Mr G Davidson The human population is different from all other populations in that a number of the selection pressures have been overcome We have no natural predators We have created and developed areas for food production to prevent starvation ID: 751814
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National 5
Human Impact on the Environment
Mr G DavidsonSlide2
The human population is different from all other populations in that a number of the selection pressures have been overcome.
We have no natural predators.We have created and developed areas for food production to prevent starvation.We have developed medicines to help combat disease.Tuesday, 18 March 2014
Mr G Davidson
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Human PopulationSlide3
Tuesday, 18 March 2014
Mr G DavidsonSlide 3
Human PopulationSlide4
Because the human population is growing so quickly, there is a much greater demand for food, and this has lead to
intensive farming.This involves: growing high yielding plants.high dependence on chemical fertilisers.high dependence of pesticides.
Tuesday, 18 March 2014
Mr G Davidson
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Intensive FarmingSlide5
Intensive farming can involve growing “monocultures” where only one type of crop is grown over large areas.
This has advantages and disadvantages.Advantages include:In some cases more than one crop per year.Increase in yield.Lower labour costs due to more machinery used.
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Mr G Davidson
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Intensive FarmingSlide6
Disadvantages include:
Machinery can cause the soil to become compacted.Loss of biodiversity.A high risk of disease since all plants are genetically identical.Tuesday, 18 March 2014
Mr G Davidson
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Intensive FarmingSlide7
Fertilisers are chemicals added to soil to replace lost nutrients.
Magnesium and nitrates are two such nutrients.Nitrates are required for the production of nucleic acids, amino acids and proteins.Magnesium is a constituent of chlorophyll.Tuesday, 18 March 2014
Mr G Davidson
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FertilisersSlide8
One of the main problems with fertilisers is
leaching.This is when the water, carrying the fertilisers, runs off the land into rivers and lochs.This causes a rapid growth of algae which results in algal blooms.
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FertilisersSlide9
The rapid growth of algae across the surface of the water prevents light from reaching the plants beneath the surface.
This, in turn, prevents these plants from photosynthesising and so releasing oxygen into the water, and this results in the oxygen concentration of the water decreasing.Tuesday, 18 March 2014
Mr G Davidson
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Algal BloomsSlide10
When these plants die, the bacteria which decompose them also use up any oxygen in the water, lowering the oxygen concentration of the water even further.
This low oxygen concentration can have a severe effect on the biodiversity within the fresh water ecosystem.Tuesday, 18 March 2014
Mr G Davidson
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Algal BloomsSlide11
Pesticides are important chemicals used in farming to overcome competition from other plants.
They include:Fungicides – used to kill fungi.Insecticides – used to kill insects.Bactericides – used to kill bacteria.Herbicides – used to kill weeds.
Tuesday, 18 March 2014
Mr G Davidson
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PesticidesSlide12
Some pesticides can have adverse effects on populations, e.g. DDT.
The pesticide DDT was used a lot during and after WWII, but it was discovered that it built up in the bodies of animals that ate plants containing it.Tuesday, 18 March 2014
Mr G Davidson
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P
esticidesSlide13
This is called
bioaccumulation.As the pesticide travels along the food chain, the level of toxicity increases.This can often be fatal for the top carnivores.A lot of pesticides used nowadays are biodegradable.
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Mr G Davidson
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P
esticidesSlide14
Pollution is the addition of harmful substances to the environment.
There are some species which can live in polluted areas while there are some which can’t.Any species which can indicate a level of pollution by its presence or its absence, is called an indicator species.Tuesday, 18 March 2014
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PollutionSlide15
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Pollution Indicators
Some animals are only able to live in water which contains a lot of oxygen.
Others can survive in water which contains little or no oxygen.
In which type of water do you think you would find the following organisms?Slide16
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Stonefly Nymph
UnpollutedSlide17
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Water Louse
PollutedSlide18
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Caddis Fly Larva
UnpollutedSlide19
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Rat-Tailed Maggot
PollutedSlide20
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Sludge Worm
PollutedSlide21
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Mayfly Nymph
UnpollutedSlide22
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Blood worm
PollutedSlide23
Because intensive farming can result in a loss of biodiversity, some alternative methods have been put in place, and
biological control is one of those.This is the deliberate introduction of a predator or parasite of a pest.Like any other method, it has both advantages and disadvantages.
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Biological ControlSlide24
Advantages
No chemicals being added to the food chains.The introduced predator is specific to the particular pest being dealt with.It is much cheaper after the initial set-up costs.Tuesday, 18 March 2014
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Biological ControlSlide25
Disadvantages
Sometimes the introduced species can, itself, become a pest.It doesn’t guarantee that all pests will be killed.The introduced predator can leave the environment.Tuesday, 18 March 2014
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Biological Control