NCERT solutions for Class 10th Science Our Environment

Trophic Levels:

Trophic levels are the different steps in a food chain. Each step represents a level of feeding or energy transfer in an ecosystem.

Example of a Food Chain:
Grass → Grasshopper → Frog → Snake → Hawk

Trophic Levels in this Food Chain:

1. Grass – Producer (1st trophic level)
2. Grasshopper – Primary consumer (2nd trophic level)
3. Frog – Secondary consumer (3rd trophic level)
4. Snake – Tertiary consumer (4th trophic level)
5. Hawk – Top consumer or quaternary consumer (5th trophic level)

Role of Decomposers in the Ecosystem:

Decomposers are organisms like bacteria and fungi that break down the dead bodies of plants and animals into simpler substances.

Their main roles are:

1. Break Down Dead Matter: -  They decompose dead plants, animals, and waste materials.
2. Recycle Nutrients: -  They return important nutrients like nitrogen, carbon, and minerals back to the soil, making it fertile.
3. Maintain Balance in the Ecosystem:-  By cleaning up dead matter and waste, they help keep the environment clean.
4. Support Producers: -  The nutrients they release into the soil are used by plants (producers) to grow.

Substances are classified as biodegradable or non-biodegradable based on how they are broken down in nature.

Biodegradable Substances:

These are materials that can be broken down by natural processes, mainly by microorganisms like bacteria and fungi.
Examples: Food waste, paper, wood, cotton.
Reason:- These substances are made from natural materials that microorganisms can easily decompose into simpler, harmless substances.

Non-biodegradable Substances:

These are materials that cannot be broken down by natural processes or take a very long time to decompose.
Examples: Plastic, glass, synthetic fibers, metals.
Reason: -These substances are made from synthetic (man-made) materials or chemicals that microorganisms cannot break down easily. They remain in the environment for a long time and can cause pollution.

Two ways in which biodegradable substances affect the environment:

1. They make the soil fertile:--  When biodegradable substances like food waste and dead plants break down, they release nutrients into the soil. This helps plants grow better.
2. They can cause pollution if not managed properly:--  If too much biodegradable waste is thrown in one place and left to rot, it can smell bad and attract flies and insects. It can also pollute the land and water around it.

Two ways in which non-biodegradable substances affect the environment:

1. They cause land and water pollution: - Non-biodegradable substances like plastic and glass do not break down easily. When they are thrown into the environment, they stay there for a long time and pollute the soil and water.

2. They harm animals and plants: -   Animals may eat plastic thinking it is food, which can harm or even kill them. These substances can also block sunlight and air from reaching plants, affecting their growth.

Ozone (O₃) is a gas made up of three oxygen atoms. It is found in the upper layer of the atmosphere, called the stratosphere, and forms the ozone layer.

How ozone affects the ecosystem:

1. Protects living beings from harmful UV rays:
        The ozone layer absorbs most of the Sun's ultraviolet (UV) rays, which are harmful to humans, animals, and plants. Without           it, UV rays can cause skin cancer, eye damage, and harm crops.

2. Maintains balance in the ecosystem:
         By blocking harmful radiation, ozone helps protect ecosystems like forests, oceans, and farms, allowing plants and animals           to survive and grow properly.

Correct answer: (c) Fruit-peels, cake and lime-juice

Reason: All items in option (c) are natural and easily decompose, so they are biodegradable.

Correct answer: (b) Grass, goat and human

Reason: It shows a proper food chain – plant ---->   herbivore ---> human.

Correct answer: (d) All of the above

Reason: All options help reduce pollution and save resources, making them environment-friendly practices.

If we kill all the organisms in one trophic level, the food chain will get disturbed.

1. The next level will not get food and may die.
2. The previous level may increase too much and cause imbalance.

So, it will harm the balance of nature and affect the whole ecosystem.

Yes, the impact will be different for different trophic levels. Each level plays an important role in the ecosystem.

1. If producers (like plants) are removed, all other levels will die due to lack of food.
2. If primary consumers (like herbivores) are removed, carnivores will not get food, and plants may grow too much.
3. If top consumers are removed, the number of herbivores may increase a lot and harm plant life.

No trophic level can be removed without causing damage. Each level is needed to keep the balance in the ecosystem.

Biological magnification means the increase of harmful substances like pesticides in the bodies of living organisms as we move up the food chain.

These substances are not broken down, so they keep getting stored and passed on from one level to the next.

Yes, the levels of magnification are different at different trophic levels. The amount of harmful substances increases at each higher level in the food chain.

Top consumers, like humans, are affected the most.

Problems caused by non-biodegradable wastes:

1. Pollution: They cause land, water, and air pollution because they do not break down easily.
2. Harm to animals: Animals may eat plastic or get trapped in it, which can hurt or kill them.
3. Clog drains and cause floods: Plastic and other wastes block drains, leading to waterlogging and floods.
4. Take up space: They pile up in landfills and spoil the beauty of the environment.

If all the waste we make is biodegradable, it will cause less harm to the environment than non-biodegradable waste.

But if a lot of biodegradable waste is dumped in one place and not handled properly, it can smell bad, attract insects, and pollute the soil and water.

So, even biodegradable waste needs to be disposed of carefully to keep the environment clean.

Damage to the ozone layer is a problem because it lets more harmful UV rays from the sun reach the Earth. This can cause skin cancer, eye problems, and harm animals, plants, and crops.

To stop this damage, people are reducing the use of harmful chemicals like CFCs found in old refrigerators and spray cans. International agreements like the Montreal Protocol help control these chemicals. People are also using safer alternatives and spreading awareness about protecting the ozone layer.