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 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;

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;

State two advantages of hybrid vigour

30/6/2020

K.C.S.E Biology Q & A - MODEL 2016PP1QN30

State two advantages of hybrid vigour

ANSWERS

Resistance to pests/disease/adverse weather conditions
Increase yield
Earlier maturity/early maturity

State two functions of the placenta in mammals.

30/6/2020

K.C.S.E Biology Q & A - MODEL 2016PP1QN10

State two functions of the placenta in mammals.

answers

Exchange of nutrients / oxygen / metabolic wastes between the mother and foetus circulation systems.
Secretion of progesterone hormones

State two disadvantages of sexual reproduction in animals.

30/6/2020

K.C.S.E Biology Q & A - MODEL 2016PP1QN10

State two disadvantages of sexual reproduction in animals.

answers

Harmful characteristics from the parents may be passed on the offsprings
Takes a longer time
Few offsprings are produced at a time

K.C.S.E Biology Q & A - MODEL 2016PP1QN07

30/6/2020

K.C.S.E Biology Q & A - MODEL 2016PP1QN07

Explain how the following prevent self-pollination.
(i) Protandry
(ii) Self- sterility.

answers

Explain the various ways in which seeds and fruits are adapted to dispersal.

29/6/2020

K.C.S.E Biology Q & A - MODEL 2015PP2QN07

Explain the various ways in which seeds and fruits are adapted to dispersal.

ANSWERS

Wind - dispersed seeds / fruits are light / small to be carried by air currents;
Some seeds / fruits have developed hairy structure feather-like projections; wing like structure which increase their surface area to be blown about /carried away by wind; open capsules; borne on long stalks, which are swayed by wind scattering seeds.
Water - dispersed fruits / seeds are also light; to float on water;
Some, (like coconuts) have fibrous /spongy mesocarps to trap air; making them buoyant/floating on water; Others (like the water lily) produce seeds whose seed coats trap air bubbles; making them float on water; Some have water-proof seed testa / pericarp; remain afloat without soaking /sinking immediately they are released from parent plants;
Animal - dispersed fruits have developed hooks; to stick on (the fur of passing) animals;
In some cases, fruits are succulent, brightly coloured / scented; to attract animals, birds;
The seed coats (of some seeds) are hard; and resistant to the digestive enzymes; hence passing out through the gut undigested;
Self dispersal by explosive mechanism;
Fruits have sutures/lines of weakness; which split open when drying scattering seeds.

K.C.S.E Biology Q & A - MODEL 2015PP2QN02

29/6/2020

K.C.S.E Biology Q & A - MODEL 2015PP2QN02

The diagram below illustrates the structure of the female part of a flower.

(a) Name the part labelled W.
(b) Describe what happens when the pollen tube enters the structure labelled V.
(c) What do the structures labelled R and T develop into after fertilization?
R
T

ANSWERS

(a) W - ovary wall/ovary;
(b) Tip of pollen tube bursts open; one of the nuclei fuses with the egg cell nucleus; to form a diploid zygote; while the remaining male nucleus fuses with the polar nuclei; to form a triploid endosperm nucleus;
(c) R - Endosperm/primary endosperm;
T - testa/seed coat;

K.C.S.E Biology Q & A - MODEL 2015PP1QN15

29/6/2020

K.C.S.E Biology Q & A - MODEL 2015PP1QN15

The photomicrographs below show the various stages of cell division in a certain plant.

(a) (i) Name the type of cell division illustrated.
(ii) Give a reason for your answer in (a) (i) above.
(b) (i) Name the stage of cell division labelled K.
(ii) Give a reason for your answer in (b) (i) above.

answers

(a) (i) Mitosis;
(ii) Formation of two daughter cells.
(b) (i) Metaphase;
(ii) Chromosomes are at the equator

State three differences between the end products of mitosis and meiosis.

29/6/2020

K.C.S.E Biology Q & A - MODEL 2015PP1QN13

State three differences between the end products of mitosis and meiosis.

answers

K.C.S.E Biology Q & A - MODEL 2014PP2QN01

28/6/2020

K.C.S.E Biology Q & A - MODEL 2014PP2QN01

(a) State four characteristics of fruits dispersed by animals.
(b) State two roles of each of the following hormones in menstruation:
(i) luteinising hormone;
(ii) oestrogen.

ANSWERS

(a)

Fruit fleshy/juicy/succulent;
Fruit brightly colouredJlarge/inclusters;
Fruit scented has sweet smell/sweet aroma;
Seeds have toughlhard testa;
Some seeds have sticky/mucoid secretions;
Fruits have hooks;

(b) (i) Luteinising hormone:

stimulates ovulation;
stimulates the development of remains of the graafian follicle into corpus luteium:
stimulate corpus luteum to produce progesterone;

(ii) Oestrogen:

stimulate s healing and repair of uterine lining /endometrium following menstruation;
stimulates pituitary gland to secrete luteinising honnone;

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