Answer all the questions in the spaces provided.

1. (a) State the characteristic of living organisms illustrated in the following diagram. (1 mark)

Irritability / response (to stimulus / stimuli) / living organisms respond to stimulus / stimuli / heat / temp (in their environment) Acc. Sensitivity

(b) State the significance of the illustrated characteristic to living organisms. (1 mark)

(Enables) living organisms move away from unfavourable conditions (of temp. / pressure / moisture) ; or converse.

2. Explain how relaxation of the diaphragm muscles leads to exhalation. (3 marks)

(Relaxing of the diaphram muscles) cause diaphragm assume a dome shape; reducing the volume of chest cavity; increasing pressure (hence expelling air out of the lungs / exhalation);

3. The following diagram illustrates an organelle obtained from a cell.

a) Identify the organelle

Chloroplast; acc plural

b) Name the part labelled E

Granum; acc grana

(c) Explain how the part labelled E is adapted to its function. 

Packaged / organized in stacks / highly folded; to increase S.A. for packaging of (more) chlorophyll molecules (for absorption of more light / photosynthesis); Has (more) chlorophyll molecules; for trapping (more) light for photosynthesis;

The following diagram illustrates an organism belonging to a certain Class

(a) Name the Class to which the organism belongs. Aves; rej wrong spelling

(b) Suggest the likely habitat of the organism. (1 mark)

Aquatic / Water (environment) acc Example of water bodies

(c) State two reasons for your answer in (b). (2 marks)

Webbed feet / long legs for wading in water; (Curved) beak for filter feeding; Acc Modification alone, rej function alone, rej long legs alone acc. webbed feet alone.

5. (a) Name the type of muscle found in the following parts of the body:

(i) heart; (1 mark)

Cardiac (muscles);

(ii) Alimentary canal

Smooth (muscles);

(b) State two roles of the muscle named in (a)(ii).
Contract and relax to bring about movement of food down the alimentary canal / facilitate peristalsis ; contract and relax to facilitate mixing of food in the stomach / churning ; b is tied to (a)(ii)

The following diagram shows two organisms belonging to different Divisions

(a) Name the Division to which each organism belongs.

    F -  Pteridophyta ;  rej wrong spelling (1 mark)

    G  - Spermatophyta ;        (1 mark)

(b) Explain why organism G is considered more advanced than F. (2 marks)

Organism G produces seeds/fruits/flowers (which are more advanced reproductive structures than sori through which specimen F reproduces) ; specimen G has more advanced/developed transport/vascular (phloem and xylem) system (guaranteeing efficient water/nutrient movement and/or growth and survival) ;

9. Explain why sugary foods are harmful to teeth. (3 marks) 

Bacteria (in the mouth) use sugar as (metabolic) substrates ; the metabolic waste products are acidic ; corrode tooth (enamel) ; forming cavities ; acc. formic / lactic / acetic acids ; Max 3 

10. Form 3 students constructed the following food web for organisms in a certain ecosystem

(a) (i) identify the organism which is both a tertiary and a secondary consumer. (1 mark) 

Hawk ;

(ii) construct a food chain ending with the organism named in a(i) as a tertiary consumer. (2 marks) 

Black jack → mouse → owl → ; Hawk ;

(b) Name the mode of feeding exhibited by the snake. (1 mark) 

Carnivorous ; rej Carnivore ;

11. Complete the following table on respiratory diseases and their causative agents. (2 marks) 

12. Complete the following table to show the differences between mitosis and meiosis. (2 marks)

13. The following photograph shows a feeding relationship observed in a certain plant

(a) (i) Name the feeding relationship illustrated in the photograph. (1 mark) Symbiosis ;

(ii) Explain your answer in (a)(i). (2 marks) Bacteria (in the root nodules) and (leguminous) plant benefit (mutually) from each other ; the bacteria fix nitrogen which is used by the plant ; the plant provides carbohydrates/shelter (to bacteria) a (ii) tied to a(i)

(b) Give one example of a similar feeding relationship in animals. (1 mark) Ruminant/mammalian stomachs and cellulase producing cellulose digesting bacteria / bees and flowers / oxpeckers and animals (cows/rhinos/zebras)

14. The following diagram illustrates a flower obtained from a certain plant.

(a) State the collective name given to the floral parts labelled M and N.

• M Pistil / Carpel / Gynoecium ; (1 mark)
• N Stamen / Androecium ; (1 mark) acc. Plural

(b) (i) Suggest the likely mode of pollination for the flower. (1 mark)

Insect pollinated ; acc Cross pollination ;

(ii) Give a reason for your answer in (b)(i). (1 mark) 

Large/conspicuous petals ; stigma positioned above anthers / heterostyly ; stigma located inside flower ; acc. converse

15. (a) Explain how low light intensity may bring about changes in the phenotype of some plants. (3 marks)

 (Low light intensity) results in low photosynthetic rate/little amount of glucose/sugars manufactured ; making stems stretch for light/elongate/bend (towards) ; the stems/leaves may also be weaker/thinner/smaller leaves ; (and coloured) yellow ; (due to inadequate light) low light intensity may also lead to altered flowering

 (b) Draw the diagrams to illustrate the difference between a dicotyledonous and a monocotyledonous leaf. (1 mark) 

16. The following diagram illustrates embryos of chicken, humans and fish at different stages of development.

(a) Name the type of evidence of organic evolution illustrated (1 mark) 

Comparative embryology ;

(b) Explain why the tail has been retained throughout the evolution of fish but not in humans and chicken. (2 marks) 

Used for movement/propulsion/balancing ; whereas in chicken and humans it has no function/it is a vestigial structure ;

(c) State one other component likely to be common in the blood of the three organisms that implies they have a common origin. (1 mark) Presence of (some) serum protein structure / (plasma proteins (eg albumin / fibrinogen / globulin / prothrombin / antibodies) ; similar haemoglobin structure / blood group antigen ; presence of similar all organelles ; Protein sequence ; 1st one marked 

17. The following diagram illustrates an organism belonging to a certain Class.

(a) State how the parts labelled P, Q and R contribute to the success of the organism.

• P (Antenna) detect / sense for danger (for survival) / mate (for propagation of genes) harmful / favourable environmental condition (1 mark)
• Q (Wings) for flying / movement (in search of food / mates / favourable conditions / flee from danger) (1 mark)
• R (Abdomen) has spiracles for faster / efficient gaseous exchange (to facilitate respiration) ; (abdomen) has segments for reproduction ; (abdomen) contract and relax to enhance gaseous exchange ; (1 mark)

b) Account for the difference in the pattern of growth in a mouse and the organism illustrated. (2 marks) There is (smooth) continuous growth in the mouse while the illustrated organism / insect / arthropod there is intermittent growth pattern ; occasioned by presence of (hard) exoskeleton hinders continuous growth / growth takes place when the exoskeleton is shed ; 

• Query successful

18. (a) Explain how spilling of oil in a fish pond affects the flow of energy in the pond. (3 marks) Covers water surface/clogs stomata; reducing uptake of CO2​ (for photosynthesis); reduces penetration of light for submerged plants affecting rate of photosynthesis/ production of less oxygen (as a by product); resulting to reduce respiration/air circulation; less glucose/ sugars/food are produced, less energy released to the primary consumers and subsequent trophic levels.

(b) The following organisms were found in a certain ecosystem.

 Tilapia 

Insect 

larvae 

Green algae 

Eagle 

 Sketch a pyramid of numbers for the organisms in the ecosystem. (1 mark) 

19. In an experiment, students placed soaked viable bean seeds in a vacuum flask containing wet cotton, then inserted a thermometer in the flask and left the set-up for 5 days in the laboratory.

(a) State two processes that the students were investigating in the experiment. (2 marks)

Germination; respiration;

(b) State two observations that the students made after five days. (2 marks) Increase in temperature; emergence of​ plumule/radicle; acc. germination;​
20. (a) Name the antigen and antibody present in the blood plasma of an individual with blood group A+. (2 marks) Antigen A/Rh/Rhesus factor; antibody b;​
(b) Suggest the possible recipient of the individual's blood. (1 mark) AB+/A+ acc. AB/A rej. AB−/A−​

21. (a) Name the physiological process that facilitates:

(i) uptake of water from the soil through the root hairs; (1 mark) 

osmosis;​

(ii) reabsorption of sodium ions from the kidney tubules. (1 mark) 

Active transport;​

(b) Explain why grass withers when it is continually sprayed with salty water. (3 marks) 

The salty water is hypertonic to the cell sap​ in the grass; by osmosis; water molecules​ are drawn out of the grass/the grass​ lose water; grass cells become flaccid​ (and grass wither/dry up);​

22. The following diagram illustrates a mammalian vertebra.

(a) Identify the type of vertebra illustrated. (1 mark) 

Thoracic (vertebra);​

(b) Name the bone that articulates with the vertebra at the parts labelled T. (1 mark) 

Rib(s);​

(c) Using observable features, explain how the vertebra is adapted to its function. (2 marks) Has long/extended neural spine / transverse​ process for muscle attachment; has​ neural canal / foramen for passage​ of blood vessels / neurons / spinal cord;​ Centrum / heartshaped to provide​ stability / support for thoracic cage;​ has facets / centrum for articulation​ (with other bones);​

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