Our Environment-Exercise
Biology - Exercise
Q1. 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
The biodegradable items are natural and can decompose easily by microorganisms.
Option (a) Grass, flowers and leather: Grass and flowers are plant-based and biodegradable. Leather, which is made from animal skin, is also biodegradable though it takes relatively longer to decompose naturally. So all items in (a) are biodegradable.
Option (c) Fruit-peels, cake and lime-juice: All these are organic food items that decompose easily and are clearly biodegradable.
Option (d) Cake, wood and grass: Cake (organic food), wood (plant-based), and grass (plant-based) are all biodegradable.
Option (b) contains plastic, which is non-biodegradable, so it is excluded.
Thus, the correct answers are (a), (c), and (d), since all items in these groups are biodegradable. Option (b) is the only group with a non-biodegradable item.
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 goa
Answer
Answer: (b) Grass, goat and human
Explanation
A food chain represents the transfer of energy from one organism to another in a straight sequence, starting
with producers (plants that make their own food), followed by primary consumers (herbivores that eat
plants),
and then secondary consumers (carnivores or omnivores that eat herbivores).
- Option (a) lists grass, wheat and mango, which are all producers since they are plants, so no energy transfer occurs between consumers.
- Option (b) forms a proper food chain: grass (producer) is eaten by goat (primary consumer/herbivore), which is then eaten by human (secondary consumer/omnivore).
- Option (c) lists only herbivores (goat, cow, elephant), with no producer or predator link.
- Option (d) is incomplete and mismatched: grass (producer) to fish (typically aquatic consumer) to "goa" (likely a typo, but disrupts the logical sequence even if meant as goat).
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
Answer: (d) All of the above
Explanation
Environment-friendly practices reduce waste, conserve energy, and lower pollution, aligning with NCERT Class
X
Science Chapter 13 goals of sustainable living.
- Option (a) promotes cloth bags over plastic, minimizing non-biodegradable waste that harms soil and water.
- Option (b) saves electricity, cutting down fossil fuel use and greenhouse gas emissions from power plants.
- Option (c) cuts vehicle emissions by avoiding scooter fuel, reducing air pollution from petrol combustion.
All options support eco-friendly habits like the 3Rs (reduce, reuse, recycle), making (d) the complete choice.
Q4. What will happen if we kill all the organisms in one trophic level?
Answer
Answer: Removing all organisms from one trophic level disrupts the entire food chain, causing the collapse of levels above and below it, leading to ecosystem imbalance.
Explanation
Trophic levels form interconnected energy flow sequences in ecosystems, where producers (first level)
support
herbivores (second), which sustain carnivores (higher levels).
- Levels above the killed one starve due to lack of food, causing population crashes and potential extinction of dependent predators.
- Levels below face overpopulation of consumers without predators, leading to overgrazing or resource depletion by survivors.
- This triggers trophic cascades, disrupting biodiversity, nutrient cycling, and stability across the ecosystem.
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
Answer: Yes, the impact varies across trophic levels; no trophic level can be fully removed without ecosystem damage.
Explanation
Removing organisms from different trophic levels causes distinct disruptions due to their roles in energy
flow
and population control.
- Producers (base level): Elimination starves all consumers above, collapsing the entire food chain as no energy enters the system.
- Herbivores (primary consumers): Higher carnivores die from food scarcity, while unchecked plant growth leads to resource imbalance.
- Carnivores (higher levels): Prey populations explode, causing overgrazing, habitat destruction, and eventual producer depletion.
No level can be removed harmlessly, as interconnections trigger cascades affecting biodiversity and stability throughout the ecosystem.
Q6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer
Answer: Biological magnification is the increasing concentration of non-biodegradable toxic substances in organisms as they move up trophic levels in a food chain. Yes, the levels of magnification increase at higher trophic levels in the ecosystem.
Q7. What are the problems caused by the non-biodegradable wastes that we generate?
Answer
Answer: Non-biodegradable wastes cause biological magnification, soil and water contamination, air pollution from burning, wildlife harm, and ecosystem disruption due to their persistence.
Key Problems
- They accumulate progressively in food chains at higher trophic levels, leading to toxic concentrations in predators and humans, known as biological magnification.
- Accumulation in landfills and soils blocks water/air penetration, depletes nutrients, leaches chemicals, and renders land infertile for agriculture.
- They pollute water bodies through leaching toxins into groundwater and rivers, harming aquatic life and making water unsafe for consumption.
Additional Impacts
- Burning releases harmful gases like dioxins, furans, and greenhouse gases, worsening air quality and contributing to climate change.
- Animals ingest plastics mistaking them for food, causing blockages, starvation, and death; they also clog drains and create unsightly litter.
Q8. If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer
Answer: No, even if all waste is biodegradable, it will still impact the environment through excessive organic buildup, nutrient overload, methane emissions, and disease spread.
Key Impacts
- Biodegradable waste decomposes via microbes but in large quantities overwhelms natural processes, leading to anaerobic decay in landfills that releases methane—a potent greenhouse gas contributing to global warming.
- Excess decomposition produces foul odors, attracts pests like rats and flies, and spreads pathogens, posing health risks to nearby communities.
Ecosystem Effects
- Nutrient leaching from rotting waste causes eutrophication in water bodies, triggering algal blooms that deplete oxygen and kill aquatic life.
- Soil fertility declines due to unbalanced organic matter accumulation, disrupting microbial balance and plant growth.
Proper management like composting is essential; unchecked biodegradable waste harms air, water, soil, and biodiversity
Q9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer
Answer: Damage to the ozone layer is a cause for concern because it increases harmful ultraviolet (UV) radiation reaching the Earth’s surface, which can cause skin cancer, cataracts, immune system weakening in humans, and disrupt ecosystems by harming plants and aquatic life. Steps like international agreements are being taken to limit this damage.
Why Ozone Layer Damage is Concerning
The ozone layer filters out most of the sun’s harmful UV-B rays. When it depletes, more UV-B rays penetrate the atmosphere, causing:
- Health problems in humans such as skin cancer, eye cataracts, and weakened immunity.
- Reduced growth and productivity of plants, affecting food supply and biodiversity.
- Damage to marine life, especially plankton that forms the base of aquatic food chains.
- Disruption of ecological balance and biogeochemical cycles.
Steps to Limit Ozone Layer Damage
The main efforts to protect the ozone layer include:- The Montreal Protocol, an international treaty that controls and phases out the production and use of ozone-depleting substances (ODS) like chlorofluorocarbons (CFCs) and halons.
- Encouraging the use of eco-friendly alternatives to harmful chemicals in industries and consumer products.
- Monitoring and research programs to track ozone levels and ensure compliance with regulations.
These measures have already contributed to a gradual recovery of the ozone layer, but continued vigilance is essential to prevent further damage.
