(a)(i) Man - XHY;
(ii) Woman - XHXh ;

(ii) Probability of a carrier child ? = 1/4 or 25%
c) Males have only one X chromosome which if it carries the single recessive allele, it will express itself fully ;
Females can only express the gene in the homo-zygous recessive state ; thus reducing their chances

(a) A - Epicotyl ;
B - Cotyledon ;
C - Hypocotyl ;
(b) (i) Oxygen
- For oxidation of stored food substances releasing energy needed for cell division and growth ;
(ii) Water
- Activate enzymes ; hydrolyses and dissolves food substances ; softens testa for emergence of embryo ; medium of enzymatic reactions ; Transports nutrients to the developing embryo;
(iii) Optimum temperature - Activates enzymes of hydrolysis for the breakdown of stored food substances into simple soluble products ;
rej temp alone
(c) (i) Apical dominance ;
(ii) Removal of apical bud removes source of auxins/reduces /lowers concentration of auxins.
Low concentration of auxins stimulates development of lateral buds into side branches;

(a) To expel air / remove air ;
(b) Not to denature enzymes of yeast / Not to kill the yeast.
(c) To prevent entry of air ; into glucose and yeast mixture.
(d) To supply oxygen more faster ; to break down the lactic acid ; (to CO2 + water and energy)
(e) Alcohol / Ethanol; Energy / ATP;
(f) Use of boiled yeast ; Use of yeast without glucose ; / Use of glucose without yeast ;mark any 1

(a) H - Eustachian tube ;
J - Semi - circular canals ;
(b) H - Opens during swallowing, yawning, chewing and vomiting to equalise air pressure in the middle ear with the
atmospheric air pressure since it is open on both ends ; Acc converse.
M - Curved / funnel shaped to receive or collect and concentrate / direct sound waves into the auditory meatus ;
N - long / highly coiled / spiral to increase surface area for attachment of sensory cells that bring about hearing ;
(c) Total deafness
(d) Endolymph
(e) Maintains body balance and posture ; acc any 1

(a) Diffusion ;
(b) (i) Reducing sugars / simple sugars / glucose ;

(ii) Diastase converts starch to reducing sugars ; So present in visking tubing. Due to their small size and semi-permeability of the visking tubing ;the molecules moved across the semi-permeable wall of visking to the beaker ; so present
in the beaker. Rej. Second mark if size and semi-permeability are not indicated
(c) (i) Proteins rej amino acids.
(ii) Proteins are large molecules / big size molecules so cannot pass through the pores of the visking tubing ;
(d) Turgid ; Acc turgidity .

(a) Labelling axes @ 1 mk - 2
Correct scales @ 1 mk - 2
Plotting @ 1 mk - 1
Smooth curve @ 1 mk - 1
Total 6 mks
(b) (i) Gas evolved increases with increase in light intensity ; increased light intensity leads to more splitting of water
molecules into hydrogen atoms/ions and oxygen ; hence increase in rate of photosynthesis ;
(ii) Amount of gas evolved remained constant ; as the rate of photosynthesis is constant due to other limiting factors ;
(c) Glucose formed is converted into starch ; which is osmotically inactive hence stored ;
(d) By heating the leaves in an oven at 1100 C and weighing them ; then heating and weighting several times ; till a constant
weight is obtained ;
(e) - Has stroma with enzymes ; where CO2 fixation occurs ;
- Has grana containing chlorophyll ; which traps light energy from the sun for photosynthesis ;
- Has intergrana lamellae ; that hold the grana in position ;

(a) - Highly vascularised / Dense network of capillaries ;
- Large surface area ;
- Thin membrane / epithelium / one cell thick/ Thin lining rej thin walls.
- Moist lining / surface
(b) During the day in the presence of light ; photosynthesis occurs in the guard cells ; because they have chloroplasts ; This
reduces the concentration of CO2 (used as a raw material) ; thus reducing the acidity of the guard cells). Lowered acidity /
increased pH ; favours conversion of starch into glucose ; which is osmotically active ; thus increasing the osmotic pressure of guard cells ; compared to the neighbouring epidermal cells ; water is drawn from the neighbouring cells into the guard cells by osmosis ; causing them to expand thus becoming turgid ; The outer walls which are thinner than inner walls stretch more ;
causing the guard cells to bulge outwards ; making the stomata to open; For opening max 10
At night when there is no light; photosynthesis does not take place in the guard cells ; CO2 accumulates in the guard cells causing an increase in acidity (lowered pH). This low pH/ increased acidity favours the conversion of glucose into starch ;
which is osmotically inactive ; thus reducing the osmotic pressure of the guard cells ; Guard cells then lose water to the neighbouring cells by osmosis ; becoming flaccid ; making the stomata to close ; (max 6 mks)

1. Comparative anatomy ;
- Organism have common embryonic origin ; but structures become modified differently to perform different functions ;
These are called homologous structures ; others have different embryonic origin ; but structures become modified and adapt in the same environment thus perform similar functions ; such structures are called analogous structures ; Others have become reduced in size due to disuse in the environment ; These are called vestigial structures ; mark any correct example in each case ; max 5
2. Fossil records / palaeontology ;
Fossils are remains of organisms that became preserved in naturally occurring materials many years ago ; They show morphological changes of organisms over a long period of time ; max 2
3. Comparative embryology ; Study of embryo development ;Different vertebrate groups have a lot of similarities during their embryonic stage ; suggesting their common origin / ancestry ; max 3 acc - any 2 named embryos of vertebrates ;
4. Geographical distribution ;
Present continents are thought to have been one large land mass (pangea) ; As a result of continental drift ; Isolation occurred bringing about different patterns of evolution ; of related organism e.g Ilamas in the amazon resemble the camel ;
acc Jaguars, Panthers with their counterparts etc max 4
5. Comparative serology / cell biology ;
- Similarities of cell structures in different organisms; indicate evolutionary relationship between them ; while differences in cellular reactions indicate different ancestry ; max 3
6. Taxonomy / classification ;
Organisms with common features are grouped together suggesting a common ancestry; Differences between them indicate no phylogenetic relationship ; max 3 Total 20 mks​