONS

1. You are provided with Solution Z, 15 cm³ solution labeled Q, test tubes, dilute Hydrochloric, and dilute sodium hydroxide solution W, Water bath, Bunsen burner, Iodine solution, Benedict’s solution, Stop watch and labels. Follow the procedure below and record your observations and conclusions in the table below.
   Procedure
   Place 5cm³ each of solution Q into 3 test tubes and label them 1A, 2A and 3A.
   1. To test tube 1A add 1cm³ of dilute Hydrochloric acid and shake. Add 1cm³ of the solution Z and shake.
   2. To test tube 2A add 1cm³ of dilute sodium hydroxide and shake. Add 1cm³ of the solution Z and shake
   3. To test tube 3A add 1cm³ of solution W and shake. Add 1cm³ of the solution Z and shake
   4. Place the three labeled test tubes into a water bath and maintained at 37°C for 20 minutes then divide the portions into another separate test tube as 1A and 1B, 2A and 2B, 3A and 3B respectively.
   5.  
      1. Using the reagents provided carry out food test and fill in the table below (12marks)
         

         Tes Tube	Test with iodine using the A portion		Test with Benedict's using the B portion
         	observation	Conclusion	Observation	Conclusion
         Dilute Hydrochloric acis+solution Q+ solution Z
         Dilute sodium hydroxide +Q + solution Z
         solution W+solution Q+solution Z

      2. What is the identity of solution Z ? (1mark)
      3. What is the significance of maintaining them at a temperature of 37°C? (1mark)
2. The photograph P is a pumpkin fruits with seeds .The seeds were germinated under different conditions as shown in photograph Q1 andQ2
   
   
   1. Study the photograph Q1and Q2 carefully;
      1. Identify the conditions under which seedling in photograph Q1and Q2 were grown ( 2marks)
         Q1:
         Q2:
      2. Give a reason for your response of set up in photograph Q2? ( 1mark)
      3. State the differences between seedling in photograph Q1andQ2? ( 2marks)
         

         Photograph Q1	photograph Q2

      4. A farmer transplanted one of the seedling as shown in photograph Q1 and it transformed specimen into photograph R.The specimen in photograph R has developed a certain response to aid in its support:
         1. Name the response shown in the shoot of specimen in photograph R ( 1mark)
         2. Explain how the response occurs? ( 3marks)
         3. What is the significance of this response ( 1mark)
   2. An ecologist observed one of the leaves from the plant in in photograph R and noted it to have aphids as shown in photograph S .Count the number of the aphids and sketch a pyramid of numbers ( 2marks)
   3. Comment on the adaptive advantage that confer the aphids to their habitat ( 1mark)
   4. A farmer has tried using a certain aphicide for a long time but it was not able to eliminate the aphids .Explain the reason for this? ( 1mark)
3. The photographs below represent structures of certain animal species. Study them and answer the questions that follow.
   
   
   1. Identify the type of structure represented by photographs A and B (2marks)
      A
      B
   2. What is the specific function of the three structures shown in the photograph A? (1 mark)
   3. Differentiate between the structures you’ve name 3(a) above (4marks)
   4. Name the type of evolution exhibited by photographs A and B. (2marks)
      A
      B
   5. Using Darwin’s theory of evolution, explain how the whale’s flipper E would have evolved. (3 marks)

CONFIDENTIAL

Each candidate will require the following

• 3cm³ Solution Z (ptyalin) 3cm3
• 15 cm³ Starch solution labeled Q
• 6 Test tubes
• Dilute Hydrochloric acid (2cm3)
• Dilute sodium hydroxide (2cm3)
• Solution W ( distilled water)
• Water bath
• Source of heat
• Iodine solution
• Thermometer
• Benedict’s solution
• Stop watch
• Measuring cylinder
• 6 Labels
• Stop watch

MARKING SCHEME

1. You are provided with Solution Z, 15 cm³ solution labeled Q, test tubes, dilute Hydrochloric, and dilute sodium hydroxide solution W, Water bath, Bunsen burner, Iodine solution, Benedict’s solution, Stop watch and labels. Follow the procedure below and record your observations and conclusions in the table below.
2. Procedure
   Place 5cm³ each of solution Q into 3 test tubes and label them 1A, 2A and 3A.
   1. To test tube 1A add 1cm³ of dilute Hydrochloric acid and shake. Add 1cm³ of the solution Z and shake.
   2. To test tube 2A add 1cm³ of dilute sodium hydroxide and shake. Add 1cm³ of the solution Z and shake
   3. To test tube 3A add 1cm³ of solution W and shake. Add 1cm³ of the solution Z and shake
   4. Place the three labeled test tubes into a water bath and maintained at 37°C for 20 minutes then divide the portions into another separate test tube as 1A and 1B, 2A and 2B, 3A and 3B respectively.
   5.  
      1. Using the reagents provided carry out food test and fill in the table below (12marks)
         

         Tes Tube	Test with iodine using the A portion		Test with Benedict's using the B portion
         	observation	Conclusion	Observation	Conclusion
         Dilute Hydrochloric acis+solution Q+ solution Z	blue black	starch present-(unsuiable PH)	blue color persist	reducing sugar absent
         Dilute sodium hydroxide +Q + solution Z	brown	starch absen-(ideal PH for enzyme)	green/yellow colour	reducing sugar present
         solution W+solution Q+solution Z	blue black	sarch present-(unsuitable ph0)	blue color persist	reducing sugar absent

      2. What is the identity of solution Z ? (1mark) 
         • Enzyme; pyalin
      3. What is the significance of maintaining them at a temperature of 37°C? (1mark) 
         • optimum temperature
3. The photograph P is a pumpkin fruits with seeds .The seeds were germinated under different conditions as shown in photograph Q1 andQ2
   
   
   1. Study the photograph Q1and Q2 carefully;
      1. Identify the conditions under which seedling in photograph Q1and Q2 were grown ( 2marks)
         Q1: well lied/light
         Q2: dark/absence of light
      2. Give a reason for your response of set up in photograph Q2? ( 1mark) 
         • the seedling are etiolated
      3. State the differences between seedling in photograph Q1andQ2? ( 2marks)
         

         Photograph Q1	photograph Q2
         green/bigger leaves	yellow/small leaves
         thicker stems srong/seady/firm	thinner stems weak

      4. A farmer transplanted one of the seedling as shown in photograph Q1 and it transformed specimen into photograph R.The specimen in photograph R has developed a certain response to aid in its support:
         1. Name the response shown in the shoot of specimen in photograph R ( 1mark) 
            • thigmotropism/haptotropism
         2. Explain how the response occurs? ( 3marks) 
            • when the tendrils come ino contact with the hard objec. auxins move away from the side of contact; the outer side elogates faster than the part in contact thus the tendril to continue to coil round the hard object
         3. What is the significance of this response ( 1mark) 
            • enables weak plant to reach light for photosynthesis to occur; enables weak stem to acquire support
   2. An ecologist observed one of the leaves from the plant in in photograph R and noted it to have aphids as shown in photograph S .Count the number of the aphids and sketch a pyramid of numbers ( 2marks)
      

      15 aphids

      1 leaf

   3. Comment on the adaptive advantage that confer the aphids to their habitat ( 1mark) 
      • Aphids are green in colour, blends/carmouflages well with the background therefore not spoted easily by predatory organisms
   4. A farmer has tried using a certain aphicide for a long time but it was not able to eliminate the aphids .Explain the reason for this? ( 1mark) 
      • Aphids have with time acquired mutant genes against the aphicide thus developing resistance
4. The photographs below represent structures of certain animal species. Study them and answer the questions that follow.
   
   
   1. Identify the type of structure represented by photographs A and B (2marks)
      A Analogous structures
      B homologous structures
   2. What is the specific function of the three structures shown in the photograph A? (1 mark) 
      • swimming/locomotion in water
   3. Differentiate between the structures you’ve name 3(a) above (4marks) 
      • Homologous structures are structures of similar embroymic origin but are modified to perform different functions in different ecological niches while Analogous structures are structures of different embronic origin that become modified in the course of evolution(evolved) to perform simillar functions in the same ecological niches(due to exploitation of common ecological enviroment or niche.)
   4. Name the type of evolution exhibited by photographs A and B. (2marks)
      A convergent evoluion
      B divergent evolution
   5. Using Darwin’s theory of evolution, explain how the whale’s flipper E would have evolved. (3 marks) 
      • small variations occured in locomotory structures within the population brough about by the prevalling enviroments Hindlimbs began to regress as the ancestors of whale entered the aquatic enviroment: over time whale decendants spent more and more time in the water and their bodies became adapted for swimmimg. their front legs became flippers.