KNEC KCSE BIOLOGY TOPICAL QUESTIONS

K.C.S.E Biology Q & A - MODEL 1995PP1QN16

25/5/2020

Comments

(a) Describe how insect pollinated flowers are adapted to pollination
(b) Describe the role or each of the following hormones in the human menstrual cycle
(i) Oestrogen
(ii) Progesterone
(iii) Luteinising hormone ( 9 mks)

KNEC ANSWERS

(a)
(i) Large; brightly coloured corolla/ inflorescence/ florets/ bracts to attract Insect
(ii) Scented to attract insects
(iii) Have nectary guides/ nectarines/ that directs insects/ secret nectar to attract insects.
(iv) Pollen grains rough/ spikey/ sticky/ surface; to stick on insects body
(v) Special shaped corolla tube; to enable insects to land
(vi) Anthers are situated inside the flowers to ensure that they are in contact with the insect
(vii) Sticky stigma; for pollen to stick or to adhere

(b)
(i) Oestrogen
Repair/ heal endometrium/ wall of uterus; which is destroyed in menstruation
(ii) Progesterone
Stimulates the thickening of the uterus; increases the blood supply to the endometrium. Inhibits the production of follicle stimulating Hormone.
(iii) Luteinising hormone
Responsible for maturation of the graafian follicles/ causes ovulation/ stimulates corpus luteum; to secrete progesterone.

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN15

25/5/2020

Comments

The graph below represents the increase in the number of yeast cells over a period of 48 minute:

(a)
Name the type of curve shown (1 mk)
(b)
Determine the number of yeast cells after 26 minutes (1 mk)
(c)
Work out the rate of cell division between 24 and 28 minutes (2 mks)
(d)
After how long was the population of yeast cells 128? (1 mk)
(e)
Name the phase of the curve labeled
- (i) A to B
- (ii) B to C
(f)
Give reasons for the shape of the graph between points C and D (3 mks)
(g)
State five factors, which would cause human population growth to assume the shape of the graph curve between points B and C (5 mks)
(h)
Describe how the quadrant method can be used to estimate the population of various species of plants in a given habitat (5 mks)

KNEC ANSWERS

(g)

Low death rate/ low mortality; [Rej. Decrease in death rate/ reduced death rate]
High birth rate/ high fertility acc. Increased birth rate
Improved medical services: Acc. Increased medical facilities
Enough food/ availability of food
Absence of war/ political stability/ peace
Improved standard of living

(h)

Measure the total area of the habitat, throw or mark out the quardrat in the area for the study; at random. Identify label the various species of the plants in the quardrat; count plants of each species; record the numbers, repeat the process (owtte) work out the average per quardrat for each species in the area/ calculate the population for the total area in Nairobi.

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN14

25/5/2020

Comments

The diagram below represents growing seedlings which were subjected to unilateral light at the beginning of an experiment:

(a)
- (i) State the results of P,Q and R after 5 days? ( 5 mks)
- (ii) Account for your answer in (a) (i) above. ( 3 mks)
(b) If the tin foil were removed from the tip of the seedling R, what results would be observed after 2 days? (1 mk)
(c)State the expected results after 3 days if the box were removed (1 mk)

KNEC ANSWERS

(a)
- (i)
  P – will tend/ grow towards light
  Q – will remain straight/ little/ no growthR – will remain/ grow straight / Acc. Grow upwards
- (ii)
  P – Growth substances or hormones/ auxins/IAA are produced by the stem tip. They move downwards and get disturbed to the side away from the side of light. Where they cause more rapid growth/ cell division/ elongation ( that results in bonding)
  The source of auxin has been removed and the auxins are not affected by light because the era has been covered.
(b) Tip will bend towards the light
(c) All the seedlings will grow upwards.

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN17

25/5/2020

Comments

Describe how excretion takes place in
(i) Mammalian Kidneys
(ii) Green plants

KNEC ANSWERS

(i) Mammalian Kidney

Blood reaches the kidney from the renal/ renal artery enters the kidney; then branches into capillaries/ glomeruli/ in the Bowmna’s capsule, blood vessels leaving the capsule/ efferent are those entering it/ afferent causing high pressure to develop in the glomeruli. This forces the plasma/ causes ultra filtration into the capsule. The filtrate contains waste products (acc. One example) The filtrate moves into the proximal/ first convolulated tubule; where selective reabsorption of glucose amino acids, some water and vitamins take through the loop of henle; excretory products/ urea, excess water and salts acc, one example) pass into the distal tubule, where the remaining useful substance (acc. One example e.g salts and water) are reabsorbed; The filtrate passes into the collecting tubule; where more reabsorption of water takes place: Excess water, urea and salts ( all three must appear)/Urine are removed through the ureter.

(ii) Green plants

CO2 / O2 /H2O diffuse through the stomata lentils/ hydrathods some toxic wastes are converted into non – toxic substances; these are deposited in certain tissues of the plant/ stored in ageing structures. Resins/ tannins – are exuded though the bark of the stem; or lost during leaf fall.

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN13

24/5/2020

Comments

The chart below shows a feeding relationship in a certain ecosystem

(a) Construct two food chains ending with a tertiary consumer in each case (2 mks)
(b) Which organism has the largest variety of predators in the food web? (1 mks)
(c) Name secondary consumers in food web (2 mks)
(d) Suggest three ways in which the ecosystem would be affected in there was a prolonged drought.

KNEC ANSWERS

(a)
- Green plants – Grasshoppers – Lizards – snakes
- Green plants – Grasshoppers – Lizards – Cats
- Green plants – Mice – Snakes – Hawkers
- Green plants – Mice – Snakes – cats
(b)
- Mice
(c)
- Lizards eat Hawk snakes, Rej. If any primary, tertiary consumer is given
(d)
- (i) Most plants will die / dry
- (ii) (same) organisms may starve to death
- (iii) (same) organisms may migrate

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN12

24/5/2020

Comments

The diagram below shows an experimental soil up to investigate an aspect of germination.

(a) Why are sodium hydroxide pellets used in this experiment? (1 mk)
(b) Why is moist cotton wool used in this experiment? (1 mk)
(c)
- (i) By means of an arrow, indicate on the diagram the direction in which red dye would move during the experiment. (1 mk)
- (ii) Give reasons for your answer in (c) (i) above (3 mks)

KNEC ANSWERS

(a) To absorb CO; reacts with CO2
(b) To provide moisture to generating seeds. Accept water for moisture
(c)
- (i)
- (ii) Oxygen in the tube is taken up for germination CO absorbed by higher pressure outside tube

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN11

24/5/2020

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN11

The diagram below represents a transverse section of a young stem

(a)Name the parts labeled A and B (2 mks)
(b)State the functions of the parts labeled C, D and E (4 mks)
(c)List three differences between the section shown above and one that would be obtained from the root of the same plant

(3 mks)

KNEC ANSWERS

(a)
- A – Epidermis
- B – Pith
(b)
- C – Transport manufactured food / translation; Rej. Digested food
- D – Produces new cells/ divides to give new cells. Accept secondary Thickening/ growth/ produces phloem & xylem.
- E- transport minerals salts/ minerals/ salts alone
(c)
- Xylem in central/ Star shaped
- Phloem in arms of xylem
- Root hairs present in root / has pilferous layer
- No pith in root

Comments

K.C.S.E Biology Q & A - MODEL 1995PP1QN10

23/5/2020

Comments

An experiment was carried out to investigate the rate of reaction shown below;
Sucrose →Fructose + Glucose

For the products fructose and glucose to be formed, it was found that substance K was to be added and the temperature maintained at 37⁰C. When another substance L was added, the reaction slowed down and eventually stopped.

(a) Suggest the identify of substances K and L ( 2 mks)
(b) Other than temperature state three ways by which the rate of reaction could be increased ( 3 mks)
(c) Explain how substance L slowed down the reaction ( 2 mks)