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CIE IGCSE 0610 BIOLOGY PAPER 1 & 3 DOUBTS !!!!!!

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rida.12.!!

rida.12.!!

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AS SALAM O ALAIKUM !!!
HI GUYS!!
ALRIGHT, SO I MADE THIS THREAD FOR ANY DOUBTS IN BIOLOGY .....
IF YOU'VE GOT ANY DOUBTS POST THEM HERE ,ME ALONG WITH THE OTHER MEMBERS WOULD TRY TO DO OUR BEST TO CLEAR OFF YOUR DOUBTS!!!!
MA'AS'SALAMA!!
:D :) :p
 
rida.12.!!

rida.12.!!

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guys some notes for pollution:
POLLUTION

Pollution is harm done to the environment by the release of substances produced by human activities. These substances are called pollutants.

water pollution by sewage and chemical waste

* Sewage includes human and livestock waste. It contains urea, ammonia, phosphates ,organic matter and pathogens.

* If sewage is not treated to remove nutrients and pathogens before disposal it can contaminate water and transmit disease such as cholera and typhoid.

* Untreated sewage released into water bodies (streams, rivers, ponds, lakes, seas) can also cause eutrophication.



* Chemical waste includes heavy metals ( mercury nickel, lead, cadmium).

* These metals can inhibit the activity of enzymes in organisms.

* They can damage the central nervous system and can result in death.

* These metals may be dumped into rivers, seas in small amounts in which they are not toxic.

* But if they enter the food chain ,they can harm the organisms at the top trophic levels through bioaccumulation along the food chain.

* Oil may be spilled into the sea and it can also disrupt the food chain.



* air pollution by sulfur dioxide

* Burning of fossil fuels release sulphur dioxide into the air.

* Sulfur dioxide causes irritation in the respiratory tract and skin irritation in some people.

* Increases the risk of asthma attacks and bronchitis .



Acid rain

Causes : release of sulphur dioxide and oxides of nitrogen into the air. These gases are produced by burning

fossil fuels.

* Sulfur dioxide comes mainly from burning coal in thermal power stations.

* Oxides of nitrogen is produced mainly in car engines by burning petrol.

* These gases dissolve in water droplets in clouds forming acids which fall to the ground as acid rain.

* Acid rain is rainfall with a pH of less than 5.6.Oxides of nitrogen also contribute to acid rain

Effects on the environment of acid rain

* Damage plant leaves, gradually killing the plants.

* May kill the plant roots making it difficult for them to absorb the mineral ions they need.

* Presence of acids in the soil dissolves nutrients which are then leached away reducing soil fertility.

* Acids in the soil dissolve aluminium ions which can be washed into lakes and rivers and poison the fish and invertebrates.

* Acidified water that enters the rivers, streams and lakes lowers the pH of the water. Some invertebrates and fish cannot tolerate the low pH and they die.

* Acid rain corrodes stonework on buildings.



Measures that might be taken to reduce incidence of acid rain



* use of low sulphur fuels. (Sulphur content in coal can be reduced by crushing it and then washing it with a

solvent that dissolves the sulphur compounds in the coal)

* use, alternative renewable sources of energy ; examples nuclear power ,wind power , wave power , solar power ,hydrogen power

* reduce use of coal

* flue gas desulfurisation by neutralising the waste gases with lime

* use catalytic converters to reduce the nitrogen oxides in the exhaust fumes of cars.

* Increase use of public transport , car sharing, electric cars, walking / cycling ;

* use biofuels instead of fossil fuels.



Effects of pollution due to pesticides including insecticides and herbicides

* Pesticides are chemicals that are used to kill unwanted organisms. These include insecticides which kill insects and herbicides which kill weeds.

* Farmers use insecticides to kill the insects that damage their crops.eg. aphids

* They are also used to kill insects that transmit human diseases. Eg. mosquitoes.

The undesirable effects of using insecticides are:

* may destroy useful species of insects such as pollinators ,predators

* may accumulate in food chain and disrupt food chains

* allow other species to flourish and become pests as competition is reduced.

* Some insecticides like DDT remain in the environment for a long time .



Herbicides reduce numbers of weeds so crop plants have less competition with weeds for light, water,or minerals This increases crop yield.

The undesirable effect of herbicides is that they may also kill useful or rare species of plants near the field where the herbicides are sprayed.



Effect of pollution by nuclear fallout

* Nuclear fallout refers to very small particles of radioactive materials produced by by a leak from a nuclear power station or from a nuclear explosion

* These radioactive particles can be carried in wind or water over long distances.

* These may remain in the environment and may be absorbed by living organisms.

* The radioactive material can bioaccumulate in food chains and can cause cancer in top carnivores.

* It can also cause mutations.



Effects of non-biodegradable plastics in the environment



* Plastics that are not broken down by decomposers are called non-biodegradable.This means they remain in the ground, taking up space and also cause visual pollution .

* Small animals may be trapped in discarded plastic bags or bottles.

* Burning of plastics release toxic gases.



The greenhouse effect

* Solar radiation passes through the atmosphere and warms the surface of the earth.

* The earth radiates heat energy back into space. This is mainly infra red radiation.

* Some of this heat energy is absorbed by the greenhouse gases. (carbon dioxide, water vapour and methane)

* This causes the air to warm up

* The greenhouse effect is a natural process which is necessary to keep the earth warm enough for living organisms.

Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming



* Human activities are causing an increase in the concentration of the greenhouse gases so the atmosphere is getting warmer. This is causing the enhanced greenhouse effect or global warming.

* The surface of the earth has warmed by 0.7oC over the past century.

* Power stations, factories, domestic heating and transport use fossil fuels and release large amount of carbon dioxide into the atmosphere. At the same time because of deforestation in different parts of the world there are fewer plants to absorb carbon dioxide

* There has also been an increase in methane due to expansion of rice cultivation and cattle rearing.

* Methane is released by cattle and by bacteria in the anaerobic conditions in the flooded rice fields.

* There is also an increase in methane released by anaerobic breakdown in waste dumps.

Global warming can:

* melt polar ice caps causing a rise in sea level and flooding of low-lying areas.

* Change wind patterns and distribution of rainfall leading to more extreme weather. Some areas may become very dry reducing food production.

* Outline the undesirable effects of the overuse of fertilisers.
 
rida.12.!!

rida.12.!!

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thx i found that already :
THE ABILITY TO DETECT CHANGES IN THE ENVIRONMENT AND THEN MAKE RESPONSES!!!
 
rida.12.!!

rida.12.!!

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describe two ways in which the leaves of desert plants reduce water lost in transpiration??
 
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