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BIOLOGY

PAPER 2

MARKING SCHEME

SECTION A (40 MKS)

1a)Beam of electrons;

b)i)Diaphragm

ii)Eye-piece/ objective lenses;

iii)Coarse adjustment knob

c)i)Nucleolus;

ii)Centriole;

iii)Golgi bodies;

d)Mitochondria;

2a)F1 chicken BW (blue feathered)

P. genotype

Genetes

BW BW;

BBBWWBWW;;

F2 genotype

Phenotype ratio: 1 black: 2 blue: 1 white;

BBxBW

BBBW

genes

BBBWBBBW

2BB; 2BW; 2mks

c)Hemophilia/ Hairy Nose/ ear

Colorblindness/ Baldness;

3. a)i)Mouth:

Stomach acid/ Hcl kills bacteria or saliva contains enzymes that destroy bacteria

ii)Wounds:

Blood clots; blocking entry of micro-organisms

iii)Micro-organism trapped by mucus; then expelled by cillia action/ sneezing/ vomiting/ coughing; Nosal secretion contain lytic enzymes that kill bacteria;

b)Phagocytes/ neutrophilis/ macrophages

Ingest- and destroy micro-organisms/ by lysozymes;

Lymphocytes produce antibodies;

Neutralize/ destroy micro-organisms; antigens3mks

4. a)i)To find out whether energy/ heat is released in anaerobic respiration/ fermentation;

ii)To investigate the gas produced during fermentation/anaerobic respiration

2mks

b)i)(significant) rise in temperature; color of bicarbonate indicator turns yellow

2mks

ii)Yeast will respire aerobically releasing energy/ and carbon dioxide gas that turn indicator yellow;

1mk

iii)Expel/ drive out oxygen; 1mk

c)Use glucose rotation without yeast cells/ killed yeast cells; 1mk

5.a)Walls of stomach

b)Stimulates the secretion/ production of gastric juice; 1mk

c)Presense of food in stomach 1mk

d)-Produces plenty of mucus to lubricate coarse/ indigestible material during peristalsis

-Wide lumen accommodates/ store indigestible food

-Elongate to increase surface area for absorption of wastes;

-Has muscles to facilitate peristalsis when they contract;

3mks

6a)i)Pseudopodia/ amoeboid

ii)Cillia

iii)Flagella;

3mks

b)i) Exoskeleton

ii)Chitin;1mk

c)i)Look for food/ prey and water

ii)Search for mates for reproduction

iii)Escape danger / predators

iv)Migrate/ to favorable lands/ escape unfavorable conditions;

3mks

SECTION B (40 MKS)

7.a)Graph

6 mks

b)i)Photometer;1mk

ii)-Stem cut under water⁄ twig cut under water

-Apparatus must be air tight ∕ connections smeared with petroleum jelly

2mks

c)Q;

Reasons:

Less water/ lower rate of water loss; 1mk

d)i)210gh-1 in L

ii)11.00 am and 3.30 pm (+- 5 minutes)

iii)2.00-6.00 am

Low water loss/ constant

Dark/ night hence stomata are closed;

Low temperature3mks

iv)6.00am and 1.00 pm

Steady increase in rate of water loss;

Sun rises/ increasing light-intensity/ temperature;

Stomata open, hence faster evaporation of water3mks

d)- Fewer/ smaller stomata;

-Stomata on lower epidermis only;

-Sunken stomata;

-Reversed stomata rhythm;3mks

8.a)-Use of sweep net to catch grasshopper in school farm

-Mark each grasshopper with a small light colored paint (dorsal surface)/ cellolose paint/ brightly colored nail vanish;

-Count them; record and release them where they were collected;

-Repeat the procedure many times (x10) i.e. catch; mark; count; record and release;

-After 24 hrs catch many grasshoppers from the same area; count and record the second capture and those with marks (MR);

The HP represents the total population

FM/P=MR/SCwhere; Fm-First marked

Sc-Second captured

Mr-Marked register

P-Total population;9mks

b) -Light intensity; affect distribution of grass/ vegetation; and hence grasshoppers which

feed on them;

-Temperature; affects water loss from grasshoppers; biochemical processes; hence grasshoppers will prefer shades when very hot

-Humidity; Low humidity results in higher water loss by the grasshoppers/ high humidity less water loss;

-Wind; Increases the rate of water loss from the grasshoppers;

-Rainfall; Higher rainfall leads to more vegetation; hence more grasshoppers; since it offers food/ hiding place/ shades 15mks

  1. Auxins/ IAA

-Induces pattenocarpy in horticulture;

-Stimulates growth of adventitious roots in cuttings for vegetative, propagation;

-Stimulate cell division and elongation in shoots; promotes growth in stem

-Selective weed killers;

-Inhibits formation of side branches by removing apical bud; used in pruning tea, coffee

-Ripening of fruits;

-Leaf fall

Total 10 mks

Max 4 mks

Gibberellins/ Gibberilic acid;1mk

-Stimulation of rapid growth; dwarf variety to grow to normal height/ bolting;

by cell elongation/ cell division;

-Inhibit growth main root; patternocapy

-Stimulate growth side branches;

-Inhibit growth of adventurous roots

Total 7 mks

Max 4 mks

Cytokinns;1mk

-Promote cell division in presence of auxin and growth in plant

-Breaks seed dormancy;

-Repair of wounds in plants/ callus tissue

-Promotes flowering; retards aging

-Promotes fruit growth; of leaves6mks

Absissic acid; 1mk

-Promotes fruit fall

-Promotes leaf fall

-Prevents seed from germinating/ dormancy of buds;

-Growth inhibitor;4mks

Ettene;

-Ripening of fruits

-Causes leaf fall

-Breaks dormancy in seeds/ buts;4mks

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