BIOLOGY FORM 4 NOTES CHAPTER 9 : ENDANGERED ECOSYSTEM

CHAPTER 9: ENDANGERED ECOSYSTEM

9.1 Human Activities That Endanger Ecosystem

Human activities that threaten the ecosystem:

*        Human activities often affect the whole ecosystem.

*        The negative effects of hasty and unplanned development and mismanagement of the ecosystem result in various environmental problems.

*        These problems bring about negative effects that are increasingly threatening the economic resources, health and survival of the ecosystem.

9.1.1 The impact of human activities on the ecosystem

(1) Deforestation:

*        The rapid destruction of woodlands or removal of trees from forests is known as deforestation.

*        Tropical rainforests play important ecological roles:

*        Oldest ecosystem on earth and house of flora n fauna

*        Contain many unique species which provide food, medicine and other biological products.

*        Regulate the world’s climate by influencing wind, rainfall, humidity and temperature patterns.

*        Called the ‘carbon sink’ of the Earth because they absorb vast amount of carbon dioxide during photosynthesis and release oxygen into the atmosphere.

*        Serve as water catchment areas

Deforestation results in :

*        Soil erosion

*        Flash flood

*        Landslides

*        Changes in the recycling of materials

*        Severe climatic changes

*        The loss of biodiversity

Deforestation cause soil erosion, landslides and flash flood

*        Soil erosion is the removal and thinning of the soil layer due to physical and climatic process.

*        The absence of plant root systems makes the soil structure unstable.

*        When it rain heavily for a long period of time, the top layer of the soil disintegrates easily and this leads to landslides on steep hillsides.

*        The eroded soil is then carried away by moving water and deposited at the bottom of river.

*        Together with depletion of  water catchment areas, cause flash flood during rainy seasons.

*        Soil erosion causes the land to be depleted of minerals and natural resources, making the land useless for cultivation.

Deforestation results in the loss of biodiversity

The destruction by human activities:

*        The removal of the base of numerous food webs.

*        The loss of habitats for many species of flora and fauna

*        The extinction of countless species and varieties of plants and animals, many of which have never been catalogued scientifically. Extinction of flora and fauna species reduces biodiversity

*        The destruction of storehouse of genetic diversity on Earth. The Earth’s biodiversity is a rich source of food and priceless medicines for mankind

Deforestation affects carbon and nitrogen cycles

*        The removal of plants in the rainforests disrupts the natural cycle of nutrients.

*        The level of atmospheric carbon dioxide rises as less carbon dioxide is removed by plants while the level of atmospheric oxygen drops as less oxygen is released during photosynthesis.

*        The recycling of nitrates and other ions is slowed down.

*        Tree roots bind soil particles together, and the tree canopy reduces the force of rain beating down on the soil and cause nutrients to be lost through leaching and run-off.

Deforestation cause climates change

*        Deforestation disrupts normal weather patterns, creating hotter and drier weather and causing global climatic changes.

*        Removal of trees reduces transpiration and rainfall cause the increase in carbon dioxide level in atmosphere and prevent heat from escaping from atmosphere.

*        This is known as greenhouse effect and lead to global warming.

(2) Burning of fossil fuels and its effects

*        Contributes about 75% of carbon dioxide

*        Cause greenhouse effect and global warming

(3) Intensive farming and its effect

*        Excessive use of land for intensive farming decrease the space and resources available for other species

(4) The effect of an increase in domestic waste and industrial waste

*        A rapidly expanding human population also generates an increase in both domestic and industrial waste.

9.1.2 Air Pollution

1.    Air pollution is caused by the presence of pollutants in the air which are harmful to life and the environment.

2.    Sources of pollution are as follows:

a)    Burning

-          Rubbish

-          Forest

-          Solid waste

b)    Factories and industries

-          Burning of fossil fuels such as petroleum, diesel and gas in factories and power stations.

-          Agricultural industries that use agrochemicals such as fertilizers, pesticides, insecticides and herbicides.

c)    Motor vehicles

-          Release harmful gases in car exhaust fumes.

3.    Burning of fossil fuels produces gases such as sulphur dioxide and nitrogen dioxide. Burning of rubbish and emission of smoke and fumes from car exhausts and chimneys in factories produce carbon dioxide, carbon monoxide and soot (unburnt carbon particles).

4.    Increase in carbon dioxide (a greenhouse gas) in the atmosphere will trap the Sun’s radiation and retain it as heat in the Earth’s atmosphere. This contributes to the greenhouse effect.

5.    This will cause an increase in the Earth’s temperature.

Source of pollution:

(a) Pollutant: Dust and soot

-Cement factories, quarries, sawmills, burning of rubbish and motor vehicles.

(b) Pollutant: Carbon monoxide, carbon dioxide, sulphur dioxide and nitrogen dioxide

-Burning of fossil fuels and rubbish

-Car exhaust fumes.

(c) Pollutant: Lead

-Car exhaust fumes which contain lead

(d) Pollutant: Agrochemical substances

   -Activities of agricultural industry

(e) Pollutant: Radioactive radiations

   -Nuclear power stations

(f) Pollutant: Chlorofluorocarbon (CFC)

   -Aerosol and foam industries

Acid Rain

(I) Causes of acid rain:

1.    The combustion of fossil fuels (cool, air and gas) in power station, factories, domestic boilers and internal combustion engines releases large quantities of sulphur dioxide (SO2 ) and oxides of nitrogen (NO and NO2).

2.    Both sulphur dioxide and oxides of nitrogen combine with water vapour in the atmosphere to form sulphuric acid and nitric acid respectively.

3.    Then, they fall to earth as acid rain.

4.    Rain is naturally acidic, with pH of about 5.6. This acidity is due to the carbon dioxide in the air, which dissolve in rain to form carbonic acid.

5.    However, the pH of acid rain is less than 5.0.

(II) Effects:

    (a) Agricultural:

1. The soil becomes very acidic and unsuitable for the cultivation of crops.

2. Acid rain causes the leaching of minerals such as potassium, calcium, and magnesium. This affects the growth of crops.

(b) Aquatic ecosystem:

1. Acid rain causes insoluble aluminum ions to accumulate in lakes and rivers.  The concentration of aluminum ions eventually reaches a toxic level which can kill aquatic organisms such as fish and invertebrates.

(c) Health:

1. Acidic soil releases the ions of certain heavy metals such as cadmium, lead, mercury which may contaminate the supply of drinking water.

2. Increased acidity in the aquatic ecosystems also kills phytoplankton which changes the food chain.

3. Photosynthesis tissues are destroyed.  Plant leaves turn yellow and fall off.  The roots are damaged and cannot absorb minerals.

(d) Buildings:

1. Metal railings and bridges corrode.

2. Limestone, stonework and marble monuments are eroded due to chemical weathering.

(III) Solutions:

Acid rain can be reduced by:-

1. Cleaning up emissions from vehicle exhausts through the use of catalytic converters.  The pollutants react with one another in the catalytic converters to produce less harmful products.

2. Cleaning emissions from power stations and industrial plants wit scrubbers. This process involves the spraying of water to trap pollutants. 

Air Pollution Index (API)

1. The Air Pollution Index (API) is used as a measure of air quality.

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

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

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

Air Pollution Index

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 groups
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 a health

9.1.3  WATER POLLUTION

Sources, Components, Effects, Solution of water pollution

Sources	Components	Effects	Solutions
Agricultural run-off and waste	Nitrates and phosphates	Lead to eutrophication	Control the use of fertilisers a)     Applying only when crops are growing. b)     Not applying in empty fields. c)     Not spraying when there is a forecast of rain. d)     Not disposing of them into rivers and ponds. e)     Reducing the usage of excess nitrates from fertilisers and ammonia.
	Herbicide and pesticide residues	-Have toxic effects on organisms in water and human -Pesticides levels can be magnified as they pass through food chain -Accumulation of pesticides in consumers may kill them or affect their metabolism -Lead to lower sperm counts, decreased ovulation, inability to conceive and birth defects.	-Use biodegradable pesticides -Use alternative method (biological pest control) -Planting genetically modified crops that can resist attacks by insects as this may reduce the need to use chemical pesticides
Untreated sewage – human faeces and domestic  waste	Suspended solids	Reduce light penetration -High demand for oxygen	-Treat sewage before it enters rivers -Prevent slurry (liquid manure) from farms from entering rivers and ponds
	Nitrates and phosphates	Leads to eutrophication
	Detergents	-‘Hard’ detergents create foam which reduces the availability of oxygen to organisms living in the water -‘Soft’ detergents are biodegradable but may contain high levels of phosphates which can lead to eutrophication	-Use biodegradable detergents with low phosphate contents
	Microorganisms (viruses, bacteria, and protozoa)	- Cause cholera	-Drink properly treated and boiled water
Effluent from industries -Electronics and electroplating plants -Food and beverage processing industry -Rubber products processing industry	Heavy metals (copper, mercury, zinc, and chromium), oil, grease, and suspended solids, waste water contains numerous contaminants, (including hydroxide sulphide).	-Highly toxic accumulate in the organisms via food chains -Mercury causes acute nervous disorder in humans.	-Treat effluents before discharging into water sources -Taking legal action against illegal dumping of toxic wastes
Underground pipes	Lead (highly toxic heavy metal)	-Accumulate in the tissues of living organisms -Impair the mental performance of children	-Replace lead pipes used in plumbing with copper-based pipes.

Eutrophication

Defination: Artificial nutrient enrichment of an aquatic system with organic material or inorganic nutrients, causing an excessive growth of aquatic plant life.

Causes by

a)    Leaching of inorganic fertilisers, especially nitrates and phosphates, from agricultural lands

b)    Input of untreated sewage as well as discharge from sewage treatment plants

c)    Run-off of animal waste from pastures and farmlands into lakes, rivers or ponds.

Process of eutrophication

1)     Run-off of excess nutrients into water encourage rapid growth of algae, results in a population explosion known as an algae bloom

2)     At night, high respiration rate of the algae results in a high demand for oxygen.

3)     Excessive growth of algae restricts the penetration of light into the water. The rate of photosynthesis of aquatic plants reduced and further reduced the supply of oxygen in water.

4)     The algae grow faster than their consumers. Most of algal population dies without being consumed.

5)     Decomposing microorganisms especially aerobic bacteria used up the oxygen in deeper water at a fast rate.

6)     Untreated sewage or animal wastes from farm that contain high concentration of organic matter encourage the rapid growth of aerobic bacteria.

7)     The aerobic bacteria use up oxygen faster than it can be replenished. An increase in biochemical oxygen demand (BOD) results in a severe depletion of oxygen.

8)     Low level of oxygen concentration kills larger aerobic aquatic organisms and organisms that require higher oxygen levels (freshwater shrimps and mayfly nymphs)

9)     If the oxygen levels continues to drop and water become completely deoxygenated, anaerobic bacteria will grow and release toxic gases (eg. hydrogen sulphide), causing the death of aquatic organisms.

10)   During the growth of algae, certain blue green bacteria also produce toxins.

11)   At night BOD levels, organisms that are more tolerant of lower concentration of dissolved oxygen (eg. leeches, Tubifex worms, and sludge worms) may appears and multiply.

What is BOD?

1. Biochemical oxygen demand (BOD) is the amount of dissolved oxygen required by the microoganisms to decompose the organic matters in the water.
2. The measurement of BOD is an indication of the level of water pollution.
3. If there is a large amount of organic waste in the water, the population of aerobic bacteria will increase to decompose the organic matter. The dissolved oxygen level in the water decreases, and the value of BOD will be high.

A lower BOD level (or higher dissolved oxygen level) indicates better water quality. A higher BOD level (or lower dissolved oxygen level) indicates poor water quality.

9.1.4 Thermal Pollution

In thermal pollution, the temperature of a body of water is unintentionally raised as a

result of human activities

1. Causes:

¾     Hot water is discharged into nearby lake and river from the effluent of industrial processes and cooling tower of electrical power station, which use water as a cooling agent.

¾     The excess heat that is released into the environment leads to thermal pollution.

2. Effects:

¾     Thermal pollution causes the temperature in a body of water to rise above the normal value.

¾     Water temperature can affect the level of dissolved oxygen.

¾     As the temperature of the water increases, oxygen become less insoluble in water.

¾     If the temperature increase persists over a longer period, this may result in permanent changes in the species composition of the aquatic ecosystem.

3. Ways to prevent:

¾     Control the amount of hot water discharged into still or slow - moving rivers.

¾     Control the amount of hot water discharged from industrial plants and power station to the surrounding lakes and rivers.

9.1.5 Noise Pollution

1. Causes:

¾     Noises from cars, motorcycles, aeroplanes, construction sites, agriculture and industrial machinery.

¾     Noise level of residential areas should not exceed 55 decibels (dB).

2. Effects:

¾     Prolonged exposure to noise level at or above 80 decibels can lead to deafness.

¾     High level of noise can contribute to the development and aggravation of stress – related problems such as high blood pressure, coronary disease, ulcers, depression and headache.

¾     Loud noise can cause an arousalresponse in which a series of reactions occurs in the body.

¾     Adrenaline is released into the bloodstream. A person’s heartbeat, blood pressure and

¾     respiration rate are likely to increase.

¾     The blood vessels constrict and the muscles become tense.

¾     Constant exposure to noise can contribute to a deterioration in health.

9.2 The Greenhouse Effect and the Thinning of Ozone Layer  

The Greenhouse Effect

Causes:

1.  Increases of the greenhouse gases especially carbon dioxide in the atmosphere due to:

            (a) combustion of fossil fuels

            (b) deforestation

            (c) industrial production

2. As the concentration of greenhouse gases rises, more heat is trapping in the atmosphere and raising the average temperature on earth. Hence, this phenomenon brings to global warming.

Effects:

1.    Occurrence of floods

·         As the average temperature rises, the polar ice caps and glaciers melt.

·         This increases the sea level causing low-lying areas to be flooded.

2.    Climate changes

·         Global warming leads to changes in wind directions and distribution of rainfall. As a result, agricultural activities are affected.

·         Global warming causes weather patterns to change. This affects the distribution of species which may lead to the extinction of species in certain region.

3.    Occurrence of droughts

·         Global warming increases the frequency of droughts.

·         The land becomes dry and infertile. This leads to a drop yields.

4.    Spread of diseases

·         With warmer climates, pests and vectors may spread to new areas.

·         The warmer conditions lead to an expansion of territories for disease-carrying vectors, resulting an increase in the outbreak of diseases.

Solutions to global warming:

1. Reduce the burning of fossil fuels.

2. Develop alternative sources of energy such as wind, solar and geothermal energy.

3. Reduce deforestation

4. Replant trees which have been cut down.

The Thinning of the Ozone Layer

Causes of ozone depletion:

1. The increasing levels of chlorofluorocarbons (CFCs) in the atmosphere.

In the stratosphere, CFCs molecules are broken down by ultraviolet rays, releasing chlorine radicals which destroy ozone in a chain reaction.

Effects of ozone depletion:

1. Prolonged exposure to ultraviolet radiation can lead to higher risks of:

(a)  skin cancer

(b)  cataracts

(c)  sunburns

2. Ultraviolet radiation weakens the immune system and the ability of the body to resist infectious diseases.
3. Ultraviolet radiation reduces nutrient contents and crop yield of plants.
4. Ultraviolet rays destroy the leaf cells and chlorophyll. This lowers the rate of photosynthesis and reduces crop yield.
5. Ultraviolet rays kill microorganisms and phytoplankton that are at the bottom of the marine food chain.
6. Leads increases in the temperature on Earth.
7. High levels of ultraviolet radiation can damage the eggs of amphibians.

Ways to reduce ozone depletion:

1. Reduce or stop the use of CFCs.
2. Replace chlorofluorocarbons (CFCs) with hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs).

9.3 Measure taken in the management of Development activities

Implementation of laws

*control pollution

~Enviromental Quality Act,1974

 (water quality management)

~Enviromental Quality Regulation,1989

(waste treatment & disposal facilities)

~Enviromental Quality Regulation,1977

(crude palm oil)

~Enviromental Quality Regulation,1979

(sewage & industrial effluents)

~Protection of Wildlife Act,1972

Use of Technology

*catalytic converters (clean up exhaust emissions & convert harmful gasses)

*use unleaded petrol 

*treat sewage treatment plants

*treat toxic waste produced in factories

*use microorganisms to clean up the environment

*develop hydrogen-basedfuel-cell vehicles

*use technology to capture carbon dioxide emissions

*use methods to reduce & capture methane emissions,a by-product of cattle & other

livestock waste & uses better controls on nitrous oxide emissions from nitrogen

fertilizers

Education on the management of resources

*4Rs (recycle,reuse,reduce & renew)

~RECYCLING means collecting &

segregating waste materials according to their types & turning them into new products.

~REUSE means to reuse things instead of throwing them away.

~REDUCE means reducing the use of materials.

~RENEW means to renew the use of materials after they are cleaned.

Preservation & conservation of soil , water , flora & mangrove swamps

*Preservation involves efforts to protect an ecosystem so that natural resources are utilised in a suitainable manner & the equilibrium of the ecosystem is maintain.

*Conservation involves effort to return an affected ecosystem to its natural equilibrium.

*Sustainable agricultural development is the effective use & preservation of soil to ensure continuous agricultural production.

~good farming techniques & agricultural pratices

*Water sources & catchment areas must be preserve

~rivers must not be regarded as dumping sites

~the use of nitrates & phosphate in agriculture must be control

*Forests

~establishing a level of selective harvesting

~reforestation

~restoration programmes

~forest reserves

~greater productivity must be reduce

*Mangrove swamps (flood control,nutrient & toxicant retention,sediment control,coastal erosion prevention,barrier against rising sea level)

The practice of biological control

*Biological control is the use of natural predators to control the population of pest species.

~cheap

~will not pollute the environment

The use of renewable energy

*RENEWABLE ENERGY is the energy flow that occurs naturally in the environment &

can be harnessed for the benefit of human.(inexhaustible & does not pollute the

environment)

~solar , wind , wave , flowing water , geothermal , biomass & palm oil fuel energy

The efficient use of energy

*reduce the use of coal , petroleum & other fossil fuels

*substitude natural gas for coal*improve fuel efficiency

*use cleaner fuel

*improve energy effiency

*use more hybrid car which combine electric & gasoline engines