1.
Define the term "ecosystem".
2.
Name the organisms that form the base of every food chain.
3.
What percentage of energy is transferred from one trophic level to the next?
4.
Give one example of a biodegradable and one example of a non-biodegradable waste.
5.
Name the phenomenon by which harmful chemicals accumulate and become more concentrated at higher trophic levels.
6.
Which layer of the atmosphere contains the ozone layer?
7.
Name the chemical compounds primarily responsible for ozone layer depletion.
8.
What is a food web?
9.
Distinguish between producers and consumers in an ecosystem with one example each.
10.
Name two types of decomposers and state their role in the ecosystem.
11.
What is the 10% law of energy transfer? If 10,000 J of energy is available at the producer level, how much energy reaches the secondary consumer?
12.
Explain the difference between a food chain and a food web. Which one is more realistic and why?
13.
Why are shorter food chains more energy-efficient than longer ones? Support with an example involving at least three trophic levels.
14.
State two harmful effects of ozone layer depletion on living organisms.
15.
Differentiate between biodegradable and non-biodegradable pollutants. Give two examples of each.
16.
What is biological magnification (biomagnification)? Why does it particularly affect organisms at higher trophic levels?
17.
Explain how decomposers are essential for the continuity of life on Earth.
18.
What is the role of ozone in the stratosphere? How does UV radiation reach the Earth's surface when ozone is depleted?
19.
Draw a food web involving at least five organisms from a terrestrial ecosystem. Identify the producers, primary consumers, secondary consumers, and tertiary consumers in it.
20.
Explain the flow of energy through different trophic levels in an ecosystem using a diagram. Why is the number of trophic levels in a food chain limited to 3–4?
21.
The following food chain exists in a pond ecosystem:
Phytoplankton → Zooplankton → Small fish → Large fish
- If 50,000 J of energy is available at the phytoplankton level, how much energy reaches the large fish?
- At which trophic level does biological magnification of DDT occur at the highest concentration?
- What happens to the 90% energy that is not transferred to the next level?
22.
Explain the formation and breakdown of ozone in the stratosphere under natural conditions. How do CFCs disrupt this natural balance?
23.
State the three R's of waste management. For each, give a specific example from daily life and explain how it helps reduce environmental damage.
24.
What is a trophic level? Construct an ecological pyramid of numbers for a grassland ecosystem and explain why it is always upright.
25.
Differentiate between the following with one example each:
- Autotrophs and Heterotrophs
- Herbivores and Carnivores
- Scavengers and Decomposers
26.
(a) Describe the structure and components of an ecosystem with a suitable example. Explain the difference between biotic and abiotic components.
(b) "The human beings occupy the highest trophic level in the food chain and therefore are most severely affected by biological magnification." Justify this statement with a relevant example. (3 + 2)
27.
(a) Explain the problem of ozone layer depletion. Name the main chemicals responsible, describe their mechanism of action, and state three measures being taken internationally to address this problem.
(b) State two ill effects of increased UV radiation reaching the Earth's surface on (i) human health and (ii) ecosystems. (3 + 2)
28.
In the 1990s, India experienced a catastrophic decline in vulture populations — by over 95% in less than a decade. Scientists eventually traced the cause to diclofenac, a veterinary anti-inflammatory drug given to cattle. When vultures fed on the carcasses of treated cattle, the drug caused fatal kidney failure in the birds. Vultures are nature's "clean-up crew," feeding on dead animals and preventing the spread of diseases. Their decline led to an increase in feral dog and rat populations, which in turn caused an increase in rabies and other diseases.
- At which trophic level do vultures feed? Are they herbivores, carnivores, or scavengers? (1)
- How does the loss of vultures disrupt the food web of a terrestrial ecosystem? (1)
- The diclofenac that harmed vultures is a non-biodegradable compound. Explain how its concentration would increase across trophic levels if it persisted in cattle tissue. (1)
- Suggest two measures to protect vulture populations and restore the ecosystem balance. (1)
29.
Every year, millions of tonnes of plastic waste enter the world's oceans. Marine animals such as sea turtles and whales mistake plastic bags for jellyfish and ingest them, causing internal injuries and death. Microscopic plastic particles (microplastics) are now found in the bodies of fish, zooplankton, and even in humans who consume seafood. Scientists have found that microplastics carry toxic chemicals and heavy metals, which become more concentrated as they move up the marine food chain.
- Why is plastic classified as a non-biodegradable substance? What happens to it in the environment over time? (1)
- Construct a simple marine food chain (3 organisms) in which microplastics would show biomagnification. Indicate at which level the concentration is highest. (1)
- If a fisherman regularly eats large predatory fish caught from a polluted ocean, what health risk does he face? Name the phenomenon. (1)
- Suggest two effective solutions — one at the individual level and one at the policy/government level — to reduce plastic pollution in oceans. (1)
30.
The Montreal Protocol (1987) is considered one of the most successful international environmental agreements. It was signed by nations across the world to phase out the production and use of ozone-depleting substances (ODS) such as CFCs, halons, and HCFCs. Scientists had discovered that a massive "ozone hole" was forming over Antarctica each spring. By 2019, measurements showed that the ozone layer is slowly recovering, with the hole being the smallest since 1982.
- What is the "ozone hole"? Where was it first observed, and in which season? (1)
- Explain the chemical mechanism by which CFCs destroy ozone molecules. (1)
- State two UV-related consequences that would have occurred if the ozone layer had continued to thin. (1)
- What are two alternatives to CFCs that are now used in refrigerants and aerosols? Why are they considered safer? (1)
← Back to Practice Arena