Biology Paper 1 Questions and Answers - Form 4 Term 2 Opener Exams 2023

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Biology Paper 2 Questions and Answers - Form 4 Term 2 Opener Exams 2023

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Instructions to Candidates

Write your name and index number in the spaces provided above.
Sign and write the date of examination in the spaces provided above.
Answer all the questions in the spaces provided.
This paper consists of 8 printed pages
Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing.

FOR EXAMINER’S USE ONLY

Questions 1- 24	Maximum score	Candidates score
Questions 1- 24	80

QUESTIONS

Name the cell organelles which are abundant in (2 mks)
Muscle cells-
Pancreas –
Explain why the fine adjustment knob is used only when using high power objective lens. (1 mk)
Distinguish between osmotic pressure and osmotic potential. (2mks)
Describe two adaptations of a leaf to the process of photosynthesis. (2mks)

The diagram below illustrates part of a nephron from a mammalian kidney.
1. Name the fluid in the part labelled Q. (1mk)
2. Identity the process responsible for the formation of the fluid named in (a) above. (1mk)
3. Which two hormones exert their effect in the nephron? (1mk)
1. The figure below illustrates a portion of a chromosome with genes named A, B, C, S, Q and R.
  
  A
  
  B
  
  C
  
  S
  
  Q
  
  R
  
  Use the diagrams similar to the ones above to illustrate the changes if the above chromosome undergoes the following mutations affecting only gene C and S.
  1. Deletion. (1mk)
  2. Inversion. (1mk)
2. Human-inherited features can be grouped under two headings as follows.
  
  Group A Group B
  
  Weight, intelligence, height tongue rolling, blood group, eye Color.
3. What is the genetic explanation for the difference between the two groups? (2mks)
1. Calculate the respiratory quotient of the oxidation reaction below. (2mks)
  2C₅₁H₉₈O₆ + 145O₂ → 102CO₂ + 98H₂O + Energy
2. Name the possible food being oxidised. (1 mk)
The wings of a bird and that of insects are analogous structures.
1. What are analogous structures? (1 mark)
2. Name this type of evolution. (1 mark)
3. Name two vestigial structures found in man. (2 marks
1. The diagram below represent the structure of a nerve cells.
  1. Identify the nerve cell. (1 mark)
  2. Give a reason for your answer in a (i) above. (1 mark)
2. State the function of part labelled T. (1 mark)
3. Using an arrow show the direction of an impulse on the diagram. (1 mark)
The diagram below represents a bone of a mammal.
1. Identify the bone? (1 mark)
2. Name the part marked X. (1 mark)
3. Name the bone that articulates at the part labelled F. (1 mark)
4. State two adaptations of the bone to its function. (2 marks)
The diagram below shows a phenomenon which occurs during cell division.
1. Identify the stage of cell division in which this phenomenon occurs. (1 mark)
2. State the importance of the phenomenon taking place in the part labeled B. (2 marks)
Mutiso is unable to read history textbook held at arm’s length but read clearly at normal length.
1. Identify the defect he is suffering from. (1 mark)
2. Why was he unable to read the book clearly at arm length? (1 mark)
3. How can the defect be corrected? (1 mark)
State two functions of blood in a human body. (2 marks)
State 3 significance of water in seed germination. (3 marks)
State two differences between complete and incomplete metamorphosis. (2 marks)
The diagram below represents a fern.
1. Name Parts labeled A and B. (2mk)
  A –
  B –
2. To which division does the plant belong? (1mk)
1. Define the term immunity. (1mk)
2. Distinguish between natural immunity and acquired immunity. (2mks)
3. Identify one immunizable disease in Kenya. (1mk)
The diagram below shows a stage during fertilization in flowering plant.
1. Name the parts labeled Q, R, and S. (3 mks)
  Q –
  R –
  S –
2. State the function of the pollen tube. (1mk)
1. State the major cause of the ‘Global warming’ experienced in the world today.(1mk)
2. Suggest two ways of reducing the Global warming. (2mks)
An experiment was set to investigate a certain aspect of response. A seedling was put on a horizontal position as shown in figure M below. After 24 hours, the set up was as shown in figure N.
1. Name the response exhibited. (1mk)
2. Explain the curvature of the shoot upwards. (3mk)
The diagram below represents an experimental set up to investigate a certain scientific concept.

The potted plant was first de-starched by keeping it in dark for four days.
The set up was then placed in sunlight for five hours and leaves were tested for starch.
1. What scientific concept was being investigated? (1mk)
2. 1. Give the results likely to be obtained after starch test for A and B.
    A and B.
    A – (1mk)
    B – (1mk)
  2. Account for the results in leaf A in b (i) above. (1mk)
3. Why was leaf C included in the set-up? (1mk)
Give two reasons why primary productivity decreases with increase in depth in an aquatic ecosystem. (2 mks)
Explain why certain drugs become ineffective in curing disease after many years of use. (2mks)
Name two kidney diseases. (2mks)
The diagram below represents a transverse section of an ovary from a certain flower.
1. Name the structure labelled W. (1mk)
2. Name the type of placentation illustrated in this diagram. (1mk)
Liver damage leads to impaired digestion of fats. Explain. (2marks)
1. A person who is blood group AB has an advantage over a person who is blood group O. Explain. (2marks)
2. Give two reasons for screening blood before transfusion. (2marks)

MARKING SCHEME

Name the cell organelles which are abundant in (2 mks)
Muscle cells- mitochondria
Pancreas – Golgi bodies
Explain why the fine adjustment knob is used only when using high power objective lens. (1 mks)
To move small distances hence bringing an image into focus.
Distinguish between osmotic pressure and osmotic potential. (2mks)
Osmotic pressure is the tendency of a solution to take up water when separated from pure water by a semi-permeable membrane while osmotic potential is the tendency of water molecules to diffuse out of a solution.
Describe two adaptations of a leaf to the process of photosynthesis. (2mks)
Has chlorophyll, a pigment that traps light.
Has a large number of chloroplasts on the upper surface to increase the surface area for photosynthesis.
Thin layer of cuticle to allow penetration of light.
The diagram below illustrates part of a nephron from a mammalian kidney.
1. Name the fluid in the part labelled Q. (1mk)
  Glomerular filtrate
2. Identity the process responsible for the formation of the fluid named in (a) above. (1mk)
  Ultra filtration
3. Which two hormones exert their effect in the nephron? (1mk)
  Aldosterone
  Anti diuretic hormone
1. The figure below illustrates a portion of a chromosome with genes named A, B, C, S, Q and R.
  Use the diagrams similar to the ones above to illustrate the changes if the above chromosome undergoes the following mutations affecting only gene C and S.
  1. Deletion. (1mk)
    
    A
    
    B
    
    Q
    
    R
  2. Inversion. (1mk)
    
    A
    
    B
    
    S
    
    C
    
    Q
    
    R
2. Human-inherited features can be grouped under two headings as follows.
  What is the genetic explanation for the difference between the two groups? (2mks)
  - Group A shows continuous variation while group B shows discontinuous variation.
1. Calculate the respiratory quotient of the oxidation reaction below. (2mks)
  2C₅₁H₉₈O₆ + 145O₂ → 102CO₂ + 98H₂O + Energy
  - RQ = amount of CO₂ produced = 102 = 0.7
    Amount of oxygen used 145
2. Name the possible food being oxidised. (1 mks)
  - Lipids/fats
The wings of a bird and that of insects are analogous structures.
1. What are analogous structures? (1 mark)
  - These are structures with different embryonic origin but have been modified to perform similar functions.
2. Name this type of evolution. (1 mark)
  - Convergent evolution
3. Name two vestigial structures found in man. (2 marks)
  - Coccyx
  - Appendix
The diagram below represent the structure of a nerve cells.
1. 1. Identify the nerve cell. (1 mark)
    - Motor neurone
  2. Give a reason for your answer in a (i) above. (1 mark)
    - It has a cell body located at one end of the axon within the CNS. Its terminal dendrites terminate in the effectors.
2. State the function of part labelled T. (1 mark)
  - It fastens the transmission of nerve impulses
3. Using an arrow show the direction of an impulse on the diagram. (1 mark)
The diagram below represents a bone of a mammal.
1. Identify the bone? (1 mark)
  - Scapula
2. Name the part marked X. (1 mark)
  - Neural spine
3. Name the bone that articulates at the part labelled F. (1 mark)
  - Humerus
4. State two adaptations of the bone to its function. (2 marks)
  - It has a neural spine that provides large surface area for muscle attachment
  - It has the glenoid cavity that articulates with the Humerus to form a ball and socket joint that rotates at 360 ͦ c
The diagram below shows a phenomenon which occurs during cell division.
1. Identify the stage of cell division in which this phenomenon occurs. (1 mark)
  - Prophase 1
2. State the importance of the phenomenon taking place in the part labeled B. (2 marks)
  - Recombination of genes; leading to variation
Mutiso is unable to read history textbook held at arm’s length but read clearly at normal length.
1. Identify the defect he is suffering from. (1 mark)
  - Short sightedness.
2. Why was he unable to read the book clearly at arm length? (1 mark)
  - Long eye ball thus image formed before reaching retina.
3. How can the defect be corrected? (1 mark)
  - Wearing concave/diverging lens.
State two functions of blood in a human body. (2 marks)
- Regulation of the body temperature
- Regulation of pH of fluids
- Defence against disease – causing organism/ pathogens/ infection.
State 3 significance of water in seed germination. (3 marks)
- Activate enzymes; provide a medium for enzymatic activities (to break down stored food to soluble form.
- Hydrolyses; dissolves food material;
- Is a medium of transportation of dissolved food substances to growing regions of radical and plumule
- Softens seed coat to facilitate emergence of radicle

State two differences between complete and incomplete metamorphosis. (2 marks)

Complete metamorphosis	Incomplete metamorphosis
a) involves 4 series of changes i.e egg-larva-pupa-adult	a) involves 3 series of changes i.e egg-nymph-adult
b) growing stage in larva is different in form from adult form	b) growing state in nymph is similar to adult form

The diagram below represents a fern.
1. Name Parts labeled A and B. (2mk)
  - A – Sori rej. sorus
  - B – Rhizome
2. To which division does the plant belong? (1mk)
  - Pteridophyta
1. Define the term immunity. (1mk)
  - Ability of the body to identify/ recognize foreign antigens and develop mechanisms of destroying them / ability to resist infection
2. Distinguish between natural immunity and acquired immunity. (2mks)
  - Natural immunity is inborn /inherited /passed from parents to offspring while acquired immunity is obtained in life
3. Identify one immunizable disease in Kenya. (1mk)
  - Tuberculosis; poliomyelitis; diphtheria; whooping cough; measles
The diagram below shows a stage during fertilization in flowering plant.
1. Name the parts labeled Q, R, and S. (3 mks)
  - Q – Antipodal cell(s)
  - R – Polar nucleus / body
  - S – Functional egg cell
2. State the function of the pollen tube. (1mk)
  - Pathway through which male nuclei reach the embryo sac / improves efficiency of fertilization; its tip produce lytic enzyme which dissolves the embryo sac wall to allow entry of male nuclei
1. State the major cause of the ‘Global warming’ experienced in the world today. (1mk)
  - Carbon (IV) Oxide; rej. Carbon (iv) Oxide
2. Suggest two ways of reducing the Global warming. (2mks)
  - Reducing use wood / fossil fuels; planting more trees / afforestation or re-afforestation
An experiment was set to investigate a certain aspect of response. A seedling was put on a horizontal position as shown in figure M below. After 24 hours, the set up was as shown in figure N.
1. Name the response exhibited. (1mk)
  - Geotropism
2. Explain the curvature of the shoot upwards. (3mk)
  - Gravity causes high concentration of auxins on the lower part of the shoot; this causes faster elongation of cells on the lower part compared to the upper part; making the shoot to curve upwards
The diagram below represents an experimental set up to investigate a certain scientific concept. The potted plant was first de-starched by keeping it in dark for four days.

The set up was then placed in sunlight for five hours and leaves were tested for starch.
1. What scientific concept was being investigated? (1mk)
  - Photosynthesis
2. 1. Give the results likely to be obtained after starch test for A and B.
    - A and B.
    - A – Negative test / starch absent (1mk)
    - B – Positive test / starch present (1mk)
  2. Account for the results in leaf A in b (i) above. (1mk)
    - Sodium hydroxide absorbed all the Carbon (IV) Oxide hence no photosynthesis
  3. Why was leaf C included in the set-up? (1mk)
    - Control experiment
Give two reasons why primary productivity decreases with increase in depth in an aquatic ecosystem. (2 marks)
- Decrease in light intensity hence low photosynthesis.
- Decrease in oxygen for respiration.
Explain why certain drugs become ineffective in curing disease after many years of use. (2mks)
- Disease causing organism mutate; and become resistant
Name two kidney diseases. (2mks)
- Nephritis
- Kidney stones
The diagram below represents a transverse section of an ovary from a certain flower.
1. Name the structure labelled W. (1mk)
  - ovule
2. Name the type of placentation illustrated in this diagram. (1mk)
  - axile
Liver damage leads to impaired digestion of fats. Explain. (2marks)
- No production of bile to emulsify fats.
1. A person who is blood group AB has an advantage over a person who is blood group O. Explain. (2marks)
  - Shall be a universal recipient ; can receive blood from any blood group ; while a person with blood group ‘O’ can only receive blood from a person with blood group O/ AB has no antibodies while O has no antigen
2. Give two reasons for screening blood before transfusion. (2marks)
  - To check for compatibility
  - To make sure the blood is free from diseases (such as HIV, Hepatitis B)