Human influences on environment

• Why is it important to maintain crop yield?

  -We can meet the demands of a growing population

  -The farmer can make a profit
• Factors that affect crop yield

  -Soil mineral ions

  -Soil structure

  -Soil pH

  -Carbon dioxide, heat and light
• How is soil mineral ions controlled?

  Adding fertiliser to the soil or growing in a hydroponic culture
• Why does soil mineral ions need to be controlled?

  Extra mineral ions can be taken up and used to make proteins and other important compound
• How is soil structure controlled?

  Ploughing the fields to break up compacted soil
• Why do you need to control soil structure?

  Good aeration and drainage allow better uptake of mineral ions and water
• How is soil pH controlled?

  Add lime (calcium hydroxide)
• Why do you need to control soil pH?

  Soil pH can affect crop growth as an unsuitable pH reduces uptake of mineral ions
• How is carbon dioxide, heat and light controlled?

  Cannot be controlled in fields but in greenhouse or polytunnels all can be altered to maximise yield
• Why does carbon dioxide, heat and light need to be controlled?

  All may limit the rate of photosynthesis and the production of organic substance for growth
• Nitrogen cycle on a farm diagram

  
• What are pests?

  Organism that reduce yield of crop plants or stock animals
• How do pests harm crops?

  -Spreading diseases

  -Feeding on crop plants

  -Competing with crop pants for water, nutrients and light
• How can pest be controlled?

  Pests can be controlled by spraying pesticides which are chemicals that kill pests
• What does biological control involve?

  The use ofanother organism which kills the pest
• What is bioaccumulation?

  Pesticide can build up in the tissue of organism, it doesn't get broken down and excreted
• What is biomagnification?

  A trophic level always has less mass than the one below it so the pesticide becomes more concentrated as it moves along the food chain
• What is DDT used for and when?

  To kill malaria carrying mosquitoes and the lice that carried typhus and was first used in 1939
• What is an environmental problem with DDT?


  It doesn't just kill pests but kills any type of insect including harmless ones - can damage the ecosystem by disrupting food chains
• How can biomagnification and bioaccumulation disrupt the food web of an ecosystem?

  Bioaccumulation happens when an herbivore eats a plant contaminated with a pesticide, it won't get broken down or excreted - instead it becomes concentrated in fatty tissues of the animal

  Biomagnification happens when the process above is repeated but it is for a carnivore eating the herbivore meaning the pesticide will builds up in concentration along the food chain.

  The top of the food chain may be toxic leading to the death of the top carnivores in the chain disrupting the food web of ecosystem
• In fish farming, how is water quality monitored?

  Measuring the temp, oxygen and chlorophyll levels
• What is interspecific competition?

  The completion that occurs between individual of different species
• In fish farming, how is interspecific competition controlled?

  Placing different species of fish in separate cages
• In fish farming, what selective breeding used to do?

  Improve the quality of fish, such as growth rates
• In fish farming, how is disease treated?

  By giving the fish antibiotics
• What is intraspecific competition?

  It is a competition which occurs between individuals of the same species
• In fish farming, how is intraspecific competition controlled?

  Sorting the fish regularly by size and placed into different cages
• In fish farming, how can pests be killed?

  Using pesticides or a biological predator
• In fish farming, how can fish be protected from predatory birds?

  By placing a cover on the cages
• In fish farming, how can water quality be improved?

  By filtering the water to remove waste products of the fish
• Advantages of fish farming

  -High proteins food to maximise growth and therefore profits

  -Fish are much easier to catch (less time/energy/effort/cost)

  -Selective breeding results in faster growing fish

  -Many fish in a small area reduces energy loss due to movement

  -Similar sized fish reduces competition

  -Nets prevent predators from eating fish

  -Wild fish stocks are maintained and not subjected to wild
• Disadvantages of fish farming

  -Food may contain protein from wild source

  -Disease can spred to wild fish

  -Disease spreads rapidly due to the close proximity of the fish; they are oven antibiotics to help prevent this

  -Escaped fish can compete and breed with wild populations affecting genetic diversity

  -Waste from the fish farm can pollute environment and cause eutrophication
• What is the greenhouse effect?

  1. Heat is the form of short wavelength infrared radiation from the sun is transmitted to Earth

  2. The Earth's surfaces absorb the short wavelength radiation and heats up

  3. The earth's hot surface emit infrared radiation with a longer wavelength

  4. Some gases in the atmosphere absorb the long wave radiation and re-emit back to earth, keeping it hot - this is called greenhouse effect
• The greenhouse effect diagram

  
• What is the enhanced greenhouse effect?

  It is global warming and is caused by human activity releasing the greenhouse gases
• What are the 4 greenhouse gases?

  -Carbon dioxide

  -Methane

  -Nitrous oxide

  -Fluorinated gases
• What is the source of carbon dioxide?

  It enters the atmosphere by burning fossil fuels, solid waste, trees and other biological materials as a result of a chemical reaction
• What is the source of methane?

  Emitted during production and transport of coal, natural gas and oil. Results from livestock, land use and decay of organic waste
• What is the source of nitrous oxide?

  Emitted during agricultural, land use and industrial activities, combustion of fossil fuels, solid waste and during treatment of waste water
• What is the source of fluorinated gases?

  Emitted from a variety of household, commercial and industrial application. Emitted in smaller quantities