NCERT Solutions for Class 10 Science Chapter 13 Our Environment

NCERT Solutions for Class 10 Science Chapter 13 Our Environment includes latest edition answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on Our Environment chapter.

NCERT Solutions for Class 10 Science Chapter 13 Intext Questions

Page No. 212

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 in the food chain at which transfer of food energy takes place are called trophic levels.

Food chain operating in a grassland.
Grass → Insects → Frogs → Snakes

  1. Grass  → 1st trophic level
  2. Insects → 2nd trophic level
  3. Frogs → 3rd  trophic level
  4. Birds→ 4th  trophic level

Question 2: What is the role of decomposers in the ecosystem?

Answer: Decomposers are microorganisms that play a crucial role in ecosystems. They break down dead plants and animals, along with waste materials, into simpler substances. This process returns nutrients back into the soil, which are then used by plants for growth. Decomposers help in recycling nutrients, maintaining soil health, and ensuring the continuity of the ecosystem’s nutrient cycle. Without decomposers, dead matter and waste would accumulate, disrupting the balance of the ecosystem.

Page No. 214

Question 1: Why are some substances biodegradable and some non-biodegradable?

Answer: Some substances which are degraded and broken down into simpler substances by the microorganisms, are called biodegradable substances.

For example: Cotton, wood, paper, wool, etc.

Substance (mainly man-made) that do not degrade or broken down into simpler substances by the action of enzymes secreted by microorganisms are called non- biodegradable substances.

For example: Plastic, polythene, DDT, etc.

Question 2: Give any two ways in which biodegradable substances would affect the environment.

Answer:Biodegradable substances affect the environment in two main ways:

  1. Enhancing Soil Fertility: As biodegradable materials break down, they turn into compost or organic matter. This enriches the soil, improving its quality and fertility, which benefits plant growth.
  2. Reducing Pollution: Biodegradable substances decompose naturally and don’t accumulate in the environment. This helps in reducing pollution and waste buildup, unlike non-biodegradable materials that can lead to pollution and harm wildlife and ecosystems.

Question 3: Give any two ways in which non-biodegradable substances would affect the environment.

Answer: Non-biodegradable substances impact the environment in two significant ways:

  • Pollution and Waste Accumulation: Since non-biodegradable materials don’t break down easily, they accumulate in the environment. This leads to pollution in landfills, water bodies, and natural habitats, harming ecosystems and wildlife.
  • Threat to Wildlife and Ecosystems: Non-biodegradable waste, like plastic, can be mistaken for food by wildlife, leading to harmful ingestion and entanglement. These materials can also disrupt natural processes in ecosystems and affect the health of both animals and plants.

Page No. 216

Question 1: What is ozone and how does it affect any ecosystem?

Answer: Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone protects living things by blocking a lot of the Sun’s harmful ultraviolet (UV) rays. This is really important for keeping ecosystems safe, as too much of these rays can damage plants and animals. UV radiation is highly damaging to organisms, for example, it is known to cause skin cancer, cataract and damage the immune system in human beings. It also destroys plants and reduces photosynthesis process.

Question 2: How can you help in reducing the problem of waste disposal? Give any two methods.

Answer: To help reduce the problem of waste disposal, we can use the following two effective methods:

  1. Recycling and Reusing: By recycling materials like paper, glass, and plastic, and reusing items whenever possible, you reduce the amount of waste that goes into landfills. This not only conserves resources but also decreases environmental pollution.
  2. Composting Organic Waste: Composting kitchen scraps and garden waste turns them into nutrient-rich compost for gardens. This reduces the volume of garbage that needs to be disposed of and provides a natural fertilizer for plants.


We can use the following methods to reduce problem of waste disposal

  • Separating biodegradable and non-biodegradable waste before dumping them.
  • By minimizing the use of disposal items and promoting the use of recycled articles.
  • Recycling the non-biodegradable waste material.

NCERT Solutions for Class 10 Science Chapter 13 Exercise Questions

Question 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) Fruit-peels, cake and lime-juice
(b) Cake, wood and grass

Question 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

Question 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

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

Answer: If we kill all the organisms in one trophic level, the transfer of food energy to the next trophic level will stop. This will cause a break in the food chain resulting in ecosystem imbalance. As a result, the organisms of the higher trophic level will also die, while the individuals of the lower trophic level will exhibit enormous growth in their population. Both the conditions will result in an ecological upset.


Eliminating all organisms in one trophic level would severely disrupt the ecosystem. Higher-level organisms that rely on them for food would face starvation and possible extinction. Simultaneously, the lower trophic levels, now without their natural predators or consumers, might experience overpopulation. This could lead to a shortage of their food sources, causing further imbalance. Such a disruption could have a domino effect, potentially leading to the collapse of the entire ecosystem, as each trophic level is essential for maintaining ecological balance.

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: If we remove all organisms from a trophic level, the effect on the ecosystem would depend on which level is removed, but in every case, it would cause harm. For instance, removing plants, the primary producers, would starve all animals that depend on them, eventually leading to a breakdown of the ecosystem. On the other hand, removing predators would cause their prey to overpopulate, which could lead to overgrazing and depletion of vegetation. In essence, each trophic level, whether producers, consumers, or decomposers, has a vital role, and removing any level disrupts the natural balance of the ecosystem.

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

Answer: Biological magnification, also known as biomagnification, is the process where certain substances, like pesticides or heavy metals, accumulate in higher concentrations in the bodies of organisms at each successive trophic level of a food chain. These substances are often not easily broken down or excreted, so they build up in organisms over time.

Yes, the levels of biological magnification will be different at different levels of the ecosystem. Typically, the higher you go in the food chain, the greater the concentration of these substances. For instance, small fish might have a certain level of a toxic substance, but larger fish that eat many small fish will accumulate higher levels of the toxin.

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

Answer: Non-biodegradable wastes cause several problems:

  1. Pollution: They lead to pollution of the land, water, and air because they don’t break down easily. This can harm wildlife and natural habitats.
  2. Health Hazards: These wastes can release harmful chemicals and microplastics, posing health risks to humans and animals.
  3. Landfill Overload: They accumulate in landfills, taking up a lot of space and lasting for many years.
  4. Wildlife Harm: Animals can mistake these materials for food, leading to ingestion and entanglement, which can be fatal.

Overall, non-biodegradable waste is a major environmental concern due to its persistence and harmful effects.

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

Answer: The following are the problems caused by non-biodegradable wastes:

  • They lead to pollution of the land, water, and air because they don’t break down easily.
  • They take up a lot of space in landfills, as they don’t break down, leading to more landfills needed.
  • Non-biodegradable wastes like heavy metals may enter the food chain in the upper trophic levels.
  • They may escape to the groundwater which causes soil infertility and disturbance in pH of the soil.

    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 is a protective shield around the earth. It prevents harmful ultraviolet radiation of the sun from reaching the earth. Air pollutants, like chlorofluorocarbons (CFCs), are causing depletion of ozone layer. This is allowing greater amount of UV radiation to reach the earth. UV radiation can upset the ecosystem by affecting photosynthesis in plants, destroying planktons and decomposers. In human beings, UV radiation may cause skin cancer, cataract of eyes and damage to immune system.

    To limit this damage, various steps are being taken:

    1. International Agreements: The most significant is the Montreal Protocol, an international treaty agreed upon in 1987 to phase out the production of numerous substances responsible for ozone depletion, like chlorofluorocarbons (CFCs).
    2. Regulations on Harmful Substances: Many countries have established regulations to control or eliminate the use of chemicals that damage the ozone layer.
    3. Research and Monitoring: Continuous research and monitoring of the ozone layer help in understanding its condition and the effectiveness of measures taken to protect it.
    4. Public Awareness: Educating the public about the importance of the ozone layer and how to protect it is also a key step.

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