SAMPLE PAPER 2 231/2 1

SECTION A:

ANSWER ALL QUESTIONS
1. Bile and pancreatic juice are important secretions in animal nutrition
a) In which part of the digestive system do they exert their influence? (1 mark)
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b) i). For efficient digestion, which of the two secretions should be mixed with chyme first?
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ii). Explain your answer above (2 marks)
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c) Explain why:
i). It is not necessary to eat too much protein in the diet (2 marks)
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ii). Liver is recommended in the diet of anaemic persons (2 marks)
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2. Below is a representation of an independent unit of the biosphere. Use it to answer the questions that follow

a) Identify the unit represented above (1 mark)
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b) i). Compare the primary productivity of the plants R and Q (1 mark)
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ii). Account for your answer above (2 marks)
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c) Give two differences between the chloroplasts of plants Q and R (2 marks)

d) Name
i). The instrument that you can use to measure light penetration in the unit above (1 mark)
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ii). The class to which the animal in the illustration belongs (1 mark)
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3. Study the diagram below and use it to answer the questions that follow

a) Name I, V and VII (3 marks)
I ……………………………………………………………………………………………………… V………………………………………………………………………………………………………
VII……………………………………………………………………………………………………
b) Briefly explain the role of:
VI (1 mark)
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VII in parturition (2 marks)
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c) Explain how dizygotic twins result (2 marks)
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4. Some aspects of the circulatory system were measured during a 50-minute period for an observed mammal. The table below show the recorded data. Study the data carefully and use it to answer the questions that follow.

Heart stroke volume (ml)
a) Comment on the state of the mammal at:
10 minutes (1 mark)
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20 minutes (1 mark)
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b) Account for;
i. The change in blood pH between 30 and 50 minutes (2 marks)
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ii. Change in heart stroke volume between 10 and 30 minutes (2 marks)
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iii. High oxygen supply at 40 minutes (2 marks)
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5. a). Define biodiversity (1 mark)
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b). During an ecological trip along the coastal strip, students of Marereni secondary School collected an organism that had two body parts and two body parts and two pairs of antennae.
i. Name the class to which this organism belonged (1 mark)
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ii. Predict the number of legs the organism most likely had (1 mark)
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iii. All the observed members of this species were found to hide under rocks and leaves. Suggest the benefits that this behavior confers to the organisms (2 marks)
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c). Declining population of insects world wide should be a great concern to the human population. Explain (3 marks)
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SECTION B: Answer question 6 and any other ONE question
6. Form one students of St. Josephine carried out an experiment to determine the percentage change in weight of two tender stems of two different plants when placed in two different sucrose solutions of different concentrations.

a) On the same axes, in the graph provided below, plot a graph of percentage weight change of the plant stem tissues against sucrose concentration (8 marks)

b) Account for the results obtained for the plant tissues at 15 mg/ml sucrose concentration (2 marks)

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c) From the graph, determine the concentrations of the cells saps of the two plants
Plant N (1 mark)
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Plant D (1 mark)
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d) i). Identify the plant that was most likely obtained from a more saline environment?
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ii). Explain your answer above (2 marks)
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e) Describe the effect of high osmotic pressure of body fluids on urine formation (5 marks)
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7. Describe the role of hormones in the female menstrual cycle (20mks)
8. Describe the structural adaptations of the mammalian heart (20 marks)

MARKING SCHEME

SECTION A: ANSWER ALL QUESTIONS

1.      Bile and pancreatic juice are important secretions in animal nutrition

a)      In which part of the digestive system do they exert their influence? (1 mark)

Duodenum;

b)      i). For efficient digestion, which of the two secretions should be mixed with chyme first?

Bile;

ii). Explain your answer above (2 marks)

Bile contains bile salts which emulsify fats/break fat molecules into tiny droplets; to increase surface area for action of pancreatic lipase in pancreatic juice;

c)      Explain why:

i). It is not necessary to eat too much protein in the diet (2 marks)

Body does not have mechanism for storing excess amino acids; the excess amino acids will be deaminated;

ii). Liver is recommended in the diet of anaemic persons (2 marks)

Anaemic people have low red blood cell count/low haemoglobin count; liver contains iron needed to synthesize haemoglobin in anaemic persons;

2.      Below is a representation of an independent unit of the biosphere. Use it to answer the questions that follow

a)      Identify the unit represented above (1 mark)

Ecosystem;

b)      i). Compare the primary productivity of the plants R and Q (1 mark)

Q has a higher primary productivity;

Accept reverse statement

ii). Account for your answer above (2 marks)

Q receives light of higher intensity (compared to R leading to higher primary productivity);

Q is at a higher temperature (compared to R leading to higher rate of primary productivity);

c)      Give two differences between the chloroplasts of plants  Q and R (2 marks)

Chloroplast of Q	Chloroplast of R
-          Have fewer chlorophyll	-Have more chlorophyll;
-          Have less sensitive chlorophyll	-Have more sensitive chlorophyll;

d)      Name

i). The instrument that you can use to measure light penetration in the unit above (1 mark)

Seechi disc;

ii). The class to which the animal in the illustration belongs (1 mark)

Pisces;

3.      Study the diagram below and use it to answer the questions that follow

a)      Name I, V and VII (3 marks)

I – Placenta;

V- Vagina/Birth canal;

VII- Myometrium; Accept: Uterine wall;

Reject uterus alone

Reject wrong spelling

b)      Briefly explain the role of:

VI              (1 mark)

Secretes a plug of mucus that prevents the entry of pathogens into the uterus during pregnancy;

VII in parturition (2 marks)

(During parturition/birth) its muscles/muscles of the uterine wall/myometrium contract; to expel the foetus out of the uterus;

c)      Explain how dizygotic twins result (2 marks)

Result when two Graafian follicles are stimulated to mature in an ovary/the two ovaries in the same cycle; and both get fertilized;

4.      Some aspects of the circulatory system were measured during a 50 minute period for an observed mammal. The table below show the recorded data. Study the data carefully and use it to answer the questions that follow.

Time (min)	0	10	20	30	40	50
Oxygen supply (arbitrary units)	12.3	12.3	16.1	16.1	16.0	12.3
Blood pH	6.9	6.9	6.5	6.4	6.7	6.9
Heart stroke volume (ml)	110	110	160	171	143	118

a)      Comment on the state of the mammal at:

10 minutes (1 mark)

At rest;

20 minutes (1 mark)

Active;

b)      Account for;

                                i.            The change in blood pH between 30 and 50 minutes (2 marks)

Blood pH rises; due to increased exhalation of carbon (IV) oxide at the lungs (occasioned by high breathing rate)/due to oxidation of lactic acid that had accumulated during activity;

                              ii.            Change in heart stroke volume between 10 and 30 minutes (2 marks)

Heart stroke volume increases; to supply more oxygen and glucose to the tissues for respiration (to generate energy required for activity)

                            iii.            High oxygen supply at 40 minutes (2 marks)

To provide the extra amount of oxygen; required to get rid of the lactic acid in tissues;

5.      a). Define biodiversity (1 mark)

The measure of the total number of species in an ecosystem;

b). During an ecological trip along the coastal strip, students of Marereni secondary School collected an organism that had two body parts and two body parts and two pairs of antennae.

                                i.            Name the class to which this organism belonged (1 mark)

Crustacea;

Reject crustacea

                              ii.            Predict the number of legs the organism most likely had (1 mark)

5 pairs;

                            iii.            All the observed members of this species were found to hide under rocks and leaves. Suggest the benefits that this behavior confers to the organisms (2 marks)

-          Minimizes predation/protects/hides them from predators;

-          Minimizes desiccation/water loss from their bodies;

c). Declining population of insects world wide should be a great concern to the human population. Explain (3 marks)

-Insects are vital in scientific research;

-Some insects are source of food;

-Insects are important pollinators ensuring crop productivity;

-Insects are part of food chains ensuring ecological stability;

SECTION B: Answer question 6 and any other ONE question

6.      Form one students of St. Josephine carried out an experiment to determine the percentage change in weight of two tender stems of two different plants when placed in two different sucrose solutions of different concentrations.

Sucrose concentration (mg/ml)	0	5	10	15	20	25	30	35
Percentage change in weight for plant N	7.0	6.6	5.0	3.6	1.6	-0.8	-2.3	-2.8
Percentage change in weight for plant D	3.2	2.2	0.8	-0.6	-1.4	-2.2	-2.8	-3.4

a)      On the same axes, in the graph provided below, plot a graph of percentage weight change of the plant stem tissues against sucrose concentration (8 marks)

             S=2mks, C=1mk,   A =2mks,   P=2mks, I=1mk,          Total =8mks

b)      Account for the results obtained for the plant tissues at 15 mg/ml sucrose concentration    (2 marks)

The tissues had a positive change in weight/increased in weight; the cells gained water by osmosis; since at 15mg/ml the solution was hypotonic to the plant cell saps;

Total 3 marks

Maximum 2 marks

c)      From the graph, determine the concentrations of the cells saps of the two plants

Plant N (1 mark)

23.5 mg/ml

Plant D (1 mark)

12.5 mg/ml

d)      i). Identify the plant that was most likely obtained from a more saline environment?

Plant N

ii). Explain your answer above (2 marks)

It has a highly concentrated cell sap; to enhance uptake of water by osmosis in the saline habitats;

e)      Describe the effect of high osmotic pressure of body fluids on urine formation (5 marks)

High osmotic pressure of body fluids will stimulate pituitary gland to secrete more antidiuretic hormone; which causes increase in permeability of the kidney tubules; leading to reabsorption of more water; leading to production of little volume; of concentrated urine;

7.      Describe the structural adaptations of the mammalian heart (20 marks)

ü  The heart has vagus and sympathetic nerves to control the rate of heartbeat

ü  The heart has cardiac muscles which are myogenic and do not fatigue for continuous pumping of blood.

ü  The heart has atrioventricular valves to prevent backflow of blood into the auricles

ü  The heart has a solid muscular septum to separate right and left sides of the heart to prevent mixing of oxygen poor and oxygen rich bloods

ü  The heart has semi lunar valves at the bases of the origin of the major arteries to prevent backflow of blood into the ventricles.

ü  The heart has valve tendons which are inelastic to prevent the atria-ventricular valves from turning inside out due to the changes in the pressure in the ventricles.

ü  The heart has coronary artery to supply nutrients to the heart tissues and the coronary vein to remove metabolic wastes from the heart tissues.

ü  The heart has a double pericardium membrane for protection/The pericardial membrane secretes pericardial fluid to lubricate the heart reducing the friction on its walls as it pumps.

ü  The heart has thicker left ventricle to generate the high pressure required to pump blood to distant parts of the body

ü  The heart has the Sino Atrial Node at the base of the right atrium to generate the primary impulse and transmit it towards the atrioventricular node.

8.      Describe the role of hormones in the female menstrual cycle            (20mks)

   
Folicle stimulating hormone (FSH) – development of graafian follicle
- stimulates ovary; to produce oestrogen
Oestrogen; - repairs the uterine walls; at high levels; stimulates; pituitary gland; to produce luternizing hormone; suppresses Follicle stimulating Hormone (FSH)
Luternizing hormone: - cause ovulation; cause development of corpus luteum ; (from graafian)
- Corpus luteum produces progesterone
Progesterone; - inhibits production of FSH; causes the development / thickening of uterine walls;
maintains pregnancy; inhibits production of oestrogen; suppresses the production of luteinizing hormone from the pituitary gland stops ovulation 

(20mks)