Intext Questions 1
Question 1
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer
The various steps or levels in a food chain at which the transfer of energy takes place are called trophic levels.
An Example of food chain is:
Grass → grasshopper → frog → snake
The autotroph or the producer — In the above given food chain grass is the producer. It is at the first trophic level. It fixes up the solar energy and makes it available for heterotrophs or the consumers.
The herbivores or the primary consumers — They are the second trophic level. In the above given food chain grasshopper is the primary consumer as it feeds on grass.
Secondary Consumers — They are third trophic level. Small carnivores like frog in the given food chain is the secondary consumer.
Tertiary consumer — They are the fourth trophic level. Larger carnivores like snake in the given food chain constitute the fourth trophic level.
Different organisms may be on different trophic levels depending upon their position in different food chains.
Question 2
What is the role of decomposers in the ecosystem?
Answer
The microorganisms, comprising bacteria and fungi, that break-down the dead remains and waste products of organisms are called decomposers. They break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants. Thus they help to clean up by decomposing dead remains and also maintain the nutrient cycle by returning the plant nutrients back into the soil.
Intext Questions 2
Question 1
Why are some substances biodegradable and some non-biodegradable?
Answer
Natural or organic materials like wood, paper, and leftover food are biodegradable because their compounds can be broken down by biological processes, facilitated by microorganisms. These substances decompose into inorganic elements without leaving toxic residues.
On the other hand, substances like plastic, metals and paints cannot be broken down by biological processes and are known as non-biodegradable. Their persistence in the environment can lead to long-term pollution, as they do not break down into simpler components.
Question 2
Give any two ways in which biodegradable substances would affect the environment.
Answer
Two ways in which biodegradable substances would affect the environment are:
- They decompose and enrich the soil fertility by adding different elements that are reused by growing plants.
- Decomposing material release carbon dioxide and methane into the atmosphere that contributes to an increase in global warming.
Question 3
Give any two ways in which non-biodegradable substances would affect the environment.
Answer
Two ways in which non-biodegradable substances would affect the environment are:
- Non-biodegradable substances, such as plastic, contribute to environmental pollution by accumulating in ecosystems, water bodies, and soil disrupting the ecological balance and harming wildlife.
- They can cause bio-magnification if their hazardous chemicals enter the food chain.
Intext Questions 3
Question 1
What is ozone and how does it affect any ecosystem?
Answer
Ozone is formed when an oxygen molecule (O2) combines with another oxygen atom (O). Thus Ozone (O3) is a molecule formed by three atoms of oxygen.
Ozone is present at the higher levels of the atmosphere and it shields the surface of the earth from ultraviolet (UV) radiation of the Sun. Therefore, it helps to protect all ecosystems/organisms from highly damaging radiations that can cause problems like skin cancer and cataract in humans and potential damage to some marine organisms and plants. Ozone also helps to maintain the temperature of earth.
Question 2
How can you help in reducing the problem of waste disposal? Give any two methods.
Answer
Two methods that can help in reducing the problem of waste disposal are:
- Minimizing use of single use/disposable items.
- Use of biodegradable items.
Exercises
Question 1
Which of the following groups contain only biodegradable items?
- Grass, flowers and leather
- Grass, wood and plastic
- Fruit-peels, cake and lime-juice
- Cake, wood and grass
Answer
1, 3, 4
Reason — Grass, flowers, leather, wood, fruit-peels, cake, lime-juice are examples of biodegradable items.
Question 2
Which of the following constitute a food-chain?
- Grass, wheat and mango
- Grass, goat and human
- Goat, cow and elephant
- Grass, fish and goat
Answer
Grass, goat and human
Reason — In the given food chain, grass is producer which is consumed by herbivorous or primary consumer i.e. goat. Human is secondary consumer as it consumes goat.
Question 3
Which of the following are environment-friendly practices?
- Carrying cloth-bags to put purchases in while shopping
- Switching off unnecessary lights and fans
- Walking to school instead of getting your mother to drop you on her scooter
- All of the above
Answer
All of the above
Reason — Minimal use of plastic, saving electricity and less use of fossil fuels are steps that are environment-friendly.
Question 4
What will happen if we kill all the organisms in one trophic level?
Answer
In a food chain, organism at each trophic level is responsible for flow of energy. If we kill all the organisms in one trophic level this flow of energy would stop, creating an imbalance in the ecosystem. It will result in increase in population of organisms at previous trophic level and decrease in population of organisms at next trophic level. If all primary consumers die, the number of plants will increase immensely and the secondary consumers will die due shortage of food.
For example, in the given food chain,
Plants → Deer → Lion
if all deer and other herbivores die, the number of plants will increase and animals like lion will die due to starvation as there will be no herbivores left.
Question 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 of removing all the organisms in a trophic level will be different for different trophic levels.
- Primary Producers (Plants) — Removing plants will cause the collapse of the entire food chain as without photosynthesis the energy input into the ecosystem would stop.
- Primary Consumers (Herbivores) — Removing all herbivores would result in a surge in plant population. Also, carnivores that rely on herbivores as a food source would face a shortage of prey and ultimately die of starvation.
- Secondary Consumers (Carnivores) — Removing all carnivores would result in a surge in herbivores population leading to overgrazing and potential damage to plant population.
No, the organisms of any trophic level cannot be removed without causing any damage to the ecosystem.
Question 6
What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer
The phenomenon of accumulation of harmful chemicals progressively at each trophic level is called biological magnification.
The levels of the biological magnification increases with increase in levels of the ecosystem i.e. the concentration of chemicals rises with successive trophic level.
Question 7
What are the problems caused by the non-biodegradable wastes that we generate?
Answer
Non-biodegradable wastes cause various problems like:
- Soil and water pollution — The unused chemical fertilizers, residual pesticides, plastics etc. cause contamination of soil and water.
- Bio-magnification — The chemicals or heavy metals from non-biodegradable wastes enter the food chain and increase in their concentration in successive trophic level. These chemicals may cause cancer and other diseases.
- Dumping — Since they do not degrade, their dumping becomes a serious problem. Chemicals leach from dumping grounds and contaminate ground water.
- Microplastics — Microplastics are extremely small pieces of plastic that may enter the body through food or water. They are very harmful for our body.
- Clogging of drains — Non-biodegradable wastes, mostly plastic lead to clogging of drains.
- Ecological imbalance — Non-biodegradable wastes lead to ecological imbalance in following ways — many stray cattle die by consuming polythene bags, contamination of water bodies kill many aquatic organisms, non-biodegradable chemicals lead to eutrophication killing aquatic animals.
Question 8
If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer
Even if all the waste generated is biodegradable, it will still harm the environment in the following ways:
- Large amount of biodegradable waste will require a larger land area for decomposition disturbing the natural habitat of organisms.
- The decomposition of biodegradable waste, especially in landfills, can produce methane, a potent greenhouse gas leading to an increase in global warming.
- Accumulation of waste will lead to breeding grounds for mosquitoes, worms and flies which may be the carrier of many diseases.
- Slow decomposition of biodegradable waste can produce foul smell and harmful gases posing health risks such as irritation, nausea, and dizziness when inhaled by humans.
Question 9
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer
Ozone layer shields the surface of the earth from harmful ultraviolet (UV) radiations from the Sun. Damage to the ozone layer will allow these harmful UV radiations to reach the earth's surface and harm the environment in the following ways:
- It can cause many diseases in human beings like skin cancer and cataract.
- It can result in the death of many phytoplanktons leading to increased global warming.
- It can disturb the ecological balance in marine ecosystem.
- It can cause genetic disorders which ultimately affect heredity.
Following steps are being taken to limit the damage to the ozone layer:
- Use of products that contain CFC's to be replaced by alternative products.
- Regulations against release of CFCs directly in environment.
- Minimize the emission of gases that are harmful for Ozone layer such as nitrogen oxide.
- UNEP agreement to freeze CFC production at 1986 levels.