2014 KCSE BIOLOGY (231) Biology Paper 1 (231/1)

Answer all the questions.

1.       State the importance of each of the following in living organisms:[2m]

(a) Nutrition

(a) Acquisition and utilization of nutrients; (1 mark)

(b) Excretion.

(b) Elimination of metabolic wastes to prevent accumulation to toxic level; (1 mark)

2.       (a) What is meant by the term seed dormancy?

(a) A period of rest in which a seed performs its physiological processes slowly and utilizes
little food; (1 mark)

(b) State three causes of seed dormancy. [1m]

(b) - Chemical/growth inhibitors;
- Hard/impermeable seed coat;
- Low/freezing temperatures;
- Under developed embryo/immature embryo;
- Low concentration of hormones;
- Lack of appropriate light wavelength;
(max 3 marks)

3.       State two functions of the placenta in mammals. [3m]

- Exchange of nutrients /metabolic wastes/gases between the mother and foetal circulatory systems;
- Secretion of progesterone hormone;

 (2 marks)

4.       The diagram below illustrates a growing pollen tube.

 

(a) Name the part labelled B. [1m]

(a) Tube nucleus;

(b) Explain the role of the parts labelled A. [1m]

(b) - One male nucleus fuses with the egg cell nucleus to form a zygote;
- The other male nucleus fuses with the polar nuclei to form the endosperm;

(2 marks)

5.       The diagram below shows a set up for an experiment to demonstrate a certain physiological process.

 

(a) What nature of solution is represented by 20% sugar solution? [1m]

(a) Hypertonic solution; (1 mark)

(b) Explain the observation made on the set up after one hour. [2m]

(b) Volume of sugar solution increases in the thistle funnel while that of distilled water in the beaker reduces; because the thistle funnel gains distilled water by osmosis.
(2 marks)

6.       State three roles of auxins in a plant stem.[2 marks]

 - Cell division;
- Cell elongation;
- Development of adventitious roots;
- Formation of callus tissue;
- Causes apical dominance;
- Causes tropic responses.
3x1 (3marks)

7.       A student drew a 6cm long diagram of a plant flower. If the actual length of the flower was 12cm, calculate the magnification of the drawing made by the student. Show your working. [2m]

Object length = 12cm
Drawing length = 6 cm
Mg =   Drawing length 6
            Object length — 12
       = X0.5; MgX0.5
   (2 marks)

8.       Differentiate between phenotype and genotype as used in genetics. [1m]  

- Phenotype is the outward appearance of an organism while Genotype is the genetic makeup
of an organism; (1 mark)

9.       State two functions of intervertebral discs in the mammalian skeleton. [2m]

- Act as shock absorbers;
- Allow smooth movement between the vertebrae/reduce friction;
(2 marks)

10.   (a) Explain the role of diffusion in human beings. [4m]

- Absorption of materials e.g. diffusion of digested food into the blood stream;
- Gaseous exchange e.g. C02102 diffuses from capillaries into the alveoli.
- Excretion of nitrogenous wastes; e.g. urea diffuses from blood capillaries into the
elimination sites. (Max 4 marks)

(b) What is meant by each of the following terms?

(i) Crenated cell. [1m]

(i) Crenated cell is a shrunk animal cell that has lost water by osmosis;
(1 mark)

(ii) Flaccid cell. [1m]

(ii) Flaccid cell is a flabby /shrunk plant cell that has lost waster by osmosis; (1 mark)

11.   State three differences between tactic and tropic responses. [1m]

Tactic Responses	Tropic Responses
- Are locomotory	- Are growth responses;
- Are fast	- Are slow;
- Not influenced by growth hormones	- Are caused by growth hormones;
- Temporary	- Permanent;

(3 marks)

12.   The diagram below represents a model used to demonstrate breathing in mammals.

 

(a) Name the mammalian structure represented by the parts labelled D and E. [2m]

D Rib-cage/chest cavity; (1 mark)

E (ii) Diaphragm; (1 mark)

(b) State the observation made when the string is pulled downwards. [1m]

(b) The balloons are inflated; (1 mark)

(c) Explain the observation in (b) above. [2m]

(c) Pulling down the string increases the volume of D, hence decreasing the pressure inside;
the low pressure causes external atmospheric air to rush in and inflate the balloons;
(2 marks

13.   State one function of each of the following parts of a mammalian eye:

(a) Eye lashes

(a) Trap foreign particles entering the eye;
Produce fluid/tears; (1 mark)

(b) Lachrymal glands.

(b) – Moistens the cornea;
- Wash foreign materials out of the eye;
- Antiseptic /kills harmful microorganisms; (max 1 mark)

14.   State three structural differences between DNA and RNA. [3m]

DNA	RNA
Double stranded/double helix	Single stranded:
Has Thy mine	Thy mine is replaced by uracil/reject Thiamine;
Has the four nitrogen base pairing pattern	Lack the four nitrogen base pairing pattern;
Deoxyribose sugar	Ribose sugar;

15.    (a) Which type of mammalian muscles is voluntary? [1m]

(a) Skeletal muscles / striated muscles; (1 mark)

(b)   Distinguish between a tendon and a ligament.[1m]

(b) Tendon is a (inelastic) tissue that attaches muscles to bones while Ligament is a
(inelastic) tissue that attaches a bone to another bone of a movable joint;
(1 mark)

16.   The diagram below illustrates a nerve cell.

 

(a) Name the type of nerve cell illustrated. [1m]

(a) Sensory neuron; (1 mark)
(ii) Insulates the axon/accept dendron for axon; (1 mark)

(b) Give a reason for your answer in (a) above. [1m]

(b) Cell body is located off the axon/tied outside the CNS; (1 mark)

(c) Identify the part labelled J. [1m]

(c) Schwann cell; (1 mark)

(d) State one function of each of the parts labelled G and H.

(d) (i) Receipt/transmits impulses to neighbouring neurons in the CNS from sense
organs; (1 mark)

(ii) Insulates the axon/accept dendron for axon;

17.   Give a reason why the image is not formed when light is focused on the blind spot. [1m]             

The blind spot lacks both cones and rods hence images are not perceived; (1 mark)
Accept photoreceptor cells for cones and rods;

18.   Explain why

(a)    Mammalian testes are located to hang outside the body. [2m]

(a) To provide a cool environment; that is conducive for sperm formation and storage; (2 marks)

(b)Four months after fertilization, ovaries can be removed from a human female, without terminating pregnancy.[2m]

(b) Progesterone hormone; is secreted by the placenta to maintain the pregnancy;
(2 marks)

19.   Why is a burning charcoal stove in a poorly ventilated room likely to cause death of the inhabitants? [3m]  Due to limited oxygen, haemoglobin combines with carbon (II) oxide to form carboxyhaemoglobin;
Carboxyhaemoglobin does not readily dissociate hence reduces the capacity of haemoglobin to
transport oxygen; Carbon (II) oxide is therefore a respiratory poison if breathed in for a long
time;
(3 marks)

20.   State one function of each of the following cell organelles:

(a) Golgi bodies                [1m]

(b) a) Packaging of substances/glycoproteins/ transportation of glycoproteins; Secretion of synthesized proteins and carbohydrates; formation of lysosomes/modification n of carbohydrates to form glycoproteins;
(1 mark)

(c) Lysosomes.  [1m]

(b) - Digestion of food/Breakdown large molecules;
- Destroy worn out organelles or cells/tissue;
(max 1 mark)

21.   Name the type of skeleton that makes up each of the following animals:

(a)    Locust[1m]

(a) Exoskeleton; (1 mark)

(b)   Bird [1m]

Endoskeleton; (1 mark)

22.   (a) Name two vestigial structures in human beings. [2m]

(a) Appendix/accept nictating membrane; caecum and ear drum;
Tail/coccyx; (1 mark)

(b) Why are some bacteria able to resist the effect of antibiotics? [2m]

(b) They have a gene for resistance/acquire it through mutation;
The gene for resistance is passed to offspring establishing a population
of resistant forms;
(2 marks

23.   Below is an illustration of a cross section of a plant root showing the transportation of substances in the plant.

     

(a)    Name the substances transported along the paths labelled K and L. [2m]

K ---K - Photosynthetic products/manufactured foods example vitamins/glucose/proteins/
sucrose/maltose/fructose/lipids/nitrates; (1 mark)

L ---L - Water and mineral salts; (1 mark)

(b)   Give a reason for your answer in L above. [1m]

(b) The substances are moved into the star shaped xylem; (1 mark)

24.   The table provided shows the transportation of substances in the human body.

Substance	Transported by blood
	From	To
Oxygen	M	Whole body
N	Liver	Kidneys
P	Intestine	Whole body

Name the substances represented by: - [3m]

M --lungs; (1 mark)

N --- Urea, ammonia; (1 mark)

P--- Digested food, water; mineral ions; (1 mark)

25.   State two roles of luteinizing hormone in human reproduction. [2m]  

- Stimulates maturation of the Graafian follicle/stimulates ovulation;
- Stimulates corpus luteum to secrete progesterone hormone;
- Stimulates release of androgens;
- Stimulates development of corpus luteum;
(2 marks)

26.   The table provided shows the concentration of sodium and iodine in sea water and cell sap of a plant.                  

	Sodium ion concentration	Iodide ion concentration
Sea water	250	35
Cell sap	100	550

               

a.       (i) Name the process through which the plant cells take up sodium ions.[1m]

  (i) Diffusion; (1 mark)
(b)

(ii) Give a reason for your answer in (a) (i) above. [1m]

(ii) Sea water contains a higher concentration of sodium ions than the cell sap;
(1 mark)

b.      If the plant was sprayed with a chemical that inhibits respiration:

(i)      Which of the two ions uptake will be affected? [1m]

(i) Iodide ions; (1 mark)

ii. Give a reason for your answer in (b) (i) above. [1m] (ii) Sea water has a lower concentration of

iodide ions than the cell.
The plant requires energy to take up the iodide ions (by active transport);
(1 mark)

27.   The diagram below shows the gaseous exchange system of a locust.

   

(a)    Name the structure labelled Q.[1m]

(a) Spiracle; (1 mark)

(b)   State the function of the part labelled R.[1m]

(b) Keep the trachea open for air passage; (1 mark)

(c)    How is the part labelled S structurally adapted to its function?

(c) - Lacks spiral bands of chitin / to make it thin; for diffusion of gases;
- Moist; to dissolve respiratory gases;
(2 marks)