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Our Environment - Q&A

1. 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: (a), (c) and (d)
Explanation:
- Biodegradable items are those that can be broken down by bacteria and other decomposers. Natural materials like grass, flowers, leather (animal skin), fruit peels, cake, lime juice, and wood are all biodegradable.
- Plastic (in option b) is non-biodegradable and cannot be broken down by microbes.
Therefore, groups (a), (c), and (d) contain only biodegradable items.

2. 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
Explanation: A food chain shows the flow of energy where one organism eats another.
- Option (b): Grass (Producer) → Goat (Herbivore/Primary Consumer) → Human (Omnivore/Secondary Consumer). This is a logical sequence.
- Option (a): Wheat and mango do not eat grass.
- Option (c): Cow and elephant do not eat goats.
- Option (d): Goats are terrestrial (land) animals and do not usually eat fish.

[Image of food chain diagram]

3. 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
Explanation:
- (a) Cloth bags reduce the use of non-biodegradable plastic bags.
- (b) Switching off lights saves electrical energy.
- (c) Walking saves fuel (petrol) and reduces air pollution.
Since all three are good for the environment, "All of the above" is the correct answer.

4. What will happen if we kill all the organisms in one trophic level?

Answer: If we remove all organisms from one trophic level, it will disrupt the entire food chain and ecosystem balance.
1. Overpopulation of the lower level: The organisms at the previous level (which were eaten by the killed group) will increase in number uncontrollably because they have no predators.
2. Starvation of the upper level: The organisms at the next level (which ate the killed group) will die of starvation because their food source is gone.
Example: In a Grass → Deer → Lion chain, if all deer are killed, grass will grow excessively, and lions will die of hunger.

5. 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:
Yes, the impact will be different:
- Removing Producers (Plants): This is the most dangerous. No food will be produced, so all animals (herbivores and carnivores) will eventually die.
- Removing Top Carnivores (e.g., Tigers): This will lead to an explosion in the herbivore population (e.g., deer), which will overgraze and destroy all vegetation, eventually turning the land into a desert.

No, organisms of any trophic level cannot be removed without damage. Every level is connected. Removing any link disrupts the flow of energy and the balance of nature, leading to instability in the ecosystem.

6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer:
Definition: Biological magnification (or biomagnification) is the increase in the concentration of harmful, non-biodegradable chemicals (like pesticides, DDT, mercury) in the bodies of organisms as we go up the trophic levels of a food chain.

Yes, the levels will be different. The concentration increases with each step up.
- Lowest Level (Producers): Have the least concentration of chemicals.
- Highest Level (Top Carnivores/Humans): Have the maximum concentration.
Reason: These chemicals are not digested or excreted; they accumulate. Since one predator eats many prey, the chemicals from all the prey get collected and concentrated in the predator's body.

[Image of biological magnification diagram]

7. What are the problems caused by the non-biodegradable wastes that we generate?

Answer: Non-biodegradable wastes (like plastics, glass, Styrofoam) cause several problems:
1. Land Pollution: They do not decay and remain in the soil for hundreds of years, reducing soil fertility.
2. Clogging: Plastic bags choke drains and sewer systems, leading to waterlogging.
3. Animal Death: Stray animals (like cows) may accidentally swallow plastics while eating garbage, which can choke and kill them.
4. Biological Magnification: Harmful chemicals from these wastes can enter the food chain and harm human health.
5. Air Pollution: Burning plastics releases toxic gases causing respiratory problems.

8. If all the waste we generate is biodegradable, will this have no impact on the environment?

Answer: Even if all waste is biodegradable, generating it in excess can still impact the environment:
1. Slow Decomposition: If the amount of waste is huge, the natural decomposers (bacteria/fungi) may not be able to break it down fast enough.
2. Foul Smell & Gas: Large heaps of rotting waste produce bad odours and release greenhouse gases like methane, contributing to global warming.
3. Disease Breeding: Accumulation of waste becomes a breeding ground for flies, mosquitoes, and rats, which spread diseases.
So, while better than non-biodegradable waste, excessive biodegradable waste still needs proper management.

9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Answer:
Why it is a concern: The ozone layer (O₃) in the upper atmosphere acts as a shield. It absorbs the sun's harmful Ultraviolet (UV) radiation. Damage (holes) in this layer allows UV rays to reach the earth, causing:
- Skin cancer in humans.
- Eye cataracts.
- Damage to crops and immune systems.

Steps taken to limit damage:
1. Banning CFCs: The main cause of ozone depletion is Chlorofluorocarbons (CFCs) used in ACs, fridges, and fire extinguishers. In 1987, the United Nations Environment Programme (UNEP) forged an agreement (Montreal Protocol) to freeze CFC production.
2. Safe Alternatives: Manufacturers now use ozone-friendly alternatives (like HFCs) in refrigerators and aerosol sprays instead of CFCs.

[Image of ozone layer depletion]

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Quick Review Flashcards - Click to flip and test your knowledge!

Question

What constitutes an 'ecosystem' in a given area?

Answer

All interacting living organisms together with the non-living constituents of the environment.

Question

Which two categories of components make up an ecosystem?

Answer

Biotic components and abiotic components.

Question

List three examples of physical factors that form abiotic components of an ecosystem.

Answer

Temperature, rainfall, and wind (also soil and minerals).

Question

Ecosystems such as forests, ponds, and lakes are classified as _____ ecosystems.

Answer

Natural

Question

Why are gardens and crop-fields considered 'artificial' ecosystems?

Answer

They are human-made rather than occurring naturally.

Question

Which group of organisms can produce organic compounds like sugar and starch from inorganic substances using solar energy?

Answer

Producers

Question

Producers use the radiant energy of the Sun in the presence of _____ to perform photosynthesis.

Answer

Chlorophyll

Question

Organisms that depend on producers either directly or indirectly for sustenance are called _____.

Answer

Consumers

Question

How are consumers classified based on their diet?

Answer

Herbivores, carnivores, omnivores, and parasites.

Question

What is the primary role of decomposers in an ecosystem?

Answer

They break down the dead remains and waste products of organisms.

Question

Which types of organisms typically act as decomposers?

Answer

Microorganisms, specifically bacteria and fungi.

Question

Decomposers convert complex organic substances into simple _____ substances that enter the soil.

Answer

Inorganic

Question

What is a 'food chain'?

Answer

A series of organisms taking part at various biotic levels where each feeds on the previous one.

Question

Each step or level of a food chain is known as a _____ level.

Answer

Trophic

Question

Which organisms occupy the first trophic level?

Answer

Autotrophs (producers).

Question

Which organisms occupy the second trophic level?

Answer

Herbivores (primary consumers).

Question

Small carnivores, also known as secondary consumers, occupy the _____ trophic level.

Answer

Third

Question

Larger carnivores or tertiary consumers occupy the _____ trophic level.

Answer

Fourth

Question

In a terrestrial ecosystem, what percentage of the energy from sunlight is captured by green plants?

Answer

Approximately $1\%$.

Question

What happens to the majority of energy when green plants are eaten by primary consumers?

Answer

It is lost as heat to the environment or used for digestion, work, growth, and reproduction.

Question

What is the average percentage of food eaten that is turned into an organism's own body and made available for the next consumer level?

Answer

$10\%$

Question

Why do most food chains generally consist of only three or four steps?

Answer

The loss of energy at each step is so great that very little usable energy remains after four levels.

Question

Which trophic level in an ecosystem typically contains the greatest number of individuals?

Answer

The producers (lowest level).

Question

A series of branching lines showing complex feeding relationships is called a _____.

Answer

Food web

Question

Describe the direction of energy flow in an ecosystem.

Answer

The flow of energy is unidirectional.

Question

Why is energy that passes to herbivores no longer available to autotrophs?

Answer

Energy flow is unidirectional and moves progressively through trophic levels without reverting.

Question

How do pesticides typically enter a terrestrial food chain from the soil?

Answer

They are absorbed by plants along with water and minerals.

Question

Define 'biological magnification'.

Answer

The progressive accumulation of non-degradable chemicals at each higher trophic level.

Question

Why do human beings often have the maximum concentration of harmful pesticides in their bodies?

Answer

Humans occupy the top level of many food chains, leading to maximum biological magnification.

Question

What is the chemical formula for ozone?

Answer

$O_3$

Question

How does ozone affect organisms at ground level?

Answer

It is a deadly poison.

Question

What essential function does the ozone layer perform in the higher atmosphere?

Answer

It shields the Earth's surface from ultraviolet ($UV$) radiation from the Sun.

Question

List one specific health risk to humans caused by increased exposure to $UV$ radiation.

Answer

Skin cancer.

Question

How is ozone formed in the upper atmosphere from molecular oxygen ($O_2$)?

Answer

High-energy $UV$ radiation splits $O_2$ into free $O$ atoms, which then combine with other $O_2$ molecules.

Question

The sharp drop in atmospheric ozone levels in the 1980s was linked to which synthetic chemicals?

Answer

Chlorofluorocarbons ($CFCs$).

Question

What are two common industrial uses for chlorofluorocarbons ($CFCs$)?

Answer

Refrigerants and fire extinguishers.

Question

What did the 1987 $UNEP$ agreement seek to achieve regarding $CFCs$?

Answer

A freeze on $CFC$ production at 1986 levels.

Question

What are 'biodegradable' substances?

Answer

Substances that are broken down by biological processes (action of bacteria or saprophytes).

Question

What are 'non-biodegradable' substances?

Answer

Substances that are not broken down by biological processes and persist in the environment.

Question

Why do enzymes in the human body only break down specific substances?

Answer

Enzymes are specific in their action, requiring a particular enzyme for a particular substance.

Question

Why do human-made materials like plastics persist for a long time in the environment?

Answer

They are not broken down by the action of bacteria or other saprophytes.

Question

How has the shift to disposable packaging affected the environment?

Answer

It has resulted in a much higher proportion of our waste becoming non-biodegradable.

Question

Why was the large-scale use of 'kulhads' (clay cups) in trains discouraged?

Answer

Making them on a large scale would result in the loss of fertile top-soil.

Question

What is the primary advantage of disposable paper cups over plastic cups?

Answer

Paper is biodegradable and has less long-term environmental impact.

Question

The various components of an ecosystem are _____.

Answer

Interdependent

Question

What percentage of energy captured by autotrophs reverts back to solar input?

Answer

$0\%$ (energy flow is unidirectional).

Question

Identify the primary source of energy for all activities in the living world.

Answer

Sunlight (solar energy).

Question

What happens to the organic matter present at each trophic level when it reaches the next?

Answer

Only an average of $10\%$ is available to the next level of consumers.

Question

Which international organisation succeeded in forging the 1987 agreement to control $CFC$ production?

Answer

United Nations Environment Programme ($UNEP$).

Question

Which trophic level consists of autotrophs?

Answer

The first trophic level.

Question

Why cannot pesticide residues be easily removed from food grains by washing?

Answer

They are absorbed into the plant's internal structure during growth.

Question

What is the relationship between trophic levels and available energy?

Answer

The energy available at each trophic level diminishes progressively.

Question

In the chemical reaction $O + O_2 \rightarrow O_3$, what does $O_3$ represent?

Answer

Ozone

Question

Name one type of human-made ecosystem.

Answer

A garden (or crop-field/aquarium).

Question

Which group of organisms makes solar energy available to the rest of the ecosystem?

Answer

Producers.