Our Environment — Practice Quiz

Microorganisms that break down dead matter

Step 1: Decomposers are mainly bacteria and fungi that break down dead organisms and waste. Step 2: They convert complex organic matter into simple inorganic substances. Step 3: These simple substances go back into the soil and can be used by plants again. Step 4: Without decomposers, dead matter would pile up and nutrients wouldn't be recycled. Step 5: They play a crucial role in maintaining the nutrient cycle in ecosystems.

Chlorofluorocarbons (CFCs)

Step 1: CFCs were commonly used in refrigerators and fire extinguishers. Step 2: When released into atmosphere, CFCs rise to the ozone layer. Step 3: There, they break down ozone molecules, creating 'holes' in the ozone layer. Step 4: This allows more harmful UV radiation to reach Earth's surface. Step 5: Due to this damage, CFC production has been banned worldwide, and companies now make CFC-free refrigerators.

Accumulation of harmful chemicals at higher trophic levels

Step 1: Harmful chemicals like pesticides enter food chains through water and soil. Step 2: These chemicals are not easily broken down by organisms. Step 3: As they pass from producers to consumers, they accumulate in body tissues. Step 4: At each trophic level, the concentration increases. Step 5: Humans, being at the top of food chains, get the highest concentration of these harmful chemicals in their bodies.

Plastic bags

Step 1: Biodegradable materials like vegetable peels and food scraps decompose quickly (weeks to months). Step 2: Paper waste also decomposes relatively fast as it's made from natural materials. Step 3: Plastic bags are non-biodegradable synthetic materials. Step 4: Bacteria and other decomposers cannot break down plastic polymers. Step 5: Plastics can persist in the environment for hundreds of years, causing long-term pollution.