Natural Resources & Environment

Hello everyone! Welcome to your A-Level Biology summary notes.

In this chapter, we will study "Natural Resources and the Environment," which falls under the biodiversity and ecology section. I want to tell you that this is one of the "easiest" chapters to score points in because the content is very relatable and focuses on understanding phenomena we see in the news every day.

If you feel overwhelmed by all the English terminology in biology, don't worry! In this chapter, we will focus on conceptual understanding, and I'll help you summarize it in the easiest way possible. Ready? Let's go!

1. Types of Natural Resources

We can categorize natural resources into large groups based on their ability to be replenished:

1. Inexhaustible Resources: Resources that are available in such huge quantities that they will never run out, such as sunlight, wind, and air.

2. Renewable Resources: Resources that nature can replenish after use, though it may take time. If we consume them too quickly, they can become degraded, such as water, soil, forests, and wildlife.

3. Non-renewable Resources: Resources that, once used, are gone or require millions of years to regenerate, such as minerals, oil, natural gas, and coal.

Key takeaway!

Forests are classified as renewable resources, but if we clear-cut them, the ecosystem will collapse and might not return to its original state. Therefore, careful management and conservation are crucial.

Summary: Resources are like an "all-you-can-eat buffet" (sunlight), "groceries in the fridge that need restocking" (forests), and "cash in your wallet that runs out once spent" (oil).

2. Environmental Issues: Water Pollution

This topic appears on exams frequently, especially the section on "water quality assessment." You must clearly distinguish between these two terms:

1. DO (Dissolved Oxygen): The amount of oxygen dissolved in water.
- In clean water: The DO value is high (fish can breathe easily and are happy).
- In polluted water: The DO value is low (low oxygen, fish die).

2. BOD (Biochemical Oxygen Demand): The amount of oxygen required by microorganisms to decompose organic matter in the water.
- In polluted water: There is a lot of waste, so microorganisms have to work hard, requiring a lot of oxygen; therefore, the BOD value is high.
- In clean water: There is little waste, so microorganisms don't need much oxygen; therefore, the BOD value is low.

Easy study tip:

High BOD = Bad water (Think of BOD as "Badly Oxygen-Depleted" water).

Eutrophication

This occurs when water contains excessive levels of nutrients like nitrogen (N) and phosphorus (P) from fertilizers or detergents. This causes algal blooms, which block sunlight and cause microorganisms to consume all the oxygen, ultimately leading to fish death and water pollution.

Summary: Good water = High DO, Low BOD / Polluted water = Low DO, High BOD.

3. Global Warming

This topic usually asks about the "Greenhouse Effect."

The mechanism: Earth has greenhouse gases acting like a blanket, similar to parking a car in the sun with the windows closed. Sunlight enters, but the heat cannot escape, causing the temperature to rise.

Important Greenhouse Gases:
- Carbon Dioxide \( (CO_2) \): Comes from burning fossil fuels and deforestation (the main culprit).
- Methane \( (CH_4) \): Comes from livestock (cow flatulence), rice paddies, and landfills.
- Nitrous Oxide \( (N_2O) \): Comes from chemical fertilizers and agriculture.
- CFCs: Come from air conditioners and sprays (besides causing global warming, they also destroy the ozone layer).

Fun Fact!

Raising large numbers of cows contributes more to global warming than you might think! Because cows are ruminants, they release methane, which is many times more effective at trapping heat than \( CO_2 \) is!

Summary: Global warming is caused by an accumulation of greenhouse gases that trap too much heat on Earth.

4. Ozone Depletion

Common mistake: Students often confuse "Global Warming" with the "Ozone Hole."

- Global Warming: Relates to heat (trapped by \( CO_2 \)).
- Ozone Hole: Relates to UV radiation (CFCs destroy the ozone layer, allowing more UV light to penetrate, which is harmful to skin and plants).

Key point: The ozone layer is located in the stratosphere and acts as "sunglasses" for the Earth.

5. Conservation

When there are problems, there must be solutions. The most popular principle is the 3Rs:

1. Reduce: E.g., bringing your own cloth bag to the store to avoid plastic bags.
2. Reuse: E.g., using the back of a piece of paper or turning an old bottle into a vase.
3. Recycle: Requires a transformation process, such as melting down glass or plastic to form new products.

The Ultimate Goal: Sustainable Development

This means using resources to ensure our survival today without "encroaching" upon the resources of future generations.

Summary: Reuse = Use the same item again, Recycle = Melt/process it to create a new shape.

Exam Tips for A-Level

1. Watch the terminology: Sometimes questions use "Biological pollution," which usually refers to pathogen contamination in water.
2. DO/BOD Relationship: Never mix these up. Remember: "Polluted water = lots of microorganisms = high oxygen demand (High BOD)."
3. Greenhouse Effect: Remember the main gases responsible (\( CO_2 \) and \( CH_4 \)).
4. Don't forget Biomagnification: Toxic substances like heavy metals accumulate more at higher "trophic levels." Those at the top of the food chain (like humans or eagles) will have the highest concentration of toxins.

See? This chapter isn't hard at all! Review the highlighted points often and try doing some past papers. I believe you can definitely score full marks on this topic. Good luck!