KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

State the change that take place in a flower after fertilization

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN18b

State the change that take place in a flower after fertilization

answers

Integument change into seed coat / testa; Zygote into embryo;
Ovary wall into fruit; Ovule into seed; triploid nucleus into endosperm
Style dried up / fall off leaving a scar / corolla dries up (falls off ) stamens dry ‘up. Ref; Degeneration disintegrates.

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Describe the process of fertilization in a flowering plant

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN18a

Describe the process of fertilization in a flowering plant

answers

pollen grains stick in the stigma surfaces; that surface of stigma producers a chemical substance; which stimulates the pollen grain to produce a pollen tube / germinate. The pollen tube/ germinate. The pollen tube grows down (into the tissues of style) from where it derives nutrients; the generative nucleaus divides to give rise to two male nuclei and the antipodal cells; when pollen tubes disintegrates and make nucleus fuses with the egg cell and forms the zygote. The other male nucleus fuss with the two polar nuclei to form a triploid nucleus. The process involves double fertilization.

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Describe how semicircular canals perform their functions

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN17b

Describe how semicircular canals perform their functions

answers

There are three semi – circular canals; arranged in planes at right angle to each other; at the end of each canal is swelling called ampulla’s which contains receptors.
The movement of the cause movement of the fluid in at least one canal, the fluid movement deflects / displaces the coperta and thus stimulating the receptors / sensory hairs, the impulse / nerve sensory impulse is transmitted / conducted to the brain; by auditory nerve, about the movement of the body / head.

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K.C.S.E Biology Q & A - MODEL 2001PP1QN17a

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN17a

State the functions of the following parts of the mammalian ear;
(i) Tympanic membrane
(ii) Eustachian tube
(iii) Ear ossicles

answers

 a) i) Tympanic membrane.
Receives sound waves (from the air); and vibrates / transforms sound wave into vibrations to transmit them to the ear osssicles / malleus; acc. Hammer for malleus.
ii) Eustachain tube.
Equalizes the air pressure in the middle ear to that in the outer ear.
iii) Ear ossicles
Amplify / transmits vibrations from the tymphanic membrane in the inner ear / venestra ovalis / oval window.

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K.C.S.E Biology Q & A - MODEL 2001PP1QN16

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN16

An experiment was carried out to investigate the nutritional value of two dry powder animals feeds X and Y over a period of six months. Twenty 5 month’s old castrated goats were use. The goats were divided into two equal groups A and B.
The animal’s in group A were fed on feed X throughout the experiment while those of group B were fed on feed Y. The feeds were supplemented with dry hay and water. The average body weight of
each group of goats and the weight of the dry powder feeds were determined and recorded each month. The faeces produced by each group was dried and weighed and the average dry faecal output per month was also recorded. The results are as shown below.

(a) (i) What is the relationship between the amount of feed and the faecal output
(ii) Work out the average increase in weight for the animal’s in group A during
The first four months
The last two months
(iii) Account for the average increase weight in goats in group A during the first four months
The last two months
(iv) Which of the two feeds is more nutritious?
Give reason for your answer
(b) State four uses of digested food in the bodies of animals
(c) State four uses of water in the bodies of animals

answers

(a) (i) The more the feed the more the feacal output
The less the feed the less the faecal output
(ii) The first four months

iii) Fast/ rapid/Active growth hence increase in weight
The last two months
Slow growth, reached maturity
iv) Feed X
Give reason for your answer
Group A gained (more) weight, on less food while group B lost
weight on more food.
b) growth, repair, protection, energy production
c) a solvent, transport medium.. Hydrolyses of food, maintenance of temperature.

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K.C.S.E Biology Q & A - MODEL 2001PP1QN15

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN15

The diagram below represents a set up to investigate the conditions necessary for seed germination.

The set up was left for 7 days
(a) What conditions were being investigated in the experiment?
(b) State three reasons for soaking seeds in set ups A and B
(c) What were the expected results after seven days?

answers

(a) water, temperature moisture (Acc. Warmth)
(b) Mobilize/ hydrolyze stored food/ active enzymes/ breaking of dormancy softening the testa / seed coat ( acc. As a solvent/ transport media.)
(c) Setup A – those in set up A will germinate
Setup B- those in set up B will not germinate
Setup C- those in set C will not germinate

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K.C.S.E Biology Q & A - MODEL 2001PP1QN14

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN14

Tallness in pea plants is due to a dominant gene Two tall pea plants were crossed and their F1 generation were in the ratio of 3 tall: 1 short. Using letter T to represents the gene for tallness and t for shortness give the
(a) (i) genotype of the parents
(ii) Gamete of the parents
(iii) Genotype ratio of the F1 generation
(b) What is meant by the term testcross in genetic studies?

answers

(a) (i) Tt, Tt
(ii) Tt and Tt
(iii) 1TT; 2Tt; 1tt/ 1 tall homozygous; 2 tall heterozygous
1 short homozygous 1:2:1
(b) Crossing a homozygous recessive organism with an organism which shows dominant characteristics.

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K.C.S.E Biology Q & A - MODEL 2001PP1QN13

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN13

The diagram below represents the nitrogen cycle

(a) State the process labeled
A
D
(b) Name the compound represented by B
(c) Name the group of organisms labeled C
(d) (i) name the group of plants which promote process A
(ii) State the part of the plant where process A takes place
(e) How would excess pesticides in the soil interfere with process A

answers

(a) A – Nitrogen fixation
D – absorption
(b) Nitrate/ nitrates/ NO2
(c) Denitrifying bacteria/ Denitrifiers
(d) (i) Leguminous plants, (acc. Legume/ acc examples e.g beans peas)
(ii) Roots nodules; rej root or nodules alone; acc; root
(e) – Killing / reducing of composers
- Killing/reduction of nitrogen fixing bacteria/ nitrogen fixing microorganisms
- Destruction of leguminous plants

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K.C.S.E Biology Q & A - MODEL 2001PP1QN12

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN12

The graph below shows the effect of substance concentration of the rate of enzyme reaction.

(a) (i) Account for the shape of the graph between A and B
(ii) B and C
(b) How can the rate of reaction be increased after point B?
(c) State two other factors that effect the rate of reaction of enzyme reaction

answers

(a) (i) More active sites of enzymes available, for a large number of molecules of substrate; hence increase in the rate of reaction ( rapid of fast increase in the rate of reaction)
(ii) B and C
Enzymes/ substrate are in equilibrium / All active sites are occupied; hence rate of reaction is constant.
(b) Raising concentration of enzymes
(c) PH, temperature, inhibitors/ cofactors

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K.C.S.E Biology Q & A - MODEL 2001PP1QN11

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2001PP1QN11

The diagram below represents a mammalian nephron

(a) Name the
(i) Structure labeled P
(ii) Portion of the nephron between point X and Y
(b) Name the process that takes place at point Q
(c) Name one substance present at point R but absent at point S in a healthy mammal
(d) The appearance of the substance you have mentioned in (c) above is a symptom of a certain disease caused by a hormone deficiency. Name the
(i) Disease
(ii) Hormone
(e) State the structural modifications of nephrons found in the desert mammals

answers

(a) (i) Efferent arteriole/ vessels
(ii) Loop of henle
(b) Ultra – filtration ( acc. Pressure filtration) rej. Filtration
(c) Glucose ( acc. Blood sugar)
(d) (i) Disease – diabetes mellitus ( acc. Sugar diabetes)
(ii) Hormone – insulin
(e) Small Bowman’s Capsule/ Groleruli`; Rej few Bowman’s capsule
Loop of Henle

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