living things in their environment

8/13/2019 Living Things in Their Environment

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Effects of human activity

on the ecosystem

Biology Study NotesGCE Study Buddy


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Impact of Humans

Humans pose a huge threat to lives of animals, plants andtheir environment

Our impact is so great due to:

- technologies that change the world so quickly

- population increase

- consumption of natural resources, and waste


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Deforestation Reasons

Urban development land has to be cleared for building

houses, roads, factories etc

Cultivation land for growing crops

Grazing large open grasslands needed for grazing by

cattle, sheep, horses, etc

Timber wood needed for construction, paper industry,

fuel

Fibres plants are useful sources of fibres for producingsynthetic textiles


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Damaging effects of

deforestation Soil erosion

Forests important in soil stability

The leafy canopy of the tress in tropical rainforests protects thesoil from the impact of falling rain

The roots hold soil and water, and release water gradually tothe soil below and to the nearby streams and likes

With trees removed, the soil is exposed directly to the force ofthe rain

Topsoil, the most fertile layer, gets washed away during heavyrain especially on steep slopes

When the whole of the topsoil is washed down sheet erosion

Without the trees forming a shelter belt, the soil is also exposedto wind erosion


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Damaging effects of

deforestation Flooding

Eroded soil may be deposited in rivers and streams

blocking flow of water

Rainwater is not retained and released slowly as trees

have been removed

The water levels in rivers rise rapidly

Water flows inland causing floods


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Damaging effects of

deforestation Desertification

Sunlight falls directly onto the soil and water evaporates directlyfrom the soil which then hardens

With the topsoil eroded, plant life cannot be supported

Other organisms which depend directly or indirectly upon plants

for food, also disappear land becomes barren The destruction of land leading to desert-like conditions is

called desertification

Desertification results in

Loss of habitats

Extinction of many species of organisms Loss of robust wild species of plants that may be useful in

treating diseases

The delicate balance between oxygen and carbon dioxidebecomes upset

Climatic changes


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Climatic changes due to

desertification In the forest, rainwater is retained and absorbed by the

roots of trees

The water is lost during transpiration

The relative humidity of the air around the forest is high

The water vapour eventually condenses andprecipitates as rain

When the trees are cleared, the area becomes dry andwarm, and annual rainfall decreases


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Pollution Air pollution

Results mainly from incomplete burning of fuels such as

coal, oil petrol and wood

The gaseous pollutants may be due to human activities or

natural occurrences such as biological decay, forest fires

or volcanic eruptions


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Air Pollutants Sulphur dioxide and nitrogen oxides

From burning of fossil fuels coal, oil, natural gases

Sulphur dioxide at high concentrations has damaging effects on

both plants and animals

Sulphur dioxide penetrates the leaves through the stomata this damages the leaves and kills the plants

In humans, sulphur dioxide irritates and damages the sensitive

lining of the eyes, air passages and lungs

Acid rain: sulphur dioxide and oxides of nitrogen react with

oxygen and rainwater directly to form sulphuric acid and nitric

acid respectively

Causes death of fish in lakes and rivers

Acid rain dissolves aluminium salts in the soil and washes them

into rivers and lakes poisonous to fishes


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Air Pollutants Smog

Main component is sulphur dioxide

Smog is a mixture of smoke and fog

Happens when a layer of warm air lies like a lid on top ofcool air the cool air together with pollutants such as

smoke and sulphur dioxide is prevented from escaping

They accumulate in the stagnant air until they reach such

high concentrations as to produce lethal results


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Air Pollutants Lead

May be present in the air, water and the food we eat

Lead poisoning occurs when lead accumulates in the

body over long periods

High concentrations of lead in the body may cause

cramps, loss of control of the hands and feet, and even

coma


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Air Pollutants Carbon dioxide

Burning of organic compounds releases carbon dioxide

into the air

Industrialization and increasing car population results in

carbon dioxide being released in increasing

concentrations into the atmosphere

The gas forms a layer over the earths surface retaining

the heat radiating from the earths surface greenhouse

effect The result may be global warming


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Global Warming

Earth

s atmosphere is an insulating layer - It lets theSuns heat in but also stops some going out

Increase in carbon dioxidedue to:

1) Deforestation (loss in photosynthesis)

2) Combustion of fossil fuels

Increase in methanedue to:

1) livestock farming

2) rotting plant material

3) drilling for oil and gas


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Air Pollutants Chlorofluorocarbons (CFCs)

Non-toxic, unreactive chemicals

Used as aerosol propellants, as cooling agents in

refrigerators and air conditioners, and in foam packaging

Ozone is a gas that forms a layer over the earth. It

absorbs much of the UV rays from sunlight

When CFCs are released into the atmosphere from

aerosols, etc, they break down the ozone layer, allowing

more UV light penetrate into the earth increases risk ofskin cancer


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Ways of reducing air pollution Use catalytic converters in cars

Less use of cars

Use filters or scrubbers on chimneys to remove sulphur

dioxide

Use non-fossil fuels in factories or less use of fossil fuelsespecially near more densely populated areas

Use alkalis to neutralize acidic waste products from factories

before they are released to the environment

Use ozone-friendly products to prevent ozone depletion


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Water pollution Waste materials dumped into rivers and streams

Sewage

Untreated sewage discharged into rivers and lakes containsbacteria

Sewage is a good source of food for bacteria

Bacteria grow and multiply rapidly using up oxygen in the water

Other organisms, including fishes, die due to lack of oxygen

Anaerobic bacteria then continue breaking down the organicwastes releasing foul-smelling gases like hydrogen sulphideand ammonia

Untreated sewage may contain bacteria that cause diseaseslike cholera and typhoid


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Water pollution

Inorganic wastes

Poisonous metals such as mercury, arsenic and cadmium

Contaminates fish, seafood which are then consumed by

humans


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Water pollution Fertilisers containing plant nutrients are sprayed onto fields

so that plants can grow faster and boost crop yields.

Contain nitrates and phosphates which are useful nutrients forthe growth of algae and plants

Rain means may wash nutrients from the fields and intorivers and lakes (this is called run-off).

Eutrophication (hyper-nutrition from fertiliser pollution)occurs

Profuse growth and multiplication of algae and green plants occur Algae grows fast using up lots of oxygen and blocking sunlight

Plants begin to die providing food for microbes

Microbes increase the competition for oxygen

Water becomes de-oxygenated causing aquatic life to die


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Water pollution

Pesticides used to kill insects and other crop damaging micro-organisms can effect

the food chain

Pesticides can be absorbed by small aquatic animals

Fish each the animals, which have eaten pesticide

Birds eat the fish

Insecticides Used to kill insects

Some insecticides eg DDT (dichloro-diphenyl trichloroethane) are non-

biodegradable means that cannot be broken down by bacteria

Insecticides may be carried by rainwater into streams, rivers and lakes

In high concentrations, they may poison fish or animals that drink the

polluted water or feed on the contaminated fish

DDT is insoluble in water

It is not excreted but instead is stored in the fatty tissues of animals

accumulates in the bodies of consumer results in the insecticide being

passed along food chains, increasing in concentration in the bodies of

organisms along the trophic levels


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Water pollution Herbicides

Used to kill weeds

Certain herbicides eg 2:4:5T, contain an impurity called

dioxin which is harmful to human beings

When it is washed by rainwater into streams and rivers, it

pollutes the water supply

Dioxins may cause miscarriages in women, physical and

mental abnormalities in children and increase risk of

cancer

Ad t d


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Advantages and

Disadvantages of PesticidesAdvantages Disadvantages

Healthier crops Non-biodegradable pesticides may

cause pollution, and may increase

in concentration along the food

chain

Higher yields of crops Useful organisms in the

environment may be killed

Socio-economic advantages eg

more food is available, more profit

for farmers

Some pesticides are expensive

Pests may develop resistance

against the pesticides


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Conservation Protection and preservation of natural resources in the environment

Reasons for conservation

Ensure protection of plant and animal species and to prevent theirextinction

Maintain a stable and balanced ecosystem prevents disruption ofnatural cycles and global warming

Maintain a large gene pool

wild plants and animals possess favorablegenes by cross-breeding the different varieties of wild plants and

animals, can improve yield, vigor and quality of organisms

Ensure conservation of marine life, as marine fisheries are a majorsource of human food

Ensure conservation of tropical rainforests as they are of economicimportance sources of raw material for industries, medicinal drugs,natural insecticides and food

Scientific value useful information for Mans survival

Preserves the natural scenery and wildlife for people to appreciate,maintain natural resources for outdoor recreational activities


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Conserve fishing grounds Measures

Ban use of drift nets which indiscriminately trap all forms

of sea life

Use nets with a certain mesh size so that young fish are

not caught

Regulate size of ships allowed into fishing grounds

Limit period of fishing in the grounds

Ban the harvesting of endangered species, encourage

raising of these fish in hatcheries and release them intofishing grounds


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Recycling of materials Recycling:

Reduces waste disposal

Reduces pollution

Recycling sewage saves water

Saves energy and money

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