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

• Answer ALL questions in the spaces provided.
• All workings must be clearly shown where necessary.

1. Name three sites of gaseous exchange in frogs. (3mks)
2.  
   1. What is organic evolution   (1mk)
   2. Distinguish between divergent and convergent evolution giving example in each case. (4mk)
3. State three applications of plant hormones in agriculture (3 marks)
4.  
   1. Give an equation to show that respiration involves oxidation of glucose (1mk)
   2. How is an energy rich molecule rebuilt after muscle contraction             (2mks)
   3. apart from energy, name another end product  of anaerobic respiration in animals(1mks)
5. Give the functions of the following ecological instruments (2mks)
   1. Seechi disc
   2. Photographic light meter
6. Which genetic disorder is caused by lack of a gene which causes production of Melanin. (1mk)
7. List down two phenotypic characteristics that have been selected for the production of strains suitable for modern agricultural purposes (2mks)
8. A plant was observed to have parallel venation and fibrous root system. Name.
   1. Subdivision of this plant. (1 mk)
   2. Class to which the plant belongs. (1 mk)
9. Name the organism that;
   1.  
      1. causes malaria 1 mark)
      2. Transmits malaria 1 mark)
   2. State two control measures for malaria           (2 marks)
10. Explain two milestones in the evolution of man that have made him the most dominant species on earth. (2marks)
11. 50 black mice and 50 white mice were released into an area inhibited by a pair of owls. After four months 38 of the black mice and 9 of the white mice were recaptured.
    1. How this observation would be explained. (2 marks)
    2. Name the theory of evolution that support the results in (a) above. (1mark)
    3. Name one vestigial structures in man. (1 marks)
12. State the functions of the following apparatus.
    1. Bait trap (1mk)
    2. Pooter (1mk) 
13.  
    1. Define the term ‘parthenocarpy’. (1mk)
    2. Name two plant growth hormones that promote parthenocarpy. (2mks)
14. What is the biological importance of the larval stage during metamorphosis (2mks)
15.  
    1. State one structural and one functional difference between motor and sensory neurone. (2mks)
    2. What name is given to the gap between the sensory neurone and intermediate  neurones. (1mk)
    3. Name the transmitter substance found in the gap named in (b) above. (1mk)
16. Name the type of response shown by: (2mks)
    1. Sperms when they swim towards ovum.
    2. Euglena when they swim towards the source of light.
17. Give two reasons why the pressure of blood is greater in the arteries than in the veins in mammals. (2 marks)
18.  
    1. What is the importance of heartbeat in blood circulation? (1mk)
    2. If the nerve supply to the heart of a mammal is severed, the rhythmic heart movement will still go on and the heart continues to beat. Explain this observation. (1mk)
19. What happens when respiration exceeds photosynthesis in the guard cells of terrestrial plants? (3 mks)
20.  
    1. Name the hard body covering found in organisms of the phylum arthropoda. (1mk)
    2. Give two uses of the structure mentioned in (a) above. (2mks)
21. Describe how the following conditions promotes cross pollination
    1. heterostyly    ( 1 mark)
    2. self sterility ( 1 mark)
22. Distinguish between plasmolysis  and  deplasmolysis as used in cell physiology( 3 marks)
23. Explain how surface area to volume ratio affect the rate of diffusion in living organisms  ( 2 marks)
24. State two differences between the product of mitotic division  and those meiotic division ( 2 marks)
    

    mitosis	meiosis

25. Explain  why fresh water aquatic animals excrete nitrogenous waste inform of a ammonia ( 3 marks)
26. Alongside alimentary canal are enzyme that digest food into simpler absorbable forms. study the illustration below to answer questions that follows
                    enzyme K                        enzyme L
    protein   peptide aminoacids
    1. Identify enzyme K and its site of action in alimentary  canal (2 marks)
    2. Identify enzyme L and  state its pH under which it works best ( 2 marks)
27.  
    1. What makes young herbaceous plants remain upright (2 marks)
    2. Why should herbaceous plant remain upright ( 2marks)
28.  
    1. Name the main excretory product stored in the coffee berries   (1mk)
    2. What is the economic use of the products named in a  (a) above ( 1 mark)
29. state one advantages of asexual reproduction (1mk)
30. Define the term photolysis (1 marks)
31. Outline one functions of the femur bone (2 marks)

MARKING SCHEME

1. Name three sites of gaseous exchange in frogs. (3mks)
   • Skin; buccal/mouth cavity; lungs;
2.  
   1. What is organic evolution   (1mk)
      • Organic evolution is the theory that more recent types of plants and animals have their origins in other pre-existing forms and that the distinguishable differences between ancestors and descendents are due to modifications in successive generations.
   2. Distinguish between divergent and convergent evolution giving  example in each case. (4mk)
      • Emergence of present fauna and flora/ new life form/ species/ organisms from pre-existing forms gradually over a long period of time.
      • Divergent basic structural form is modified to serve different functions; e.g. vertebrate forelimbs, break structure in birds/ feet in birds’ convergent different structures are modified to perform similar functions e.g. wings and birds and insects/ eye of human  and octopus, vertebrates for humans acc.  legs of vertebrate and mouthparts of insects
3. State three applications of plant hormones in agriculture (3 marks)
   • Induce fast growth in stem cut to curl  around support e.g climbers;   
   • Selective weed killers;
   • Encourage apical dominance;
   • Encourage sprouting of side branches;
   • Breaking seed dormancy;
   • Induce pathenocarpy
   • Promotes flowering
   • Induce fruit falls;                                    any four
     Accelerate ripening of fruits e.g. tomatoe
4.  
   1. Give an equation to show that respiration involves oxidation of glucose (1mk)
      glucose + oxygen              carbon(IV) oxide + water + energy
      C₆H₁₂O₆ + 6O₂             6CO₂ +6H²O + 2880 kJ;must be balanced;
   2. How is an energy rich molecule rebuilt after muscle contraction             (2mks)
      • Adenosine diphosphate combines with a phosphate and 34kJ of energy; to form adenosine triphosphate/ATP
   3. apart from energy, name another end product  of anaerobic respiration in animals(1mks)
      • Lactic acid
5. Give the functions of the following ecological instruments (2mks)
   1. Seechi disc
      • Measure  light penetration in water;
   2. Photographic light meter
      • measure light intensity
6.  Which genetic disorder is caused by lack of a gene which causes production of Melanin. (1mk)
   • albinism
7. List down two phenotypic characteristics that have been selected for the production of strains suitable for modern agricultural purposes (2mks)
   • Increased length of productive season; higher yields; ease of harvesting where dwarf varieties are prefered; flowers such as roses are selectively bred for their color, shape and aroma;          acc; the 1st 3; (3mks)
8. A plant was observed to have parallel venation and fibrous root system. Name.
   1. Subdivision of this plant. (1 mk)
      • Angiosopermaphyta;
   2. Class to which the plant belongs. (1 mk)
      • Monocotyledonae; (Rej monocot/monocotyledon)
9. Name the organism that;
   1.  
      1. causes malaria 1 mark)
         • Plasmodium malariae/vivax/falciparum/ovale;
      2. Transmits malaria 1 mark)
         • Female anopheles mosquito
   2. State two control measures for malaria           (2 marks)
      • Use of antimalarial drugs
      • sleep under treated mosquito nets
      • Drain stagnant water
      • Clear bushes around homes
        Any two correct
10. Explain two milestones in the evolution of man that have made him the most dominant species on earth. (2marks)
    • Man has a larger brain giving him more intellectual capacity and this has enabled him to exploit their environment fully.
    • Ability to speak/use language to communicate clearly with his fellow men.
    • Bipedal locomotion, upright posture that frees the hands and  rises them to manipulate the environment and carry objects.
    • Aprehensile/grasping hand that enables him to handle things with a high degree of precision.
    • Forward facing eyes which gives him a three dimensional view for the purpose of judging distances and have wider angle of view.
      Any two correct
11. 50 black mice and 50 white mice were released into an area inhibited by a pair of owls. After four months 38 of the black mice and 9 of the white mice were recaptured.
    1. How this observation would be explained. (2 marks)
       • Black mice are better adapted / camouflage with the environment hence less are eaten by the owls compared to the white mice which are easily seen and eaten; 2mks
    2. Name the theory of evolution that support the results in (a) above. (1mark)
       • Theory of natural selection;
    3. Name one vestigial structures in man. (1 marks)
       • Caecum and appendix; Coccyx; nictating
12. State the functions of the following apparatus.
    1. Bait trap (1mk)
       • Attracts organisms using food as bait; and traps them.
    2. Pooter (1mk)
       • Sucks small organisms from bark of a tree; 
13.  
    1. Define the term ‘parthenocarpy’. (1mk)
       • Fruit formnation without fertilization;
    2. Name two plant growth hormones that promote parthenocarpy. (2mks)
       • Auxins;
       • Gibberellins;
14. What is the biological importance of the larval stage during metamorphosis (2mks)
    • Feeding and growth;
    • Reduce competition within the species;
15.  
    1. State one structural and one functional difference between motor and sensory neurone. (2mks)
       Structural
       

       Sensory	Motor
       Cell body outside CNS	Cell body inside CNS
       Bipolar	Unipolar

       Functional:-
       • sensory neurone transmit impulses from the receptor to the CNS while moyor neurone transmit impulse from the CNS to effectors
    2. What name is given to the gap between the sensory neurone and intermediate neurones. (1mk)
       • Synapse, neuro junction
    3. Name the transmitter substance found in the gap named in (b) above. (1mk)
       • Acetylcholine;/Noradrenaline;
16. Name the type of response shown by: (2mks)
    1. Sperms when they swim towards ovum.
       • Positive (chemo) taxis
    2. Euglena when they swim towards the source of light.
       • Positive phototaxis
17. Give two reasons why the pressure of blood is greater in the arteries than in the veins in mammals. (2 marks)
    • Arteries have narrow lumen to maintain pressure;
    • Havemore muscular walls;
    • Receive blood at high pressure from the heart;
18.  
    1. What is the importance of heartbeat in blood circulation? (1mk)
       • It ensures sufficient supply of nutrients and oxygen to the cells;
       • It ensures exchange and removal of waste products of metabolism from the body cells to excretory organs;
       • It ensures that blood flows out of the heart to all parts of the body;
    2. If the nerve supply to the heart of a mammal is severed, the rhythmic heart movement will still go on and the heart continues to beat. Explain this observation. (1mk)
       • The rhythmic contractions of the heart arises from within special cardiac muscles/the heart muscles are myogenic;
19. What happens when respiration exceeds photosynthesis in the guard cells of terrestrial plants? (3 mks)
    • Carbon(IV)oxide increases in the guard cell; pH increases leading to conversion of glucose to starch; starch is osmotically inactive compared to glucose; this leads to guard cells loosing water to the surrounding epidermal cells; guard cells becomes flaccid and hence stoma closes.
20.  
    1. Name the hard body covering found in organisms of the phylum arthropoda. (1mk)
       • exoskeleton
    2. Give two uses of the structure mentioned in (a) above. (2mks)
       • Protection against desiccation
       • Protection against mechanical injury
       • For muscle attachment
21. Describe how the following conditions promotes cross pollination
    1. heterostyly    ( 1 mark)
       • when the style is longer than th filaments, its not easy for pollein grains to reach the stigma of the same flower
    2. self sterility ( 1 mark)
       • pollein grains becomes sterile or incompatible to the stigma of the same flower;
22. Distinguish between plasmolysis  and  deplasmolysis as used in cell physiology( 3 marks)
    • plasmolysis is a process by which plant cells lose water by osmosis ( when placed in hypertonic solution) becoming flaccid; while deplasmolysis is process by which flaccid/plasmolysed cell gains water by osmosis; (when placed in distilled water);becoming turgid;
23. Explain how surface area to volume ratio affect the rate of diffusion in living organisms  ( 2 marks)
    • the larger the surface area to volume ratio the greater the rate of diffusion; since most parts of of the organisms are closer to the medium of exchange/ surroundings;
24. State two differences between the product of mitotic division  and those meiotic division ( 2 marks)
    

    mitosis	meiosis
    2 daughter cells produced Daughter cells are diploid	4 daugter ells produced Daughter cells are haploid

25. Explain  why fresh water aquatic animals excrete nitrogenous waste inform of a ammonia ( 3 marks)
    • Ammonia is very toxic/ poisonous; hence it requires a lot of water to eliminate; which is available in large amount;
26. Alongside alimentary canal are enzyme that digest food into simpler absorbable forms. study the illustration below to answer questions that follows
                    enzyme K                        enzyme L
    protein   peptide aminoacids
    1. Identify enzyme K and its site of action in alimentary  canal (2 marks)
       

       Enzyme	Site of action
       Pepsin	Stomach
       Trypsin	Duodenum

    2. Identify enzyme L and  state its pH under which it works best ( 2 marks)
       

       Enzyme	pH
       Peptidase	Alkaline

27.  
    1. What makes young herbaceous plants remain upright (2 marks)
       • Cell turgidity; turgor pressure
       • Presence of collenchymas tissue;
    2. Why should herbaceous plant remain upright ( 2marks)
       • to expose to leaves to light energy for photosythensis
       • to expose the flowers to pollinating agents
       • to expose seeds/ fruits to dispersal agents;
28.  
    1. Name the main excretory product stored in the coffee berries   (1mk)
       • Caffein
    2. What is the economic use of the products named in a  (a) above ( 1 mark)
       • used as a mild stimulant
29. state one advantages of asexual reproduction (1mk)
    • favorable characteristics of parents retained
    • exploit favorable conditions of the parents
    • shorter life cycle/ early maturity/ faster reproduction
    • independent of two parents/ fertilization/ pollination
    • large supply/ store of food
    • new plants produced in conditions already favorable to parent
30. Define the term photolysis ( 1 marks)
    • breakdown of water molecules into hydrogen  atoms and oxygen gas; by light energy; ( on light stage of photosythensis)
31. Outline one functions of the femur bone ( 2 marks)
    • provide site for ( thigh ) muscle attachment
    • provide support hind-limbs/body
    • bone marrow is a site for blood cells/ white blood cells formation
    • articulate with tibia (knee joint) and  pelvic bone (hip joint/ball and socket joint)