A Level Biology - Cycles

A Level Biology - Cycles
Covers:
Important definitions,
Carbon cycle,
Greenhouse effect,
Nitrogen cycle,
Eutrophication.

Transcript

1. Cycles – important definitions • Agricultural exploitation – the increase of efficiency and intensity of food production • Biodiversity – number of species and the number of individuals in each species in a particular area • Biofuel – fuel made by a biological process (anaerobic digestion) rather than geological processes (fossil fuels) • Carbon footprint – the equivalent amount of CO2 generated by an individual, product or service in a year • Conservation – protection, preservation, management and restoration of natural habitats and their ecological communities. Aim to maintain species and genetic biodiversity whilst allowing human activities to continue • Coppicing – cutting down trees close to the ground and leaving them to regrow over years • Core boundary – crossing a boundary would drive the earth into a new and unpredictable state with severe consequences for the biosphere • Deforestation – complete loss of trees in a defined area by human activities
2. Important definitions - continued • Ecotourism – responsible travel to natural area that conserves the environment and improves the well being of local people • Eutrophication – artificial enrichment of aquatic habitats by excess nutrients often caused by runoff fertilizers • Freshwater – low concentration of dissolved salts, AKA sweet water • Global warming – the increase of average temperature of Earth’s surface, in excess of the greenhouse effect caused by the atmosphere’s historical concentration of CO2 • Long rotation time – many years are left between harvesting adjacent areas and a variety of habitats develop, this favours diverse wildlife • Monoculture – growth of large numbers of genetically identical crop plants in a defined area • Overfishing – rate at which fish are being harvested exceeds the rate at which they are reproducing • Planetary boundary – a threshold value for a global process that is affected by human activity, crossing these could generate abrupt or irreversible environmental damage
3. Important definitions - continued • Saprobionts – microorganisms that obtain food from dead or decaying remains of other organisms. They ultimately release CO2 back into the atmosphere • Selective cutting – felling only some trees, leaving others in place
4. Carbon cycle
5. Plants CO2 in atmosphere Animals Decomposers Fossil fuels Volcanoes Oceans Respiration Respiration and deforestation Death and decay Death, decay and fossilisation Combustion Diffusion Volcanic eruptions Compacting sediments
6. Man’s impact on atmospheric CO2 levels • Levels have drastically increased over the past few hundred years following the industrial revolution • Combustion of fossil fuels has released more CO2 that was previously held in coal, oil and peat • Deforestations remove huge amounts of photosynthesizing plants, especially in the rainforests
7. The Greenhouse effect
8. Greenhouse gases (CO2 and methane) • CO2 – most important because there is so much of it and it stays in the atmosphere for much longer than the other greenhouse gases. Deforestation increases CO2 in atmosphere by removing photosynthesising plants and burning or letting the trees decay (both of which add CO2). 2 major reasons for the increase are deforestation and burning fossil fuels • Methane – microbes breaking down organic molecules which occurs during decomposition and digestion of organic matter in primary consumer intestines. A methane burp is a release of methane into the atmosphere when methane clathrates warm as a result of rising sea temperatures. It is also released by rice paddy fields
9. Effects of global warming • No certain effects (all estimations) • Levels could reduce naturally if phytoplankton and plants increase their rate of photosynthesis • Extinction of some species as the polar ice caps melt • Low lying land could flood due to rising sea levels as a result of the ice caps melting • Failure of crops due to less rainfall and higher temperatures • More rainfall and intense storms could cause a change in species distribution • Life cycles and populations of insects would alter as they adapt and tropical diseases could spread towards poles as temperatures increase • Reservoirs could fill • Crops could be grown where it was previously too cold • Rate of photosynthesis may increase, leads to possible two harvests per year
10. Nitrogen cycle
11. N2 in atmosphere NH4+ Ammonia NO2- Nitrite ions NO3- Nitrate ions Ammonium containing compounds in producers Ammonium containing compounds in consumers Ammonium containing compounds in decomposers Fixation by Azotobacter Fixation by Rhizobium Nitrosomonas Nitrobacter Root absorption Death and decay Excretion Ammonification Nitrification Denitrification by Pseudomonas
12. Processes in the nitrogen cycle Process Carried out by Involves/biochemistry Ammonification Decomposers (bacteria and fungi) Production of ammonium ions from dead/decaying plants and animals and faeces and urine Nitrification (1) Nitrifying bacteria (Nitrosomonas) Ammonium ions converted to nitrates Nitrification (2) Nitrifying bacteria (Nitrobacter) Nitrite ions converted to nitrate ions Nitrogen fixation Nitrogen fixing bacteria (Rhizobium in root nodules of legumes)(Azotobacter) Atmospheric nitrogen converted to ammonia Denitrification Denitrifying bacteria (Pseudomonas) Reduces nitrates and ammonium ions back into nitrogen
13. Human activities improving circulation • Ploughing fields – improves soil aeration so favours: aerobic, free-living nitrogen fixers (Azotobacter), nitrifying bacteria (Nitrosomonas and Nitrobacter) and plant roots respiring aerobically • Draining land – loss of nitrates reduced and reduced anaerobic conditions favoured by Pseudomonas • Artificial nitrogen fixation – augment ammonium ions by nitrogen fixing bacteria and nitrates by nitrifying bacteria • Spreading large amounts of animal waste – improves soil structure, encourages microbial activity and releases nitrogen compounds • Planting legumes – alfalfa and clover, when dead are ploughed into the soil as ‘green nature’ and its value is in its high nitrogen content
14. Eutrophication • Increased nitrate levels in lakes and rivers cause a massive increase in microscopic plants (algal blooms) • Sunlight is unable to penetrate to lower depths and plants are unable to carry out photosynthesis and die • Algae dies and is decomposed by aerobic bacteria which uses up a lot of dissolved oxygen • This creates a biological oxygen demand (BOD) • All but the upper layers of water become deoxygenated/anaerobic and so fish and other oxygen reliant species die • Anaerobic bacteria in the water may reduce the nitrate to ammonium
15. Regulations In areas where high nitrate levels is particularly serious, farmers must: • Restrict the amount of fertilizers they apply to the soil • Only apply fertilizers at a time when the plants are actively growing • Leave a strip of at least 10m wide between where fertilizers are applied and waterways • Dig drainage ditches which protects natural water courses and ensures eutrophication is isolated