Our Environment
This chapter covers ecosystems, food chains and food webs, the flow of energy, biodegradable and non-biodegradable waste, and the depletion of the ozone layer.
An ecosystem is a community of living organisms (biotic components) interacting with each other and with their non-living physical environment (abiotic components) such as air, water, and soil, functioning together as a unit.
A food chain shows the transfer of energy from producers (green plants) to primary consumers (herbivores), secondary consumers (carnivores), and so on. At each trophic level, only about 10% of energy is transferred to the next level; the rest is lost as heat, used in life processes.
Q. Why do some substances get biomagnified as they move up a food chain?
Harmful, non-biodegradable chemicals (like pesticides) do not break down and accumulate in the bodies of organisms at each trophic level. Since energy decreases up the food chain but the chemicals persist, their concentration increases, becoming highest in top-level consumers, a phenomenon called biological magnification.
The ozone layer in the upper atmosphere absorbs harmful ultraviolet (UV) radiation from the sun. Its depletion, caused largely by chlorofluorocarbons (CFCs), increases the risk of skin cancer and other UV-related harm to living organisms.
Q. Why is it important to manage waste materials properly?
Improper waste disposal pollutes soil, water and air, harms wildlife, and can spread disease. Managing waste through recycling, composting biodegradable waste, and safely disposing of non-biodegradable waste helps protect the environment and conserve resources.
Which of the following is a non-biodegradable substance?
Correct answer: (D) Plastic
Organisms that make their own food, such as green plants, are called _______.
Producers
Decomposers play no significant role in an ecosystem.
False — decomposers like bacteria and fungi break down dead organic matter and waste into simpler substances, recycling nutrients back into the soil, which is essential for the functioning of any ecosystem.