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NANDI CENTRAL JOINT DISTRICT MOCK 2014
231/2 – BIOLOGY PAPER 2 - MARKING SCHEME
1. (a) (i) Phytoplanktons;
(1mk)
(ii) Hawks;
(1mk)
(b) Phytoplanktons
snails
hawk;
(1mk)
(c) Zooplanktons would increase due to decreased predation;
Water snails would decrease due to lack of food (competition);
(2mks)
(d) Oil prevents dissolving of oxygen in water hence fish die due to suffocation; / Oil clogs
fish gills;
(1mk)
(e) - Domestic waste and sewage;
- Silting;
- Industrial effluent;
- Agricultural chemicals;
(any first two) (2mks)
2. (a) (i) Oxygen;
(1mk)
(ii) Carbon (IV) oxide;
(1mk)
(b) Oxyhaemoglobin;
(1mk)
(c) (i) The blood plasma except blood cells and proteins; that has filtered out of the
capillaries;
(1mk)
(ii) It is a medium of exchange of substances / materials capillaries and body cells;
supply nutrients to cells / supply oxygen to cells / remove waste products from cells;
(2mks)
(d) (i) Hepatic portal vein;
(1mk)
(ii) Pulmonary artery;
(1mk)
3. (a) Kingdom Protoctista;
(b) B – Vacuole;
Y – Pyrenoid; 
(c) A – for movement; 
X – for photosynthesis; 
(d) Because the nucleus is surrounded by a nuclear membrane; 
(e) Paramecium; euglena; amoeba;
(any first two).
4. (a)
Parental phenotype
Black
Black
Parental genotype
Bb
x
Bb
Gametes
B
b
B
b
(1mk)
(1mk)
(1mk)
(1mk)
(1mk)
(1mk)
(2mks)
fur


F1 generation
BB
BB
Bb
bb
(b) It brings variation; it leads to formation of hybrids;
(1mk)
(c) Organisms tend to produce more offspring than the environment can support; hence
they must struggle to exist; individuals that have favourable characteristics will have a
better chance of survival in the struggle and reproduce;
(3mks)
5. (a) Antidiuretic hormone;
(b) Pituitary gland;
(c) (i) Distal convoluted tubule;
(ii) Collecting duct;
(d) Negative feedback;
(e) It causes body dehydration;
(f) Osmoregulation;
(g) Diabetes insipidus;
(1mk)
(1mk)
(2mks)
(1mk)
(1mk)
(1mk)
(1mk)
(1mk)
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6. (a)
(b) 33 + 0.50C;
51.5 + 0.50C;
(2mks)
(c)
(i) As temperature is increased rate of reaction is increased; / more products are formed
(per unit time) because enzymes become more active;
(2mks)
(ii) As temperatures increase rate of reaction decreases; /less products are formed (unit per
time) / because enzymes become denatured by high temperatures;
(2mks)
(d) Increase in enzyme concentration; and increase in substance concentration;
(2mks)
Rj. Increasing number of enzymes.
Acc. Increasing number of enzyme.
(e) (i) Pepsin;
(1mk)
(ii) Wall of stomach / gastric gland / oxyntic / parental / cell produced Hydrochloric acid;
(2mks)
(f) (i) Duodenum;
(1mk)
(ii) Bile juice / SANS any correct salt e.g. NaHCO3;
(1mk)
Acc. Bile
7.
(i) Auxins / Indole Acetic acid
- Promote fruit formation / parthenocarpy;
- Promote cell division;
- Influences cell elongation / tropic responses;
- Promote formation of abscission layers / bring about fruit fall / leaf fall;
- Cause apical dominance / inhibit growth of lateral branches / buds;
- Promote growth of adventitious roots;
2
(ii) Cytoninins / kinetic / zeatin
- Promote root formation;
- Stabilizes proteins and chlorophyll;
- Promote flowering in some plant species;
- Breaks seed dormancy in some plant species;
- In low concentration it promotes leaf aging;
(iii) Ethylene / ethane
- Induces stem thickening;
- Inhibit stem elongation;
- Induces ripening of fruits;
- Promotes germination of certain seeds;
- Promotes development of abscission layer leading in fruit / leaf fall;
(iv) Gibberellins / GBA
- Promotes parthenocarpy;
- Initiate formation of IAA;
- Promote ripening of fruits after fertilization;
- Inhibit growth of adventitious roots;
- Slow down leaf abscission;
- Activates hydrolytic enzymes during seed germination;
- Promote cell division / cell elongation in dwarf varieties;
(v) Abscisic Acid / ABA
- Causes seed dormancy / bud dormancy;
- Causes abscission of leaves / fruit fall;
- Inhibit seed germination;
- In high concentration it leads to closure of stomata;
(vi) Florigens
- Promote flowering
(1 x 34 = 34 marks max. 20mks)
8. (a)
- Both involve transmission of a message, stimulus and response;
- Target organs of hormones are like effectors organs for impulses;
- Both involve chemical transmission;
(4mks)
Differences
Endocrine
Nervous
Chemical substance hormone to evolve
response.
Electrical / nerve impulse evolve.
Message / hormone transmitted through Message / nerve impulse
blood.
through nerves / nerves fibres;
Slow response;
Quick response;
Effect widespread;
Effect localized;
Effect long lasting / involve growth
Effect rapid acid short lived;
transmitted
(5mks)
Total 9 marks
Max. 8 marks
(b) Pain receptors; in the skin; are stimulated generate impulse; transmitted through sensory
neurone; then across a synapse; to the relay neurone; in grey matter; / spinal cord; though
another synapse; to a motor neuron; to the flexor muscles; which contracts; to cause the
jumping;
(max = 12mks)
3