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BIOLOGY PAPER 2 (PRACTICAL) MARKING SCHEME

KCSE 2005

 

Each candidate will require the following

A shoot of maize plant with some leaves labeled specimen X

A leafy shoot of Bidens pilosa labeled specimen Y

Iodine solution

Benedict’s solution

Means of heating / water bath

Means of cutting / scalpel

6 test tubes

Test tube rack

Test tube holder

Water in 50ml beaker

Dropper

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Means of labeling

Pestle and mortar

A hand lens

Dissecting needle / pins

A leafy twig of hibiscus plant with regular flowers labelled specimen S1

A leafy twig of bougainvillea with some mature flowers labeled specimen S2

An onion bulb with growing roots and growing aerial leaves labelled specimen p.

A shoot of tradescantia with flowers labeled specimen Q

 

Note: onion bulbs can be made to develop roots and leaves by planting

them in saw dust / sand.

Fleshly picked growing onions with roots intact can be used.

 

1.

Specimen

Steps followed

Identity

S1

S2

Q

X

Y

1a,2a,3b,4b,6b

1a,2a,3b,4a,5b,8a

1a,2b,

1a,2a,3a

1b,

Malvaceae

Nyactaginaceae

Commelinaceae

Graminae

Asteraceae

 

b)  i)  S1–  Dicotyledonous

Q-  Monocotyledonae

ii)  S1 –  Floral parts in threes (3, s0 multiples of 3/6 stamens / 6 anthers

/3 petals.

 

c)  -Presence of large brightly coloured bracts / petals / perianth, to attract insects.

 (Reject it is brightly coluored )

 -Anthers and stigma enclosed in a tube, to be reached by insects

 – Scented to attract insects.

 

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D1 – Continuous outline

– No shading

D2 – Proportionality and accuracy

– Long stigma (feathering) stigma thinner than stigma and ovary

– Oblong ovary

Magnification = Length of drawing / image (units)

Length of actual specimen (units)

= x (2-10)

* No units = Ref. answer

Wrong computation = Ref. answer

 

2. (a)  T1 – Molar tooth

Reasons

i)  Presence of cusps / ridges

ii)  Presence of three roots

 

T2  – Incisors

Reasons

i)  Chisel shaped / wide (sharp) edge / wedge shaped

Ref. one root

 

b)  Cusps /ridges any upper white part

Crown – Black part below cusps

Neck  – Boundary between white and black parts

Root – white lower part divided into 3

Enamel – All over the part seen

Dentine – Upper part below the cusps

 

c)  J – vegetation, grass, shrubs, herbs, plants / leaves

Ref. vegetative , pasture, greens, grass eaters, herbivore, herbivorous but mark reason.

Reasons

 -Presence of diastema

 – Absence of teeth (incisors and canines) at the front part of the upper jaw

 -Presence of horny pad

 -Presence of( premolars)cusps(for grinding vegetation)

K- Flesh/meat

Rej; carnivores/carnivorous, flesh eater but mark reason

Reasons

Presence of (pronounced) long curved sharp pointed canines for gripping / tearing, holding/grasping prey

Ref;  large

 -Presence of carnassial teeth, for cutting and crushing bone

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Inset – last on both sided

Photo – 2nd to the inside

 

e)  J – 2 (10/3Co/1pm3/3m 3/3 ) = 32

K – 2 (13/3C1/1pm4/4m 2/3 ) =42

*teeth types must be identified using letters

Rej; If missing

*Demacating lines must be present

f)  J

g)  Refer to diagram area below main white part.

 

3.  P(onion bulb with leaves and roots)

a)  i)  Inner succulent/ juicy /flesh while outer is dry

– Inner is thicker while outer is thin / membranous / scally

NB: Comparison must be seen otherwise deny a marks

ii)  Inner swollen with food for storage and outer for protection against dessication /mechanical injury / excessive loss of water/ microorganisms / invasion by fungi.

Rej: Storage of water alone, & prevent water loss.

 

Extract

Procedure

Observations

Conclusion

Roots

Add iodine

No colour changed colour of iodine Brown yellow retained / persist

Starch absent

 

Add benedicts solution and boil/ heat/warm/place in a hot water bath

Blue to green to orange/ brown (acc. brick red,ref.red

Reducing sugars present/simple sugars.

Bulbs

Add iodine

No colour change colour of iodine

Starch absent

 

Add benedict solution and boil

Green to yellow to orange /brown

Reducing sugars present

Aerial leaves

Add iodine

No colour change

Starch absent

 

Add benedicts solution and boil

Green to yellow to orange to brown

Reducing sugars present

* Green end – conclusions must be traces of reducing sugars

* Wrong procedures, deny observation and conclusion marks

 

c)  Roots

 –  Presence of reducing sugars translocated from the bulb/aerial

Leaves, for provision of energy/respiration for growth and development/respiration for growth and development/metabolic activities.

 –  Absence of starch because roots are not a storage organ.

 

ii)  Bulb

 –  Presence of reducing sugars translocated from aerial leaves, for storage

to be stored.

–  Absence of starch because fleshy leaves of the bulb do not

store starch (Stores Volatile oils)

 

Aerial leaves

–  Presence of reducing sugars due to photosynthesis

–  Absence of starch because the reducing sugars had not been

converted into starch.

 

 




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