Effects of Human Activities

  • Created by: ava.scott
  • Created on: 28-03-15 12:11


Superpests have evolved through the use of drugs and pesticides. These have eliminated competition allowing a resistant form to thrive.

Resistance: The ability of an organism to survive exposure to a poison which would normally be lethal.

Bacteria are RESISTANT to antibiotics- not immune.  They do not have an immune system!

Rats resistant to Warfarin.


  • Animals are fed antibiotics to keep disease away from herds.
  • The bacteria have now become resistant to the antibiotics.
  • This occured by random mutations giving an advantage to some bacteria against the antibiotic.
  • These mutated bacteria could survive and reproduce, so the mutated allele becomes greater in frequency in the gene pool
  • The resistance can also be spread ebtween bacteria via plasmid DNA, during conjugation.
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Biodiversity: The total number of species  on earth

Extinction: the loss of species

A lack of biodiversity and high rate of extinction has arised from human influence, such as use of resources.

Conservation of species ensures the conservation of existing gene pools.

Conservation is important because:

  • ethical reasons
  • there are potentially useful genes to man and the species.
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Reasons for extinction/endangerment 5 points

  • Natural selection
  • habitat destruction e.g. deforestation, loss of hedgerows
  • pollution such as PCBs and oil
  • hunting and collecting
  • competition from domestic animals
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Conservation: the PLANNED  maintenance of the biosphere and enhancement of biodiversity.


  • nature reserves and SSI protecting habitat e.g. wetlands, coral reef
  • international cooperation restricting trade e.g. in ivory and whaling
  • breeding programmes 
  • Pollution control

Breeding programmes:

  • zoos
  • botanic gardens
  • sperm banks and seed stores
  • reintroduction programmes .e.g. Red Kite in mid Wales
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Why is conservation important? 6points

  • To ensure survival of species
  • conserve existing gene pools
  • to conserve potentially useful genes
  • E.G.- disease resistance
  • GENE BANK to cross with  highly cultivated varieties
  • Conservation of plants with medicinal properties.
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Agricultural exploitation:results 5 and monocultur

The increased efficiency and intensity in agricultural practices to meet demands of more food for human consumption.

The mechanisation of farming resulted in:

  • removal of hedgerows to allow machinery to work.
  • Monoculture to thrive, where there is a simultaneous growth of crop plants of the same age and type within a defined area.
  • fertilisers leaked into rivers resulting in eutrophication and ALGAL BLOOMS.
  • Reduction of species diversity in grasslands.
  • Drainage ditches have a detrimental effect on habitats>> decreased biodiversity.

Monoculture practices year after year results in poor yield because:

  • Mineral depletion- resulting in increased use of nonorganic fertilisers.
  • Increase in pests and disease- resulting in increased use of pesticides.
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Agricultural exploitation: farmer efforts

Farmers are being encouraged to increase biodiveristy by:

  • land is given to conservation, and farmers are provided a subsidy to pay for lost income.
  • Hedgerows have been replanted, providing habitat for many species. Birds nest in them, and they act as a wildlife corridor between woodlands, increasing biodiversity.
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Nitrogen-containing fertilsers effects and legisla

  • Reduced plant species diversity in grassland. Nettles and other plants grow very fast compared to smaller plants.
  • Eutrophication- Increased salt levels in rivers destroy natural equilbirium, resulting in more algae blooms. Plants at bottom of pond cannot photosythesise (as ligh cant reach them).This reduces O2 concentration ( because of decomposers moving in and less photosynthesis), and can kill fish and other species.


  • Less fertiliser used
  • only apply fertilsier in times of active growth
  • leave a ***** atleast 10 metres wide next to water courses.
  • Dig drainage ditches.

HOWEVER the last is destructive to habitats.

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Cause of Deforestation


  • Large scale timber extraction- demand for timber is huge 
  • Wood is used as fuel and for paper and packaging
  • Clearing land for farming
  • Cash crops
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Consequences of deforestation

  • Reduced biodiversity
  • soil erosion resulting in increased sediment deposits
  • loss of valuable sources of plamnt chemicals that may have potential benefits for humans.

Soil erosion: The removal of topsoil containing valuable nutrients.

Tree roots help bind soil together, so deforestation makes it more easy to remove.

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Forest management

Forests anmd woodlands have been a valuable source of timber for thousands of years. We must manage it to continue using ti without destroying habitats.

Management includes replanting and regeneration via: 

  • Coppicing- cutting trees close to teh ground then leaving tehm to grow for several years. Most decidous trees grown from thebase when their trunks are cut down.
  • Selective cutting- Felling only the laregst trees, and allwoing smaller ones to remain. This reduces soil erosion and maintains  transpiration levels. This also helps maintain the nutrients in the soil.
  • Long rotation time- leaving ecah parts of the forest for a long time before reharvesting.
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Increasing forestry efficiency

  • Planting trees optimum distance apart. Too close results in intra specific competition.
  • Controlling pests and diseases: Trees will grow better resulting in a higher quality harvest.
  • Cutting simialr amounts of timber every year so an ecosystem can be maintained. Species and habitats are left intact.
  • Native woodland must be maintained to enhance biodiversity.
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Overfishing: Consequences

Overfishing: The rate at which fish are harvested exceeds the rate at which they reproduce.

Fish stocks then decrease rapidly.

Drift netting: Suspending a piece of net between two boats so fish swim into it.

Trawling: Dragging a large net through the water and catching everything in its way.


  • Herring are eaten by cod
  • herring are fished
  • cod population decreases
  • Krill are eaten by whales
  • kill is fished, whale population decreases.
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Measures to reduce overfishing

  • Imposing fish quotas from scientific estimates of fish stock size.
  • Restricting fish net emsh size- this allows baby fish to swim through and reproduce.
  • Enforcing exclusion zones where no fishing may take place.
  • Closing certain areas in different seasons.
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Fish Farming

This is more efficient as fish grow very rapidly in warm waters from factories.


  • Spread of disease
  • Overuse of antibiotics
  • Pesticides
  • Eutrophication--- incraese of fertilsers in waters, decreases O2 levels
  • Pollution around fish farms AND EVEN IN FISH THEMSELVES.


  • Farme dsalmon each 3x their weigh in food, which is made form other fish--- ????
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The Carbon Cycle

Deforestiation and burning fossil fuels amy lead to a greater greenhouse effect.

Greenhouse effect: The layer of gas above the atmosphere taht allow high energy solar radiation into the atosphere but not back out. This results in the earth heating up-- global warming.

Climate change: global warming may resust in a change of rainfall patterns, a rise in sea level, a wide range of impacts on wildlife and plants and humans.

Carbon footprint:  total amount of CO2 attributable to the actions of an individual/product/service over a period of one year.

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CONSEQUENCES of global warming

  • Scarcity of water in future food production--- drought-restiant crops may be developed.
  • Polar icecaps melting- coastal areas may flood.
  • Increase crop yields--- increased insect population!
  • increase CO2 dissolving into teh sea, decreasing pH and effecting fish popilations and marine life.
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Biofuel:any kind fo fuel that is biolgical in origin e.g. ethanol ansd diesel made from crops such as sugar cane and rapeseed.

May be a way to reduce greenhouse emissions, as the crops they are made from absorbs CO2, so ca be called 'carbon enutral'.


  • Reduce in biodiversity as large monoulture crops reduce the habitat available for species.
  • Crabon neutral isn't real because CO2 is used when transporting and processing the crops.
  • Food rpices may go up, as more crops are used for fuel rather than food.
  • Less focus of reducing energy use?? This should be the main aim to cut greenhosue emissions.
  • Cellulose cannot be processed immedicately by the fermenting pricess, so a lot of carbon watse comes from this.
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human pressures

The need to achieve sustainability by changes in human attitudes and informed choices.

  • education
  • advertisement
  • awareness

The need for political decision making to be informed by knowledge based on sound scientific principles.

  • Environmental monitoring and the need to provide data which is reliable and valid.
  • Issues surrounding the collection of data; possibility of conflicting evidence and interpretation.
  • Recognition of the possible tentative nature of conclusions.
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