Free O level Notes

Human Influences on the Environment

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18.1 Pollution

  • Pollution: The introduction of harmful substances or products into the environment that adversely affect ecosystems and human health.

Types of Pollution:

  1. Air Pollution: Release of harmful gases like carbon dioxide (CO₂), sulfur dioxide (SO₂), nitrogen oxides (NOx), and particulate matter.
    • Sources: Factories, vehicles, and burning of fossil fuels.
  2. Water Pollution: Contamination of water bodies by chemicals, heavy metals, sewage, and plastic waste.
    • Sources: Industrial waste, agricultural runoff, and untreated sewage.
  3. Soil Pollution: Contamination of the soil with chemicals, waste products, and pesticides.
    • Sources: Industrial waste, agricultural chemicals, and improper disposal of waste.

Effects of Pollution:

  • Health Problems: Respiratory diseases, cancer, and other health issues.
  • Ecosystem Disruption: Harm to wildlife, plants, and habitats.

18.2 Global Warming and Climate Change

  • Global Warming: Increase in Earth’s average temperature due to the greenhouse effect.
  • Greenhouse Gases: CO₂, methane, nitrous oxide trap heat in the atmosphere.
  • Causes:
    1. Burning Fossil Fuels: Releases CO₂.
    2. Deforestation: Reduces the absorption of CO₂ by trees.
    3. Agriculture: Livestock release methane.

Effects of Global Warming:

  1. Rising sea levels due to melting ice caps.
  2. More frequent and severe weather events.
  3. Habitat destruction and loss of biodiversity.

18.3 Acid Rain

  • Formation: SO₂ and NOx gases react with water vapor to form sulfuric and nitric acids, which fall as acid rain.
  • Effects:
    1. Damage to Ecosystems: Acidifies water bodies, making them uninhabitable.
    2. Soil Degradation: Leaches minerals from the soil.
    3. Building Damage: Corrodes buildings and monuments.

18.4 Deforestation

  • Deforestation: The large-scale clearing of forests for agriculture, urban development, and logging.
  • Effects:
    1. Loss of biodiversity.
    2. Contribution to global warming (fewer trees to absorb CO₂).
    3. Soil erosion and reduced water retention.

18.5 Overfishing

  • Overfishing: Harvesting fish at a rate faster than they can reproduce.
  • Effects:
    1. Depletion of fish populations.
    2. Disruption of marine ecosystems.
    3. Economic impact on fishing communities.

18.6 Conservation Efforts

  • Conservation: Protecting and preserving natural resources and biodiversity.
  • Methods:
    1. In-situ Conservation: Protecting species in their natural habitat.
    2. Ex-situ Conservation: Protecting species outside their natural habitat (e.g., zoos).
    3. Sustainable Development: Using resources at a rate that allows for their regeneration and supports future generations.