(i)

Function of labelled parts

I → Carries blood from the heart/left ventricle to the circulatory system
II → Brings (oxygenated) blood from lungs to heart/left auricle/atrium
IX → Brings (deoxygenated) blood from the body to heart/right atrium/right side of heart
X → Carry (oxygen deficient) blood from heart to lungs/right side of heart/right ventricle to lungs

(ii)

Why the left lower part of the heart has a thicker muscle

Contracts to pump (oxygenated) blood with high pressure to all parts of the body

OR

To generate high pressure to allow blood to reach all parts of the body

(iii)

Ways by which the flow of blood to and from the mammalian heart can be kept at acceptable levels

1. Exercising
2. Not smoking
3. Taking iron rich foods/balanced diet
4. Regulating one's blood pressure
5. Stress management
6. Get enough sleep
7. Healthy weight
8. Limit alcohol consumption
9. Manage diabetes
10. Regular health check-up

(iv)

Parts of the heart where oxygenated blood can be found

1. Aorta
2. Pulmonary vein
3. Left atrium
4. Left ventricle

(i)

How P (Maize grains) is planted on seedbed

1. Make holes (using cutlas or stick/dibber)
2. Place 2 or 3 seeds per hole and cover with soil

How Q (Tomato seedlings) is planted on seedbed

1. Remove a plant seedling from a nursery gently
2. Place the seedling in a prepared hole
3. Firm the soil around the seedling with hands
4. Water immediately

How R (Cassava cuttings) is planted on seedbed

1. Dig a hole/loosen the soil/dig trenches
2. Turn the cutting with the nodes/buds facing upwards
3. Place (two thrifts of) cutting into the hole
4. Firm soil around the cutting

(ii)

Conditions under which R(Cassava cuttings) can be cultivated to produce high yield

1. Adequate rainfall/water/irrigation
2. Fertile soil
3. Soil with good structure
4. Absence of diseases
5. Absence of pests
6. Sunlight

(i)

Function of labelled parts

I → Converts chemical energy to electrical energy/generates voltage
II → Closes and opens circuit/allows charges to flow or not flow
III → Stores electric charges
IV → Opposes flow of charges/current

(ii)

V = IR

R = $\frac{\mathrm{V}}{\mathrm{I}}$

Voltage (V) = 2.4 V

Current (I) = 0.8 A

Resistance (R) = $\frac{\mathrm{2.4\; V}}{\mathrm{0.8\; A}}$ = 3 Ω

Note: Mark is deducted for answer without a unit (Ω)

(iii)

Way of conserving the value of the part labelled I (Cell/Battery) in the circuit

Open key/switch when not taking readings.

(iv)

Observations that can be made when the circuit is closed

1. Ammeter will read/deflect
2. Voltmeter will read/deflect

(i)

Description of the process of the experiment

1. Make the set-up as shown in the diagram
2. Put two immiscible liquids into the separating funnel/I
3. Allow the mixture to stand
4. And separate into two layers
5. Open the tap to drain the liquid at the bottom into the conical flask/III
6. Close the tap after draining the liquid at the bottom

Note: the steps must be in sequence. When sequence is broken, marking is stopped.

(ii)

Function of the labelled parts

II → Regulate/control of the flow of liquid
IV → To hold the separating funnel

(iii)

Precautions that should be taken to obtain reliable results when performing this experiment

1. The tap should be opened gently to release only the bottom liquid
2. The retort stand should be firm enough to hold the separating funnel
3. The mixture should be left to stand for sometime to settle and separate
4. The retort stand should be placed on a flat surface

(i)

How a shadow can be formed

(ii)

Change in volume = (75 - 50) cm³ = 25 cm³

Density = $\frac{\mathrm{Mass}}{\mathrm{Volume}}$

Method I

Calculating density in kg dm^-3

Note: when using the mass in kilogram (4 kg) the volume must be in dm³.

25 cm³ = $\frac{25}{1000}$ = 0.025 dm³

Density = $\frac{4}{0.025}$ = 160 kg dm^-3 or 160 kg/dm³

Method II

Calculating density in g cm^-3

Note: when expressing the density in g cm^-3, the kilogram must be changed to gram.

4 kg = 4 x 1000 g = 4000 g

Density = $\frac{4000}{25}$ = 160 g cm^-3 or 160 g/cm³

Note: Mark is deducted for answer without correct unit

(iii)

Precautions that must be taken to obtain reliable results

1. The object should be dropped gently to avoid splashing the water
2. The volume should be read at the correct meniscus

(i)

Composting

1. Microorganisms in organic matter make use of oxygen
2. and decompose/breakdown organic matter into nutrients

(ii)

Recycling

1. Involves processing/conversion/physically and chemically changing waste materials
2. Into new products

(iii)

Incineration

1. Involves burning of waste materials at high temperatures
2. and converting them into gas/ash to destroy contaminants

(i)

(ii)

Reasons for the sequence

1. Break in disease cycle
2. Return of nutrients to the soil
3. Break in pest cycle
4. Weed control
5. Cowpea is leguminous, so it fixes nitrogen, planted second
6. Cassava is deep rooted crop and must be followed by shallow rooted crops

(i)

Symptoms of COVID-19

1. Fever
2. Persistent cough
3. Loss of appetite
4. Loss of taste
5. Loss of smell
6. Shortness of breath/lack of breath
7. Dizziness
8. Chills
9. Sore throat
10. Aching of muscles
11. Heavy arms or legs
12. Fatique/tiredness
13. Sneezing
14. Headache
15. Sore throat

(ii)

Ways to prevent the spread of COVID-19

1. Keep physical/social distance
2. Clean/wash hands frequently with soap
3. Cover mouth/nose when coughing
4. Wearing a properly fitted mask
5. Vaccination
6. Use of sanitizer
7. Avoid hand shake/hugging

(iii)

Reasons why COVID-19 was declared as a pandemic

1. It caused a large social disruption - no funerals, no weddings, etc
2. It spread to a large part of the world
3. It killed a lot of people
4. The virus has ability to mutate regularly

(i)

Acceleratin = $\frac{\mathrm{Final\; velocity\; (v)\; -\; Initial\; velocity\; (u)}}{\mathrm{Time}}$

Final velocity = 150 ms^-1

Initial velocity = 100 ms^-1

Time = 10 s

Acceleratin = $\frac{\mathrm{150\; -\; 100}}{10}$ = 5 m^-2

(ii)

Force = Mass x Acceleration

Mass = 1000 kg

Acceleration = 5 ms^-2

Force = 1000 x 5 = 5000 N

(iii)

Momentum = Mass x Velocity

When the vehicle comes to a stop, the velocity is 0

Final momentum = 1000 x 0 = 0

(i)

Light emitting diode (LED) is a device that emits light when an electric current is passed through it.

(ii)

Devices that use LED in their operation

1. Traffic lights
2. Smart phone screens
3. Aviation lights
4. Digital watch

(i)

Tools that could be used in the raised nursery bed preparation

1. Rake
2. Hoe
3. Shovel
4. Garden fork/digging fork
5. Watering can

(ii)

Function of the tools

1. Rake → For levelling the soil
2. Hoe → For digging/gathering/weeding
3. Shovel → For scooping/fetching/moving soil
4. Garden fork/digging fork → For digging/levelling/breaking lumps
5. Watering can → For watering

(i)

Observable features of an animal cell

1. Mitochondrion
2. Cytoplasm
3. Nuclear membrane
4. Lysosome
5. Irregular shape

(ii)

Functions of a nerve cell

1. Release chemical regulators
2. Respond to physical and chemical stimuli
3. Transmits electrical impulses/messages

(i)

$\frac{1}{{\mathrm{R}}_{\mathrm{T}}}$ = $\frac{1}{{\mathrm{R}}_1}$ + $\frac{1}{{\mathrm{R}}_2}$

$\frac{1}{{\mathrm{R}}_{\mathrm{T}}}$ = $\frac{1}{4}$ + $\frac{1}{5}$

$\frac{1}{{\mathrm{R}}_{\mathrm{T}}}$ = $\frac{\mathrm{5\; x\; 1\; +\; 4\; x\; 1}}{20}$

$\frac{1}{{\mathrm{R}}_{\mathrm{T}}}$ = $\frac{\mathrm{5\; +\; 4}}{20}$

$\frac{1}{{\mathrm{R}}_{\mathrm{T}}}$ = $\frac{9}{20}$

Cross multiply.

R_T x 9 = 1 x 20

Divide both sides by 9

R_T = $\frac{20}{9}$ Ω or 2$\frac{2}{9}$ Ω or 2.2 Ω

Note: mark is deducted for answer without unit (Ω)

(ii)

Voltage (V) = Current (I) x Resistance (R)

Voltage (V) = 6V

Resistance (R) = $\frac{20}{9}$ Ω

6 = I x $\frac{20}{9}$

Multiply both sides by the denominator 9

6 x 9 = 20 x I

Divide both sides by 20

I = $\frac{\mathrm{6\; x\; 9}}{20}$ = $\frac{27}{10}$ = 2.7 A

Note: Mark is deducted for answer without or incorrect unit.

(i)

Distinction between organic fertilizer and inorganic fertilizer

Organic fertilizers are derived from natural sources/plants and animals whereas inorganic fertilizers are manufactured artificially from physical and chemical processes.

(ii)

Steps involved in preparing raised beds

1. Clearing of vegetation/weeds
2. Digging/loosening of top soil
3. Digging a path/furrow round the bed area
4. Breaking large lumps
5. Removing roots and stones
6. Shape the bed into size and firm the edges/Build the frame
7. Rake to level the surface of the bed
8. Water the bed

(i)

Function of the components of blod:

(ii)

Impact of organisms on humans: