SOLVED TOPICAL PAST PAPERS

Food supply

Modern technology has dramatically increased food supply: 

• Agricultural machinery to use in larger land areas and improve efficiency
• Chemical fertilizers to improve yields
• Insecticides to improve crop quality and yield
• Herbicides to reduce competition with weed
• Selective breeding to improve production by crop plants and livestock

Monocultures and livestock production

Large scale mono-cultures of crop plants

Monoculture farming means that on a given agricultural land is grown only one species of a crop at a time. If two or more species are sown in the field together (for example beans and corn), it is not a monoculture but a polyculture system.

The main benefits of monoculture farming are:

• Easier to manage 
• More efficient 
• Promotes technological advances in agriculture 
• Offers higher earnings

The disadadvantages of monoculture farming are:

• Reduced diversity in ecosystem
• Increased pests 
• Problems associated with insecticides 

Intensive live stock production

Livestock farming involves the rearing of animals for food and other human uses, such as producing leather, wool and even fertilizer. This type of farming primarily applies to cattle or dairy cows, chickens, goats, pigs, horses and sheep. 

The benefits of intensive livestock production are:

• Helps the economy and the agricultural industry 
• Provides food security 

The disadvantages of are:

• Easier spread of disease 
• Welfare issues of livestock i.e. living in confined space

Providing sufficient food for the world population

Famine is an extreme scarcity of food. There are various factors as to why it exists today:

• Uneven distribution of food 
• Drought/flooding
• Poverty
• Increasing population

Nearly 1 000 million people do not get enough to eat and over 400 million are chronically malnourished today. 

It is therefore important to understand what it takes to find a solution to this problem: 

• Social implications
  • Strategic plans that incorporate population concerns such as population growth, distribution and rural-urban migration patterns are crucial
  • Community development strategies which integrate essential social services as well as production resources should be encouraged
• Economic implications
  • Financial support must be given to research on the integration of technologies for food production.
• Environmental implications 
  • Reducing soil erosion and impoverishment, deforestation, falling agricultural output, and poor water management should be implemented,

Habitat destruction

Animal habitat destruction is a big issue that exists today. Whilst habitats can be destroyed naturally i.e. tsunami, earthquakes etc, a lot of it cause solely from human activity: 

• Increased area for food crop growth, livestock production, and housing 
• Extraction of natural resources (such as trees) 
• Marine pollution 

Deforestation is the permanent destruction of forests in order to make the land available for other uses. 

There are many undesirable effects of deforestation: 

• Loss of habitat for animals living in the forest 
• Reduction of food resources and breeding grounds of animals, potentially leading to extinction 
• Soil erosion due to the lack of soil support from tree roots 
• Less photosynthesis leading to increased atmospheric CO2 levels and thus contributing to the greenhouse ffect
• Reduction of rainfall due to less plants to transpire water in the water cycle 

Pollution

Pollution is the presence in or introduction into the environment of a substance which has harmful or poisonous effects.

There are various causes of land and water pollution you need to be aware of. 

Land & water pollution

Insecticides 

Insecticides are used to kill pests to enhance crop yields but they can often also kill other harmless animals. 

For example, DDT was used to kill mosquitots but it also remained in the environment and was absorbed into food chains resulting in bioaccumulation which killed a lot of other good animals. DDT is now banned. 

Herbicides

Herbicides are used to kill weeds and other unwanted crops to reduce competition and increase crop yields. 

Herbicides can get washed int water systems and kill aquatic plants which result in a disruption of the food chain. 

Nuclear fall-out

This is a leakage from a nuclear power station. Radioactive particles can get carried into the environment and settle. Organisms then absorb these particles which can result in cancer. 

Chemical waste

Inorganic waste waste (i.e. nickel, aluminium, lead, mercury) that are dumped into water bodies can lead to the bioaccumulation of these metals. 

Plastics

Plastics can not only physically trap and harm animals, but they can deteriorated into smaller pieces and be consumed by them too. To make matters worse, toxic gases are produced when plastics are burned. 

Untreated sewage

Sewage is untreated organic waste produced along with household and industrial waste material. 

Dumping untreated sewage into the environment can lead to a lot of problems such as: 

• Eutrophication 
• Death of aquatic animals due to pathogens in the sewage 
• Spread of water borne diseases which can infect people by drinking polluted water

Eutrophication has come up multiple times in previous examinations, so make sure you learn this!

Eutrophication is the excessive richness of nutrients in a lake or other body of water, frequently due to run-off from the land, which causes a dense growth of plant life.

The stages of eutrophication are as follows: 

1. Sewage or fertilizers somehow leak into a water body i.e. lake 
2. Various things are present in sewage/fertilizers such as phosphates, organic matter, bacteria
3. Phosphates promote algae growth while bacteria reproduce by feeding on organic matter 
4. Excessive algae forms a blanket on the water surface
5. Aquatic plants die due to the lack of light 
6. As plants die, bacteria aerobically decompose dead matter 
7. Oxygen supply becomes depleted and aquatic animals die 
8. The entire food chain becomes disrupted

Now that we understand the damage that untreated sewage can do, it is important to know how we actually treat it.

 The treatment of sewage provides clean, drinkable water. 

1. Large objects such as sticks are screened out 
2. Suspended grit is allowed to settle in the grit settling chamber’ 
3. Organic matter is digested via the ‘sludge digester’ and allowed to settle in the ‘sludge settling tank’ 
4. The remaining liquid goes into an aeration tank which contains stones that have microorganisms on the surface to digest other remaining organic matter 
5. Water passes out and may be chlorinated to kill any remaining bacteria 

Greenhouse effect (climate change) 

Greenhouse gases are gases in the atmosphere that prevent infrared radiation to pass through.

These gases are very important in maintaining the surface temperature of the earth.  

Examples of greenhouse gases are: 

• Carbon dioxide 
• Methane 
• Chlorofluorocarbon (CFCs)
• Nitrogen oxides
• Water vapour 

With industrial revolution we are now produced excessive amounts of greenhouse gases. This leads to the enhanced greenhouse effect, where more and more infra-red radiation is becoming trapped. This is resulting unstable climate conditions which is causing harm to the entire globe. 

Acid rain

Acid rain is rainfall made so acidic by atmospheric pollution that it causes environmental harm. 

Acid rain is caused by the release of nitrogen oxides and/or sulfur dioxides into the atmosphere. 

• Nitrogen oxides are made from the reaction of nitrogen + oxygen in high temperatures of car engines
• Sulfur dioxide is release by coal factories, cars, and oil refineries 

These two gases can react with rain water to produce acid rain.

Acid rain can do a lot of damage to the environment: 

• Damages leaf cuticles and kills plants 
• Acidifies lakes and kills aquatic animals 
• Damages buildings made of limestone 
• Aluminium ions are leached out of the soil and washed into watery bodies

Some solutions to reduce the incidence of acid rain may include:

• Using oil instead of coal (since coal contains more sulfur) 
• Switching to more renewable resources of energy 
• Using catalytic converters in cars (which removes nitrogen oxides from car exhausts)

Conservation

Extinction and endangerment of a species

Extinction is the dying out or extermination of a species. Some factors that may cause extinction are: 

• Climate change
• Habitat destruction
• Hunting
• Pollution
• Introduced species i.e. species that are not native to a particular location, and has the tendency to spread and cause damage to the environment 

An endangered species of animal or plant that is seriously at risk of extinction.

Conservation of endangered species

It is important to conserve endangered species in order to prevent extinction. 

Conservation may involve: 

• Monitoring and protecting habitats 
• Education
• Captive breeding programes
• Seed banks 
• Conservation programmes