Ecosystems and Environment

Welcome to the Lesson: Ecosystems and the Environment 🌿

Hello everyone! This chapter is part of the Biological Science section of the A-Level Applied Science exam. I can tell you right now, this chapter is a "gold mine" for points because the content is very close to home—it relates to the nature around us and the real-world environmental problems we face today.

If you feel like science is difficult or contains too many formulas, don't worry! In this chapter, we will focus primarily on understanding, making connections, and practical application. Are you ready? Let's dive in!

1. What is an Ecosystem?

Imagine that our world is a big house. An ecosystem is like the various rooms in that house, consisting of both "residents" (living organisms) and "furniture" (non-living things) that rely on one another to function.

Components of an Ecosystem

They can be easily divided into two main parts:

1. Biotic Components:

• Producers: Those that can make their own food through photosynthesis, such as plants and algae.
• Consumers: Those that cannot make their own food and must eat others, such as various animals (divided into herbivores, carnivores, and omnivores).
• Decomposers: The "big-hearted" ones that help break down the remains of plants and animals into nutrients for the soil, such as mushrooms, fungi, and bacteria.

2. Abiotic Components:

• Examples include sunlight, temperature, water, pH levels, and minerals in the soil.

Key Takeaway: For an ecosystem to stay balanced, "decomposers" are essential! Without them, our world would be full of carcasses, and plants wouldn't have fertilizer to grow.

Did you know? Even a "sidewalk" or a "backyard" can be considered an ecosystem! As long as there is an interaction between living organisms and the environment, it counts!

2. Energy Transfer in an Ecosystem

In an ecosystem, energy doesn't disappear; it "flows" from one individual to another through consumption!

Food Chains and Food Webs

- Food Chain: The linear path of eating, e.g., Grass → Grasshopper → Frog → Hawk.

- Food Web: In real life, an animal doesn't eat just one thing. This creates an overlapping of many food chains, forming a complex network.

The 10% Rule

This is the heart of the exam! When consumption occurs, only \(10\%\) of the energy is passed on to the next consumer level. The other \(90\%\) is lost as heat and used for the organism's own biological processes.

Example: If a plant has \(1,000\) units of energy, the organism that eats the plant receives only \(100\) units, and the next one in the chain receives only \(10\) units.

Memory Tip: The further down the food chain you are, the "less" energy you receive.

Summary of this section: Energy in an ecosystem flows in a linear direction (it does not cycle back), whereas nutrients move in cycles.

3. Relationships Between Living Organisms

Living organisms that coexist can be loving, dependent, or even enemies. We use the symbols +, -, 0 to make it easier to remember.

• Mutualism (+/+): Cannot live without each other; they would die. Example: Lichen (fungi and algae).
• Protocooperation (+/+): It’s good to be together, but they can survive separately. Example: Cattle egrets and water buffalo, bees and flowers.
• Commensalism (+/0): One benefits while the other is unaffected. Example: Sharks and remoras, orchids on large trees.
• Parasitism (+/-): One benefits while the other loses (the host). Example: Ticks on a dog, tapeworms in humans.
• Predation (+/-): There is a predator (benefits) and prey (loses). Example: A tiger hunting a deer.
• Competition (-/-): Fighting for resources; both sides lose out in the long run.

Common Mistake: Many people confuse "Mutualism" and "Protocooperation." Just remember: Mutualism means "separate and die," while Protocooperation means "separate and survive."

4. Natural Resources and Environmental Issues

This section focuses on application in daily life and current events.

Types of Resources

1. Inexhaustible: Sunlight, wind, air.

2. Renewable (takes time): Forests, wildlife, soil, water.

3. Non-renewable: Oil, natural gas, coal, minerals.

Greenhouse Effect

This is a popular topic! Greenhouse gases (like \(CO_2\), \(CH_4\)) act like a "glass" that prevents heat from escaping the Earth.

- Pros: It keeps the Earth warm enough for life to exist.

- Cons (Global Warming): If there are too many of these gases (from burning fuels or deforestation), the Earth will become too hot, causing polar ice caps to melt and weather to become erratic.

Sustainable Resource Management

We often use the 3Rs principle to help:

- Reduce: Lower consumption, e.g., carrying a cloth bag instead of a plastic one.

- Reuse: Using the same item for the same purpose, e.g., using paper on both sides.

- Recycle: Processing materials to create something new, e.g., melting old glass bottles into new ones.

Key Point: "Recycling" requires energy for processing, so "Reducing" and "Reusing" are better choices for the planet.

Conclusion 💡

If you understand that "everything in nature is connected," you will definitely pass this chapter on the exam!

• If water becomes polluted → Producers die → Consumers have no food → The ecosystem collapses.
• If forests are cut down → Water cycling is disrupted → Rain doesn't fall as expected → Drought occurs.

Advice for the Exam: The test will usually provide a "simulated situation" and ask what will happen next or ask for solutions. Focus on using reason and logic based on the principles above.

Do your best! Let’s get all the points from this chapter! ✌️