The natural world, the environment, the climate and the weather

🌍 The World Around Us

🌱 Natural World & Biodiversity

Think of the Earth as a giant ecosystem garden. Every plant, animal, and microorganism is a plant or tool that keeps the garden thriving. Just like a garden needs sunlight, water, and soil, ecosystems need energy, nutrients, and space.

  • 🌳 Forests: 31% of land, 80% of terrestrial biodiversity.
  • 🐠 Oceans: 70% of life forms, 90% of carbon sequestration.
  • 🌾 Grasslands: 30% of the planet, key for grazing animals.
Exam Tip: Remember the food chain and food web concepts. Use the “producer → consumer → decomposer” sequence when answering questions about ecosystems.

🌍 Human Impact & Environmental Issues

Humans are like gardeners who can both nurture and damage the garden. Key impacts include:

  1. 🌬️ Deforestation – cutting trees reduces oxygen and increases CO₂.
  2. 🚗 Pollution – cars emit $CO_2$ and $NO_x$, harming air quality.
  3. 💧 Water scarcity – overuse of rivers and lakes affects aquatic life.
Exam Tip: Use the “cause → effect” structure. For example, “Deforestation → loss of habitat → species extinction.”

🌡️ Climate Change & Greenhouse Gases

The Earth’s climate is like a thermostat that keeps temperatures stable. Greenhouse gases act as a blanket trapping heat. The main gases are:

Gas Abbreviation Global Warming Potential (GWP)
Carbon Dioxide $CO_2$ 1
Methane $CH_4$ 28–36
Nitrous Oxide $N_2O$ 265
Exam Tip: When asked to compare gases, mention their GWP and typical sources (e.g., agriculture for $CH_4$, combustion for $CO_2$).

☀️ Weather Patterns & Forecasting

Weather is like a daily weather report for the planet. Key terms:

Term Definition Example
Front Boundary between two air masses. Cold front → sudden drop in temperature.
Pressure System High or low atmospheric pressure. Low pressure → rain.
Humidity Amount of water vapor in the air. High humidity → muggy feeling.
Exam Tip: When describing weather, use the “what, where, when, why” framework. For example, “A cold front moved in from the north, causing temperatures to drop by 5°C and wind speeds to increase.”

Revision

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