Human Impact on the Env.

Question 1

Describe global warming.

Answer 1

The gradual rise in the average
temperature of the Earth due to increasing atmospheric levels of carbon dioxide and methane gas.

Question 2

What is the greenhouse effect?

Answer 2

The increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere.

Question 3

How might global warming affect the natural world?

Answer 3

• 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

Question 4

What is the nitrogen cycle?

Answer 4

The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification.

Question 5

How do plant roots take up nitrogen?

Answer 5

Taken up via active transport and facilitated diffusion as ammonium (NH +) and nitrate ions (NO2-).

Question 6

Name the four types of bacteria involved in the nitrogen cycle.

Answer 6

• Nitrogen-fixing bacteria
• Nitrifying bacteria
• Denitrifying bacteria
• Decomposers

Question 7

Describe ammonification.

Answer 7

The production of ammonium
compounds when decomposers feed on organic nitrogen-containing molecules.

Question 8

Describe nitrification.

Answer 8

The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes.

Question 9

Give some examples of nitrifying bacteria.

Answer 9

• Azotobacter - lives freely in the soil
• Rhizobium - lives inside the root nodules of leguminous plants

Question 10

Describe nitrogen fixation.

Answer 10

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

Question 11

Name the two types of nitrifying bacteria. State their functions.

Answer 11

• Nitrosomonas - oxidises ammonium compounds into nitrites
• Nitrobacter - oxidises nitrites into nitrates

Question 12

Describe denitrification.

Answer 12

The conversion of nitrate ions to nitrogen gas by denitrifying bacteria.

Question 13

What are denitrifying bacteria?

Answer 13

Anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas.

Question 14

Describe the economic importance of the
nitrogen cycle.

Answer 14

Maximises plant growth and crop yield, increasing food production.

Question 15

How can farmers increase the nitrate
content of soil?

Answer 15

• Ploughing and drainage to aerate the soil
• Application of fertilisers
  Growing legumes

Question 16

What are fertilisers?

Answer 16

Natural or artificial materials that are added to soils to provide essential nutrients and improve plant growth.

Question 17

Give some examples of natural
fertilisers.

Answer 17

Manure Compost
Treated sewage

Question 18

Give an example of an artificial fertiliser.

Answer 18

Ammonium nitrate

Question 19

What is eutrophication?

Answer 19

The process by which pollution by nitrogen-containing fertilisers results in algal blooms and subsequent oxygen level reduction in bodies of water.

Question 20

Describe how fertilisers can cause
eutrophication.

Answer 20

1. Fertiliser run-off into rivers and lakes
2. Nutrients build-up in water
3. Algal bloom blocks sunlight
4. Aquatic plants cannot photosynthesise.. less oxygen produced
5. They die and decompose
6. Decomposers further deplete oxygen levels
7. Animals can no longer respire aerobically so die

Question 21

How does digging drainage ditches
affect habitats?

Answer 21

• Habitat loss
• Reduction in biodiversity
• May lead to eutrophication

Question 22

Describe what is meant by an endangered species.

Answer 22

A species that due to a loss of habitat or rapid decrease in population numbers is at risk of extinction.

Question 23

When is a species described as extinct?

Answer 23

When all members of the species are dead.

Question 24

Outline the potential causes for the extinction of a species.

Answer 24

• 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

Question 25

What is conservation?

Answer 25

The maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources.

Question 26

Describe how conservation can be
achieved.

Answer 26

· 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

Question 27

Why is the conservation of gene pools important?

Answer 27

• 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

Question 28

What is agricultural exploitation?

Answer 28

The increase in efficiency and intensity
of food production in order to meet growing demands

Question 29

What is deforestation?

Answer 29

The removal of trees from land which is subsequently used to grow crops or provide space for cattle

Question 30

Outline the consequences of
deforestation.

Answer 30

Loss of biodiversity
Climate change
* Habitat loss
* Soil erosion
* Desertification
* Lowland flooding

Question 31

What do managed forests involve?

Answer 31

Sustainable replanting and regeneration. Examples
of methods include:
* Coppicing
Selective cutting
Long rotation time

Question 32

What is overfishing?

Answer 32

The excessive fishing of an area at a rate which exceeds potential replenishment of the species.

Question 33

Outline the methods employed to regulate fishing.

Answer 33

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

Question 34

What is fish farming?

Answer 34

The breeding of fish commercially in enclosures for food to combat
overfishing.

Question 35

Describe the problems of fish farming.

Answer 35

• 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)

Question 36

Define sustainability.

Answer 36

Using resources in a way that also maintains them for future generations.

Question 37

Environmental monitoring is required for conservation. Give some examples of factors that can be monitored.

Answer 37

Air quality
Water quality
* Soil quality

Question 38

What are planetary boundaries?

Answer 38

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.

Question 39

Which four planetary boundaries have
been crossed?

Answer 39

Climate change
Biosphere integrity
* Land system change
* Biogeochemical flows

Question 40

Which two planetary boundaries are
avoidable?

Answer 40

Ocean acidification
Fresh water use

Question 41

Which planetary boundary has been
avoided?

Answer 41

Ozone depletion in the stratosphere.

Question 42

Which planetary boundaries are not
quantified?

Answer 42

• Atmospheric aerosols
• Introduction of novel entities