Human Impact on the environment Flashcards
If trees are cut down from a forest with machinery, why could this increase the concentration of co2 in the atmosphere?
- Combustion of diesel fuel by machinery releases CO2 gas into the atmosphere
- Lack of trees means less photosynthesis to fix co2 (so less CO2 being used up
- Discarded plants/branches/leaves/debris gets decomposed by saprophytes
What are the effects of human activities on the carbon cycle?
-Deforestation
-Climate change
-Global warming
-Ocean warming
How does deforestation affect the carbon cycle?
•Increases the carbon dioxide content in the atmosphere:
aremoval of trees so less uptake of CO2 from the atmosphere due to less photosynthesis.
-Plants store carbon as biomass so burning the woody parts of trees releases carbon dioxide into the atmosphere.
-Forested is replaced by crops which store less carbon dioxide and when crops die, decomposers undertake decay, releasing carbon dioxide.
-Forest is often replaced with cattle that produce high levels of carbon dioxide and greenhouse gases such as methane.
What is the cause of climate change and what is the reason?
-cause is thought to be the huge rise in atmospheric carbon dioxide levels and the rise in other greenhouse gases e.g. carbon dioxide, methane, nitrous oxides and water vapour.
-The two main reasons for the rise in carbon dioxide are combustion, the burning of fossil fuels releases carbon dioxide that was previously locked up and deforestation.
How has carbon dioxide lead to global warming and what has this caused?
-CO2=important greenhouse gas, as it absorbs radiation from the Earth. If it accumulates in excess, it leads to global warming.
-resulted in 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, which reduces biodiversity.
-In some regions, there may be increased crop yields, but pest populations may also increase.
How does ocean warming link to CO2?
Oceans can store a lot of heat so there is a time lag between warming of the atmosphere (which Is linked to global atmospheric CO- levels) and the warming of the ocean.
What does an increase in CO2 levels in water result in?
-CO2 + H2O= H2CO3
-this means increase in H+ so decrease in pH
-so water dissolved shells/skeletons
What is agriculture particularly vulnerable to and what is the cause of this?
the impacts of climate change and is affected through changes in temperature, and timing and quantity of rain e.g. more flooding in the UK. (Extreme events, such as droughts and floods are likely to be more frequent due to climate change)
-As global warming increases, fresh water will be critical to sustain food production and feed the growing human population.
What are possible changes in farming practices due to climate change?
-Feeding cows high-sugar grasses with less cellulose to reduce the release of the greenhouse gas methane.
-Improving drainage to aerate water-logged and anaerobic soils. Re-instating meadows.
-Salt-tolerant crops to overcome rising sea levels.
-Keeping the soil healthy by using minimal preparation of land for growing crops (tillage) and cover crops like clover to protect and improve soils between crops
-Drought-resistant crops to tackle the low and fluctuating water supply
-Rotating crops to reduce pests and mineral depletion.
What is carbon footprint?
the total amount of carbon attributable to the actions of an individual, a product or service over a period of one year
How can we reduce our carbon footprint?
Recycling packaging material
•Driving less
•Using less air-conditioning and heating – insulating, clothing etc
•Choosing a diet low in animal protein, especially red meat
•Avoiding food waste – turn it into compost
•Planting trees
What is the nitrogen cycle?
the flow of organic and inorganic nitrogen within the abiotic and biotic components of an ecosystem, where there is an interchange between nitrogenous compounds and atmospheric nitrogen.
Why is nitrogen important to all living organisms?
-building blocks of nucleic acids- (DNA,RNA)
-amino acids for protein synthesis (nitrogen is in the NH2 amine group for protein synthesis)
-Nitrogenous bases in nucleotides (a,t,g,c,u)
-chlorophyll
-ATP is a nucleotide (contains adenine, ribose and 3 phosphate groups)
How do plants and animals get nitrogen?
-Plants and animals cannot use atmospheric nitrogen and so nitrogen enters the food chains when plants absorb ammonium or nitrate ions through their roots.
-Nitrogenous compounds then pass to consumers when they consume plants.
By which processes do nitrates get taken up by plant roots?
-Facilitated diffusion
-Active transport
What are two pathways that these ions can take when travelling through the cortex cells of a plant root?
Symplast – water & ions move through cytoplasm & plasmodesmata
Apoplast – water & ions move through the cell walls
What are the 5 main processes in the nitrogen cycle?
-Ammonification
-Nitrification
-Nitrogen fixation
-Assimilation
-Denitrification
What is ammonification?
Decomposers (saprotrophs and detritivores) result in the decay of dead plants and animals, faeces and urine into ammonium ions
What is nitrification?
-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.
What are the key nitrifying bacteria?
-Nitrosomonas convert ammonium ions to nitrites.
•Nitrobacter convert nitrites to nitrates .
What is nitrogen fixation?
Nitrogen-fixing bacteria can directly fix nitrogen gas into ammonium ions.
What are key nitrogen-fixing bacteria?
•Azotobacter free-living in the soil.
•Rhizobium found in root nodules of leguminous plants.
What are rhizobium and what do they do?
-symbiotic bacteria found in root nodules of legumes, e.g. clover and pea plants.
-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.
-However, nitrogenase is inhibited by oxygen.
-Therefore, Haemoglobin is present in root nodules to bind with the oxygen. -The presence of haemoglobin gives them a pink colour.
Why can the relationship between the bacteria in the root nodule and the legume be classed as a symbiotic relationship?
Bacteria gain sugars from plant photosynthesis, plant gains nitrogenous compounds.
What is assimilation?
-The formation of organic nitrogen compounds (e.g. amino acids) from inorganic nitrogen compounds present in the environment.
What is denitfrication?
-Denitrifying bacteria (e.g. Pseudomonas) convert nitrate from the soil into nitrogen gas.
-This is a problem as it removes useful nitrogenous compounds from the soil.
-Anaerobic conditions are required for this and it occurs most often in waterlogged soils.
What does rhizobium do?
Fix nitrogen gas into ammonium ions root nodules
What does azobacter do?
fix nitrogen gas into ammonium ions in the soil
What does nitrosomonas do?
Convert ammonium ions into nitrites in nitrification
What does nitrobacter do?
convert nitrites to nitrates in nitrification
What are human activities to aid the nitrogen cycle?
-Ploughing and drainage of soil to improve aeration
-Cultivation in soils lacking nitrogen
-Application of artificial fertilisers and manure to soil
-that will enable a greater yield of crop plants.
What does ploughing and draining of soil do?
-improves aeration
-this enables nitrifying bacteria to convert ammonium ions into nitrate and prevents denitrifying bacteria from completing denitrification.
What does cultivation of legumes in soils lacking nitrogen do?
-Cultivation of legumes in soils lacking nitrogen so that Rhizobium will carry out nitrogen fixation within the plants and then when the plants die these nitrogenous compounds will enter the soil to be broken down by decomposers in ammonification.
What do fertilisers contain?
Nitrates, potassium and phosphate
What do crop fertilisers need?
-Nitrate – nitrogen for amino acids, nucleic acids.
-Potassium for stomatal opening
-Phosphate for nucleic acids + ATP
What is the process of eutrophication?
1.Fertilisers leach into watercourses, increasing levels of nutrients.
2.There is a bloom of algae, blocking out the light to plants below.
3. These plants die as they can’t photosynthesis.
4. Decomposers such as bacteria and fungi decompose the dead organic matter.
5. As these bacteria respire aerobically they use most of the available oxygen. 6. This creates a biological oxygen demand (BOD).
7. Aquatic animals die due to lack of oxygen.
8. Anaerobic bacteria then flourish.
How can high nitrate levels in waterways be overcome?
by-
-Restricting the amount of fertiliser added to soil.
-Only applying fertiliser when 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 lead to a drop in invertebrate biodiversity and has reduced species diversity in nearby grasslands.
What are endangered species
those that are at serious risk of extinction.
What is extinction?
-when there are no living members of a species left.
-It is a natural process
What are the main threatens to species?
-Natural Selection
-Non-contiguous Populations
-(Deforestation
-Drainage of wetlands
Hedgerow loss
-Crop Sowing seasons)- loss of habitat
-Overhunting
-Competition from other introduced species
-Pollution
What is the explanation and an example of natural selection as a threat to species?
-Humans are changing environments faster than new mutations allow organisms to adapt
-mutations in DNA can create new beneficial alleles needed for advantageous phenotype- this increases survival and reproduction so species can pass alleles to next generation (but mutation rate is too slow to respond)
-Javan tiger
What is the explanation and an example of non-contagious populations as a threat to species?
-If small populations are isolated from each other and are unable to interbreed there may not be enough genetic diversity to ensure a healthy population.
-smaller isolated populations= smaller gene pool means fewer alleles
-Black rhinos in Africa
What is the explanation and an example of deforestation as a threat to species?
-Permanent removal of trees removes habitats.
-Habitat=site of reproduction/feeding/shelter
-Javan tiger
What is the explanation and an example of drainage of wetlands as a threat to species?
-Wetlands are drained to allow agriculture or building. This destroys habitats
-Large copper butterfly is now extinct in the UK.
What is the explanation and an example of hedgerow loss as a threat to species?
-Removal of hedgerows which have separated fields for centuries removes breeding sites, feeding sites and wildlife ‘corridors’ which allow animals to move from one area to another
Dormouse may face extinction in the UK
What is the explanation and an example of crop sowing seasons as a threat to species?
-Sowing during autumn rather than spring means plants are unsuitable heights for birds to build nests
-Skylark and lapwing are in decline.
What is the explanation and an example of crop growing seasons as a threat to species?
-For trophies, traditional medicine, ‘bush meat’, overfishing, agricultural exploitation
-Pyrenean Ibex
What is the explanation and an example of competition from other introduced species as a threat to species?
-Domestic animals and accidentally introduced animals predate or outcompete native species
-Dodo, red squirrels in uk
What is the explanation and an example of pollution as a threat to species?
-Pollutants kill organisms or make it more difficult for them to survive in their habitat
-Oil spills, PCBs
What is conservation?
the protection, preservation, management and restoration of natural habitats and communities; enhancing biodiversity whilst still allowing human activity
What are conservation techniques?
-International cooperation
-Gene banks
-Legislation
-Ecotourism
-Protecting habitats
-Education
What does international cooperation do?
(e.g. restricting trade in ivory or whaling) -Helps prevent species becoming endangered extinction of endangered species
What do gene banks do?
-Conservation of existing gene pools involves:
-Breeding programmes in zoos & botanic gardens.
-Re-introduction of species e.g. red kites.
-Sperm banks.
-Seed banks.
(keeps rare alleles- may help organisms survival)
What is legislation?
-National & international laws protecting habitats and wildlife e.g. EU
habitats directive preventing overfishing by imposing fishing quotas, preventing overgrazing
-large net size that some mature fish out of the net- maintains breeding populations
-limit size of boats/fishing and only certain times of the year
