1. Human Impact on the Environment
Mr G Davidson
National 5
Human Impact on the Environment

2. Human Population
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.
Monday, 17 September 2018
Mr G Davidson

3. Human Population
Monday, 17 September 2018
Mr G Davidson

4. Intensive Farming
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.
Monday, 17 September 2018
Mr G Davidson

5. Intensive Farming
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.
Monday, 17 September 2018
Mr G Davidson

6. Intensive Farming Disadvantages include:
Machinery can cause the soil to become compacted.
Loss of biodiversity.
A high risk of disease since all plants are genetically identical.
Monday, 17 September 2018
Mr G Davidson

7. Fertilisers
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.
Monday, 17 September 2018
Mr G Davidson

8. Fertilisers 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.
Monday, 17 September 2018
Mr G Davidson

9. Algal Blooms
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.
Monday, 17 September 2018
Mr G Davidson

10. Algal Blooms
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.
Monday, 17 September 2018
Mr G Davidson

11. Pesticides
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.
Monday, 17 September 2018
Mr G Davidson

12. Pesticides
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.
Monday, 17 September 2018
Mr G Davidson

13. Pesticides 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.
Monday, 17 September 2018
Mr G Davidson

14. Pollution
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.
Monday, 17 September 2018
Mr G Davidson

15. 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?
17 September, 2018
G Davidson

16. Stonefly Nymph
Unpolluted
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G Davidson

17. Water Louse
Polluted
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G Davidson

18. Caddis Fly Larva
Unpolluted
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G Davidson

19. Rat-Tailed Maggot
Polluted
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G Davidson

20. Sludge Worm
Polluted
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G Davidson

21. Mayfly Nymph
Unpolluted
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G Davidson

22. Blood worm
Polluted
17 September, 2018
G Davidson

23. Biological Control
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.
Monday, 17 September 2018
Mr G Davidson

24. Biological Control 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.
Monday, 17 September 2018
Mr G Davidson

25. Biological Control 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.
Monday, 17 September 2018
Mr G Davidson