Wednesday, 14 March 2012
Human population Factors affecting human population size -Birth rate The birth rate isthe number of live babies born ina year for every 1000 people. A high birth rate: -Early marriges -Lack of knowledge of birth control -Death rate The death rate is the number of people dying in a year for every 1000 people. A high death rate: -diseases -famine - natural disasters -Decrease in population size A people considered ageing when: -people under the age of 15 make less than 30% of the population. - people above the age of 65 make up more than 6% of the population. People density Human migration is human movement from one area to another. Immigration Immigration takesplace when people move to another country permanently. Emmigration Emigration takes place when people move out of the country permanently.
Pollutions Air Pollution Air pollution occurs when harmful subtances are realeased into the air. Causes of air pollution -burning of fuels,rubbish and forests Burning of fuels produces black smoke which are harmful to the environment. Burning of rubbish released poisonous into the air. Burning of forests also cause huge amount of smoke into the air. -Dust and dirts in the air When we breathe the air in lookedto be clean but actually there are a lot of dusts and dirts in the air. -Smoke from cigarettes Cigerretes consists of harmful subtances which is harmful to the environment. Effects of air pollution -health prolems Dirts in the air causes eye iritation. Cigerrets can leat us to lung cancer. -Haze haze is caused by the smoke when forests is burnt. -Acid rain When smokes is released into the airthey contain gases which dissolves in the rainwater. Water pollution Water pollution occurs when subtances is released into the water. Causes of water pollution -Harmful chemicals from factories nd farms Chemical that is wasted from the factories is realeased to the water. Pesticides and fertilisers from farms are released in to water. -Rubbish Rubbish is dump in to the water and cause the water to be dirty. -Human waste Some people do not have proper places to get rid of their wates so they dump it in rivers and seas. -Oil spills Oil are harmful when it leaks from ships and could cause an oil spill. Effects of water pollution -Harms organisms in water Rubbish and chemical waste contains harmful subtances which could kill the organisms in water. -Harms human Polluted water is unsafe to drink. Soil pollution Soil pollution occurs when subtances are released into the soil. Causes of soil pollution -Rubbish When rubbish is dumped on land,the soil is pollutedand they seep into the soil. -Harmful chemicals from farms Excessive in farms can pollute the soil. Effects of soil pollution -Air pollution When rubbish can't be brokened down it releases harmful gases into the Air. -Water pollution The waste of the soil pollution can go to water. -Deterioration of soil condition Pesticides can kill living things living underground. -Growth of germs and pests As the number of rubbish grew bigger,the bacterias are growing rapidly.
Subscribe to:
Posts (Atom)