K.C.S.E Biology Paper 3 Answers
| Test tube contents | Amount of effeverscence observed |
Explanation | |
|---|---|---|---|
| 1.(a) | HCL + macerated specimen N + H₂O |
No/little effervescence/foam / frothing/bubbling; |
Although there was adequate surface area exposed (by macerating the potato) for enzymatic action, the acidic rnedium/low pH did not favour the working of the enzymes/ catalyze/increase rate of enzymatic reaction/denature enzyme; |
| NaOH + macerated specimen N + H₂O₂ |
Vigorous/rapid/ high/a lot of /more effervescence; |
Adequate surface area exposed (by macerating the potato) for enzymatic action; favourable/suitable pH/alkaline medium/high pH for enzymatic action; |
|
| NaOH + cube of specimen N N + H₂O₂ |
Moderate/ average/medium effervescence | Less/little surface area exposed for enzymatic action; |
10 Marks
| Procedure | Observation | Confirmation | |
|---|---|---|---|
| 1.b) | Add (a drop of the) iodine solution provided to specimen N; |
Blue-black colour observed; | Starch present (in specimen N); (3 marks) |
13 Marks
| 2.a)(i) | Specimen G | Division : Spermatophyta/Spermaphyta; Reason : Seed-bearing/naked seeds/green; |
((2 marks) |
|---|---|---|---|
| (ii) | Specimen E | Kingdom : Fungi/Mycopliyta; Reason : feed on dead matter/saprophytic/have hyphae/ Rhizoids/myce1ium/lack chlorophyll/non-green; |
(2 marks) |
| (iii) | Specimen M | Division : Spermatophyta/Spermaphyta; Reason : Presence of leaves/stems/roots; Have chlorophyll/are green; Remains of fruit/seed/cotyledons; |
(2 marks) |
| (iv) | Specimen H | Phylum : Arthropoda; Reason : Segmented body/presence of limbs/jointed appendages; Presence of exoskeleton/external skeleton/ bilateral symmetry; |
(2 marks) |
b)(i) Specimen F has its body covered with hair while the body of specimen K (crocodile) is covered with scales; Specimen F has the opposable thumb in its pentadactyl limb while the limbs of specimen K are uniform; Specimen F has marnmary glands while specimen K does not have;Specimen F is viviparous while specimen K is oviparous; (2 marks)
b(ii) Specimen M and J
• Specimen M has narrow; (leaves) with parallel veins; while specimen J has broad leaves; with net veins;
• Specimen M has fibrous root (system); while specimen J has tap root (system);
• Specimen M has a sheath while specimen J has a petiole;
Specimen J (bean) is a flowering plant, reproduces sexually; specimen E reproduces a asexually/sporulation/by spores;
3.a) Pisces;
- Body covered with scales;
- Streamlined body;
- (Presence) of gills;
- (Presence) of fins;
- (Presence) of operculum;
- (Presence) of lateral line:b) Adaptations
- Streamlined body enables it to move fast in water with minimum/reduced resistance/friction;
- Scales pointed backwards/overlapping to reduce friction during movement in water;
- Body covered with a slimy substance/mucoid for easier movement/reduce friction;
- Has fins for movement/swimming/balancing/propulsion in water
- Swim bladder to vary its depth/buoyancy;
- Inflexible head to enable/maintain forward thrust;
- Myotomes that contract and relax alternately enabling side to side movement;c)
- Protection of the (delicate) gills;
- Opening/closing to let water out for ventilation/act as a valve/allow water to flow in one direction; d(i) For gaseous exchange; (1 mark)(ii)
- Gill filaments are: • Numerous to increase the surface area for gaseous exchange;• Thin to reduce the diffusion distance/for easier/efficient/ faster diffusion of respiratory gases (in/out);
• Are wet/moist to dissolve respiratory gases for efficient gaseous exchange;
• Highly vascularized/numerous capillaries for transport of respiratory gases/maintain/create a steep concentration gradient;
- Gill bar is long for attachment ofsupport the gill filaments; is bonny/rigid /hard to support the gill rakers/ gill filaments;
- Gill rakers are sharp/pointed/rake-like to filter/trap foreign objects/protect the (delicate) gill filaments;
