The students caught 500 frogs, marked them and then released them back into pond. After ten days, they laid traps and caught frogs. Out of the 380 frogs, 95 frogs were found to be marked.

Using this data, calculate the population size of the frogs in the pond.(2mks)

State two assumptions made in the study.(2mks)

State three characteristics that helps to promote cross-pollination in flowering plants.(3mks)

State two advantages of metamorphosis in the life of an insect.(2mks)

(a)Explain the meaning of the following terms ;
Hybrid vigour

Polyploidy

(b) State two causes of chromosomal mutations.(2mks)

(a)State two advantages of natural selection to organisms.(2mks)

(b) Give a reason why organisms become resistant to chemicals.(1mk)

(a)Name the external feature which is common in birds ,fish and reptiles.(1mk)

(b) State two characteristics of fungi.(2mks)

List three symptoms of diabetes mellitus.(3mks)

(a) State two adaptations of mitochondria to their functions.(2mks

(b) Name the chemical substance that is oxidized to lactic acid in muscles in insufficient oxygen.(1mk)

(a) State what is tissue fluid.(1mk)

(b) What is the importance of the tissue fluids?(2mks)

Name three factors that may affect transpiration and absorption at any given time.(2mks)

(a) State two roles of mucus in the stomach (2mks)

(b) Give a reason why digestion of starch stops in the stomach.(1mk)

Below is a diagram of germinating seed.

Name the type of germination.(1mk)

State the functions of the part labeled x during germination.(2mks)

(a)Explain the meaning of the term non-disjunction.(1mk)

(b)Name two examples of continuous variations.(2mks)

(a) Name two ovarian hormones (2mks)

(b) What is the name given to male hormones that generally regulate reproduction?(1mk)

Name three characteristics of a population.(3mks)

Explain how the following factors determine the daily energy requirements in humans:
Age(1mk)

Occupation (1mk)

Sex (1mk)

Explain how an increase in temperature affects the rate of active transport.(2mks)

(a) State the adaptation that enables red blood cells to move in blood capillaries.(1mk)

(b)How are red blood cells adapted to their function?(2mks)

FORM 4 BIOLOGY PAPER 1

THEORY PAPER MARKING SCHEME.

(a) Packaging and transport of materials;

-formation of lysosomes;

-synthesis of cell secretions

Any 2 @ (1mk)

(b) – synthesis of ribosomes ;( 1mk)

Are lignified /thickened to prevent inward collapsing;

-have long and narrow lumen to facilitate capillarity;

-are made of dead cells to ensure passage of water;

Any 2@ (1mk)

(a) 0+0+3+3=6×2 = 12

3+1+3+3=10×2 = 20

32 teeth; (1mk)

(b)-herbivorous ;( 1mk)

-Lack of canines /incisors on the upper jaw/has a horny pad of gum on the upper jaw for biting ;( 1mk)

(a) Tracheole;(1mk)

-moist to dissolve gases;

-are thin walled to shorten diffusion distance;

Branched to increase surface area for gaseous exchange;

Any 2@ (1mk)

(i) Mycobacteriumtuberculosis (1mk)

(ii_ Bodetellapertusis;(1mk)

–to increase oxygen supply to tissues to oxidize lactic acid;

-to remove it from the tissues as it is poisonous;

(a) Diabetes insipidus;(1mk)

(b) Anti-diuretic hormone ;(1mk)

120

; = 120 micrometers;(1mk)
The Rh- antigen of B+ person caused production of Rh – antibodies by B- person against them; resulting in agglutination in B- blood; (2mks)

Open closed

i)fluid not transported through vessels	Blood transport through vessels
ii)Fluid makes direct contact with tissues	Blood not in direct contact with tissues
iii)Fluid transported at low pressure	Blood transported at high pressure.

(a) A goat has a larger S.A/V ratio than a mouse hence loses heat at a lower rate than the mouse;

(b) Lactic acid ;( 1mk)

(a) sporangium;

(b) Absorption of water and mineral salts;

(a) 500 x 380; 2000 frogs;(1mk)

95 1mk

(b)-There was no movement in or out of the pond by the frogs;

-that the marked frogs were evenly distributed in the pond;

-that the marked frogs mixed freely with others not marked;

Any 2mks

-Portogyny;

-self sterility;

-brightly coloured petals/bracts;

-production of sweet scented nectar to attract pollination agents;

Any 3(3mks)

–adults and larvae feed on different foods to avoid competition;

-pupa can survive adverse conditions /pupa can survive adverse conditions as it does not feed;(2mks)

(a) (i) A group of superior characteristics in an organism resulting from a cross between unrelated organisms;

(ii) Where an individual has more than two sets of chromosomes ;(1mk)

(b) X-rays /u.v light/gamma rays /alpha particles.Acc Radiations alone.

-Colchicine; Rej.chemicals alone.

-Lead /mercury; rej. Metals alone

Acc.Heavymetals.

-Papilloma virus;

Any 2 @ (1mk)

(a) –Helps to perpetuate advantageous characteristics;

-Helps to eliminate disadvantageous characteristics ;( 2mks)

(b) Disease causing micro-organisms mutate after repeated exposure to the chemical; and transmit this mutation to their offspring during reproduction (2mks)

(a) scales;(1mk)

(b)-Most have their cells made of chitin;

-most reproduce by sporulation/production of spores;

-are eukaryotic;

-some are saprophytic and others are parasitic;

-their basic unit is the hypha;

-they store food as glycogen and oil droplets.

Any 2 @ 1mk

–presence of glucose in urine;

-a feeling of thirst constantly;

-Frequent urination;

-Weight loss

-Loss of sight

-Unhealing wounds; any 3@ 1mk

(a)inner membrane is highly folded to form crystae to hold more respiratory enzymes;

Presence of enzymes for respiratory reactions(2mks)

(b) Pyruvic acid ;( 1mk)

(a)the fluid formed in tissues by ultra-filtration and lacking blood cells and plasma proteins;

(b) It supplies nutrients and oxygen to tissue cells;

-it is the medium of exchange between blood capillaries and tissues cells; (2mks)

–humidity;

-temperature;

-atmospheric pressure;

-light intensity

-wind Any 2 @ 1mk

(a) protection of the stomach wall from hydrochloric acid and digestive enzymes ;

-to lubricate food ;( 2mks)

(b) Due to the low pH/acidic medium which affects enzyme amylase ;( 1mk)

(a) Epigeal germination;(1mk)

(b) to protect the plumale;

-to elongate and pull the cotyledons above the ground ;( 2mks)

(a) –it is failure of homologous chromosomes to separate during meiosis /anaphase I hence chromosomes enter a common gamete;(1mk)

(b) -body height;

– Skincolour;

Weight;

Finger prints

Any 2 @ (1mk)

(a) – Oestogen;

-Progestone 2mks

(b)Androgens (1mk)

– population density;

Population distribution/dispersion;
Age structure
Population growth
Sex ratio any 3 @ 1mk

(a) Young people are active and grow rapidly hence need more energy for cell division/growth;(1mk)
b) Manual work requires more energy than simple work ;( 1mk)

An increase in temperature activates the respiratory enzymes ;which increases energy for active transport;(2mks)
(a) –they are flexible /are able to change shape to fit in the human of the capillary;

(b) Havehaemoglobin to trap oxygen;

-Theyhave an enzyme called carbonic anhydrase to speed up loading of carbon (iv) oxide gas.

Have a disc –shape to accommodate more haemoglobin lack a nucleous to pack more haemoglobin;

Have a thin membrane for faster diffusion of gases;

Any 2 ½(1mk)

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