Biology Form 4

Human activities often have a widespread impact on the ecosystem.

Since older days, human have hunted, fished and cleared forests. Sheep, cattle and goats grazed on vast areas of grasslands, harming the ecosystem.

Today, expectation of better living conditions, better modes of transport and industrial revolution have brought about clearing of more forests to grow food, build factories, houses and roads.

The negative effects of unplanned development and mismanagement of the ecosystem give rise to various environmental problems such as:

Ozone depletion

Soil erosion, landslide, flash flood

Greenhouse effects

Global warming

Pollution

EnvironmetalProblems

Human activities usually affect the ecosystem. The activities that endanger the ecosystem is shown below:

a) DEFORESTATION….

Human activities that endanger the ecosystem.

Industrialisation pollution

Burning pollutionGreenhouse effects

Farming pollution

Urbanisation pollution

Deforestation Soil erosion Landslides Flash flood

Extinction of flora and faunaGlobal warmingGreenhouse effect

Deforestation is an act of extensive cutting down or burning the trees in the forest.

The vast areas of forests are being cleared away for extracting timber or fuel wood, agriculture and urban development.

There are many impacts of deforestation such as: Soil erosion, flash floods and

landslides. Landslides occurs when the top

layer of soil loosens and slides down because of rains for a long period of time during rainy seasons.

The landslides happen because of the

stability of soil is lost due to deforestation.

Clearing of trees causes the loss of tree leaves to protect the soil from the impact of raindrops and also

causes the loss of tree roots to hold the soil in places.

Thus, the soil is exposed directly to the force of the rain. Heavy rainfall will easily washed away the top layer of the soil. This leads to soil erosion.

The eroded soil is carried away by water and may be deposited into the river.

During heavy rains, rainwater flows quickly into rivers because there is no retention of water by plant roots as well as water catchment areas.

Due to silting in the rivers, the water

flows is blocked. Thus, water flows inland and causes flash flood in low areas.

Soil erosion also leads to DEPLETION OF MINERALS for the land. The land cannot be used for cultivation.

Extinction of flora and fauna

Deforestation leads to the loss of habitats for many species of flora and fauna.

This will cause an increased rate of extinction of plants and animals. As a results, it reduces biodiversity and the source of food and valuables medicines for humans.

Greenhouse effect and global warming. Deforestation causes weather and

climatic changes. When a large scale of trees are

destroyed by cutting and burning, it will reduce rainfall, transpiration rate and the rate of using carbon dioxide during photosynthesis by plants.

Clearing and burning of forests also release vast amounts of greenhouse gases such as carbon dioxide into the atmosphere.

Deforestation is believed to contribute about 20-30% of all carbon dioxide in the atmosphere for every year.

Carbon dioxide can prevent heat from escaping from the atmosphere. Thus, the level of carbon dioxide increases and global temperature also increases. This leads to greenhouse effect and global warming.

Increasing global temperature may change the ecosystem.

b) FARMING Excessive use of land for farming and

stock rearing lead to infertile land and may expose soil to erosion by wind.

Use of inorganic fertilisers in farming also leads to eutrophication.

c) URBANISATION Dumping of domestic waste as well as

sewage discharge from houses causes pollution.

The waste materials in landfills act as toxic substances which pollute nearby water sources.

d) INDUSTRIALISATION Industrial plants discharge industrial and

heated waste water causing water pollution and thermal pollution.

Toxic gases released by industries contribute to air pollution.

e) BURNING

Open burning of rubbish, farms and forests release more carbon dioxide into the atmosphere which aggravates the greenhouse effect.

Burning of fossil fuels causes air pollution as well as increase the carbon dioxide content.

As a result, it causes the greenhouse effect and global warming.

Pollution is an undesirable change in the chemical, physical or biological characteristics of the natural environment. The environment is polluted with harmful substances or pollutants.

Pollutant is any substance that is present in an excessive amount in the environment as a result of human activities. It has damaging effects on living organism.

Pollutants may be toxic substances such as pesticides or natural constituents of the atmosphere, such as carbon dioxide. They may affect the soil, rivers, seas or the atmosphere.

There are four types of pollution:

AIR POLLUTION Air pollution occurs when pollutants such as

smoke, dirt, dust and poisonous gases are released into the air endangering human lives and other living organisms.

Most air pollutants come from burning of fossil fuels from motor vehicles.

Examples of air pollutants are carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxide (NO) and sulphur dioxide (SO2).

Pollutant Sources EffectsCarbon monoxide (CO) Odourless,

colourless and toxic gas.

Incomplete combustion of fossil fuels.

Combustion sources such as motor vehicle exhaust, smoke from fires, engine fumes.

Health Combines with haemoglobin to form

carboxyhaemoglobin which reduces the ability of the blood to transport oxygen.

Early symptoms of carbon monoxide poisoning are headaches, nausea and fatigue.

Prolonged exposure can lead to brain damage and even death.

Carbon dioxide (CO2) Odourless,

colourless gas.

Combustion of fossil fuels.

Health Causes emphysema. Affects respiration.Building Contributes to acid rain which damages

buildings.

Water pollution

Thermal pollution

Noise pollution

Air pollution

Types of

pollutions

Climate Contributes to greenhouse effect and

global warming.Nitrogen monoxide (NO) and nitrogen dioxide(NO2) NO-odourless,

colourless gas. NO2-browmish

gas

Combustion of fossil fuels.

Motor vehicle exhaust

Health Damages lung tissues. May cause bronchitis. Irritates the eyes. Lowers the body’s defence against flu.Agriculture Contributes to acid rain which reduces the

pH of soil, lakes and rivers.Building Contributes to acid rain which destroys

buildings.Climate Contributes to acid rain.

Sulphur dioxide (SO2) Colourless,

pungent and acidic gas.

Dissolves in water.

Combustion of fossil fuels which contain sulphur.

Industries.

Health Irritates and damages the lining of the

eyes, air passages and lungs. Causes coughing and wheezing. Combines with rainwater to form acid rain

that may cause skin diseases.Agriculture Reduces the growth of plants. Damages the leaves and may kill the

plants. Contributes to acid rain which lowers the

pH of soil, lakes and rivers.Buildings Contributes to acid rain which corrodes

iron, copper, steel, aluminium and stonework, thereby destroying buildings.

Climate Causes acid rain.

Fine particular matter. (Includes smoke, fumes, dust, ash and pollen) Tiny and

invisible The composition

of particulate matter varies with place, season and whether conditions.

Combustion of fossil fuels from motor vehicles, agricultural burning and industries.

Forest fire Quarries and

asbestos factories

Health Irritates the eyes and respiratory tract. Contributes to haze which can cause

asthma attack, conjunctivitis, sore throat, bronchitis and reduced visibility.

Agriculture Deposits on leaves and darkens

vegetation. Blocks stomata, thus lowering the rate of

photosynthesis. The crop yield is reduced.

Buildings Soot can darken building.Climate

Contributes to formation of haze and smog which can reduce light intensity.

Lead Combustion of fossil fuels

Health Reduces the sensitivity of the hands and

feet coordination. Retards mental development in children. Disrupts body’s ability to produce new

cell.Hydrocarbon Combustion of

fossil fuels from motor vehicles

Health Affects growth Causes cancer

Other than that, air pollution also causes acid rains. Acid rain only occurs when the pH of the rain is less

than 5.0(natural rain water has a pH of about 5.4)

Combustion of fossil fuels releases sulphur dioxide and oxides of nitrogen which contribute to acid rain.

Sulphur dioxide and oxides of nitrogen form acidic solutions when dissolves in water.

Sulphur dioxide combines with water vapour to form sulphuric acid.

2SO2(g) + O2(g) + 2H2O(l) 2H2SO4(aq)

Oxides of nitrogen combine with water vapour to form nitric acid.

Then, these acid will fall back as acid rain. Carbon dioxide in the air also contributes to

acid rain. It dissolves in water to form carbonic acid.

The effect of acid rain is shown below:

The air quality is measure by Air Pollution Index (API)

It is normally includes the major pollutants which could cause potential harm to human health.

Increases the acidity of aquatic

ecosystems leading to the killing of planktons and

aquatic organism

Leaching of minerals from the

soil such as calcium, causing

infertile soil

Releases ions of heavy metals such as lead which may

contaminate the water

Reduces the pH value of the soil

making it unsuitable for farming

Destroyed plant tissues and

damages plant roots

Corrodes metals, marble, rubber,

plastics, stonework and other materials

Effects of acid rain

In Malaysia, the air pollutants included are ozone, carbon monoxide, nitrogen dioxide, sulphur dioxide and suspended particulate matter.

This index is calculate by using the concentrations of major air pollutants, but it is developed in easily understood ranges of values as shown below

API Status Level of pollution 0-50 Good Low, no ill effects on health 51-100 Moderate Moderate pollution, no ill effects on health 101-200 Unhealthy Mild aggravation of symptoms among high risk

group 201-300 Very unhealthy Significant aggravation of symptoms and

decreased exercise tolerance among high risk groups

301-500 Hazardous Severe aggravation of symptoms and a danger to health

Above 500 Emergency Severe aggravation of symptoms and a danger to health

This index helps us to take precautionary measures by drinking more water, staying indoors and wearing masks when the air pollution index exceeds 200.

Water pollution. Water pollution occurs when people discharging

agriculture wastes, industrial waste, domestic waste and sewage into rivers.

The sources of water pollution and the effects of water pollution are shown below.

Fertilisers and pesticide from farms

Nitrates PhosphatesPesticides Herbicides

Effluent from factories

Heavy metalsChemicalsOil Grease

Sewage effluent

Detergent FaecesNitrates

Oil spillsGreaseOil

Non-biodegradable

rubbishSuspended

solidsRubbishOil

Sources and pollutants of

water pollution

Effects of water pollution

Human healthUntreated water contains pathogen such as Vibrio bacteria which causes cholera.Pesticides and herbicides passed to humans through the food chain are harmful.Heavy metals such as mercury cause nervous disorders, blindness, paralysis and even death

Animals and plants Excess nitrates and phosphates

lead to eutrophication.Rubbish and oil reduce light

penetration and diffusion of oxygen into water. Aquatic organisms may die due to lack of light and oxygen.

Oil covers the gills of fishes affecting their respiration.

Decomposition of decayed materials by saprophytic bacteria reduces the oxygen content in the water

Eutrophication is a natural process whereby an aquatic ecosystem becomes enriched with nutrients causing an excessive growth of aquatic plants

Nutrients can come from many sources such as

a. Fertiliser(especially nitrates and phosphate) from agriculture fields

b. Sewage treatment plant dischargesc. Run-off of animal waste

The increased nutrients promote rapid growth of algae when they are deposited in rivers, lakes and streams.

This excessive growth of algae is often called an algae bloom

Algae blooms endanger the ecosystem in two main

ways. 1.The densely populated algae cover the water

surface and block sunglight. Unable to carry out photosynthesis, the aquatic plants die.

When these plants die, aquatic animals lose their food sources and habitats. As a result, the food chains and ecosystem change.

Algae also reduce the level of dissolved oxygen in the water.

2. When the algae die, decomposing organisms especially saprophytic bacteria use up oxygen for its activities

This reduces the oxygen content in the water. A depletion in oxygen results in an increases in biochemical oxygen demand (BOD)

Eutrophication increases the BOD value in the water.

BOD refers to the amount of oxygen utilised by microorganisms to oxidise all organic matter in one litre of water

The higher the BOD value, the more polluted the water as the dissolved oxygen level decreases.

Thermal pollution Thermal pollution occurs when there is an increases

in the temperature of a water source or excessive heat in the environment.

Hot water is discharged into nearby rivers, streams, lakes and ponds from the effluent of industrial processes, cooling towers of power stations and reactor plants.

Many industries use water for cooling the machines. The hot water is discharged to rivers causing the temperature of water to increase by 10C.

Reflection of heat from glass buildings also leads to an increase in temperature of the surroundings.

An increase in temperature of water will cause the following.

a) It reduces the level of dissolved oxygen in water. This affects the life of aerobic aquatic organisms

b)It causes some aquatic organisms to die because they only survive at suitable

temperatures. Some organisms also move away. This affects the food chain and also the entire ecosystem.

c) It encourages some algae to grow rapidly which can lead to a higher BOD value.

Noise pollution Noise pollution occurs when our daily lives are

disturbed by high levels of noise. There are many sources and most of them are

related to urban development. Examples are:a)Vehicles b)Jet planesc) Construction sitesd)Entertainment outletse)Machines

World Health Organisation (WHO) recommends a noise level of not more than 55 decibels(dB)

When the surrounding noise level reaches 80 dB or more, it causes discomfort and affects the human health.

Excessive exposure to a noise level of 80 dB or more for a long period of time may cause headache, emotional and mental disturbances and in certain cases, may cause deafness.

Energy from the sun reaches the earth through radiation. Some of this radiation is absorbed by the earth to warm the surfaces of sea and land.

As the earth is warmed, heat in the form of infrared radiation is radiated back into space.

However much of this radiation is prevented from escaping into space by greenhouse gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFC)

As a result the infrared radiation is radiated back to the earth’s surface, warming the earth further.

This phenomenon is known as the greenhouse

effect. It is similar to a greenhouse used in farming in countries which experience temperate climates. The glass of a greenhouse allows light to enter but retards the loss of heat. The heat is used to keep the soil and air warm in the greenhouse.

An increase in greenhouse gases is caused by human activities, mainly burning of fossil fuels and deforestation.

Data collected has shown that atmospheric carbon dioxide has increased by nearly 25%, methane by 20% and concentrations of chlorofluorocarbons have doubled.

The increasing amount of greenhouse gases increases the greenhouse effect causing more heat to be trapped in the atmosphere. The earth’s average temperature increases and is known as global warming.

Some scientists predicted that the earth’s temperature may rise by 1.5C to 4.5C by 2030.

Melting of polar ice and glaciers causing a rise in

sea level

Intense rains in some regions

Decline in the yield of crops due to dry and infertile soil

Increases of droughts

Change in wind directions and

weather patterns

Spread of pests and disease-

carrying vectors to new areas

increases the outbreak of

diseases

Floods in low-lying countries

Effects of

global warming

Ozone layer is present in the stratosphere, which is approximately 12-25 kilometres above the earth’s surface.

This ozone layer shields the earth from the harmful effects of ultraviolet(UV) radiation.

High concentrations of ozone (O3) in the ozone

layer can absorb large quantities of UV radiation. Ozone, although a form of oxygen, once depleted

will not be replenished naturally. Evidence of ozone depletion was first discovered

over the Antarctic in 1985 by the British Antarctic survey.

The main cause of ozone depletion is the increasing level of chlorofluorocarbons(CFC) in the atmosphere.

The use of CFCs as coolants in air conditioners and refrigerators, as propellants in aerosol cans, as solvents in the electronics industry and as foaming agents in the making of polystyrene boxes has released large amounts of CFCs into the atmosphere.

CFCs are reactive and can remain unchanged for over 100 years.

UV radiation breaks down CFCs, releasing chlorine radicals which destroy ozone in a chain reaction.

It is estimated that a single chlorine atom can destroy 100 thousand molecules of ozone in a year.

With the thinning of the ozone layer, more UV radiation would be able to reach the earth’s surface. Prolonged exposure to UV radiation leads to the following effects.

a)Human health Skin cancer or melanoma Eye damage such as cataract Lowering of body’s immune system

b)Plants Damage of leaf cells and chlorophyll, reducing photosynthesis. Decrease in nutrient content and crop yields Killing of phytoplanktons

c) The environment Increase in surrounding temperature Change in wind directions Climate changes

Impact of thinning of the ozone layer

and global warming on the ecosystem

Sea water becomes warm due to global

warming. Decline in zooplanktons. Ecosystem’s food

web affected.

Ecosystems such as coral reef,

wetlands, polar seas and

temperate forests are slowly losing

its flora and fauna.

Drought due to global warming

causes the land to dry. Ecosystem

becomes unstable as the producers, the plants are not be

able to thrive.

UV radiation affects

photosynthesis. Aquatic

organisms are sensitive to UV.

There are many steps can be taken to maintain the balance of nature such as:

a)Enforcement of the environmental laws Environment quality act, 1974

Controls and prevents the pollution of the environment

Controls the type of licensing, content and quality of environment

Tests and examines the samples of substances and gas from industries

Natural forestry act, 1984 Aims at protecting and preserving our

forests and wildlife Pesticides act, 1974

Aims at controlling the use of pesticides Protection of wildlife act, 1972

Aims at protecting wildlife animals, birds and plants

Fisheries act, 1985 Aims at controlling marine pollution

b)Use of technology Use modern equipments and chemicals to

control oil spills. Recycle rubbish To look for methods to do research Change organic rubbish to biogas Use less polluting and clean fuels in motor

vehicles. Control and treat the toxic and dangerous

waste before disposingc) Education

To increase the awareness and sensitivity of the individual to the environment.

To provide the basic knowledge of environmental problems and effects of pollutions.

To teach the public the necessary skills to protect and maintain a healthy society.

To help the individuals to become responsible and sensitive to the environment.

d)Preservation and conservation of the ecosystem. Force the development companies to

replant the forest trees after deforestation. Remaining the mangrove swamps area so

that the ecosystem is protected. Restore the mining and used land for

agriculture. Put effort in rivers cleaning to ensure there

is sufficient supply of water in future

e)Practice of biological control. A method of controlling the animal pests

by using natural predators instead of using chemical substances.

Factors to choose the animals predators.1. The animals predators do not bring

any infection or disease.2. the animal predators do not eat the

other organisms in the same habitat.f) Efficient use of energy and use of renewable

energy. Energy plays an important role in our life

Non-renewable energy will be exhausted in one day. For example, coal, oil and fossil fuels Solar energy can be used as a substitute of fuels Renewable energy, such as solar energy, wave power and tidal power are environmental friendly and need to be developed.

Biology form 4 textbook. Focus Ace SPM Biology Reference book http://www.doe.gov.my/en/content/

environmental-quality-act-1974 http://en.wikipedia.org/wiki/Air_Pollution_Index Memory master through mind maps and diagrams

Biology SPM reference book.