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BIOLOGY

PAPER 2

OCT. 2010

TIME: 13/4 HOURS

KAHUHO UHURU HIGH SCHOOL

MID TERM EXAMS 2010

INSTRUCTIONS

This paper consists of two sections A: and B

Attempt all questions

SECTION A (30 MARKS)

Attempt all questions

(a) List down the main characteristics of gaseous exchange surface.	(3 marks)

(b) Briefly describe the mechanism of gaseous exchange in man. (8marks)

(c) Name the site of gaseous exchange in fish.

(1mark)

The concentration of lactic acid in blood during and after an exercise was determined. The results are as shown in the graph below:

100

80

60

40

20

20	40	60

Time in minutes

(i) By how much did lactic acid increase at the end of 13 minutes.	(1mark)

(ii) After how many minutes was lactic acid concentration 71mg/100cm3?	(2 marks)

(iii) What would be the concentration of lactic at the 60th minute?	(1 mark)

Give a reason for the high rate of production of lactic acid during the exercise.	(2 marks)

Give a reason for the decrease in the concentration of lactic acid after the exercise.(1 mark)

d. A certain sea animal has a smooth skin, regulates its body temperature and gives birth to young ones. The animal belongs to the class

(1 mark)

The diagram below shows Euglena gracillis, a single celled organism, often found in fresh water ponds.

Gullet

Contractile vacuole

Membrane

Cytoplasm

Chloroplast

Nucleus

Protein exoskeleton

Euglena shows a number of the characteristics of living things such as excretion, nutrition, and irritability.

Name three other characteristics of living things that you would expect this organisms to show.	(3 marks)

The cytoplasm of euglena contains salts that are more in concentration than those of the surrounding water. The contractile vacuole excretes any excess of water. Explain why this function of the contractile vacuole is important to this organism.	(3 marks)

Euglena has an eye spot that is sensitive to light.

Suggest and explain how the organism would respond if there was an area of brighter light nearby.	(2 marks)

Explain how the organism would benefit from this reaction.	(2 marks)

(2marks)

SECTION B (20 MARKS)

Attempt both questions.

In an effort to investigate variation in water loss in a tropical plant in 24 hours period, the data shown below was recorded.

Time	1.00 am	5.00 am	7.00 am	9.00 am	11.00 am	1.00 pm	3.00 pm	5.00 pm	7.00 pm	9.00 pm	11.00 pm	12.00 pm	1.00 pm
Net loss in gm/hr	15	15	36	146	285	325	275	234	165	65	15	15	15

(a) Draw the graph of water loss against time.	(5marks)

(i) At what time of the day was highest amount of water loss experienced.	(1 mark)

(ii) From your graph, determine the amount of water lost at 4.00 pm.	(1 marks)

Account for the amount of water lost between

9.00 am and 2.00 pm	(1marks)

11.00 am and 5.00 pm	(1marks)

Suppose the plant was placed in a room 100% humidity, what would be the effect on the data between 7.00 am and 3.00 pm?	(1 mark)

Other than relative humidity, state two other environmental factors that affect water loss in plants.	(2marks)

Discuss the four phases of a sigmoid curve	(8 marks)

Work smart

Biological sciences department

2

NAME:…………………………………………………………ADM NO:…………………….CLASS:………

Eye spot

flagellum

MoZarD

2010-10-06

LiteOS