Human Influences on the Environment

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Improving yield from crop plants and Fertilisers

Greenhouses provides right conditions for plants to grow for several reasons:

  • The transparent material allows sufficient natural light in for photosysthesis during the summer months and gives a "longer day" during the winter.
  • Short wave radiation entering the greenhouse becomes longer wave radiation as it reflects off the greenhouse's surface. They cannot leave as easily so greenhouse's heat up fast.
  • Burning fuels to raise the temperature which also produces C02 and Water Vapour.
  • The Water Vapour produces a moist atmosphere and so reduces water loss by transpiration.
  • In addition, growing plants in a hydroponic culture provides exactly the right amount of mineral ions for the specific crop being grown.

Fertilizers on the farm - Organic and Inorganic.

  • Organic contains farmyard manure whuch returns some nitrogen in the soil. But only can replace a small proportion.
  • Inorganic contains inorganic compounds such as Nitrates. Lots of farmers use this because it can replace all the lost ions. It can lead to problems like Eutrophication.
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Pests on the farm and Crop Rotation

Pests are organisms which reduce the yield of crop plants. Pests can be controlled in a number of ways. Chemicals called pesticides can be used to kill them or by using biological control. With Pests it causes economic damage.

  • Pesticides are poisonous, so theymust be used carefully too keep it below the "safe level". They also harm other wildlife as well. Some do not work as some pests will be resistant. Through chance of mutation and natural selection. This makes some pesticides useless and cause environmental damage as well.
  • Biological Control is an alternative, it means using other organisms to reduce numbers of pest.
  • The helpful organisms could be predators and parasites (some flies lay eggs inside pests).
  • Biological control can have a longer-lasting effect than spraying pesticides and less harmful.

Crop Rotation

Involves planting different crops in fields on a rotation basis. This means that when over wintering pests emerge, their "favourite food" is no longer there. This stops build-up of pests in a particular place.

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Fish Farming

There is a high demand for food due to population increase. Fish are farmed in cages in the sea:

  • They are kept in cages in the seas to stop them using as much energy and protects them from predators.
  • They are fed a diet of food pellets that's carefully controlled to maximise the amount of energy they get. They have better quality of food which means that they will grow quicker and bigger.
  • The young fish are separated from the bigger fish just in case they are eaten by the bigger one.
  • Not only they are in cages they in tanks which can be monitored to check temperature, oxygenation and water quality (pH). Usually cleans the fish feaces and food pellets as well.

Although there are some disadvantages

  • The spead of disease is greater due to they are close together. Antibiotics are used often to treat it but this is degraded by time the fish are eaten by humans.
  • There are pollution problems as well from the fish feaces and the uneaten food pellets which cause eutrophication of the water.
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Air Pollution

Air Pollution- We pollute the air with many gases. The main ones are Carbon Dioxide, Carbon Monoxide, Sulfur Dioxide, Nitrogen Oxide, Methane and CFC's.

Carbon Dioxide

  • It has been rising since because we use it in car exhausts,etc.Also due to deforestation as well as we are cutting trees for resources. Trees take in CO2 so if we cut down trees it will increase. 
  • The greenhouse gases keep the heat in. They include Water Vapour, CO2 & Carbon Dioxide. They form a layer around the earths atmosphere.
  • Short wave radiation from the Sun strikes the planet. Some is absorbed and some of it is re-emitted as longer wave radiation, which will otherwise escape to space. This is the "greenhouse effect".

Carbon Monoxide

  • Made by Incomplete Combustion. It is a colourless, odourless and tasteless gas.
  • If inhaled CO enters the blood and combines inrreversibly with haemoglobin. It forms carbohaemoglobin which stops haemoglobin from transporting Oxygen.
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Air Pollution (continued)

Sulphur Dioxide

  • Sulphur Dioxide is an important pollutant as it is a major constituent of Acid Rain.
  • Some Lichens are more tolerant to Sulphur Dioxide. Lichens incicate different levels of Sulphur Dioxide pollution. They are more sensitive in cities due to high levels of pollution.

Acid Rain

  • Sulphur Dioxide and Nitrogen Oxide dissolve in rainwater to form a mixture of acids. Including Sulphuric acid and Nitric Acid
  • It effects rivers and lakes making them acidic causing death to many organisms.
  • Acid rain also causes aluminium ions to dissolve from the soil and poison organisms. and washes out vital minerals for plants to grow.


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Water Pollution (Eutrophication) and Deforestation

  • Nitrates and Phosphates are put into fields as mineral fertilizers.
  • If too much fertiliser is applied and it rains afterwards, nitrates are easily leached into rivers and lakes.
  • The result is Eutrophication.
  • When it is in the lake, it creates Algae due to the extra nutrients. It grows really fast and blocks out light.
  • Plants in the rivers and lakes cannot photosysthesise due to lack of light and start to die.
  • With more food availiable, micro-organisms that feed on dead plants increase number and use up Oxygen in the water.
  • Organisms that need Oxygen, like Fish die

Effects of Deforestation

  • Habitat removal
  • Soil Errosion
  • Water Cycle effected- No trees, No transpiration therefore less rain water leads to drought.
  • Less photosysthesis leads to increase of CO2
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