Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Answer: (c) and (d)
Explanation: • (a) Leather is biodegradable, but often treated with chemicals that slow it down (usually accepted as biodegradable).
• (b) Plastic is non-biodegradable.
• (c) & (d) Fruit peels, cake, lime juice, wood, and grass are all organic natural substances that can be broken down by bacteria.
Note: In multiple choice questions, usually (c) or (d) are the cleanest examples, but both sets contain only biodegradable items.
Q2
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer: (b) Grass, goat and human
Reasoning: • Grass (Producer) is eaten by Goat (Primary Consumer/Herbivore).
• Goat is eaten by Human (Secondary Consumer/Omnivore).
• This represents a correct flow of energy in an ecosystem.
[Image of terrestrial food chain diagram]
Q3
Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Answer: (d) All of the above
Reasoning: All the listed practices help in conserving resources and reducing pollution. Cloth bags reduce plastic waste, switching off lights saves electricity, and walking saves fossil fuels.
Q4
What will happen if we kill all the organisms in one trophic level?
If all organisms in one trophic level are killed, it creates an ecological imbalance:
1. Population Explosion: The organisms at the lower trophic level (which were eaten by the killed organisms) will increase uncontrollably due to lack of predators.
2. Starvation: The organisms at the higher trophic level will die due to lack of food.
Example: If all deer are killed, the grass population will increase, while lions will starve and die.
[Image of trophic levels pyramid]
Q5
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Answer: No, the damage cannot be avoided.
While the specific effects vary, removing any level causes severe instability.
• Removing Producers: No energy enters the ecosystem. All life forms die.
• Removing Herbivores: Carnivores die of hunger; Producers overgrow and deplete soil nutrients.
• Removing Carnivores: Herbivore population explodes, overgrazing destroys the vegetation (desertification).
Q6
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Definition: Biological magnification is the phenomenon where the concentration of harmful, non-biodegradable chemicals (like DDT or Pesticides) increases at each successive trophic level in a food chain.
Difference in Levels: Yes, the concentration increases as we move up the chain. The top-level consumers (like humans or eagles) will have the highest accumulation of these chemicals because they consume a large number of lower-level organisms, each carrying a small amount of the toxin.
[Image of biological magnification in aquatic food chain]
Q7
What are the problems caused by the non-biodegradable wastes that we generate?
1. Soil Pollution: They persist in the environment for hundreds of years, reducing soil fertility and changing soil pH.
2. Blockage: Plastic bags block drains and sewers, causing waterlogging and breeding grounds for mosquitoes.
3. Animal Harm: Stray cows often eat plastics along with food scraps, which can choke their respiratory system or line their stomachs, leading to death.
4. Toxicity: If burnt, plastics release toxic fumes causing air pollution.
Q8
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer: It will still have an impact if generated in excess.
Even biodegradable waste needs time to decompose. If the quantity generated is massive:
1. It acts as a breeding ground for flies and pests, spreading diseases.
2. Decomposition produces bad odors and greenhouse gases (like Methane) contributing to global warming.
3. Excess nutrients from decomposition in water bodies can lead to eutrophication (algal blooms killing aquatic life).
Q9
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Cause for Concern: The ozone layer ($O_3$) acts as a shield protecting the earth from harmful Ultraviolet (UV) radiation from the sun. Damage to this layer allows UV rays to reach the surface, causing:
• Skin cancer and cataracts in humans.
• Damage to crops and the immune systems of animals.
Steps Taken:
1. Montreal Protocol (1987): An international treaty was signed to freeze the production of CFCs (Chlorofluorocarbons) at 1986 levels.
2. Ban on CFCs: Use of CFCs in refrigerators, ACs, and fire extinguishers has been banned and replaced with eco-friendly alternatives (like HFCs).