KNEC KCSE BIOLOGY TOPICAL QUESTIONS - ATIKA SCHOOL

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Describe the role of hormones in the human menstrual cycle.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP2QN07

Describe the role of hormones in the human menstrual cycle.

answers

After/at the onset of menstruation, (the anterior lobe of) the pituitary gland; secretes follicle stimulating hormone (FSH); the FSH causes the Graafian follicle; to develop into the ovary; and stimulate the ovary tissues to secrete oestrogen hormone; Oestrogen brings about repair/healing of the endometrium/uterine wall; its concentration increases to a level which stimulates the (anterior) pituitary gland; to secrete lutenizing hormone (L.H.) and stops further secretion of FSH;
The L.H. stimulates the maturation of the Graafian follicle; LH also stimulates the Graafian follicle to release an ovum into the (funnel of the) fallopian tube/causes ovulation; it also stimulates the remains of the Graafian follicle to form a yellow body/corpus luteum (in the ovary;
The corpus luteum is stimulated by the L.H. to produce progesterone; Progesterone then stimulates the thickening of the endometrium/inner lining of the uterine wall; in readiness for implantation; as progesterone level increases, it inhibits (the pituitary gland) from secreting FSH; further increase in progesterone level inhibits the pituitary gland from secreting L.H. This causes the corpus Luteum to degenerate; this reduces the amount of progesterone; the sudden drop in secretion of progesterone causes the endometrium to slough off/menstruation occurs; and the cycle is repeated;

Describe the mode of reproduction in a named fungus.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP2QN07

Describe the mode of reproduction in a named fungus.

answers

Rhizopus/mucor/mould; reproduce asexually; by sporulation; spores develop from a single cell forming sporangium; which bursts on maturity releasing spores; which are dispersed by air currents/wind germinating; to form new generation/ form a mycelium (if it lands on a suitable medium); Or
Yeast/Saccharomyces/Schizosaccharomyces; reproduce asexually;by budding; parent cell forms an outgrowth/projection/bud; this is followed by division of the nucleus into two; one of the nuclei moves into the bud; which grows and develops into a new cell;

K.C.S.E Biology Q & A - MODEL 2018PP2QN06

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP2QN06

The effect of auxin concentration on growth response of two parts of a plant, X and Y was investigated over a period of time. The results were tabulated as shown in the table below.

(a) On the same axis, draw line graphs of the effect on growth of the two parts, X and Y (percentage inhibition or stimulation) against the concentration
(b) With reasons, name the two parts of the plant, X and Y.
X
Reason
Y
Reason
(c) From the graph identify: .
(i) the point at which the percentage stimulation was the same for both X and Y.
(ii) the optimum concentration of auxins required for part Y
(d) State three ways in which the effects of auxins on plants is applied in flower farming.
(e) Distinguish between simple and conditioned reflex action

answers

b) X—root;
Reason
Low auxin concentration stimulates (rapid/faster) cell division and elongation/growth in roots;
High concentration of auxins inhibits growth in roots;
Y—shoot;
Reason
Low auxin concentration has little effect on the growth of shoots/shoots are stimulated to grow with high auxin concentration (up to a given optimum);
c) i. 33%±2;
ii. 1.0 parts per million;
(d)Faster maturity of flowers/earlier flower formation/flowering;
Prunning/decapitating shoot tips to allow sprouting of lateral buds, hence more yield;
Keeping flowers fresh;
Stimulate formation/development of (adventitious) roots;

K.C.S.E Biology Q & A - MODEL 2018PP2QN02

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP2QN02

Below is a graphical representation of students’ height in a classroom.

(a) Name the type of curve illustrated.
(b) (i) State the type of variation represented by the curve.
(ii) State two meiotic processes that lead to variation among organisms.
(iii) Explain the role of variation in organisms.
(c) Explain the need for genetic counselling in present day health facilities.

answers

a) Normal distribution curve;
b) i. Continuous (variation);
ii. Independent assortment;
Crossing over;
iii. Organisms/individuals with advantageous traits/variations are favoured/selected by nature; and survive to reproduce/pass on/propagate the advantageous/favourable traits to their off-spring;
Or
Variation ensures propagation of desirable/favourable traits; to the future generations/off-spring, ensuring improved/quality population;
c) Provides information/advice to individuals/families/communities about genetic disorders;
Helps identify/test/advice families/communities on possible risks of genetic disorders;
Provides supportive services/serves as patient advocates/refer individuals/families to relevant health professionals;

K.C.S.E Biology Q & A - MODEL 2018PP1QN23

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP1QN23

State two characteristics of living things illustrated in the photograph below.

answers

Growth; and development;
. Reproduction;

K.C.S.E Biology Q & A - MODEL 2018PP1QN14

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP1QN14

The diagram below illustrates a germinating seedling.

(a) Name the type of germination illustrated in the diagram
(b) Describe how the type of germination named in (a) above is brought about.

answers

(a) Epigeal;
(b) Hypocotyl elongates faster than the epicotyl; pushing cotyledons above the ground;

State two limitations of using a quadrat to estimate the population of organisms.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2018PP1QN13

State two limitations of using a quadrat to estimate the population of organisms.

ANSWERS

Cannot be used for most animals/plants;
Assumes organisms are evenly distributed;
Inaccuracy (over/under-estimation);

K.C.S.E Biology Q & A - MODEL 2017PP2QN07

1/7/2020

K.C.S.E Biology Q & A - MODEL 2017PP2QN07

Explain the importance of protecting the forest ecosystem with reference to the following:
(a) climate change
(b) biodiversity
(c) biotechnology
(d) water conservation
(e) pollution.

answers

a) Climate change

Promote(regular) rainfall/precipitation/prevent desertification;
Act as wind breakers;
Keep earth temperatures cool/reduce global warming;
Keeps biogeochemical cycles going e.g. hydrological, carbon,nitrogen, phosphorous, sulphur cycles;

b) Biodiversity

Conserve diverse flora/ fauna;
Conserve genetic variety;
Prevent extinction of rare species;
Source of research/employment;
Aesthetic/attracting tourism in foreign exchange;
Have impact on culture/religion/politics; ‘
Food and shelter for other organisms and man;
Source of oxygen;

c) Biotechnology

Manufacture of medicines/directly used as medicinal;
Source of food/food products;
Provide fuel (when regulated);
Provide paper and related by-products (when regulated);
Provide timber (when regulated);
Products used in other industries e.g. tannin, wax, rubber, oil, honey;

d) Water conservation

Increased ground water/high water tables;
Adds into rivers/lakes/permanency ¡n existing water bodies/reservoirs;
Water towers/water catchment;

e) Pollution .

Minimize soil pollution/ensuring cover against surface run-off/wind erosion/denudation;
Trees/vegetation clean the soil surface by absorbing nutrients from decomposed matter e.g. sewage;
Large scale clean-up of polluted air/dust;
Muffle noise pollution;

Name the hormone responsible for the development of secondary sexual characteristics in human males.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2017PP2QN04

Name the hormone responsible for the development of secondary sexual characteristics in human males.

answer

Testosterone;

State the significance of diploidy.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2017PP2QN04

State the significance of diploidy.

answers

Ensures that the chromosomes/genetic constitution of the offspring is the same as that of parents;
Ensures perpetuation of a given species’ desired/favourable traits/qualities/continuity of the species;

K.C.S.E Biology Q & A - MODEL 2017PP2QN04

1/7/2020

K.C.S.E Biology Q & A - MODEL 2017PP2QN04

(i) Define the term diploidy.
(ii) Name the type of cell division that gives rise to diploid cells.
(iii) Name the type of cells in which the process named in (b) (ii) above Occurs.

answers

i. State of being/having two sets of chromosomes and therefore two copies of genes (especially in somatic/body cells);
ii. Mitosis;
iii. Body cells/somatic cells;

Explain how the sex of a male child is determined in human beings.

1/7/2020

K.C.S.E Biology Q & A - MODEL 2017PP2QN04

Explain how the sex of a male child is determined in human beings.

answers

Male produces sperm cells with X or Y chromosomes; if (by chance), Y chromosome containing sperm from male fuses with X chromosome containing egg from female ovum, an XY zygote results, giving rise to a male child;

K.C.S.E Biology Q & A - MODEL 2017PP1QN14

30/6/2020

K.C.S.E Biology Q & A - MODEL 2017PP1QN14

The photograph below illustrates a germinating seedling.

(a) Name the type of germination illustrated in the photograph.
(b) Explain the function of each of the parts labelled G and H.
G
H

answers

a. Epigeal;
b. G- Elongates to expose the foliage leaves to light photosynthesis
H- Stores food (for growth);
For photosynthesis (it is green);
Protects plumule during germination;

K.C.S.E Biology Q & A - MODEL 2017PP1QN07

30/6/2020

K.C.S.E Biology Q & A - MODEL 2017PP1QN07

The diagram below represents a stage in the division of a cell.

With a reason, identify the organism from which the cell was obtained.

answers

.Animal - accept correct examples (of organisms)/amoeba/plasmodiurn;
Constriction of the cell membrane/ presence of centrioles;

K.C.S.E Biology Q & A - MODEL 2017PP1QN05

30/6/2020

K.C.S.E Biology Q & A - MODEL 2017PP1QN05

The photograph illustrates a housefly at various stages of its development.

(a) (i) On the photograph, name the stages of the life cycle.
(ii) Using arrows, link the stages of the life cycle in the correct order.
(b) (i) State two differences between the life cycles of a housefly and that of a cockroach.
(ii) State one advantage of the life cycle of a cockroach to itself.

answers

(ii)Absence of larva and pupa shortens the life cycle of the organism; (avoiding adverse/extreme environmental conditions that would affect its growth/general life processes);

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