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;
K.C.S.E Biology Q & A - MODEL 2010PP1QN20
State two advantages of internal fertilization in humans.
answers
K.C.S.E Biology Q & A - MODEL 2010PP1QN10
State two advantages of hybrid vigour.
answers
K.C.S.E Biology Q & A - MODEL 2009PP2QN07
How are flowers adapted to wind and insect pollination?
answers
K.C.S.E Biology Q & A - MODEL 2009PP1QN08
What is the role of the testes in the mammalian reproductive systems?
ANSWERS
Pregnancies continues if the ovary of an expectant mother is removed after 4 months explain23/6/2020
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
K.C.S.E Biology Q & A - MODEL 2009PP1QN05
State two causes of chromosomal mutations
ANSWERS
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
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
K.C.S.E Biology Q & A - MODEL 2008PP1QN29
State a function of amniotic fluid.
answer
K.C.S.E Biology Q & A - MODEL 2008PP1QN28
Distinguish between protandry and protogyny.
answers
K.C.S.E Biology Q & A - MODEL 2008PP1QN28
State the mode of asexual reproduction in yeast.
answer
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
K.C.S.E Biology Q & A - MODEL 2008PP1QN06
Give two examples of continuous variation in humans
ANSWERS
K.C.S.E Biology Q & A - MODEL 2008PP1QN06
What is meant by non- disjunction?
ANSWERS
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