KCSE Past Papers 2014 Biology Paper 2 (231/2)

Biology Paper 2 (231/2)

SECTION A (40 marks)

1. (a) ‘ Fruit fleshy/juicy/succulent;


  • Fruit brightly coloured/large/inclusters;
  • Fruit scented has sweet smell/sweet aroma;
  • Seeds have tough/hard testa;
  • Some seeds have sticky/mucoid secretions;
  • Fruits have hooks;(max 4 marks)

    (b) (i) Luteinising hormone:-

    stimulates ovulation;

    stimulates the development of remains of the graafian follicle into corpus luteum;

    stimulate corpus luteum to produce progesterone; (max 2 marks)

    (ii) Oestrogen:-

    stimulates healing and repair of uterine lining /endometrium following menstruation;

    stimulates pituitary gland to secrete luteinising hormone; (2 marks)

    2. (a) Carbonic acid/carbaminohaemoglobin/hydrogen carbonate;

    (1 mark)

    (b) (i) Water;

    (ii) Carbonic acid; (1 marks)

    Role: catalyses reaction between carbon IV oxide and water to form (weak) carbonic acid; (2 marks)

    (c) Prevents accumulation of acidity/maintains pH of blood since hydrogen ions combine with haemoglobim to form Haemoglobinc acids;

    Faster; due to the catalytic effect of carbonic anhydrase;

    (max 2 marks)

    (d) Activates thromboplastin; thrombokinase to neutralize heparin/convert prothrombin to thrombin;

    (2 marks)

    3. (a) O2 concentration is higher outside than inside the lenticels; O2 diffuses into lenticels;

    then into the cells;

    CO2 concentration is higher inside the lenticels than on the outside CO2 diffuses out of the lenticels into the atmosphere; (4 marks)

    (b) (i) To provide a large surface areal make them thin; for gaseous exchange/ to reduce diffussion distance for respiratory gases;

    (ii) This increases the volume of the buccal cavity while decreasing the pressure; which forces water to rush into the mouth;

    (2 marks)

    4. (a) Males have two dissimilar chromosomes X and Y/heterogametic;

    Females have two similar chromosomes X and X/homogametic;

    Male gamete/sperms have either X or Y chromosome, while all ova have X chromosome;

    If a sperm with X fuses with an ovum a female is formed and if a sperm with Y fuses with an ovum a make is formed;

    (4 mark)

    (b) (i) Sickle-cell trait is heterozygous while sickle cell anaemia is a homozygous condition;

    (2 marks)

    (ii) People with sickle cell trait are resistant to malaria; because the plasmodium cannot survive in sickle shaped red blood cells.

    (2 marks)

    5. (a)H – cell body; (1 mark)

    (b) — Has nutrients for nourishment of neurons, brain, spinal cord;

    — Acts as a shock absorber for protection of spinal cord from mechanical damage; (2 mark)

    (c) Contains myelin sheaths (of neurons which are made up of fats that make it have a shiny white appearance); (1 mark)

    (d) Cholinesterase; (1 mark)

    Breaks down Acetylcholine; to acetic acid and choline;

    (2 marks)

    (e) Correct arrow on neurone 1 points towards the grey matter; (1 mark)

    SECTION B (40 marks)

    6. (a) Scale Zx1 mark

    Identity of axes Zx1 mark

    Plotting of points Zx1 mark

    Labelling of curves 1 mark (% >< 2)

    Smooth curves 1 mark (% >< 2)

(c) (i) The higher the carbon (IV) oxide content in air, the higher the nitrogen uptake and vice versa; (1 mark)

(ii) More Carbon (IV) oxide in the air makes the seedlings to photosynthesize more; hence more amino acids/protein; are formed in the dark stage;

formation of amino acids/protein requires nitrogen;

(max 3 marks)

(d) (i) The concentration of nitrogen would remain constant; (1mark)

(ii) Despite decline in CO2; the nitrogen already absorbed/taken up by the plant Will still remain; (3 marks)

(iii) Lightning;

By free-living bacteria/micro organisms;

By Rhizobium (in root nodules of legumes);

(3 marks)

7. (a) (i) Reactions in photosynthesis are catalysed by enzymes; at optimum temperature photosynthesis proceeds faster;

Below optimum temperature the rate of photosynthesis decreases because enzymes are inactivated by the low temperatures / above optimum the rate of photosynthesis decreases because enzymes are denatured;

(2 marks)

(ii) Chlorophyll traps energy from sunlight for photosynthesis;

The higher the chlorophyll concentration the higher the rate of photosynthesis and vice versa;

(2 marks)

(b) In the mouth;

Food is chewed; to increase surface area for enzyme activity/saliva contains salivary amylase;

Saliva mixes with food and provides an alkaline medium; for amylase enzymes;

Salivary amylase acts on starch and converts them to maltose;

In duodenum;

Food is mixed with bile; and pancreatic juice;

Bile provides alkaline medium; for activity of duodenal enzymes; and neutralizes acidic chyme from the stomach;

Pancreatic juice contains pancreatic amylase; which converts starch to maltose;

In the Ileum;

Epithelial cells in Ileum secrete succus entericus; which contains enzymes;

sucrase; which acts on sucrose and converts it to fructose and glucose;

Lactase; which acts on lactose and converts it to galactose and glucose;

Maltase; acts on maltose and converts it to glucose;

max 16 marks

8 a ‘ Diffusion of Carbon (IV) Oxide; and oxygen; through stomata and lenticels;

Some wastes are stored in tissues in non-toxic form e.g. calcium oxalate;

Some of these tissues or organs drop off from plants e.g. leaves, flowers, fruits and bark of caffeine, nicotine, quinine;

Some wastes are released by transpiration through stomata and lenticels such as water vapour;

Others are released by guttation through hydathodes as water;

Others are released by exudation. (max 4 marks)

When body temperature is lowered below normal;

arterioles in the skin constrict;

blood is diverted to a shunt system;

less blood flows to the skin/less heat is lost;

when body temperature is raised above normal;

arterioles in the skin dilate;

more blood flows to the skin;

more heat is lost by convection and radiation;

when body temperature is lowered below normal:

erector-pilli muscles contract, hair stands erect;

more air is trapped, air is a bad conductor;

and insulates the body against heat loss;

when body temperature is raised above normal:

erector-pilli muscles relax, hair lies on skin;

less air is trapped, more heat is lost;

when body temperature is lowered below normal:

less fluids are absorbed by sweat glands;

less sweating, less vaporisation of water;

when body temperature is raised above normal:

sweat glands are more stimulated and more sweat is produced;

water in sweat evaporates and takes up heat from the body;

body is cooled/body temperature is lowered;

(max 20)

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