BIOLOGY FORM 3 END TERM EXAMS PLUS ANSWERS IN PDF

Citizen digital | April 24, 2024 | Teachers' Resources | No Comments

Name____________________________________Class_______________AdmNo:__________

Date__________________________________________Sign_______________

END OF TERM EXAMINATION

FORM THREE

BIOLOGY

TIME: 2 HOURS

INSTRUCTION TO THE CANDIDATES.

Write your name and admission number in the spaces provided
Sign and write the date of examination in the spaces provided
Answer all questions in section A and In section C, answer questions 11 (compulsory) and either 12 or 13 in the spaces provided.
Answer all the questions in the spaces provided.
Candidates should answer all the questions in English.

FOR EXAMINERS USE ONLY

Question/section	Maximum score	Candidates score
Section A	40
Section B	40
Total score	80

SECTION A: (34MKS)

Answer all the questions

a) What is transpiration 1mk

………………………………………………………………………………………………………………………………………………………………………………………………………………………………

b) Give the importance of transpiration in green plants 3mks

Name three mechanisms that hinder self-fertilization in green plants 3mks

Name two classes of phylum Arthropoda that has cephalothorax 2mks

a) Give two roles of testes in humans 2mks

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

b) Name two organs that produce the hormone progesterone in female 2mks

a) Give two reasons why an electron microscope cannot be used to view live specimens 2mks

b) State the function of eye piece tube in a light microscope 1mk

Name the organelle that is involved in each of the following 2mks

manufacture of lipids

…………………………………………………………………………………….

formation of lysosomes

………………………………………………………………………………………………………………

Process X

Large fat droplets small fat droplets

a) Name process X 1mk

………………………………………………………………………………………………………………………

State the significance of the process named above 2mks

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

State the use of the following apparatus used in collection of specimens. 3mks

pooter…………………………………………………………………………………………………………………………………………………………………………………………………………..
Baittrap

……………………………………………………………………………………………………………………………………………………………………………………………………..

Fishnet

……………………………………………………………………………………………………………………………………………………………………………………………………………………

The diagram below shows how gaseous exchange occurs across the gills of a fish

According to the diagram, water and blood flows in opposite directions across the gills
Give the term used to describe the flow 1mk

……………………………………………………………………………………..

Explain the advantage of the flow named above 2mks

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………..

What difference would be observed if water and blood flowed across the gills in the same direction 2mks

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….. ………………………………………………………

Name two organs in man which displays the flow system named in a) i) above 2mks

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

How are the gill rakers found in the gills of a fish adapted to perform their function 1mk

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

The temperature of a person was taken before during and after bath. The results are shown in the graph below

36 Before after

Temps during

Time in minutes

Explain why the temperature decreased during the bath 3mks

What changes occurred in the skin that enabled the body temperatures to return back to normal .4mks

Name the specific part of human brain that controls body temperature 1mk

………………………………………………………………………………………………..

SECTION B : Answer question 11(compulsory) and either Question 12 or 13.

In an experiment, a mixture of starch and salivary amylase solution was uniformly mixed in a beaker. 5ml of the mixture was drawn using a syringe and transferred into a visking tubing after which both ends were tightly tied ensuring there is no leakages. Six such viskingtubings were prepared. They were rinsed with distilled water on the outside then transferred at once to water bath maintained at 37⁰c in a beaker. From time 0 and every 5 minutes interval, one visking tubing was removed from the water bath and analyzed for starch. At the same time, the contents of the water bath in the beaker were also analyzed for reducing sugars for each time intervals.

The table below shows the results

Timer in minutes	Concentration of the food substances
	Starch in the visking tubing mg\L	Simple sugars in the beaker mg/L
0	100	0
5	92	8
10	66	34
15	36	64
20	16	84
25	8	88

Using a suitable scale represent the data on the grid provided below 8mks

At what time was there an equal concentration of starch and simple sugars 1mk

…………………………………………………………………………………….

Using the graph paper indicate the times when the concentrations of starch and simple sugars were 70mg/L 2mks

………………………………………………………………………………………………………………………………………………………………………………………………………………

Why was the temperature maintained at 37⁰c 2mks

Name the enzyme that was used in the experiment 1mk

……………………………………………………………………….……………………………

State and explain the results that will be observed if the water in the beaker was tested for starch 3mks

What are the digestive roles of saliva in the mouth 3mks

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

a) Describe the structural features of the leaves that decreases the rate of transpiration in plants 10mks

b) Describe the mechanism of transport of carbon IV oxide in the mammalian blood 10mks
a) What is pollution 2mks
b) Describe various causes and effects of air pollution and for each cause state its control method

18mks

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

EXAM MARKING SCHEME

231/1

MARKING SCHEME

a) transpiration is the process by which plants lose water inform of water vapor to the atmosphere through the stomata or lenticels.
b)

brings about turgor in plants
helps to remove excess water especially to the aquatic plants
serves to cool plants in hot environment
helps in transport of mineral salts/ions and water in the plant

protandry
progyny
heterostyly
monoecious/ dioecius
incompatibility/self sterility

arachnida
crustacea

secretion of androgens/testosterone rej. Hormone
manufacture of sperms/male gametes rej. Gamete alone

ovary
placenta

specimen is mounted in a vacuum
specimen is illuminated by beam of electrons which would kill cells
dyes used are obtained from heavy metals which are toxic to cells

hold the eye piece lens( in position)

a) smooth endoplasmic reticulum
b) golgi bodies /apparatus
a) emulsification
b) used to increase surface area for enzymatic activity
a) used for sucking small animals from rock surfaces or bark of trees eg ants
b) for attracting and trapping small animals eg rats
c) used for trapping small fish and other small aquatic aninmalseg crabs
a) i) counter current flow
ii) it maintains a steep concentration gradient hence increases the efficiency of oxygenation of the blood as well as diffusion of carbon iv oxide from the blood to water,.
b) the diffusion gradient would be low leading to low rate of gaseous exchange; equilibrium between water and blood would be reached ; beyond which no further diffusion can take pklace
c)

kidney/ nephron
placenta

d) its rake like/ saw like/teeth like to trap solid particles (which may damage delicate gills filaments)
a) heat was lost by conduction/ convection fro the body/skin to cold water; the cooler blood leaving the skin enter the general circulation cooling the body
b)

vasocontriction thus less blood flowing to the skin surface reducing heat loss;
sweating stops
shivering

c) hypothalamus

11.a) plotting – 2mks

Scale – 2mks

Labelling- 1mk

Identifying curves- 2mks

Curve -1mk

b) i) 12.5min ± 0.5
ii) starch; 16min ± 5

reducing 9.5 min ± 0.5

iii) to provide a suitable optimum temperature for the activity of the enzymes

c) amylase( salivary/pancreatic) ; diastase
d) brown color of iodine is retained; because starch is still absent; the starch molecules are too larhe and cannot pass through the tiny poress of the visking tubing membrane into the water in the beaker

OWTTE

e) saliva contains salivary amylase ; that breaks down starch into maltose; and bicarbonate ions that provides a suitable alkaline ph for the activity of salivary amylase during digestion

12 a)

Leaves are modified into spines/ thorns ; to reduce surface are over which transpiration can occur
Shed their leaves during dry seasons; to reduce surface area exposed to the atmosphere
Leaves have thick waxy cuticle; to minimize rate of cuticular transpiration
Some of leaves with hinge cells hence can roll or fold to reduce rate of transpiration by exposing fewer stomata to the environment hence reducing chances of transpiration
Have sunken stomata which accumulates moisture in substomatal spaces hence low diffusion gradient thus reducing transpiration rate
Have reduced number of stomata hence low rate of transpiration since the surface area for water loss is reduced
Some have reversed stomatal rhythm to prevent excessive water loss by transpiration
Have parenchyma cell in swollen leaves for storage of water eg cactus

b)
i) a weak carbonic acid in the red blood cells/ bicarbonate ions;

carbon iv oxide on entering the red blood cells reacts with water forming carbonic acid; this process is usually enhanced by catalytic activity of enzyme carbonic anhydrase in the red blood cells; being unstable, the carbonic acid dissociates to hydrogen ions and bicarbonate ions; which acts as buffer; the bicarbonate ions diffuses into the blood plasma and transported to the lungs; on reaching the lungs, they undergo chemical processes(accept explanation of the process) resulting to the formation of the carbon iv oxide which is then exhaled

ii) when physically dissolved in plasma/ weak carbonic acid in blood plasma

carbon iv oxide is transported when physically dissolved in plasma to form a weak carbonic acid; the weak carbonic acid being unstable, dissociates to form hydrogen ions bicarbonate ions/ hydrogen carbonate ions; the hydrogen carbonate ions are transported to the lungs ; where they dissociates to water and carbon iv oxide ; from where carbon iv oxide is exhaled; the hydrogen ions remains in the blood plasma and are mainly secteted into the kidney tubules for excretion when in excess; this method is slow and hence inefficient

iii. when bound to haemoglobin in red blood cells

carbon iv oxide binds to the haemoglobin to form carbominohaemoglobin; being somewhat stable it does not dissociate and carbon iv oxide is transported in thuis form from tissues to lungs; because of high partial pressure of oxygen in the lungs the haemoglobin detaches from the carbon iv oxide; and picks up oxygen; the free carbon iv oxide is then exhaled out of the body .

a) pollution is the release of substance or forms of energy; in quantities whose effect is harmful or unpleasant to organisms
b) Sulphur based chemicals( Sulphur iv oxide, hydrogen sulphide)

produced by industries, decomposing organic matter and fumes; affects gaseous exchange ; makes acidic rain and damage leaves affecting photosyntheasis

control method– titration, dissolution and use of chemicals to remove harmful gases

smoke and fumes ; produced in areas with heavy industries, motorvehicles and contain carbon ii oxide; carbon ii oxide combines with haemoglobin to form stable carboxyhaemoglobin which is a respiratory poison; affects visibility;

control– factories should be erected far away from residential areas

dust– produced from cement, gfactories and quarries; it settles on leaves limiting photosynthesis and causes poor visibility

control– government to enact laws on environmental pollution

sound/ noise– produced by machines aeroplanes and heavy vehicles and affects heasring in animals

control– ear muffs should be used in industries and jua kali workshops that generates noise

aerosols– consist of fire particles, suspended gases in hebicides, insecticides and sprays; they contain copper metal- when copper is inhaled causes irritation and respiratory diseases, depletion of ozone layer and its non- biodegradable

control– used biological methods of pests control

oxides of nitrogen( nitrogen ii oxide, nitrogen iv oxide)

produced from burning petroleum fules and industries

nitrogencmpounds dissolves in rain water to form acidic rain , its carcinogenic; causes poor visibility on road users

control – use of public means of transport