1
Q
How does deforestation increase the carbon dioxide content in the atmosphere?
A
- Removal of trees so less uptake of carbon dioxide from the atmosphere due to less photosynthesis
- Plants store carbon as biomass so burning the woody parts of trees releases carbon dioxide
- Forested is replaced by crops which store less carbon dioxide and when crops die, decomposers undertake decay, releasing CO2
- Forest is often replaced with cattle that produce high levels of carbon dioxide and greenhouse gases such as methane
2
Q
What are the 2 main reasons for the rise in atmospheric carbon dioxide levels?
A
- Combustion - the burning of fossil fuels releases carbon dioxide that was previously locked up
- Deforestation
3
Q
What is the impact of global warming?
A
- Increased frequency of extreme weather conditions, polar ice caps melting and an increased frequency of forest fires
- Consequently species distribution may change, plants and animals may be driven to extinction if they cannot find a suitable new habitat fast enough, reducing biodiversity
- In some regions there may be increased crop yields, but pest populations may also increase
4
Q
What are some consequences of global warming and climate change on aquatic habitats
A
- Decreased pH (acidification) of oceans - corals die, damages mollusc shells
- Increased rates of photosynthesis in aquatic habitats causing algal blooms
- Less oxygen dissolves in water at higher temperatures
- Fish migrate to cooler waters
- Reduced prodctivity on fish farming industry
5
Q
What are some possible changes in farming practices due to climate change?
A
- Rotating crops to reduce pests and mineral depletion
- Salt tolerant crops to overcome rising sea levels
- Feeding cows high-sugar grasses with less cellulose to reduce the release of the greenhouse gas methane
- Drought resistant crops to tackle the low and fluctuating water supply
- Improving drainage to aerate waterlogged and anaerobic soils
6
Q
What are the 5 main processes in the nitrogen cycle?
A
- Ammonification
- Nitrificaition
- Nitrogen fixation
- Assimilation
- Denitrificationn
7
Q
Describe ammonification
A
Decomposers (saprotrophs and detritivores) result in the decay of dead plants and animals, faeces and urine into ammonium ions
8
Q
Describe nitrification
A
The ammonium ions produced by decomposers are converted into nitrites and then nitrates by nitrifying bacteria. Aerobic conditions are required for this process. Plants can then absorb these nitrate ions and incorporate them into amino acids, nucleotides and chlorophyll
9
Q
What are the 2 key nitrifying bacteria
A
- Nitrosomonas convert ammonium ions to nitrites
- Nitrobacter convert nitrites to nitrates
10
Q
Describe nitrogen fixation
A
Nitrogen-fixing bacteria can directly fix nitrogen gas into ammonium ions
11
Q
What are the 2 key nitrogen-fixing bacteria?
A
- Azotobacter - free living in the soil
- Rhizobium - found in root nodules of leguminous plants
12
Q
How are rhizobium symbiotic bacteria?
A
When nitrogen gas diffuses into the root nodule, rhizobium produces nitrogenase enzyme which catalyses the fixation of nitrogen gas into ammonium ions. These ammonium ions can then be converted into amino acids for use by the plant. Bacteria gain sugars form the plant.
13
Q
Why are root nodules of legumes pink?
A
Presence of haemoglobin. Nitrogenase is inhibited by oxygen so haemoglibin binds with the oxygen
14
Q
Describe assimilation
A
The formation of organic nitrogen compounds (eg amino acids) from inorganic nitogen compounds present in the environment
15
Q
Describe denitrification
A
Denitrifying bacteria (eg pseudomonas) convert nitrate from soil into nitrogen gas. This is a problem as it removes useful nitrogenous compounds from the soil. Anaerobic conditions are requires for this and it occurs most often in waterlogged soils
16
Q
How would ploughing and drainage of soil aid the nitrogen cycle?
A
Improves aeration of soil, enabling nitrifying bacteria to convert ammonium ions into nitrate and prevents denitrifying bacteria from completing denitrification
17
Q
How would cultivation of legumes in soils lacking nitrogen aid the nitrogen cycle?
A
Rhizobium will carry out nitrogen fixation within the plants and then when the plants die these nitrogenous compunds will enter the soil to be broken down be decomposers in ammonificaiton
18
Q
Describe eutrophication
A
- Fertilisers leach into watercourses, increasing levels of nutrients
- There is a bloom of algae, blocking out the light to plant below. These plants die as they can’t photosynthesise
- Decomposers such as bacteria and fungi decompose the dead organic matter
- As these bacteria respire aerobically they use most of the available oxygen. This creates a biological oxygen demand
- Aquatic animals die due to lack of oxygen for respiration
- Anaerobic bacteria then flourish
19
Q
How can high nitrate levels in waterways be overcome?
A
- Restricting the amount of fertiliser added to soil
- Only applying fertiliser wen crops are actively growing so that it is readily taken up and does not remain in the soil
- Digging drainage ditches for minerals to concentrate in. This however has led to a drop in invertebrate biodiversity and has reduced species diversity in nearby grasslands
20
Q
Define extinction
A
When there are no living members of a species left
21
Q
State 9 threats to species
A
- Natural selection
- Non-contiguous populations
- Overhunting
- Competition from other introduced species
- Pollution
*6. Deforestation - Drainage of wetlands
- Hedgerow loss
- Crop sowing seasons*
Itallics are a loss of habitat
22
Q
State 6 conservation techniques
A
- International cooperation eg restricting trade in ivory
- Gene banks conservation of existing gene pools includes breeding programmes in zoos, sperm and seed banks, reintroduction of species
- Legislation laws protecting habitats and wildlife eg preventing overfishing
- Ecotourism eg educating visitors, employing local visitors
- Protecting habitats eg from urban development including national parks and SSSIs
- Education public awareness campaigns on global or national scales
23
Q
What does SSSI stand for?
A
Sites of special scientific interest
24
Q
Why is conservation of existing gene pools important?
A
- Ethical reasons: each species is a unique combination of genes and alleles and is therefore valuable
- Agriculture and horiculture: breeds of animals and plants used in agriculture and horiculture have been selectively bred so may lack rare alleles that could be important in the future. Wild plants and animals can act as a gene bank for these alleles which animals and crop plants can be bred with.
- Environmental changes: a large, varied gene pool increases the chance of a species surviving environmental change
- Potential medical use: Plants and animals may have the potential to help in the development of new drugs or other medical treatments
25
What factors must scientists consider if re-introducing species is to be successful?
- **Habitat:** recieving habitat is suitable, effect of species introduction on habitat or effect on biodiversity
- **Research:** resources and expertise are available for the establishment and protection of the reintroduced species
- **Consultation:** between neighbouring landowners and local stakeholders, to make sure the majority of those consulted do not oppose reintroduction
- **Correct individuals:** a suitable disease-free donor population is identified and the correct species is reintroduced
26
How can re-introduction into areas where there are no well-established populations help?
- Fewer predators
- Less intraspecific competition for food//nest sites/habitats
- Less likely to pass on disease as fewer numbers (initially)
27
Why could illegal or unregulated re-introduction of species be a concern?
- Introduction of disease
- Destruction or loss of habitat and other effects on ecosystem
- The wrong species would not be so well adapted
28
Explain the effect that removal of hedgerows would have on biodiversity
## Footnote
Allows farmers to use larger machinery to plough the soil and harvest crops
Reduces biodiversity by removing breeding sites, feeding sites and wildlife corridoors (which allow animals to move form one area to another)
29
What effect will monoculture have on biodiversity?
Only provides one habitat, reducing the number of different microhabitats that would be available in an area with mixed crops.
Roots grow to the same length and extract the same minerals from the same depth of soil, reducing the concentrations of nutrients in the soil and increasing the use of inorganic fertilisers
## Footnote
Single crops eg maize, wheat, barley aew grown in large fields
30
What are the environmental implications of overgrazing?
Can lead to soil erosion and desertificstion. Hooves of cattle compact soil, driving out air and preventing water drainage. Roots cannot penetrate the soil and grass for grazing cannot grow.
## Footnote
Occurs when plants are exposed to intensive grazing for extended periods of time
31
Define deforestation
The removal of trees in an unsustainable way
32
Name 6 reasons for deforestation
1. Demand for timber as a construction material
2. Wood used for fuel
3. To make paper and cardboard packaging
4. To clear the land for farming
5. To improve transport infrastructure by building new roads
6. Targeting high value trees eg teak and mahogany
33
State and explain 3 consequences of deforestation
1. **Global climate change:** less CO2 removed from the atmosphere by photosynthesis. Combustion of trees releases CO2 from biomass. Logs decompose and decomposers release CO2. Fossil fuels burnt in transport of logs
2. **Destruction of habitats:** reduces biodiversity. Plants may have undiscoverred medical properties
3. **Soil erosion:** the removal of topsoil which contains valuable nutrients. Removal of trees on higher slopes can lead to lowland flooding after heavy rainfall. Topsoil in the sloped areas can be swept away by the rain.
34
What is forest management?
The sustainable replanting and regeneration of forests
35
State and explain 5 techniques to manage forests
1. **Coppicing:** tree trunk is cut but a stool a few cm high is left. New shoots energe from the stool and grow into poles.
2. **Selective cutting:** some larger trees are felled whilst others are left in place. Makes the soil less vulnerable to erosion
3. **Long rotation times:** letting trees grow for a long period of time before cutting them down
4. **Planting trees optimum distances apart:** reduces intraspecific competition which can lead to trees growing tall and thin and so producing poor quality timber
5. **Controlling pests and diseases:** ensures trees grow well and produce high quality timber, this then means that fewer trees need to be felled and the best use is made of land
36
What effects can overfishing have on other wildlife?
- Drift nets can catch non-target species such as turtles or dolphins
- Trawling damages the sea floor habitat of organisms such as molluscs
- Can catch organisms that are the prey of other species which can affect whole food webs
37
State 6 controls that can be used to reduce the impact of overfishing
- Impose quotas on catches so only a certain mass of fish can be landed
- Ensure mesh sizes of nets are large enough to let young fish escape
- Enforcement of exclusion zones in areas where fish breed and during breeding season
- Legislate size of fishing fleets and number of days at sea
- Encourage consumers to eat sustainably sourced fish
- Fish farming or aquaculture
38
What is fish farming?
Where fish are bred and grown to maturity in enclosures in ponds, lakes, estuaries or in tanks on land
39
Name 3 advantages of farming fish rather than traditional livestock
- Fish convert their food into protein more efficiently
- A greater proportion of a fish's body is edible
- Fish farming has a lower carbon footprint
40
State and explain 5 problems with fish farming
1. **Diseased fish:** high density so disease easily transmitted. Pesticides have to be used to keep the fish healthy, but can harm other organisms. Escaped fish can pass parasites and other infections to wild populations
2. **Pollution:** waste from fish farms can get into water around the fish pens and lead to eutrophication
3. **Resource use:** farmed fish eat a large amount of food, whcih is often other fish. This is inefficient.
4. **Environmental toxins:** more concentrated in famed fish than wild fish
5. **Environmental degradation:** local environment can be damaged leading to salinisation of soil and groundwater leading to destruction of mangroves
41
What are planetary boundaries?
A ssfe operating space for humanity. Once human activity has passed a certain threshold, there is risk of irreversible and abrupt environmental change
42
Has the biodiversity boundary been crossed? Why? What can we do to help?
Yes
Human activity has caused environmental changes to happen too fast for natural selection to produce organisms that are adapted to the changing environment
Monitor biodiversity, collect materials for gene banks, raise public awareness to reduce human behaviour that has generated biodiversity loss
43
Has the climate change boundary been crossed? Why? What can we do to help?
Yes
Greenhouse gases are continually being added to the atmosphere, causing an increase in global temperature, climate change, rise in sea levels
Production of biofuels. As the growth of biofuel crops takes in carbon dioxide from the atmosphere, the release of CO2 when they're burnt has less impact
44
Has the nitrogen boundary been crossed? Why? How can we help?
Yes
Denitrification due to waterlogged soils. Use of agricultural fertilisers, leading to eutrophication
Planting fields of legumes to increase nitrogen fixation. Ploughing soil to improve aeration and prevent anaerobic conditions
45
Has the land use boundary been crossed? Why? What can we do to help?
Yes
Deforestation to allow for farming and urban development has led to a conflict between the need to grow food and the need to grow biofuels and protect natural habitats
Change farming practices to concentrate it in the most productive areas. Reduce consumption of meat to reduce land being cultivated
46
Has the fresh water boundary been crossed? Why? What can we do to help?
No, it is avoidable
Decrease in supply of fresh water is due to changing landscapes, agriculture, increased demand from humans, water pollution and climate change
Water conservation, water efficiency, waste water reclamation, drip irrigation system. Desalination to produce fresh water from salt water.
47
Has the ocean acidification boundary been crossed? Why? What can we do to help?
No, it is avoidable
The pH of the oceans is decreasing due to dissolving carbon dioxide forming carbonic acid which releases hydrogen ions. Low pH leads to mollusc, coral shells and athropod exoskeletons softening, making them vulnerable
Reduction in the burning of fossil fuels
48
Has the ozone boundary been crossed? Why? What can we do to help?
No, it has been **avoided**
Chloro-fluorocarbonds (CFCs) favour the breakdown of the ozone. CFCs were widely used in spray cans, solvents, refrigerator coolants. Resulted in the thinning of the ozone. Use of CFCs in spray cans was banned. Ozone layer now recovering naturally.
49
Has the chemical pollution boundary been crossed? Why?
It is **unquantified**
Organic pollutants, radioactive materials, nanomaterials and microplastics. Could all interact with eachother and produce harmful effects
50
Has the aerosol boundary been crossed? Why?
It is **unquantified**
Atmospheric aerosols can lead to respiratory problems and casue death from lung disease. Sulphates in aerosols reflect sunlight, providing a cooling effect, but other particulated reradiate it, increasing warming
Bio Component 1
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