biology form 4 chapter 9.1
TRANSCRIPT
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Chapter 9Endangered Ecosystem
9.1 Human Activities thatEndanger the Ecosystem
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What is Deforestation?
The extensive removal of trees fromforests.
Vast area of forests are cleared foragriculture, development and loggingactivities.
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Regulating worlds climate.
Functioning as habitat of various flora andfauna.
Housing plants which produce food andpharmaceutical products.
Regulating the amount of Carbon Dioxide
and Oxygen through photosynthesis. Serving as water catchment areas.
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How does it happen?
When it rains for a long period of timeduring rainy seasons, the top layer of soil
loosens and slides down. Thus, Landslideoccurs.
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The loss of stability of soil is due todeforestation.
Clearing of trees causes the loss of tree leaves
to protect soil from the impact of raindrops.It also causes the loss of tree roots to hold thesoil in place.
Soil is exposed directly to the force of rain.
Heavy rainfall easily washed away the toplayer of soil, causing Soil Erosion.
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The eroded soil is carried by water and may bedeposited into rivers.
During heavy rains, rainwater flows quickly intoriver because there is not retention of water byplant roots, as well as water catchment areas.
Due to silting in the rivers, the water flow becomesblocked. Hence, water flows inland and causes flashflood in low area.
Flash Floods cause loss of lives and properties.
Soil erosion also leads to depletion of minerals forthe land. The land cannot be used for cultivation.
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Deforestation leads to the loss of habitats formany species of F&F.
This will cause an increased rate of
extinction of plants and animals. As a result,it reduces the biodiversity & the source offood and valuable medicines for humans.
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When many trees are destroyed, it reducesrainfall, transpiration rate and rate of usingCarbon Dioxide during photosynthesis by plants.
Clearing & burning of forests also release vast
amount of greenhouse gases, e.g. Carbon Dioxideinto the atmosphere.
Deforestation contributes 20%-30% of carbondioxide in atmosphere every year.
Carbon dioxide prevents heat from escaping theatmosphere. Thus, the level of carbon dioxideincreases and global temperature also increases,which results Greenhouse Effect and GlobalWarming.
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When forests are cleared, the areas becomehotter and drier causing Climatic Changesand changes in wind patterns.
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Excessive use of land for farming leads toinfertile land.
Use of inorganic fertilisers such as nitrates
and phosphates leads to Eutrophication.
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BOFF leads to an increase in the amount ofcarbon dioxide in the atmosphere.
As a result, this leads to Greenhouse Effect
and Global Warming.
BOFF and open burning can also cause AirPollution.
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Industrial plants discharge industrial wasteand heaved waste water causing WaterPollution and Thermal Pollution.
Toxic gases released by industries contributeto Air Pollution.
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Pollutions
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What is pollution?
An undesirable change in chemical, physicalor biological characteristics of natural
environment. Environment is polluted by pollutants.
Pollutants may be toxic substances e.g.Pesticides, or natural constituents ofatmosphere e.g. Carbon Dioxide. They mayaffect the soil, rivers, seas, or theatmosphere.
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Occurs when pollutants are released into theair.
Will affect human respiratory system,
human lives and other living organisms.
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Carbon monoxide
Reduces the ability of the blood to transportoxygen
Lead to brain damage and death
Carbon dioxide
Affects respiration
Acid rain-damage buildings
Greenhouse effect and global warming
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Nitrogen Monoxide and Nitrogen dioxide
Damages lung tissues
Irritates eyes Lowers the bodys defence
Affects enzymes functions
Acid rain-reduces the pH of soil,lakes andrivers,destroys buildings
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Sulphur dioxide
Irritates and damages eyes, air passage andlungs
Causes coughing and wheezing
Affect function of enzymes
Reduces the growth of plants Causes acid rain
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Fine particulate matter
Irritates the eyes and respiratory tract
Contributes to haze that can cause bronchitisasthma attack, conjunctivitis, sore throatand others.
Can cause mutation
Soot can dirty and darken buildings
Deposits on leaves and darken the vegetable
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Lead (combustion of fossil fuels)
Reduce the sensitivity of the hands and feetcoordination
Retards mental development in children
Disrupts bodys ability to produce new cells
May damage kidneys
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THE SOURCES OF AIR POLLUTIONAND THE EFFECTS
Hydrocarbon
affects growth
Causes cancer Causes mutation
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Acid rainCauses
Combustion of fossil fuels produces sulphur oxideand oxides of nitrogen
Forms acids when dissolve in water
Acids fall as acid rain
Oxide of nitrogen combine with water to formnitric acid
Sulphur dioxide combines with water vapour toform sulphuric acid.
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Acid rainSolution
Use scrubbers to clean emissions fromindustrial plants
Use catalytic converters to convertharmful emissions from exhaust pipes
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Acid rainEffects
Corrodes metals, marble, rubber, plastics andother materials
Leaching minerals such as calcium from the soil,
causing infertile soil Release ions of heavy metals such as lead which
may contaminate the water
Destroys plant tissues and damages plant roots
Reduce the pH of the soil making it unsuitablefor farming
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Air Pollution Index (API)
Used as a measure of air quality
Calculated based on concentrations of fiveparticles and harmful gases in atmosphere.
API Status
0-50 Good
51-100 Moderate
101-200 Unhealthy201-300 Very unhealthy
301-500 Hazardous
Above 500 Emergency
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Water PollutionCauses:
Discharging industrial, domestic andagricultural waste
Discharging sewage onto water source
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Pollutants & SourcesNitrates & Phosphates Fertiliser from farm, agricultural run-off, sewage
effluent
Pesticide & Herbicide Farms, agricultural run-off
Detergents Domestic sewage
Oil & Grease Oil spills, industrial effluent
Suspended solids &rubbish
Domestic wastes, industrial effluent
Heavy metals Industrial plants
Electronic factories
Mining industries
Factories which produce/ process paints,
metals, ink
Chemical & Radioactive
waste substances
Nuclear power station, research laboratory
Microorganisms Untreated sewage, human faeces, animal
wastes
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Eutrophication
What is Eutrophication?
- a natural process whereby an aquaticecosystem becomes enriched with nutrients
causing an excessive growth of aquaticplants.
Nutrients come from:
Fertilisers
Sewage treatment
Animal wastes
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Eutrophication
The increases nutrients in river, lakes andstreams promote rapid growth of algae.
Excessive growth of algae is called Algal
Bloom.
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How Algal blooms endangerthe ecosystem 1
The densely populated algae cover the watersurface and block sunlight. Unable to carryout photosynthesis, the aquatic plants die.
When these plants die, aquatic animals losetheir food sources and habitats. Hence, thefood chain and ecosystem change
Algae also reduces the level of dissolvedoxygen in water
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How Algal blooms endangerthe ecosystem 2
When algae and other aquatic organisms die,decomposing organisms esp. saprophyticorganisms use up oxygen to decompose thedead organic materials.
This reduces the oxygen content in thewater.
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Eutrophication
Eutrophication increases the BOD value inwater.
Higher the BOD value, the more polluted the
water as dissolved oxygen level decreases.
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Eutrophication
Depletion in oxygen results in an increase inBiochemical Oxygen Demand (BOD)
Eutrophication increases the BOD value in
the water. BOD refers to the amount of oxygen utilised
by microorganisms to oxidise all organicmatter in one litre of water.
The higher the BOD value, the more pollutedthe water as the dissolved oxygen leveldecreases.
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Water Quality Index (WQI)
WQI is used by the Department ofEnvironment to indicate the quality ofwater.
WQI Pollution level Class92.8-100.0 Very clean 1
76.6-92.8 Clean 2
52.5-96.6 Slightly polluted 3
29.7-52.5 Polluted 4< 29.7 Very polluted 5
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Thermal Pollution
Occurs when there is :
an increase in temperature of water sources
Excessive heat in the environment
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Thermal PollutionCauses
Hot water discharged from industrialprocesses, cooling towers of power stationand reactor plants- can increase rivertemperature by 10 Degree Celcius
Radiation of heat from glass building
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Thermal PollutionEffects
Reduce the level of dissolved oxygen inwater. This affects the aquatic organisms.
Cause some aquatic organisms to die because
they can only survive in a certaintemperature. Some also move away. Thisaffects the food chain and also the entireecosystem.
Encourages Algae to grow rapidly whichleads to high BOD value.
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Noise Pollution
Occurs when our daily lives are disturbed byhigh level of noises.
WHO recommends a noise level of not more
that 55 dB (decibels). When surrounding noise level reaches 80 dB
or more it causes discomfort and affects thehuman health.
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Noise PollutionSources
Vehicles
Jet planes
Construction sites Entertainment outlets
Machines
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Noise PollutionEffects
Headache
Emotional disturbance
Mental disturbance Deafness
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