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BIOLOGY PAPER 231/2 K.C.S.E 2002

PRACTICAL MARKING SCHEME

 

1. You are provided with specimens labeled D1, D2, D3 and D4. Examine them

(a) Draw and label specimens D1 and D2

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Magnification X3 – X7

(b) Giving reasons state the agent or method of dispersal of the specimens.

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Specimen

Agent or method of dispersal

Reasons

D1

Animal/ man

Presence of hooks acc. Hook like structures Rej. Spikes, spines, thorns e.t.c

D2

Wind

Presence, of pappus; light/ air like extensions

D3

Wind

Presence of wings; light/ wing like structures

D4

Explosive

Line of weakness along the ovary wall.

 

(c) State the types of gynoeciums and placentation of specimen D4.

Type of  (i) Gynoecium Monocarpus

(ii) Placentation  Marginal

 

2.  You are provided with olive oil, liquids labelled L1 and L2 and an Irish potato.

Label two test tubes A and B. Place 2 cm3 of water into each test tube. To test tube labelled A, add 8 drops of liquid L1. Shake both test tubes. Allow to stand for five minutes.

 

(a)  (i)  Record your observations

Test tube A

Oil is broken up into small droplets; which are dispersed/ spread/ throughout in liquid oil becomes emulsified/ debules/ tiny droplets; which forms a suspension/ becomes cloudy/ turbid/Forms a white ppt.

 

Testy tube B

Oil floats on water / of mixing takes place/ Two separate/ immiscible layers are seen.

 (ii)  Name the process that has taken place in test tube A.

Emulsification

(iii)  State the significance of the process named in (a) (ii) above to increase surface area.

  1. Name the digestive juice in humans that has the same effect on oil as liquid L1
    1. Bile

     

    Region of alimentary canal into which the juices is secreted

    II- Duodenum

(b)  Label two test tubes C and D. place 2cm3 of liquid L2 into each.

 Add a drop of iodine into each test tube.

 (i) Record your observation

Blue black/ black/ bluish/ blue/ grayish/ purple blue

 

 (ii) Suggest the identity of L2

Starch

Cut out a tube whose sides are 1 cm from the Irish potato provided. Crush the cub to obtain a paste. Place the paste into a test tube labelled C. Leave the set up for at least 30 minutes.

 

(iii) Record your observation.

Contents of D remain unchanged/ blue black; blue black in C

Disappeared / fades light yellow/ brown/ orange

(iv) Account for the results in (b) (iii) above

Enzymes amylase; in potato breaks down starch; into sugars; that do not give blue- black colours with iodine.

 

(c) (i) Cut another cube whose sides are 1 cm from the Irish potato.

 Crush the cube. Place the crushed paste into test tube.

 Carry out food test with the reagent provided.

 Record the procedure and results

 Procedure

Add equal amount of benedicts solution to the paste and boil; heat/ to boil/ warm.

 

Results

Grey/ yellow/ orange/ brown/ brick

(ii)  Account for the results in (c) (i) above

Starch in potato is converted to maltose/ reducing sugar/ simple sugar; by enzyme amylase/maltose (owwtte)

 

3.  You are provided with specimens labelled Q and R. examine them.

(a)  Giving reasons state the phylum of the specimens

 Phylum  Arthropoda

 Reasons Exoskeleton/ chitinous

(b)  (i) Name the class to which the specimen belong

Insecta.

 (ii) State the features common to both specimens that are

Characteristics of the class mentioned in (b) (i) above.

 – 3 body parts

 – 3 pairs of legs

 – A pair of antennae

 

 




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