KNEC KCSE BIOLOGY TOPICAL QUESTIONS - ATIKA SCHOOL

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Describe die process of fertilization in flowering plants.

24/6/2020

K.C.S.E Biology Q & A - MODEL 2010PP2QN07

Describe die process of fertilization in flowering plants.

answers

Pollen grains land onto the stigma; and adhere to it as a result of the stigma cells secreting a sticky substance; It absorbs nutrients; and germinates forming a pollen tube; The pollen tube grows down the style to the ovary; deriving nourishment from surrounding tissues; The pollen tube has tube nucleus at the tip; and generative nucleus immediately behind it; As the tube grows downwards into the ovary the generative nucleus divides mitotically; to give rise to two nuclei; which represent the male gametes; The pollen tube penetrates the ovule/embryo sac through the micropyle/chalazza; After the pollen tube enters the embryo sac, the tube/vegetative nucleus breaks down; leaving a clear passage for the entry of the male nuclei;
which enter the embryo sac; where one fuses with the egg cell nucleus; to form a diploid zygote; which develops into an embryo; The other male nucleus fuses with the two polar nuclei; to form a triploid nucleus/primary endosperm nucleus; Which becomes endosperm; This type of fertilization is called double fertilization;

State two advantages of internal fertilization in humans.

24/6/2020

K.C.S.E Biology Q & A - MODEL 2010PP1QN20

State two advantages of internal fertilization in humans.

answers

Higher chances of fertilization;
Embryo is protected from external environmental conditions;

State two advantages of hybrid vigour.

24/6/2020

K.C.S.E Biology Q & A - MODEL 2010PP1QN10

State two advantages of hybrid vigour.

answers

Resistance to diseases;
Increased yields;

How are flowers adapted to wind and insect pollination?

23/6/2020

K.C.S.E Biology Q & A - MODEL 2009PP2QN07

How are flowers adapted to wind and insect pollination?

answers

Insect pollination / Entomorphilous flowers are scented to attract insects have stick stigma for pollen grains to stick on. Are brightly coloured to attract insects.
Have nectarines to secrete nectar; nectar attracts insects
Have nectar guides to guide the insects to the nectarines
Stigma/ anthers are located inside the flower / tubular a funnel shaped corolla to increase chances of contact by insects
Sticky/ spiny/ spiky pollen grains which stick on the body of insects and on stigma
Large/ conspicuous flowers to be easily seen by the insects/ attract
Anthers firmly attached to filament for insect to brush against
Have landing platform to ensure contact with anther and stigma
Mimiory to attract (male) insects/ flowers mimic female insects which attract
Anthers firmly attached to filament for insect to brush against
Have landing platform to ensure contact with anther and stigma
Mimiory to attract (male) insects/ flowers mimic female insects which attract male insects for mating e.g. orchids.
Anthers/ stigma hang outside the flowers to increase chances of pollination; style/ filament is long to expose stigma/ anthers stigma is hairy/ feathery/ branched to increase surface are over which pollen grains land/ to trap pollen grains;
Pollen grains are smooth/ dry/ light/ small to be easily carried by wind; large amount of pollen grains to increase chances of pollination
Anthers are loosely attached to filaments to enable them sway easily to release pollen grains; pollen grains may have structures which contain air to increase buoy any 3 flowers have long stalks holding them out in the wind

What is the role of the testes in the mammalian reproductive systems?

23/6/2020

K.C.S.E Biology Q & A - MODEL 2009PP1QN08

What is the role of the testes in the mammalian reproductive systems?

ANSWERS

Production of gametes/ spermatozoa Acc male gamete/ male sex cells
Production progesterone hormone which maintains pregnancy

Pregnancies continues if the ovary of an expectant mother is removed after 4 months explain

23/6/2020

K.C.S.E Biology Q & A - MODEL 2009PP1QN08

Pregnancies continues if the ovary of an expectant mother is removed after 4 months explain

ANSWERS

The placenta/ takes the role of the ovum of producing the hormone
Progesterone (which maintains pregnancy)

State two causes of chromosomal mutations

23/6/2020

K.C.S.E Biology Q & A - MODEL 2009PP1QN05

State two causes of chromosomal mutations

ANSWERS

Radiations such as alpha, gamma, beta UV and X- rays least one
Chemicals such as calchicine, phenols, bromate, pesticides
At least one Heavy metals e.g. lead mercury
Viruses such as Papilloma

K.C.S.E Biology Q & A - MODEL 2009PP1QN05

23/6/2020

K.C.S.E Biology Q & A - MODEL 2009PP1QN05

What is meant by the following terms
(i) Hybrid vigour
(ii) Polyploidy?

ANSWERS

(i) production of plants and animals that have superior/ greater productivity/ have beneficial/ characteristics than either of their parents.
(ii) Condition in which an individual has more than two sets of chromosomes

K.C.S.E Biology Q & A - MODEL 2008PP2QN01

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP2QN01

The figure shows changes that take place during menstrual cycle in human

(a) Name the hormone whose concentrations are represented by curves F and G
(b) State the effects of the hormones named in (a) above on the lining of the uterus
(c) (i) Name the hormone which is released by the pituitary gland in high concentration on the 14th day of the menstrual cycle
(ii) State two functions of the hormone named in (c) (I ) above
(d) State the fertile period during the menstrual cycle

answers

(a) Oestrogen
Progesterone
(b) Promotes healing (promotes repair (of the uterus)
Causes thickening (of the uterine lining) vasculation
(c) (i) Leutinizing hormone
(ii) Causes ovulation
Induces graafian follicle to become corpus iterum
Stimulates corpus inteum to release progesterone
(d) 12th , 16th , 14 + 2

State a function of amniotic fluid.

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN29

State a function of amniotic fluid.

answer

Cushions foetus against shock/ mechanical damage/ provide a suitable medium for embryo to grow/ allows movement of foetus/ support reduces friction/ lubrication/ suspends foetus providing support/ prevents desiccation/ drying of foetus.

Distinguish between protandry and protogyny.

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN28

Distinguish between protandry and protogyny.

answers

Protandry - Male parts mature before carpels; Styameic
Protogyny - Carpels; pistil; female parts mature before stamen;
Styme mature before anthers

State the mode of asexual reproduction in yeast.

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN28

State the mode of asexual reproduction in yeast.

answer

Budding

K.C.S.E Biology Q & A - MODEL 2008PP1QN08

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN08

The diagram below shows a stage in mitosis in a plant cell

(a) Name the stage of mitosis
(b) Give two reasons for your answer in (a) above
(c) Name the part of the plant from which the cell used in preparation was Obtained

ANSWERS

(a) Anaphase
(b) Chromatids fails to separate off poles
Sister chromatids separate/ pair of chromatid separate
(c) Root tip/ shoot/ cambium

Give two examples of continuous variation in humans

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN06

Give two examples of continuous variation in humans

ANSWERS

Height/ skin colour/ weight

What is meant by non- disjunction?

22/6/2020

K.C.S.E Biology Q & A - MODEL 2008PP1QN06

What is meant by non- disjunction?

ANSWERS

Failure of homoslogenous same to separate during meiosis/ prophase I
Failure of sister chromosomes to separate during meiosis Prophase II

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