KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

Explain why a bony fish dies shortly after being removed from water.

1/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2018PP1QN15

Explain why a bony fish dies shortly after being removed from water.

answers

Fish uses dissolved oxygen for gaseous exchange; gill filament epithelium dries up; gill filaments clamp together; surface area for
gaseous exchange reduced; oxygen lacks moist surface for dissolution causing death(due to suffocation);

Comments

K.C.S.E Biology Q & A - MODEL 2017PP1QN19

30/6/2020

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K.C.S.E Biology Q & A - MODEL 2017PP1QN19

The table below shows the percentage concentration of certain substances in blood plasma, glomerular filtrate and urine in a human being at a particular time.

(a) Explain the likely impact on the composition of urine in case of the following:
(i) Vigorous physical exercises
(ii) a meal rich in proteins
(b) Name the processes responsible for:
(i) Presence of glucose in the glomerular filtrate
(ii) absence of glucose in urine

answers

a. i) Less water and urea; since sorne is excreted/eliminated through the skin (as sweat);
ii) increased amount of urea in the urine; due to deamination of amino acids (from proteins);
b. i) ultra filtration;
ii) Selective reabsorption;

Comments

Describe how the mammalian heart is structurally adapted to its function.

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP2QN08

Describe how the mammalian heart is structurally adapted to its function.

answers

Cardiac muscles which contract and relax continually without fatigue/myogenic
Cardiac muscles are interconnected / a synclination form of network of fibres to rapidly and uniformly spread the contractions
Divided into four chambers for Atria to receive blood and ventricles to pump blood out of the heart
Divided into two sides by a longitudinal septum to prevent mixing of oxygenated and deoxygenated blood / for double circulation
Ventricles have thicker walls to generate high prevention pressure to pump blood
Wall of the left ventricle is thicker than that of right ventricle to pump blood over a long distance.
Have valves to prevent back flow of blood
Cuspid valves have strands of connective tissues / tendinious codes / valve tendons to prevent turning in/out during systole / when ventricles contract
Has coronary artery to nourish / supply oxygen to the heart/muscles; has a coronary vein to remove metabolic wastes carbon(iv)oxide
Enclosed by a pericardium to keep it in position / prevent over dilation
Pericardium secretes pericardial fluid to reduce friction / absorbs shock
Has Sino Artrio Node (SAN) which acts as a pacemaker
Has Atrio Ventricular Node (AVN) which relays contraction waves from SAN to the puncinje tissues
Has puncinje tissue / bundle of HIS to relay waves from AVN to the ventricular myocardium
Cardiac muscles have numerous mitochondria to generate energy for the muscular contractions
Has venacava and pulmonary vein to supply blood to the heart.
Has aorta and pulmonary artery to transport blood away from the heart.

Comments

Name the opening to the chamber of the heart of an insect.

30/6/2020

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K.C.S.E Biology Q & A - MODEL 2016PP1QN27

Name the opening to the chamber of the heart of an insect.

answer

Ostium

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Name an organism which has a single circulatory system.

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN27

Name an organism which has a single circulatory system.

answer

Fish

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What is single circulatory system?

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN27

What is single circulatory system?

answer

Blood goes through the heart once in very complete circulation

Comments

State three functions of blood other than transport.

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN04

State three functions of blood other than transport.

answers

Regulation of the body temperature
Regulation of pH of fluids
Defense against disease – causing organism/ pathogens/ infection.
Prevent excessive bleeding by enhancing clotting/ prevent excessive loss of blood

Comments

Name one defect of the circulatory system in humans

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN04

Name one defect of the circulatory system in humans.

answers

Thrombosis/Varicose veins/Arterion sclerosis/ Antheroma
Antherosclerosis
cerebral vascular thrombosis

Comments

State two ways in which the muscles of the mammalian heart are special.

29/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN01

State two ways in which the muscles of the mammalian heart are special.

ANSWERS

Muscles are myogenic - able to initiate their own concentration.
Presence of intercalated discs hence Interconnencted.
Can contract continuously without fatigue.

Comments

How is a mammalian heart structurally adapted to its function?

29/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2015PP2QN08

How is a mammalian heart structurally adapted to its function?

ANSWERS

Has cardiac muscles; which contract and relax continuously/without fatigue;
Cardiac muscles are interconnected/form a network of fibres; to rapidly and uniformly spread the contractions;
Divided into four chambers; for the atria to receive blood and ventrical to pump blood out of the heart.
Divided into two sides by a longitudinal septum; to prevent mixing of oxygenated and deoxygenated blood;
Ventricles have thicker walls; to generate high pressure to pump blood;
Wall of left ventricle are thicker than those of right ventricle; to pump blood over a longer distance;
Has valves; to prevent back flow of blood for double circulation;
Cuspid valves have strands of connective tissues/cordaetandinae/tendinous; to prevent the valves from turning inside out during systole when ventricles contract;
Has coronary artery to nourish/supply oxygen/nutrients the heart muscles;
Has coronary vein; to remove metabolic wastes;
Enclosed by a pericardium; to keep it in position/prevent overdilation;
Pericardium is externally surrounded with a layer of fats; to cushion the heart against mechanical damage;
Pericardium secretes pericardial fluid; to reduce friction/absorb shock;
Has Sino Atrio Node (SAN); which acts as a pace maker;
Has Atrio Ventricular Node (AVN); which relays contraction waves from Sino Atrio Node to the purkinje tissue;
Has purkinje tissue/bundle of RS; to relay waves from Atrio Ventricular Node; to the ventricular myocardium;
Cardiac muscles have numerous mitochondria; to generate energy for the muscular contractions;
Vena cava and pulmonary vein; supply blood to the heart;
Aorta and pulmonary artery; transport blood away from the heart.

Comments

K.C.S.E Biology Q & A - MODEL 2015PP1QN03

29/6/2020

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K.C.S.E Biology Q & A - MODEL 2015PP1QN03

.An individual is of blood group B positive.
(a) Name the antigens in the individual’s blood.
(b) Give the reason why the individual cannot receive blood from a blood group A donor.

answers

(a) (Antigen) B; Rhesus (antigen)/Rhesus factor/Antigen D
(b) Has antibody a in the blood plasma of the recipient and will correspond with antigen A in the donor’s blood, hence there will be antigen antibody reaction/agglutination.

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K.C.S.E Biology Q & A - MODEL 2014PP2QN02

28/6/2020

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K.C.S.E Biology Q & A - MODEL 2014PP2QN02

The diagram below illustrates the role played by red blood cells in the transportation of carbon (1V) oxide.

(a) Other than the carbon (IV) oxide transportation in the red blood cells, name the other form of carbon (1V) oxide transportation in humans.
(b) (i) Name substance F
(ii) Name the enzyme marked C and state its role in the reaction.
Enzyme
Role
(c) Explain why transportation of carbon (1V) oxide in red blood cells is advantageous.
(d) Explain the role of calcium ions in blood clotting.

ANSWERS

(a) Carbonic acid/carbaminohaemoglobin/hydrogen carbonate;
(b) (i) Water;
(ii) Carbonic acid;
Role: catalyses reaction between carbon IV oxide and water to form (weak) carbonic acid;
(c) Prevents accumulation of acidity/maintains pH of blood since hydrogen ions combine with haemoglobin to form Haemoglobin acids;
Faster; due to the catalytic effect of carbonic anhydrase;
(d) Activates thromboplastin; thrombokinase to neutralize heparin/convert prothrombin to thrombin;

Comments

K.C.S.E Biology Q & A - MODEL 2014PP1QN24

28/6/2020

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K.C.S.E Biology Q & A - MODEL 2014PP1QN24

The table provided shows the transportation of substances in the human body.

Name the substances represented by
M
N
P

ANSWERS

M - lungs;
N - Urea, ammonia. ;
P - Digested food. water; mineral ions;

Comments

Describe the process of blood clotting in human beings.

28/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2013PP2QN07

Describe the process of blood clotting in human beings.

ANSWERS

When a blood vessel is cut/injured platelets/thrombocytes/damaged tissue/wound is exposed to the air: they release thrombokinase/thromboplastin ; an enzyme that activates the conversion of prothrombin: to thrombin: in the presence of calcium ions: vitamin K/ phylloquinone ; is needed for the formation of prothrombin; Thrombin converts (soluble blood protein) fibrinogen ; into (the fibrous form) fibrin; which forms a mesh / network across the wound: The clot so formed prevents excessive bleeding: and entry of disease agents/pathogens/micro-organisms/microbes;

Comments

Explain three protective functions of mammalian blood.

26/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2013PP1QN24

Explain three protective functions of mammalian blood.

answers

Contains antibodies that defend the body from foreign antigens;
Has white blood cells that produce antibodies/while blood cells engulf antigens;
Has platelets that initiate blood clotting to prevent excessive bleeding at an open wound prevent entry of pathogens;

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Explain why a bony fish dies shortly after being removed from water.

Explain why a bony fish dies shortly after being removed from water.

K.C.S.E Biology Q & A - MODEL 2017PP1QN19

K.C.S.E Biology Q & A - MODEL 2017PP1QN19

Describe how the mammalian heart is structurally adapted to its function.

Describe how the mammalian heart is structurally adapted to its function.

Name the opening to the chamber of the heart of an insect.

Name the opening to the chamber of the heart of an insect.

Name an organism which has a single circulatory system.

Name an organism which has a single circulatory system.

What is single circulatory system?

What is single circulatory system?

State three functions of blood other than transport.

State three functions of blood other than transport.

Name one defect of the circulatory system in humans

Name one defect of the circulatory system in humans.

State two ways in which the muscles of the mammalian heart are special.

State two ways in which the muscles of the mammalian heart are special.

How is a mammalian heart structurally adapted to its function?

How is a mammalian heart structurally adapted to its function?

K.C.S.E Biology Q & A - MODEL 2015PP1QN03

K.C.S.E Biology Q & A - MODEL 2015PP1QN03

K.C.S.E Biology Q & A - MODEL 2014PP2QN02

K.C.S.E Biology Q & A - MODEL 2014PP2QN02

K.C.S.E Biology Q & A - MODEL 2014PP1QN24

K.C.S.E Biology Q & A - MODEL 2014PP1QN24

Describe the process of blood clotting in human beings.

Describe the process of blood clotting in human beings.

Explain three protective functions of mammalian blood.

Explain three protective functions of mammalian blood.

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