Human Impact on the Env. Flashcards
Describe global warming.
The gradual rise in the average
temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas.
What is the greenhouse effect?
The increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere.
How might global warming affect the natural world?
- Temperature, rainfall, light levels etc. all affect survival
- Habitats may be destroyed by deforestation or flooding
Species may need to change their habitat, or face extinction
What is the nitrogen cycle?
The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification.
How do plant roots take up nitrogen?
Taken up via active transport and facilitated diffusion as ammonium (NH +) and nitrate ions (NO2-).
Name the four types of bacteria involved in the nitrogen cycle.
- Nitrogen-fixing bacteria
- Nitrifying bacteria
- Denitrifying bacteria
- Decomposers
Describe ammonification.
The production of ammonium
compounds when decomposers feed on organic nitrogen-containing molecules.
Describe nitrification.
The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes.
Give some examples of nitrifying bacteria.
- Azotobacter - lives freely in the soil
- Rhizobium - lives inside the root nodules of leguminous plants
Describe nitrogen fixation.
Conversion of ammonium ions to nitrate ions by nitrifying bacteria. Takes place in two stages:
Ammonium ions oxidised to nitrite ions
* Nitrite ions oxidised to nitrate ions
Name the two types of nitrifying bacteria. State their functions.
- Nitrosomonas - oxidises ammonium compounds into nitrites
- Nitrobacter - oxidises nitrites into nitrates
Describe denitrification.
The conversion of nitrate ions to nitrogen gas by denitrifying bacteria.
What are denitrifying bacteria?
Anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas.
Describe the economic importance of the
nitrogen cycle.
Maximises plant growth and crop yield, increasing food production.
How can farmers increase the nitrate
content of soil?
- Ploughing and drainage to aerate the soil
- Application of fertilisers
Growing legumes
What are fertilisers?
Natural or artificial materials that are added to soils to provide essential nutrients and improve plant growth.
Give some examples of natural
fertilisers.
Manure Compost
Treated sewage
Give an example of an artificial fertiliser.
Ammonium nitrate
What is eutrophication?
The process by which pollution by nitrogen-containing fertilisers results in algal blooms and subsequent oxygen level reduction in bodies of water.
Describe how fertilisers can cause
eutrophication.
- Fertiliser run-off into rivers and lakes
- Nutrients build-up in water
- Algal bloom blocks sunlight
- Aquatic plants cannot photosynthesise.. less oxygen produced
- They die and decompose
- Decomposers further deplete oxygen levels
- Animals can no longer respire aerobically so die
How does digging drainage ditches
affect habitats?
- Habitat loss
- Reduction in biodiversity
- May lead to eutrophication
Describe what is meant by an endangered species.
A species that due to a loss of habitat or rapid decrease in population numbers is at risk of extinction.
When is a species described as extinct?
When all members of the species are dead.
Outline the potential causes for the extinction of a species.
- Loss of habitat (e.g. deforestation, removal of hedgerows)
- Pollution (e.g. oil, PCBs)
- Overhunting by humans
- Introduction of new competitors (e.g. domesticated animals)
- Non-contiguous populations
What is conservation?
The maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources.
Describe how conservation can be
achieved.
· Protection of habitats, e.g. nature reserves, national parks, SSSIs
· Protection of endangered species, e.g. making hunting illegal, breeding programmes increase population size
International cooperation, e.g. restricting trade of endangered species and their parts
* Species reintroduction
Gene and sperm banks
Seed banks
Why is the conservation of gene pools important?
- Many plant species are yet to be discovered and may contain chemicals that could be used in future medicines
Protection of potential future food sources
· Some alleles may provide selective advantages, preventing extinction
Each species and its genes are precious
What is agricultural exploitation?
The increase in efficiency and intensity
of food production in order to meet growing demands
What is deforestation?
The removal of trees from land which is subsequently used to grow crops or provide space for cattle
Outline the consequences of
deforestation.
Loss of biodiversity
Climate change
* Habitat loss
* Soil erosion
* Desertification
* Lowland flooding
What do managed forests involve?
Sustainable replanting and regeneration. Examples
of methods include:
* Coppicing
Selective cutting
Long rotation time
What is overfishing?
The excessive fishing of an area at a rate which exceeds potential replenishment of the species.
Outline the methods employed to regulate fishing.
Using lines rather than nets
* Regulating net size
* Fishing quotas and exclusion zones
* Avoiding overfished species, fishing non-traditional species
Limiting fishing fleet sizes
* Marine stewardship council certification
What is fish farming?
The breeding of fish commercially in enclosures for food to combat
overfishing.
Describe the problems of fish farming.
- Rapid spread of disease
Escape of farmed fish - Spread disease to wild populations
O Larger, outcompete wild populations
Bioaccumulation of pesticides
Farmed fish contain high concentrations of toxic chemicals (e.g. dioxins, PCBs)
Define sustainability.
Using resources in a way that also maintains them for future generations.
Environmental monitoring is required for conservation. Give some examples of factors that can be monitored.
Air quality
Water quality
* Soil quality
What are planetary boundaries?
A set of nine limits proposed by a group of environmental and Earth system sciences within which human activity can operate without risk of irreversible damage to the planet.
Which four planetary boundaries have
been crossed?
Climate change
Biosphere integrity
* Land system change
* Biogeochemical flows
Which two planetary boundaries are
avoidable?
Ocean acidification
Fresh water use
Which planetary boundary has been
avoided?
Ozone depletion in the stratosphere.
Which planetary boundaries are not
quantified?
- Atmospheric aerosols
- Introduction of novel entities
