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Biology Paper 2

SECTION A (40 Marks)

Answer ALL the questions

8 marks


a) To investigate plant response to gravity;


(i) A- The shoot and root remained horizontal;

(ii) B-The shoot curved upwards and root-tip downwards;

c) Gravity causes greater conc. of auxins on lower sides of seeding/on shoot and root; High conc of auxins in lower side of the root inhibits cell elongation hence than on upper side;(bends downwards);

d) To nullify the effect of gravity/distribute gravity equally on the seedling;

e) Control experiment;

8 marks




B-prophase 1

C-Anaphase 1


(i) Centromere of bivalent not split;

(ii) Homologous chromosomes separate;

(iii) Homologous chromosomes moving to poles (opposite) of the cells;

Rej if homologous is not mentioned.

c) Spindles (fibres)

8 marks


a) Growth-Quantitative permanent(irreversible) increase in size of an organism; Development-Qualitative growth of an organism;



(i) ‗Intermoult;


c) Vascular cambium;

Cork cambium;

d) Promotes flowering;

8 marks



(i) They control the opening and closing of stomata; which allows air into the leaf;

(ii)Have large air spaces; hence contain air for gaseous exchange;


(i) Tracheoles;

(ii)Maintain a step concentration gradient which enables maximum absorption of oxygen from water;

c) At high altitude there is low (partial pressure of) concentration of oxygen; hence efficient many red blood cells transportation of oxygen;

8 marks

SECTION B (40 Marks)

Answer questions 6 (compulsory) and either question 7 or 8

(a) graphs

Correct scales =2mks

Correctly labelled axes =1mks

Correctly plotted points =2mks

Smooth curves =2mks

(b) Zebra;

Wide fluctuations of zebra population over the period of study;

(c) Total counts/aerial counts/photography/capture recapture;

Animals are mobile and large in size;

Giraffe population is stable ;( OWTTE)

(d) Giraffes are browsers;

They feed on Acacia which are drought resistant;

Vegetation/food (Acacia) was constantly available for giraffe to feed on;

Source of food (Acacia) is not affected adversely by changes of rainfall pattern;

Source of food (Acacia) is not affected adversely by changes of rainfall pattern;

(e) Food; predation; migration; completion; parasitism; human activity/poaching;

(f) Protection of animals from poaching;


Protection of human crops/live stokes;

Centre of research/education;

Conservation of rare species;

20 marks




Soil contains water in between its particle; Water is absorbed by root hairs through the process of osmosis; water is at higher concentration in the soil solution than in the cell sap of root hair cell; water therefore moves along the concentration gradient from the soils into the sap vacuole of the root hair cells and dilute the cell sap; It then moves to (the cortex cells, endodermis cells pericycle, and the to) the xylem;

Active transport

Generally the concentration of minerals in the soil is lower than that in the cell sap of the root hair cell; therefore the mineral salts enter the root hair against concentration gradient; Carrier molecules are involved; in moving back and forth carrying the salt ions from the soil water root hair cell membrane;


Mineral salts can also be taken into root hair cells by diffusion; this happens when concentration of the ions is lower in the root hair cell sap than the soil solution ;


- Vessels are made up of dead cells which allow for easy passage of water; dead cells do not absorb water. Dead cells allow water to move in the xylem without interference;

-Their walls are lignified this makes them firm and rigid enough to avoid collapsing in order to withstand movement of water under pressure;

-Lignifications make the vessels firm to provide mechanical support to the plant;

-Lignin makes the vessels waterproof thus cannot absorb the water being transported;

-Walls of vessels have bordered pits which allow for free movement of water and mineral salts from one vessel to another and to adjacent tissues;

-Xylem tissues do not have cross walls their cells to allow for free movement of water up the stem with less resistance;

-Xylem vessels are long continuous tubes to enhance smooth flow of water from the roots to the leaves;

-They have narrow lumen to enhance capillarity; hence faster movement of water up the stem;

-Have thick walls which enhances adhesion of water molecules to the xylem walls;

-Tracheids are similar to vessels except they have tapering end walls perforated by pits hence less efficient in conducting water and mineral salts;

20 marks



-The walls of intestines are made of smooth muscles which contract and relax causing peristaltic movement that push food substances along the lumen of the intestine;

-They are long to increase surface area for absorption of digested food substances; it also increases time of stay of food for digestion to be completed; -- They are coiled to increase surface area for digestion and absorption of food; coiling also reduces the speed of movement of food giving it maximum time for digestion and absorption;

-Has narrow lumen which brings about close contact between the food and the walls of the intestines for maximum digestion and absorption of food;

-Their walls have goblet cells which secrete mucus which protect the inner walls of intestines digestion by protolytic enzymes; also mucus lubricates food to allow for smooth movement down the gut;

-The walls have glands which secrete intestinal juice(succus enericus) containing digestive enzymes;

-The walls also have Brunner’s glands which secretes an alkaline fluid for optimum pH for enzymatic activity;

-The inner walls of ileum have villi and micro-villi that increases surface for absorption of food;villi walls are one thick to reduce the distance for diffusion; - Presence of dense network of blood capillaries on the villi to ensure that absorbed substances are effectively transported to body tissues;

-The villi have lymphatic capillaries called lacteals to facilitate absorption of fatty acid and glycerol together with some of fatty soluble vitamins;

-The cells of villi have numerous mitochondria to provide energy for efficient active uptake of substances during absorption;


Glucose is oxidized to produce energy during respiration; excess glucose is converted to glycogen by the liver cells and stored (for future use); fructose and galactose are converted to glucose ;( and utilized as above)

Amino acids used to make new cells and tissues; to repair worn out tissues; and for synthesis of hormones and enzymes; some are used to make plasma proteins e.g fibrinogen and haemoglobin; excess amino acids are delaminated in the liver;

Lipids are broken down to release energy; excess lipids are stored under the a dipose tissue; stored lipids are also used to provide energy; also they cushion delicate body organs heart, kidneys;

20 marks

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