Man and the environment notes

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  • Created on: 15-05-14 18:52
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Man and the environment
See carbon cycle handout
Fish Farming
Selected fish breed must:
- Be able to complete its lifecycle in captivity
- Be non-susceptible to disease
- Have a high conversion ratio (food flesh)
How does it work?
- Fish are kept in nets to keep natural predators and human poachers out, to keep them together, and
reduce movement (so energy used more for conversion to biomass)
- Fed high-protein diet (protein is for making muscles/bones/tissue) to minimise faeces and maximise
energy transfer from food. Less faeces less eutrophication less disease. To avoid localised
eutrophication (where only fish at bottom die), net not anchored to river/seabed. Not overfed and
cage cleaned often as wasted food could also cause eutrophication
- Kept in moving water (so it doesnt stagnate=constant oxygen supply and removal of CO2) far from
polluting factories
- Fish of same size kept together
- Healthiest fish chosen for selective breeding. Eggs artificially fertilised, then young reared in special
tank with controlled temperature, high oxygen levels, safety from predators and sometimes growth
- Danger of disease/parasites is high due to proximity of fish, but pesticides could harm fish, so
biological pest control is used more (e.g. Wrasse eats lice on salmon). Antibiotics to control disease
and fungicides to prevent/remove fungal infections, and quarantine of infected fish to contain
- Fish harvested just before fully grown to maximise profits (fully grown fish have low conversion rate)
Advantages Problems
Guaranteed harvest Diseases can also infect wild fish
No depletion of wild stocks Food can be expensive
No need to pay for boat/nets/labour cost Destruction of habitat when farm built
No overfishing/endangered species conserved Attracts predators to the area
Air pollution (=releasing substances into the environment in harmfully large amounts
which natural processes cant easily remove)
- Main polluting gases: carbon dioxide/monoxide, nitrogen
oxides, methane, CFCs
- Carbon dioxide: Increased levels, especially recently due to
increased burning of fossil fuels (e.g. Petrol, diesel). Worsened
by deforestation ( less CO2 absorbed)
- Effects of increased levels: greenhouse gases form a layer
around the Earth, contributing to global warming. Short wave
radiation from sun strikes planet some absorbed, some
converted into long wave radiation greenhouse gases
absorb longer waves that would usually escape. Greenhouse
gas=a gas that traps infrared radiation and wont release it

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Methane: produced when microbes ferment larger organic molecules to release energy (e.g.
Decomposers in landfill sites, microbes which ferment in the rumen of ruminants such as cattle,
fermentation of rice in paddy fields)
- Carbon monoxide: produced from incomplete combustion (e.g. When petrol and diesel burned in a
car).…read more

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Polytunnels Greenhouses
Protect plants from severe weather + optimum conditions (e.g.…read more

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Controlling pests
- Pest: organism that reduces crop/stock animal yield, thus causing economical damage to farmer
- Controlled by biological (to reduce numbers with another organism) or chemical (to kill all of them)
- Herbicides are to kill plants competing with desired plant (a.k.a. Weeds which also need light,
space, water and minerals), insecticides kill insects, fungicides kill fungi, molluscicides kill molluscs
(e.g.…read more


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