Lesson Notes By Weeks and Term v5 - Grade 12
Human impact on the environment (Grade 12 focus) and examination preparation – Week 2 focus
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Human impact on the environment (Grade 12 focus) and examination preparation – Week 2 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Life Sciences
Class: Grade 12
Term: Term 4
Week: 2
Theme: General lesson support
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The impact of human activities on the environment is a critical area of study in Life Sciences. Understanding these impacts is not just an academic exercise, but a vital necessity for ensuring the sustainability of our planet, particularly within the unique context of South Africa. Our country faces specific environmental challenges such as water scarcity, pollution from mining activities, and biodiversity loss. Recognizing the causes and consequences of these issues is crucial for finding sustainable solutions. This week, we'll delve into specific human impacts, focusing on pollution, alien invasive species, and the depletion of resources, as well as refining your exam preparation skills.
2.1 Pollution: Pollution is the contamination of the environment by substances that are harmful to living organisms. It affects air, water, and soil.
Air Pollution: Caused by the release of pollutants into the atmosphere.
Major sources include: Burning of fossil fuels: From vehicles, power plants (like those using coal in Mpumalanga), and industrial processes. Releases gases like sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM).
Industrial emissions: Factories release various chemicals and pollutants into the air.
Agricultural activities: Ammonia (NH3) emissions from fertilizers and livestock.
Burning of vegetation: Often used for clearing land, contributing to smoke and particulate matter.
Mining Activities: Dust and heavy metals from mining operations, particularly gold and coal mines in South Africa.
Impacts: Acid rain (SO2 and NOx), respiratory problems (PM), climate change (greenhouse gases), damage to vegetation, and reduced visibility.
Water Pollution: The contamination of water bodies (rivers, lakes, oceans, groundwater).
Major sources include: Industrial effluent: Factories release untreated or poorly treated wastewater containing chemicals, heavy metals, and organic pollutants. This is a major concern in areas with heavy industry like Gauteng.
Agricultural runoff: Fertilizers and pesticides contaminate water sources. Eutrophication (excess nutrients leading to algal blooms) is a common consequence.
Sewage: Untreated or poorly treated sewage releases pathogens and organic matter into water bodies, leading to disease and oxygen depletion.
Mining activities: Acid mine drainage (AMD) is a significant problem in South Africa, where acidic water containing heavy metals leaches from abandoned mines into rivers and groundwater.
Oil spills: Accidental releases of oil from tankers or pipelines.
Impacts: Waterborne diseases, death of aquatic life, contamination of drinking water sources, and ecosystem disruption.
Soil Pollution: The contamination of soil with harmful substances.
Major sources include: Industrial waste: Disposal of hazardous waste materials on land.
Agricultural practices: Overuse of pesticides and fertilizers can contaminate soil.
Mining activities: Heavy metals and other pollutants from mining operations contaminate soil.
Sewage sludge: Improper disposal of sewage sludge.
Acid rain: Acid deposition from the atmosphere can acidify soil.
Impacts: Reduced soil fertility, contamination of groundwater, uptake of pollutants by plants, and health risks to humans and animals.
Example: Acid Mine Drainage (AMD) in South Africa AMD is a major environmental problem, particularly in the Witwatersrand region. When pyrite (iron sulfide) in mine tailings is exposed to air and water, it oxidizes, producing sulfuric acid and dissolved iron. This acidic water mobilizes heavy metals such as lead, mercury, and arsenic. The polluted water can then contaminate surface and groundwater resources, harming aquatic life, impacting human health, and damaging infrastructure. The cost of treating AMD is enormous. 2.2 Alien Invasive Species: An alien species is one that has been introduced to an area outside of its natural range. When an alien species establishes itself and spreads, causing ecological or economic harm, it is considered an invasive species.
Characteristics of Invasive Species: Rapid reproduction and growth High dispersal ability Tolerance to a wide range of environmental conditions Lack of natural predators or diseases in the new environment Examples in South Africa: Water Hyacinth (Eichhornia crassipes): Clogs waterways, reduces sunlight penetration, and depletes oxygen levels, impacting aquatic life.
Australian Black Wattle (Acacia mearnsii): Outcompetes native vegetation, altering soil nutrient levels and reducing water availability. It is, however, a source of tannin and wood, creating a complex problem of management.
Pine trees (Pinus species): Consume large amounts of water, reducing streamflow and increasing fire risk.
American bramble (Rubus cuneifolius): Aggressively invades disturbed areas and outcompetes indigenous plants. Invasive marine species (e.g., Mediterranean Mussel, Mytilus galloprovincialis): Competes with native species for resources and can alter ecosystem structure.
Impacts: Loss of biodiversity: Invasive species outcompete native species, leading to their decline or extinction.
Ecosystem disruption: Altered food webs, nutrient cycles, and habitat structure.
Economic costs: Control and eradication efforts are expensive, and invasive species can damage agriculture, forestry, and fisheries.
Human health impacts: Some invasive species can transmit diseases or cause allergies.
Example: Management of Australian Black Wattle Efforts to control Australian Black Wattle in South Africa involve mechanical removal (cutting down trees), chemical control (herbicides), and biological control (introducing insects that feed on the wattle).