BOOK LIST 2020/2021 LOWER AND UPPER SIXTH SCIENCE

 

SUBJECTS

TITLES

AUTHORS

PUBLISHERS

Exercise Books

1

PURE MATHEMATICS

Explaining Pure Mathematics for A/L

ATANGA N.

NAARAT

300 register

2

FURTHER MATHEMATICS

An Intergrated Core Approach

PLANKEH A.

QUALITY PRINTERS

300 register

3

MECHANICS

A/L Mechanics and Probability

ATANGA N.

NAARAT

300 register

4

FURTHER MECHANICS

An Intergrated Core Approach

PLANKEH A.

QUALITY PRINTERS

200 register

5

PHYSICS

New-Look Advanced Physics

KIMAL Honour

NMI

500 ledger

6

CHEMISTRY

Advanced Chemistry

Philip MATHEWS

CAMBRIDGE

500 ledger

7

BIOLOGY

Biology Science 1 and 2

D.J. TAYLOR

CAMBRIDGE

500 ledger

8

STATISTICS

Explaining A/Level Statistics

ATANGA N.

NAARAT

200 ledger

9

ICT

Fundamentals of ICT

NKAMENEI Denis

QUQLITY PRINT

200 ledger

NEW LESSONS WEEK BEGINNING 13/04 TO 31/05/2020

2019 P2 Physics.pdf - CLICK THIE LINK BELOW
https://drive.google.com/file/d/10Kc1yMK3aioAsl4RqoOVgYhoLkAGgdn_/view
 

PAST QUESTIONS FOR GCE MATHS. FROM 2000 TO 2019 O and A LEVELS CLICK THE LINK BELOW TO HAVE ACCESS ( If any issues to open, please go to DOCUMENT page at the top right hand side or contact us through site .

https://cameroongcerevision.com/a-level/cameroon-gce-questions-mathematics-a-level/
 
http://cameroongcerevision.com/a-level/cameroon-gce-questions-mathematics-a-level/

PAST QUESTIONS FOR GCE CHEMISTRY FROM 2000 TO 2019 O and A LEVELS CLICK THE LINK BELOW TO HAVE ACCESS ( If any issues to open, please go to DOCUMENT page at the top right hand side or contact us through site mail)http://cameroongcerevision.com/o-level/cameroon-gce-questions-o-level-chemistry/

Name:  Penn Emile Nkeng

Class:  upper sixth scence GEOLOGY (23/04)

A hazard is an agent which has the potential to cause harm to a vulnerable target. Hazards can be both natural and human induced. A hazard is any agent that can cause harm or damage to humans, property, or the environment. Risk is defined as the probability that exposure to a hazard will lead to a negative consequence, or more simply, a hazard poses no risk if there is no exposure to that hazard. Natural hazards continue to pose a major threat to the entire world with prospects of even greater impacts to life and property in the future (Aini & Fakhrul-Razi 2010, Hayles 2010).

FLOODS
Flooding is as an overflowing by water of the normal confines of a stream or other body of water, or accumulation of water by drainage over areas that are not normally submerged. A flood occurs when water inundates land that's normally dry, which can happen in a multitude of ways.

Types and Causes of floods


CAUSES OF FLOODING (Triggering Mechanisms of Floods)

  These different types of flooding can be caused by the following factors;

  • Rain: When there is more rain than the drainage system can take there can be floods. Sometimes heavy rains for a very short period result in floods and light rains for many days and weeks can result in floods.
  • Dam failure: A dam triggered by an earthquake would result in flooding of the downstream
  • Strong winds in coastal areas: sea water can be carried by massive winds in hurricanes onto dry coastal lands and cause flooding. Sometimes it is made worst if the winds carry the rain themselves
  • Steep sided channels: A river channel surrounded by steep slopes causes fast surface runoff into the streams which then intend lead to rapid over flooding of the banks as floods.
  • Vegetation: The presence of woodland or vegetation increases the infiltration rate of surface water and also reduces the rate of surface runoff into streams. Thus the absence of it increases the probability of flooding to occur.
  • Drainage basins in an urban area consist largely of impermeable concrete, which encourages overland flow.  Drains and sewers take water quickly and directly to the river channel.
  • Blockages in river channels
  • Population pressure as increasing number of people, especially the poor, is settling in flood-prone areas.
  • Excessive levels of precipitation, melting of ices or a combination of these two are the major causes of river floods.
  • Tsunamis produced by earthquakes, and river ponding behind natural damps caused by mass movement and glacial advances can also result in flooding

EFFECTS OF FLOODING

  • Floodwater can seriously disrupt public and personal transport by cutting off roads and railway lines, as well as communication links when telephone lines are damaged.
  • Floods disrupt normal drainage systems in cities, and sewage spills are common, which represents a serious health hazard, along with standing water and wet materials in the home.
  • Bacteria, mould and viruses, cause disease, trigger allergic reactions, and continue to damage materials long after a flood.
  •  Floods can distribute large amounts of water and suspended sediment over vast areas, restocking valuable soil nutrients to agricultural lands.
  •  In contrast, soil can be eroded by large amounts of fast flowing water, ruining crops, destroying agricultural land / buildings and drowning farm animals.
  • Unfortunately, flooding not only disrupts many people’s lives each year, but it frequently creates personal tragedies when people are swept away and drowned.

FLOOD MONITORING

RADAR

 Radar estimation of rainfall is widely used and is not strictly “emerging”. Radar provides
an aerial indication of rainfall, and so provides a better distributed measurement than from point
rain gauge measurements, with the output lending itself well to use in grid based models.
There are a number of limitations in measurement accuracy such as range, attenuation of
signal and calibration, but second-generation radar instruments, particularly Doppler radars,
have overcome some of the attenuation problems. Smaller radar instruments (C and X-band
radars), sometimes portable, are useful for local monitoring, especially in urban areas.

 SATELLITE

Currently 28 space agencies along with 20 other national and international organizations participate in CEOS (Committee on Earth Observation Satellites) planning and activities. The NASA satellite monitoring Programme produces both real-time and research-merged 3-hour global precipitation products available on an ftp server for public access. However, this service requires considerable resources to support ground validation sites and research. Rainfall estimation from geostationary satellite platforms uses infra-red (IR) sensing based on the relationship between cloud-top growth and surface precipitation, and is best for convective rainfall.

                 PREVENTION AND MITIGATION OF FLOODING

Floods prevention and mitigation involves the management and control of flood water movement such; as reducing flood runoff through the use of flood walls and flood gates. It also involves the management of people through measures such as excavation and dry/wet proofing properties. 

MITIGATION

It can be studied in three levels

  1. Creation of a flood risk map and emergency communication plans. Flood risk maps would stipulate areas which are unsafe for habitation hence reducing the amount of property and life that would be lost to flooding. Emergency communication plans would warn the population in the floodplain in time to reduce the loss of life.
  2. Individual properties; property owners may fit their homes to stop water from entering the house. Personal flood plans may involve blocking doors and air vents, water proofing important areas and sandbagging the edges of the building.
  3. Protection of communities; when more homes, shops and infrastructures are threatened by the effects of flooding, rivers running through large urban developments are often controlled and channeled. This defense can be done by raising the edge of the water with levees, embankments or walls.

METHODS OF FLOOD PREVENTION

  1. Sea/coastal defense walls; sea walls and tide gates have been built in some places to prevent tidal waves from pushing the waters up a shore. In  some areas sandbags are made and placed in strategic areas to retain flood waters
  2. Retaining walls; retaining walls, levees, lakes, dams, reservoirs or retention ponds having been constructed to hold extra water during times of flooding.
  3. Town planning; it is important for builders to acquire permission before buildings are erected. This will ensure that water ways are not blocked. Also drainage systems most be covered and kept free from objects that may choke them. This way water can easily run through if it rains and minimize any chance of town flooding. Drainage systems should be covered to prevent litter from getting into them.
  4. Education; in many developing countries drainage systems are choked with litter and people having little knowledge of the effects that it can have during a rain. When it rains finds its way into streets and into people’s homes. Educating people on this aspect will reduce the probability of floods occurring hence saving property and lives.
  5. Detention basin; small reservoirs built and connected to water ways. They provide temporary storage or flood waters. This means in an event of flooding water is drained into the basin first giving people more time to evacuate. It can also reduce the magnitude of down slope flooding.
  6. Vegetation; trees, shrubs and grass help to protect the land from erosion by moving water. People in low lying areas must be encouraged to use a lot of vegetation to help the power of moving flood water and also help to reduce erosion.
  7. Avoid living in flood prone areas.
  8. Filling of bags with gravels along flooded areas.

Earthquakes

Earthquakes can be defined as sudden movement of the earth caused by the abrupt release of accumulated strain along a fault in the interior of the earth. The released energy passes through the earth as seismic waves (low frequency sound waves) which cause the shaking. Earth quakes are one of the most destructive natural hazards. Unlike volcanoes that occur only at certain plate margins, earth quakes occur in all plate margins. Similar to intraplate volcanism (hot spot), earth quakes also occur within plates as a result of reactivation of faults.

Spatial distribution of earth quakes in Cameroon

There are four main seismogenic zones in Cameroon (Noel et al., 2014).  The first zone is found in the south west of Cameroon (Mount Cameroon). This zone is related to volcanism, 94% of seismic events in Cameroon occur in this region. The maximum event has a magnitude of 4.4 (Noel et al., 2014). The second seismic zone is located north of mount Cameroon volcano and it is associated with central Cameroon shear zone (CCSZ). It has weak to moderate earth seismicity. The maximum magnitude recorded in this zone is 5.1(Noel et al., 2014). The third seismic zone is associated with the Sanaga fault zone. The focal depth here is 33km and the maximum magnitude of earth quake is 5.8 (figure2)

The fourth seismic zone is located at the northern boundary of the Congo craton. Focal depth of 33km has been registered and a maximum magnitude of 6(Noel et al., 2014)

They are three major types of earth quake; tectonic earth quake, volcanic earth quake and human induced earth quake.

1) Tectonic earth quake

Tectonic earth quake is caused by deformation of rocks within the earth’s crust. Faulting is the main mechanism through which tectonic earthquakes occur. The movements of lithospheric plates past one another are slowed by friction along plate boundaries. In so doing, stress builds up and rocks are strained and deformed. As the stress exceeds the strength of the rocks, the rocks rupture and produce faults (release energy contained within) hence generating earth quake. The rupture produces earth quake waves or seismic waves (elastic strain energy that propagate through the earth). The seismic waves travel through the earth surface and cause destruction of buildings and property damage.

2) Volcanic earth quake

Volcanic explosions caused by the escape of gas release elastic waves. These waves travel through the surface causing earth quake. Ascend of magma from the earth surface to the shallow magma chamber equally cause stress on the rocks resulting to earth quake.

3)  Human induced

There are human activities that can cause earth quake; loading the earth crust(building a dam and reservoir, waste disposal deep into the earth’s crust(disposal wells) underground nuclear explosions.

  1. Reservoir induced earth quake. The building of reservoir can initiate an earth quake. The water increases the load on the land and the increased water pressure on rocks below the reservoirs resulting in faulting and earth quake.
  2. Deep waste disposal wells

Disposal of liquid waste in deep wells result in faulting. For example in Denver Colorado an earth quake of magnitude 4.3 occurred as a result of disposal of liquid waste on tightly fractured metamorphic rocks. The liquid induced slippage along fractures causing earth quake.

  1. Nuclear explosions: a magnitude 5.0-6.3 earth quake occurred in Nevada Test site as a result of underground nuclear explosion. Equally, earth quakes are induced by hydraulic fracturing of rock during extraction of petroleum from reservoir rocks.

LANDSLIDES

A landslide occurs when part of a natural slope is unable to support its own weight. For example, soil material on a slope with slippery surface underneath, can become heavy with rainwater and slide down due to its increased weight.

A landslide is a downward or outward movement of soil, rock or vegetation, under the influence of gravity. This movement can occur in many ways. It can be a fall, topple, slide, spread or flow. The speed of the movement may range from very slow to rapid. The mass of moving material can destroy property along its path of movement and cause death to people and livestock. Although landslides usually occur at steep slopes, they may also occur in areas with low relief or slope gradient. Determination of causative factors of landslide in any given area will also help in demarcating the landslide prone zones.

TYPES OF LANDSLIDES AND SLOPE FAILURES:

  1. Slump: Type of slope failure in which a downward and outward rotational movement of rock or soil occurs along a curved concave up surface.
  2.  Debris fall: Free falling is not only rock but also overlying sediments and vegetation is known as debris fall.
  3. Creep: Imperceptibly slow downslope movement of earth cove or regolith. Utility poles, fence posts and gravestones etc. appear tilted or deformed on the surfaces where affected by creep.
  4. Debris Flow: Downslope movement of collapsed, unconsolidated material typically along a stream channel.

CAUSES OF LANDSLIDES

Many of the landslides are natural phenomenon that occurs independently of any human actions. There are also landslides that have been induced by the very actions taken to make land suitable for some human purposes. Landslides can be triggered due to external causes or internal causes.

External Causes
1. Undercutting of the foot of the hill slope due to river erosion, quarrying, excavation for canals and roads, etc.
2. External loads such as buildings, reservoirs, highway traffic, stockpiles of rocks, accumulation of alluvium on slopes, etc.
3. Increase in unit weight of slope material due to increased water content.
4. Vibrations due to earthquakes, blasting, traffic, etc., causing increase in shearing stresses.
5. Authropic changes caused by deforestation
6. Undermining caused by tunneling, collapse of underground caverns, seepage erosion, etc.
Internal Causes
1. Increase in pore water pressure.
2. Reduction in cohesive strength caused by progressive laterization.
3. Hair cracks due to alternate swelling and shrinkage from tension.
4. Presence of faults, joints, bedding planes, cleavage etc., and their orientation.
5. Freezing and thawing of rocks and soils.
6. Material properties such as compressive strength, shearing strength, etc., of earth
material.

TRIGGERING MECHANISM AND STRUCTURAL CONTROLE OF LANDSLIDE

Effect of Increase in Water Content

There is clear correlation between landslide activity and storms, as the saturation of earth material increases the pore water pressure. The addition of water to clay-bearing materials decrease cohesion and the angle of internal friction as well, leading to a decrease in shear strength (resisting force) and decrease in weight (driving force). Recurring landsides usually occurs in the years of high rainfall. Studies have shown that single short periods of heavy rainfall can trigger small landslides such as soil slips and debris flows, which affect only the near surface material. Deeper slides in unconsolidated materials will be triggered only by the cumulative effects of a series of storms. Bedrock slides appear to depend on the accumulation of precipitation over a long period of time during which precipitation consistently exceeds the average precipitation level for the region. A temporary rise in water pressure due to heavy rainfall in the material lying on the bedrock on a slope is sufficient to account for a decrease in strength, leading to debris slips and then debris flows.

Increase in Slope Gradient

Steeper the slope, greater is the chances of its failure. An increase in the steepness or gradient, of a slope leads to an increase in shear stress on the potential rupture plane and to a decrease in normal stress. Such increase in slope gradient may be due to undermining of the foot of the slope by stream erosion or by excavation. Exceptionally, the change of slope gradient may be produced by subsidence and upliftment of the earth’s surface.

Earthquake Vibrations

Vibration due to earthquakes not only triggers devastating landslides but also rock falls and the like. Earthquake shocks, particularly those of shorter duration, acceleration of ground motion, tilt of the slope, modifies the system of forces in a manner that driving forces get the upper hand. The vibrations generated by the vehicular traffic create oscillation of different frequency in rocks and they change the stress pattern, reducing shear strength and inducing mass movement.
 

Excess Load on the Slope

The addition of weight on the slopes like dumping of debris or wastes and the construction of dams, reservoirs, buildings, etc., increases the intensity of the driving force and reduces the slope stability.

Changes in Vegetation Cover
Vegetation helps in retaining the soil cover firmly. Trees with strong and long roots increase the cohesive strength and effectively hold the formations in to relatively weaker foundations increasing thereby the tensile and cohesive strength. However, surface growths of bushy plants promote greater seepage, which may lead to increasing pore pressure. In the absence of vegetal cover rainfall initiates, a set of process like rain slash erosion, sheet erosion and gully erosion, which ultimately results in to slope failure. The degree of effectiveness of the vegetation depends upon the condition of the soil, thickness of the overburden, slope, type of vegetation and climate.

  • MITIGATIVE MEASURES
    Certain steps can be taken to reduce the risk or damage from the landslides:
    ▪ Demarcating landslide prone areas and accordingly plan the future development activities.
    ▪ Reduce the slope angle.
    ▪ Place additional supporting material at the foot of the slope.
    ▪ Reduce the load on the slope (rock, soil or artificial structures).
    ▪ Stabilize near-surface soil by preferably fast growing plants with sturdy root system
    ▪ Build thick retaining walls at the toe of the slope (high thin walls have been less successful)
    ▪ Decrease the water content or pore pressure of the rock or soil;
    ▪ Driving of vertical piles into the foot of a shallow slide to hold the sliding block (on thin slides and on low angle slopes).
    ▪ Use of rock bolts to stabilize rocky slopes (on thin slide blocks of very coherent rocks
    on low angle slopes)
    Post-Landslide Measures

▪ Clear the blocked drainage channels.
▪ Clear the debries, especially the huge rock boulders and tree trunks on the slopes.
▪ Stabilise the depositional area (characterized by loose soil, small rock boulders, etc.) by fast growing trees/plants.

Tsunamis

Tsunamis are secondary effect of earthquakes. Tsunamis are long wave length, small amplitude waves in the deep ocean called shallow water waves and when shaol in the continental shelf increase the wave height tremendously to inflict savage destruction by inundating the coastline.

Tsunamis are caused primarily by displacement of seabed from submarine or coastal earthquakes. Tsunamis are principally generated by undersea shallow earthquakes of magnitudes greater than magnitudes of 6.5 on the Richter scale (Crawford, US Army) especially at plate boundaries such as divergent plate boundaries.

There is no record of tsunami occurrence in Cameroon and as such case studies are from the coasts of the Indian Ocean and the Pacific Ocean.

From case studies, tsunamis have distinctive characteristics that make them different from one another. Some of these characteristics are discussed below;

  • Tsunamis run up heights.
  • Tsunami inundation of water waves.
  • Tsunamis effects on population.
  • Type of deposits resulting from the hazard.

Tsunami preparedness

  • Coastal areas are more susceptible to destruction from tsunami inundation and run up heights. Thus design and construction of houses with respective codes of design are necessary in such areas.
  • Construction of houses in high risk inundation zones should be avoided and guideline for planning and design should be followed. Avoid new developments in tsunami run up areas.
  • Tsunami evacuation structures can be designed for evacuation of inhabitants when hydrophones signal tsunami waves.

Forest fires

A wildfire fire is an uncontrolled fire in an area of flammable vegetation that occurs in the countryside area. Reliant on the type of vegetation that is burned, a wildfire can also be classified as a brush fire, forest fire, desert fire, peat fire, grass fire, vegetation fire, or savannah fire.

Causes of forest fire

Causes of wildfire ignitions are natural and anthropogenic; lightning, sparks from rock falls, volcanic eruption and spontaneous combustion. The thousands of coal seam fires that are burning around the world, such as those in Centralia, Burning Mountain, and several coal-sustained fires in China, can also sparkle up and ignite nearby flammable material. The most common human sources of wildfires are firebombing, discarded cigarettes, sparks from equipment, and power line. Ignition of wild land fires by contact with hot rifle bullet fragments is possible under the right conditions.

Types of forest fires

  • Ground fires are fed by subterranean roots, duff and other buried organic matter. This fuel type is especially susceptible to ignition due to spotting. Ground fires typically burn by smoldering, and can burn slowly for days to months.
  • Crawling or surface fires are fueled by low-lying vegetation such as leaf and timber litter, debris, grass, and low-lying shrubbery.
  • Ladder fires consume material between low-level vegetation and tree canopies, such as small trees, downed logs,
  • Crown, canopy, or aerial fires burn suspended material at the canopy level, such as tall trees, vines. The ignition of a crown fire is dependent on the density of the suspended material, canopy height, canopy continuity, and sufficient surface and ladder fires, in order to reach the tree crowns.

Wildfire impacts on people, property and natural resources

  • Atmospheric pollution.
  • Smoke effects on public health in critical areas.
  • Disruption of air and ground transportation services by smoke can affecting private citizens, commercial and civil aviation and the Ministry of the Air Force.
  • Potential contributions to global climate change through the production of "greenhouse gases".
  • Reduction in water quality.
  • Disruption of electric power transmission.
  • Threats to life and property.
  • Loss of biological diversity.
  • Threats to commercial plantations of trees.
  • Networks of tracks, roads, fuel breaks, and buffer strips.
  • Supply systems for the use of water-enhancing agents such as foams.
  • Systems of regular fuel-condition assessment (models, ground observations, satellite data).
  • Systems for the assessment of fire behavior (models, ground observations, infra-red airborne systems).
  • Systems of assessment of weather conditions (models, ground measurements, radar, Satellite imagery).

Volcanic hazards

The principal products of volcanic products may be grouped into several broad categories according to the type of material ejected and its mode of transport from the vents to its place of deposition: ash falls, pyroclastic flows, lava flows, and gas emissions.

Lava Flow

Lava flows are streams of molten rock that pour or ooze from an erupting vent. Lava is erupted during either non explosive activity or explosive lava fountains. Lava flows are one of the most familiar products of volcanic activity. They result when magma reaches the surface and overflows the crater or a volcanic vent along the flanks of the volcano The speed at which lava moves across the ground depends on several factors including;

(1)  Type of lava erupted and its viscosity;

 (2) Steepness of the ground over which it travels;

(3) Whether the lava flows as a broad sheet, through a confined channel, or down a lava tube; and

 (4)  Rate of lava production at the vent.

EFFECTS OF LAVA FLOW

  • The biggest hazard of lava flows is that they destroy property.
  • Lava flows buried cars and burnt homes, buildings, and vegetation.
  • Electric power, water, and communications cut off from the community
  • They can melt snow and ice which can produce flooding.
  • Lava flows can also dam rivers which may in the future produce flooding if the dam were to break.
  • Lava flows also obstruct means of transportation

 

Poisonous Gas Emissions

Volcanoes emit gases that are poisonous to living organisms. Among these gases are Hydrogen chloride, Hydrogen sulfide, Hydrogen fluoride and Carbon dioxide. These gases can be ejected during the eruption of a volcano or without a triggering eruption. They are transported away from vents as acid aerosols, as compounds absorbed by tephra and as microscopic salt particles.

Pyroclastic activity

This is one of the dangerous aspects of volcanism. Ash falls during volcanic eruption generally do not directly endanger life, although the collapse of roof and houses under the ash load are not common. Ash falls destroys vegetation, including crops and can kill livestock that eat the ash covered vegetation. It can cause loss of agricultural activity for years after an eruption.

Lahars (mudflows)

This is a mixture of water and sediments, they move rapidly down slope along streams valleys, although they may easily top banks and flood out into surrounding area. They have properties that vary between thick water and wet concrete, and can remove anything in their paths like bridges, highways and houses.

Hazards

Destructions

Landslides

-Loss of life

- Loss of property and assets

- Loss of infrastructure and lifeline facilities

- Loss of Resources

 

 

Floods

-Floodwater can seriously disrupt public and personal transport by cutting off roads.

- Floods disrupt normal drainage systems in cities, and sewage spills are common.

- Floods can distribute large amounts of water and suspended sediment over vast areas, restocking valuable soil nutrients to agricultural lands.

Forest fires

Wildfires can cause wide damage, both to property and human life.

Volcanic hazards

-Loss of life and assets

-Loss of vegetation

 

 

GEOLOGY (REVISION)(15/04)

 

a) Describe the major folds on the map
b) Draw the stratigraphic column of the rock on the map
c) Describe the major fauslts of the map 

 

FOSSILS

    

How to identify rocks during GCE practicals

                                                                                                                                                                                                                                       a) Identify the various types of fossils,       b) Identify the above specimen 

Genetics (15/04)

Introduction

• Genetics is the study of inheritance.  • The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring.  • Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells.  • In fertilisation the nucleus of the male gamete fuses with the nucleus of the female gamete.  • The offspring show the characteristics of both the male and the female.  • Genetics is the study of how this heritable material operates in individuals and their offspring.  
Variations within Plant and Animal Species  Variation  • The term variation means to differ from a standard.  • Genetics also deals with the study of differences between organisms belonging to one species.  • Organisms belonging to higher taxonomic groups e.g. phyla or classes are clearly different.  • Although organisms belonging to the same species are similar, they show a number of differences or variations such that no two organisms are exactly the same in every respect.  
• Even identical twins, though similar in many aspects, are seen to differ if they grow in different environments.  • Their differences are as a result of the environment which modifies the expression of their genetic make-up or genotype.  • The two causes of variations are the genes and the environment.  • Genes determine the character while the environment modifies the expression of that character.  
Continuous and Discontinuous Variation  
Continuous Variations  • The differences between the individual are not clear-cut.  • There are intermediates or gradations between any two extremes.  • Continuous variations are due to action of many genes e.g. skin complexion in humans.  • In continuous variation, the environment has a modifying effect in that it may enhance or suppress the expressions of the genes.  • Continuous variation can be represented in form of a histogram.  • Example of continuous variation in humans is weight, height and skin complexion.  • Linear measurements:  • In humans, height shows gradation from tall, to tallest.  • So does the length of mature leaves of a plant.  • In most cases, continuous variation is as a result of the environment.  
Discontinuous Variations  • These are distinct and clear cut differences within a species.  
Examples include:  • Ability to roll the tongue.  • An individual can either roll the tongue or not.  • Ability to taste phenylthiourea (PTC); some individuals can taste this chemical others cannot.  • Blood groups - and individual has one of the four blood groups A, B AB or O.  • There are no intermediates.  • Albinism - one is either an albino or not.  • Discontinuous variations is determined by the action of a single gene present in an individual.  Structure and Properties of Chromosomes  • These are threadlike structures found in the nucleus.  • They are normally very thin and coiled and are not easily visible unless the cell is dividing.  • When a cell is about to divide, the chromosomes uncoil and thicken.  • Their structure, number and behaviour is clearly observed during the process of cell division.  • The number of chromosomes is the same in all the body cells of an organism.  
• In the body cells, the chromosomes are found in pairs.  • Each pair is made up of two identical chromosomes that make up a homologous pair.  • However sex chromosomes in human male are an exception in that the Ychromosome is smaller.  
Number of Chromosomes 
 Diploid Number (2n)  • This is the number of chromosomes found in somatic cells.  • For example, in human 2n = 46 or 22 pairs (44 chromosomes)  are known as autosomes (body chromosomes")  • while 1 pair is known as the sex chromosomes.  • In Drosophila melanogaster, 2n = 8.  
 
Chromosome Structure  • All chromosomes are not of the same size or shape. • In human beings; each of the twenty three pairs have unique size and structure .  • On this basis they have been numbered 1 to 23.  • The sex chromosomes formthe 23rd pair.  Properties of Chromosomes  • Chromosomes are very long and thin.  • They are greatly and loosely coiled and fit within the nucleus.  • During cell division they shorten, become thicker and are easily observable.  • Each consists of two chromatids.  • The two chromatids are held at same position along the length, at the centromere.  • Chromatids separate during cell division in mitosis and in the second stage of meiosis.  • Chromosomes take most dyes and stain darker than any other part of the cell.  • This  property has earned them the name "chromatin material"  • Each chromosome is made up of the following components:  • Deoxyribonucleic acid (DNA) - this carries the genes. •  It is the major component of the genetic material.  • Protein e.g. histones.  • Ribonucleic acid (RNA) is present in very small amounts.  • Enzymes concerned with DNA and RNA replication - these are DNA and RNA polymerases and ligases.  Structure of DNA  • The structure of DNA was first explained in 1953 by Watson and Crick.  • DNA was shown to be a double helix that coils around itself.  • The two strands are parallel and the distance between the two is constant.  
 
Components of DNA  • DNA is made up of repeating units called nucleotides.  • Each nucleotide is composed of:  • A five-carbon sugar (deoxyribose).  • Phosphate molecule.  • Nitrogenous base, four types are available i.e,  ➢ Adenine - (A)  ➢ Guanine - (G)  ➢ Cytosine - (C)  ➢ Thymine - (T)  • The bases are represented by their initials as A, G, C and T respectively.  • The sugar alternates with the phosphate, and the two form the backbone of the strands.  • The bases combine in a specific manner, such that Adenine pairs with Thymine and Guanine pairs with Cytosine.  • The bases are held together by hydrogen bonds. A gene is the basic unit of inheritance consisting of a number of bases in linear sequence on the DNA.  • Genes exert their effect through protein synthesis.  • The sequence of bases that make up a gene determine the arrangement of amino acids to make a particular protein. 
• The proteins manufactured are used to make cellular structures as well as hormones and enzymes.  • The types of proteins an organism manufactures determines its characteristics.  • For example, albinism is due to failure of the cells of an organism to synthesise the enzyme tyrosine required for the formation of the pigment melanin.  ( SUIT, GO TO DOCUMENT )
 

MORE LESSONS 

WEEK BEGINNING 13/04 TO 24/04/2020

Subject: ICT
CLASS: UPPER SIXTH
Q1.) i.) What is normalization in database management systems? (2 marks)
ii.) A company employs engineers to fix faults on photocopiers. The company has 20 engineers and
over 200 clients. The engineers will travel to client sites to fix their machines and can fix between
one and five machines a day. The company employs a ‘work controller’, who takes the call from the
client and then allocates the engineer to the job. She uses a relational database to keep track of all
the details relating to the clients, engineers and jobs. Part of the database is shown below in
standard notation: CLIENT (ClientID, Name, Address)
ENGINEER (EngineerID, Name, Address)
JOB (ID, Date, Nature of problem)
From the above explanation, answer the following questions:
a.) Suggest a suitable identifier for each table. (3 marks)
b.) Give any two relationships that may exist among the entities. (2 marks)
c.) Draw an entity-relationship diagram for the entities showing its cardinalities and primary keys.
(6 marks)
d.) Suggest foreign keys that could be used to create the relationships. (3 marks)
e.) What are the good and bad points of using a flat-file database for these purposes?

 

LESSON NO 1

WEEK BEGINNING 23RD TO 27TH /03/2020

UPPER SIXTH. ORGANIC CHEMISTRY

7.LABORATORY PREPARATION OF ALDEHYDES AND KETONES

A.OXIDATION OF ALCOHOLS

  • 1° ALCOHOLS YIELD ALDHYDES
  • 2° ALCOHOLS YIELD  A KETONES

B.FROM   METHYLBENZENE

  • C6H5CH3         SeO2/300°C      C6H5CHO      ( benzaldehydes)

II.CARTALYTIC  OXIDATION

  • 2CH3CH2OH  +  O2   Agcat/500°C       2CH3CH2CH0      +  2H20
  • 2(CH3)2CH2OH   + O2   Agcat/500°C    2CH3COCH3  (propanone)

C. BY DEHYDROGENATION OF ALCOHOL

  • CH3CH2OH    CU/300°C      CH3CHO    (ethanal)     + H2
  • (CH3)2CH2OH     CU/350-380°C        CH3COCH3     +  H2

D.DECARBOXYLATION OF CALCIUM SALT OF CARBOXYLIC ACID

  • (CH3COO)2Ca   +   (HCOO)2Ca         dry distile/400°C         2CH3CHO   +  CaCO3  + 2CaCO3
  • (C6H5COO)2Ca   +    (HCOO)2Ca      dry  distile/400°C        2C6H5CHO   +  2CaCO3  
  • (CH3COO)2Ca   +    (CH3COO)2      distill       2CH3COCH3   +  2CaCO3

E.HYDROLYSIS OF A DIHALOGENO COMPOUNDS

  • C6H5CHCL2  NaOH(aq)/REFLUX      C6H5CHO
  • CH3CHCL2     H2O/H+/REFLUX     CH3CHO  
  • CH3CCL2CH3            H2O/H+/REFLUX            CH3COCH3

F.FRIEDEL CRAFT ACYLATION

  • C6H6      +  (CH3CO)2O     ALCL3/50°C REFLUX       C6H5COCH3   + CH3COOH
  • C6H6 + CH3COCL        ALCL3/ REFLUX              C6H5COCH3 + HCL  
  • CH3COCL    + H2 POISON Pdcat/BaSO4 /HEAT           CH3CHO      (ITS IS USED FOR ALDEHYDES ONLY)

 

 

 

8.LABORATORY PREPARATION OF CARBOXYLIC ACID

A. OXIDATION OF 1° ALCOHOLS AND ALDEHYDES

  • CH3CH2OH        K2MnO4/H+/warm          CH3COOH
  • CH3CH2CHO       K2MnO4/H+/warm          CH3CH2COOH

SYNTHETIC ROUTE

B.FROM NITRILE (CN)

  • CH3CH2CN     concH2SO4/H2O       CH3CH2CONH2     H2O/H+       CH3CH2COOH

C.HYDROLYISIS OF ESTERS

  • CH3COOCH3  NaOH(aq)/ BOIL      CH3COONa + CH3OH    dilHCL      CH3COOH

D. FROM GRIGNARD REAGENT

  • CH3MgI   + CO2     ether     CH3COOMgI     H2O/H+   REFLUX    CH3COOH   + Mg(OH)I

E. FROM OXIDATION OF METHYLBENZENE

  • C6H5CH3    KMnO4/H+ /heat    C6H5COOH 

II.FROM CANNIZZERO REACTION (aldehydes)

  • 2C6H5CHO     concNaOH /40-60% at 25°C    C6H5COONa   +C6H5CH2OH   HCL(aq)    C6H5COOH  + NaOH

III.HYDROLYSYS OF TETRA-CHLOROMETHYLBENZENE

  • C6H5CCL4       dilHCL/BOIL     C6H5COOH

 

9. LABORATORY PREPARATION OF ESTERS

A. FROM ESTERIFICATION REACTION

  • CH3COOH   + CH3CH2OH   con H2SO4/HCL       CH3COOCH2CH3 + H2O

B. FROM ACID ANHYDRIDES AND ALCOHOL

  • (CH3CO)2O + CH3CH2OH    REFLUX             CH3COOCH2CH3 + CH3CH2OH  
  1. CH3COOAg + CH3I                    CH3COOCH3    + AgI

II.FROM ACID CHLORIDES

  • CH3CH2COCL   + CH3CH2OH           CH3COOCH2CH3    + HCL

 

 

 

10.LABAORATORY PREPARATION OF ACID CHLORIDES

  • CH3CH2COOH   + PCL5                  CH3CH2COCL   + POCL3 +HCL
  • CH3COOH +   SOCL2              CH3COCL   + SO2 + HCL  
  • CH3COOH + 2PCL3    HEAT   CH3COCL   + P2O3 + 3HCL

 

11.LABORATORY PREPARATION OF ACID ANHYDRIEDS

A. FROM ACID CHLORIDES AND SALT OF CARBOXYLIC ACID

CH3COCL + CH3COONa distill/reflux       (CH3CO)2O   + NaCL

 

12.LABORATORY PREPARATION OF AMINES (NH2)

A. FROM AMIDES (reduction of one carbon chain / Holfmandagradation reaction)

  • CH3CONH2   +  Br2/KOH/warm       CH3NH2

B. REDUCTION OF NITRILES (CN)

  • CH3CH2CN     LiALH4/DRY ETHER         CH3CH2CH2NH2

C.FROM HALOALKANES

  •   CH3CH2CH2Br   + NH3  seal tube       CH3CH2CH2NH2

 

 

D. FROM ALDEHYDES AND KETONES

  • CH3CHO   + NH3    H2/Nicat/high temp       CH3CH2NH2
  • CH3COCH3    +NH3   H2/Nicat/high temp      CH3CH(NH2)CH3
  • C6H5CHO   + NH3    H2/Nicat/high temp         C6H5NH2(phenylamine )  

E.REDUCTION OF NITRO GROUP ( NO2)