NCERT Class 10 Science Solutions: Our Environment

Question:

A food chain shows the flow of energy from one living organism to another. It starts with a producer (usually a plant) and moves through a series of consumers.


A food chain illustrates who eats whom. Producers are organisms that make their own food, like plants. Primary consumers eat producers. Secondary consumers eat primary consumers, and so on.

Let’s analyze the options:
A. Grass, wheat, and mango are all producers. A food chain needs to show the transfer of energy, so it must involve different trophic levels.
B. Grass is a producer. A goat is a primary consumer that eats grass. A human can be a secondary consumer if they eat the goat, or a primary consumer if they eat plants. This option shows a logical progression of energy transfer.
C. Goat, cow, and elephant are all herbivores (primary consumers) that eat plants. This doesn’t form a food chain as there’s no producer and no progression through different consumer levels.
D. Grass is a producer. A fish is typically an aquatic organism that eats plants or smaller aquatic animals. A goat eats grass. There isn’t a clear, direct energy transfer from grass to fish and then to goat in a typical food chain.

Therefore, Grass, goat, and human constitute a food-chain because it demonstrates a sequence of energy transfer: grass (producer) is eaten by a goat (primary consumer), which is then eaten by a human (secondary consumer).

Question:

Environmental consciousness involves adopting practices that minimize harm to the environment. This includes reducing waste, conserving energy, and adopting sustainable transportation methods.


The question asks to identify environment-friendly practices. Let’s analyze each option:
A. Carrying cloth-bags to put purchases in while shopping: This practice reduces the need for single-use plastic bags, which are a major source of pollution and take a long time to decompose. Therefore, it is environment-friendly.
B. Switching off unnecessary lights and fans: This conserves electricity. Generating electricity often involves burning fossil fuels, which contribute to air pollution and climate change. Conserving energy reduces this impact. Therefore, it is environment-friendly.
C. Walking to school instead of getting your mother to drop you on her scooter: This reduces the use of fossil fuels for transportation, thereby decreasing air pollution and greenhouse gas emissions. Walking is also a healthy alternative. Therefore, it is environment-friendly.
D. All of the above: Since options A, B, and C are all identified as environment-friendly practices, this option encompasses all of them.

Therefore, all the given practices are environment-friendly.

Final Answer: The final answer is $\boxed{D}$

Question:

Waste disposal refers to the process of getting rid of unwanted materials or byproducts. Reducing waste disposal problems involves minimizing the amount of waste generated and managing the waste in an environmentally sound manner. Key concepts include the principles of “Reduce, Reuse, Recycle” and proper waste segregation.


There are several ways individuals can contribute to reducing the problem of waste disposal. Two effective methods are:

1. Reduce and Reuse:
* Reduce: This involves minimizing the amount of waste we generate in the first place. For example, buy products with minimal packaging, use reusable shopping bags instead of plastic ones, and avoid single-use items like disposable cups and cutlery. Planning meals can also reduce food waste.
* Reuse: Before discarding an item, consider if it can be used again for its original purpose or for a different one. For instance, old clothes can be repurposed as cleaning rags, glass jars can be used for storage, and plastic containers can be washed and reused.

2. Recycle and Compost:
* Recycle: This is the process of converting waste materials into new materials and objects. Segregate recyclable waste like paper, plastic, glass, and metal from other waste. Ensure these materials are clean before placing them in designated recycling bins. This reduces the need to extract raw materials, saving energy and resources.
* Compost: Organic waste, such as food scraps (vegetable peels, fruit waste, tea leaves) and yard waste (leaves, grass clippings), can be decomposed naturally to create nutrient-rich soil conditioner called compost. Composting significantly reduces the volume of waste sent to landfills and provides a valuable resource for gardening.

Question:

Ozone layer, stratospheric ozone, tropospheric ozone, ozone depletion, ozone pollution, effects on plants, effects on animals, effects on ecosystem


Ozone can affect ecosystems in two primary ways, depending on its location in the atmosphere.

Stratospheric Ozone: The ozone layer in the stratosphere is beneficial. It absorbs most of the Sun’s harmful ultraviolet (UV-B) radiation. Without this layer, increased UV-B radiation would reach the Earth’s surface, causing:
* Damage to DNA in living organisms, leading to increased rates of skin cancer and cataracts in animals and humans.
* Harm to plants by affecting photosynthesis, growth, and reproduction. This can reduce crop yields and damage natural vegetation.
* Disruption of marine ecosystems, particularly by harming phytoplankton, which form the base of the marine food web.

Tropospheric Ozone: Ozone in the troposphere (the lowest layer of the atmosphere) is a harmful air pollutant. It is a component of smog and is formed by chemical reactions involving pollutants from vehicles and industrial processes. Tropospheric ozone affects ecosystems by:
* Damaging plant tissues, leading to reduced growth, decreased crop yields, and making plants more susceptible to diseases and pests.
* Irritating the respiratory systems of animals and humans, leading to breathing problems and reduced lung function.
* Contributing to the degradation of materials like rubber and fabrics.

Therefore, ozone’s impact on an ecosystem is dependent on whether it is beneficial stratospheric ozone protecting from UV radiation or harmful tropospheric ozone acting as a pollutant.

Question:

Trophic levels represent the position an organism occupies in a food chain. Food chains illustrate the flow of energy from one organism to another. Understanding producers, consumers, and decomposers is crucial.


Trophic levels are the different steps or stages in a food chain where energy is transferred from one organism to another. Each level represents organisms that have a similar feeding position.

A food chain shows how energy is transferred when one organism eats another.

Example of a food chain:
Grass → Grasshopper → Frog → Snake → Eagle

The different trophic levels in this food chain are:

1. First Trophic Level (Producers): Grass. These are organisms that produce their own food, usually through photosynthesis.

2. Second Trophic Level (Primary Consumers): Grasshopper. These are herbivores that feed directly on producers.

3. Third Trophic Level (Secondary Consumers): Frog. These are carnivores or omnivores that feed on primary consumers.

4. Fourth Trophic Level (Tertiary Consumers): Snake. These are carnivores that feed on secondary consumers.

5. Fifth Trophic Level (Quaternary Consumers / Apex Predator): Eagle. This is an organism at the top of the food chain, which is not preyed upon by any other organism. (In this specific chain, the eagle is the apex predator).

Decomposers (like bacteria and fungi) are not typically shown in a linear food chain but are essential. They break down dead organic matter from all trophic levels, returning nutrients to the ecosystem.

Question:

Bioaccumulation: The process where a substance, like a pesticide or heavy metal, accumulates in an organism over its lifetime.
Food Chain: A series of organisms where each is eaten by the next organism in the chain.
Trophic Levels: The positions organisms occupy in a food chain (e.g., producer, primary consumer, secondary consumer).
Biomagnification: The increasing concentration of a substance as it moves up the trophic levels of a food chain.


Biological magnification, also known as biomagnification, is a process that occurs in food chains. It describes how certain substances, such as persistent pesticides or heavy metals, become more concentrated in organisms at successively higher levels of the food chain. When an organism at a lower trophic level (e.g., a plant) absorbs a toxic substance, it accumulates in its tissues. When a predator consumes multiple organisms from that lower level, it ingests all the accumulated toxins. Because these toxins are often not easily metabolized or excreted, they accumulate in the predator’s body as well. This accumulation continues at each subsequent trophic level, leading to significantly higher concentrations of the toxic substance in organisms at the top of the food chain compared to those at the bottom. For example, if a small fish eats many plankton containing a pesticide, the pesticide will concentrate in the fish. If a larger fish eats many of these smaller fish, the pesticide concentration will increase further in the larger fish, and so on.

Question:

Biodegradation is the process by which organic substances are broken down by microorganisms. The ability of a substance to be biodegraded depends on its chemical structure and the presence of suitable microorganisms and environmental conditions. Non-biodegradable substances resist this breakdown process.


Some substances are biodegradable because they are made of organic materials that can be easily decomposed by microorganisms like bacteria and fungi. These microorganisms possess enzymes that can break down the complex molecules of organic matter into simpler substances such as carbon dioxide, water, and biomass. For example, food scraps, paper, and cotton are organic and readily biodegradable.

Other substances are non-biodegradable because they are composed of materials that microorganisms cannot easily break down. This often includes synthetic materials like plastics, certain metals, and synthetic chemicals. Plastics, for instance, are made from long chains of polymers that are very resistant to microbial attack. Even if microorganisms encounter them, they lack the necessary enzymes to cleave these strong chemical bonds. Non-biodegradable substances persist in the environment for very long periods, leading to pollution. The rate of biodegradation also depends on environmental factors such as temperature, moisture, and oxygen availability, which can either speed up or slow down the decomposition process for biodegradable materials.

Question:

Biodegradable substances are materials that can be broken down naturally by microorganisms into simpler components. Understanding this natural decomposition process is key to understanding their environmental impact.


Biodegradable substances can affect the environment in both positive and negative ways.

Two ways in which biodegradable substances would affect the environment are:

1. Enrichment of soil: When biodegradable materials like food scraps, plant waste, and paper decompose, they break down into simpler organic matter and nutrients. This process, known as composting, enriches the soil by adding essential elements like nitrogen, phosphorus, and potassium. This improved soil fertility can support healthier plant growth and increase agricultural productivity.

2. Production of greenhouse gases: During the decomposition of biodegradable substances, especially in anaerobic (oxygen-deficient) conditions like landfills, microorganisms produce gases. A significant byproduct of this anaerobic decomposition is methane (CH4), a potent greenhouse gas. Methane contributes to global warming and climate change. While oxygen-rich decomposition (aerobic) produces less harmful byproducts like carbon dioxide (CO2) and water, large accumulations of biodegradable waste in landfills can lead to substantial methane emissions.

Question:

Decomposers are organisms like bacteria and fungi that break down dead organic matter (plants and animals) into simpler inorganic substances. This process is crucial for nutrient cycling and waste removal in ecosystems.


Two important roles played by decomposers in the environment are:

1. Nutrient Recycling: Decomposers break down complex organic compounds in dead organisms and waste products into simpler inorganic nutrients (like nitrates, phosphates, and carbon dioxide). These nutrients are then released back into the soil, water, and atmosphere, where they become available for plants to absorb and use for growth. Without decomposers, nutrients would remain locked up in dead matter, limiting the productivity of ecosystems.

2. Waste Removal and Soil Formation: Decomposers effectively clean up the environment by decomposing dead bodies of plants and animals, as well as waste materials. This prevents the accumulation of dead organic matter, which would otherwise pile up and make the environment unhealthy. The process of decomposition also contributes to the formation of humus, a rich organic component of soil that improves its structure, fertility, and water-holding capacity.

Question:

Non-biodegradable substances: Materials that do not decompose naturally over time through biological processes.
Environmental impact: How these substances alter or harm natural systems.


Non-biodegradable substances pose significant threats to the environment due to their persistent nature. Here are two ways they can affect it:

1. Accumulation in landfills and natural habitats: Since non-biodegradable materials like plastics, metals, and glass do not break down, they accumulate in vast quantities in landfills. This leads to land pollution and takes up valuable space. When discarded carelessly, they can also pollute natural environments such as oceans, rivers, and forests, harming wildlife through ingestion or entanglement.

2. Pollution of soil and water: As non-biodegradable substances degrade very slowly, they can leach harmful chemicals into the soil and water bodies over long periods. For instance, plastics can break down into microplastics, which contaminate soil and water, entering the food chain and posing risks to both ecological health and human well-being. Metals can release heavy metals into the environment, which are toxic.

Question:

The question asks for the definition of ozone. Ozone is a molecule with a specific chemical composition. Understanding chemical formulas and nomenclature is key.


Ozone is a molecule with the chemical formula O3. This means it is composed of three oxygen atoms bonded together. It is a pale blue gas with a pungent odor. Ozone is an allotrope of oxygen, meaning it is one of the different forms that the element oxygen can take.