KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

Describe how fruits and seeds are suited to their modes of dispersal.

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN19

Describe how fruits and seeds are suited to their modes of dispersal.

answers

Water dispersed fruit / seeds

Mesocarp / seed has air spaces thus light / buoyant to float.
Therefore carried away by water.
The fruit / seeds are protected from soaking by water proud pericarp.

Animal dispersed fruits / seeds

Presence of hooks for attachment to animals; thus carried to other placed
Fruits are brightly coloured; succulent; aromatic attract animals, which feed on them.
The seed coats are registrant to digestive enzymes; thus carried to other places on them.
The seeds are dropped always from parent plant in faeces/ droppings.

Self dispersed fruits / seeds / explosive mechanisms

The dry pods / fruit split (along lines of weakness / satures)
Scattering seeds away from parent plant

Wind dispersed fruits / seeds

Censer mechanism
Perforated capsule is usually loosely attached to stalk / the long stalk is swayed by wind scattering seeds.
Presence of hairs / wing – like structure, floss / extensions which increase surface area / for buoyancy making is easy for fruits / seeds to be blown away
Fruits / seeds are light due to small size; therefore easily carried a ways by wind.

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Describe the functions of the various parts of the human eye.

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN18

Describe the functions of the various parts of the human eye.

answers

Sclerotic layer – (made up of collagen fibres thus) protects the eye maintains shape of eyeball.
Cornea

Allows light to enter the eye
Refracts light towards retina

Conjunctive - Protects cornea
Eyelids

Protects cornea from mechanical & chemical damage / protects eye form entry of foreign particles.
protects retina from bright light (by reflex action)

Choroids

(Contains black pigment which)prevents reflection of light within the eye / absorbed light.
Nourishes the eye / retina / supply oxygen / remove CO2

Ciliary muscles

Alter shape of lens during accommodation
Ciliary body produces aqueous humour.

Suspensory ligaments – adjusts shape of lens during accommodation
Lens – Refracts light rays / focuses light on retina
Vitrerous aqueous humour once.
Aqueous Humour – Nourishes cornea / lens Refracts light
Irus – ( pigmented thus) – gives the eye its colour / absorbs light controls amount of light entering the eye / adjusts size of pupil impulses.
Pupil – light enters the eyes through pupil.
Retina – has photoreceptor cells / rods / cones / image formation ;l generates impulses.
Fever / yellow spot – visual acuity / most sensitive part of retina with only cones.
Blind spot – point where nerve fibre emerges from the optic nerve / where the optic nerve leaves the eye / point where blood vessels & nerve fibres enter the eye.
Optic nerve – transmit impulses to brain.

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K.C.S.E Biology Q & A - MODEL 2003PP1QN17

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN17

Some students used a model to demonstrate the effect of sweating on human body temperature. Two boiling tubes A and B were filled with hot water. The temperature of water in the tubes was taken at the start of the experiment and then at 5 minutes interval. The surface of tube A was continuously wiped with a piece of cotton wool soaked in methylated spirit. The results obtained are shown in the table below.

a) On the same axes, plot graphs of temperature of water in the tubes against time.
b) At what rate was the water – cooling in tube A?
c) Why was tube B included in the set up?
d) Account for the rate of cooling in tube A.
e) State two processes of heat loss in tube b.
f) What would be the expected results if tube A was insulated?
g) What would the insulation be comparable to in:
i) Bird
ii) Mammals?
h) Name the structures in the human body that detect:
i) External temperature changes
ii) Internal temperature changes

answers

b)     80 – 18 = 62; 2.48C /Min
            2.5            25

    c)     Control
    d)     Rate was faster in tube A; because the film of methylated sprit evaporated; removing heat from the tube;
    e)     Convection ; radiation
    f)     Lower rate of heat loss;
    g)     i) birds
               Feather
            ii) Mammals?
                Fur
    h)     i) external temperature changes
                Temperature
            ii) Internal temperature changes
                 Hypothalamus

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K.C.S.E Biology Q & A - MODEL 2003PP1QN16

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN16

K.C.S.E Biology Q & A - MODEL 2003PP1QN16

a) What is meant by:
i) Autecology
ii) Synecology?
b) The number and distribution of stomata on three different leaves are shown in the table below:

Suggest the possible habitat of the plants from which the leaves were obtained
Leaf Habitat
A
B
C
(c) State the modifications found in the stomata of leaf C.

answers

a) i) study of a single species within a community / ecosystem /habitat / environment.
ii) Synecology?
Study of natural communities within an ecosystem
b) Leaf Habitat
A aquatic / fresh water
B Forest; Terrestrial
C Arid / semi arid; desert.
c) Sunken
Hairy
Reserved rhythm
Small stomatal pore

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Explain the role of antidiuretic hormone when there is excess water in the human body.

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN14

Explain the role of antidiuretic hormone when there is excess water in the human body.

answers

Less ADH secreted (by pituitary gland); causing less reabsorption of water in the kidney tubules; thus resulting in dilute urine.

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K.C.S.E Biology Q & A - MODEL 2003PP1QN15

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN15

A response exhibited by a certain plant tendril is illustrated below.

a) i) Name the type of response
ii) Explain how the response named in (a)(i) above occurs
b) What is the importance of tactic responses to microscopic plants?
c) State four applications of plant hormones in agriculture.

answers

a) i) Thigmotropism / haptotropism
ii) Contact with support; causes migration of auxine to enter the side; causing faster growth on the side away from centre of surface (causing tendrils curl around support.)
b) Escape injurious stimuli / seek favorable habitats; move towards light / stimuli.
c) Induce foot growth in stem cutting

Selective weed killers
Encourage apical dominance
Encourage sprouting of side brances
Breaking seeds dormancy
Induce pathencarpy
Promotes flowering
Induce fruit fall
Accelerates ripening of fruits.

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Explain how marine fish regulate their osmotic pressure.

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN14

Explain how marine fish regulate their osmotic pressure.

answers

Swallow plenty of sea water to increase amount of water in the body
Have chloride secretory cells in the gills to remove excess salts
Eliminate nitrogenous wastes in form of trimthylamine exide which requires little water for elimination.
Few / small glomeruli; thus slow filtration rate in the kidneys.

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K.C.S.E Biology Q & A - MODEL 2003PP1QN13

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN13

The diagram below shows gaseous exchange in tissues.

a) Name the gas that diffuses:
i) To the body cells
ii) From the body cells
b) Which compound dissociates to release the gas named in (a) (i) above?
c) i) what is tissue fluid?
ii) What is the importance of tissue fluid?
d) Name the blood vessel with the highest concentration of:
i) Glucose
ii) Carbon dioxide

answers

a) i) Oxygen
ii) Carbon dioxide
b) Oxyhaemoglobin
c) i) The blood plasma except blood cells and proteins; that has
filtered out of the capillaries.
ii) It is a medium of exchange of substances/ materials
between capillaries and body cells; supply nutrients to cells / supply oxygen to cells / remove waste products from cells.
d) i) Hepatic portal vein
ii) Pulmonary artery

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K.C.S.E Biology Q & A - MODEL 2003PP1QN12c

18/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN12c

In Drosophila Melanogaster, the inheritance of eye colour is sex – linked. The gene of red eye is dominant. A cross was made between a homozygous red – eyed female and a white – eyed male. Work out the phenotypic ration of F1 generation. (Use R to represent the gene for red eyes).

answers

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Name two sex – linked traits in humans.

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN12b

Name two sex – linked traits in humans.

answers

Colour blindness
Hair ears / pinna
Haemophila
Baldness

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What is meant by the term sex – linkage?

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN12

What is meant by the term sex – linkage?

answers

Genes are located on the sex chromosomes; they are transmitted along with those determining sex.

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How are leaves of submerged adapted plants for photosynthesis?

17/6/2020

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K.C.S.E Biology Q & A - MODEL 2003PP1QN10

How are leaves of submerged adapted plants for photosynthesis?

answers

Numerous chloroplasts to absorb light / epidermis have chloroplasts to absorb light.
Deeply divided / truncated leaves / branched leaves to increase surface area.
Large air spaces for storage of air / buoyancy; acc parenchyma tissue for storage of air
Have no cuticle to facilitate exchange of gases