Pollution is the cootamination of the enviroment by waste substances, produced as the result of human activity.
Many waste substances are formed from the burning of fossil fuels to produce enrgy.
Air pollution may consist of:
Hydrocarbons released from combustion of fossil fuels. This causes smog, which can irritate skin and eyes.
Carbon dioxide released from comustion fossil fuels as important 'Greenhouse gas.'
Sulfur dioxide released from combustion fossil fuels. This contributes to acid rain.
Carbon monoxide released from vehicle exhaust and many industry's. This is a poisonous gas.
Water pollution may consist of:
Sewage which bacteria feed on it and use up all the oxygen in the water. This causes other living things to die of asphyxiation.
Nitrates can be washed out of the soil into streams, rivers, ponds and lakes.
The Carbon Cycle
Carbon is one element that is recyclednaturally. Carbon dioxide is a compound that contains carbon.
The atmosphere contains approximately only 0.04%carbon dioxide. However this is enough to supply all the plants in the world. Plants use carbon dioxide to make food in photosynthesis.
As plants are eaten, the carbon in them passes on to animals. Carbon passes along food chains and animals die and decompose.
Carbon dioxide is put back into the atmosphere by:
Olants and animals respiring.
Decomposrs such as bacteria and fungi in the soil respiring.
Burning(combustion) of fossil fuels, such as coal and oil.
The world’s human population has passed 6 billion and continues to increase. The growth in the human population and the increase in the standard of living are putting strains on the global environment.
Here are some of the ways in which this is happening:
Non-renewable energy resources, such as coal, oil and natural gas, are being used up rapidly
Raw materials are being used up rapidly
More waste is being produced
More pollution is being caused.
Some characteristics, such as eye colour and the shape of the earlobe, are controlled by a single gene. These genes may have different forms.
Different forms of the same gene are called alleles (pronounced al-eels). The gene for eye colour has an allele for blue eye colour and an allele for brown eye colour.
Alleles are dominant or recessive:
The characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pair
The characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair
For example, the allele for brown eyes is dominant, while the allele for blue eyes is recessive. An individual who inherits one or two alleles for brown eyes will have brown eyes. An individual will only have blue eyes if they inherit two copies of the allele for blue eyes.