Our Environment Important Questions Class 10 Science with Solutions

Our environment lays importance on the delicate balance of ecosystems and the impact of human activities on the environment. This chapter encourages students to understand the inter-connectedness of living and non-living components and the need for sustainable development. Mastering these concepts is essential not just for exams but also for building awareness about environmental conservation. 

From Class 10 Science Chapter 13 Our Environment Important Questions, you must study thoroughly since many questions are framed. It emphasizes the importance of the environment in our lives and makes us aware about the exploitations of the environment being carried out across the world by human beings. 

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Chapter 13 Our Environment: Important Questions

1. Answer the following questions based on the given information.

Hydrogen gas is an excellent fuel. It has a high calorific value and produces only water as the product of combustion. It is considered to be a potentially important, non-polluting energy source of the future. Hydrogen is labelled with different 'colours' based on the method by which it is produced, as given below:

- green hydrogen: manufacturing process does not produce carbon dioxide

- blue hydrogen: manufacturing process produces carbon dioxide but it is separated and stored 

- grey hydrogen: manufacturing process produces carbon dioxide which is released into the air

(i) Hydrogen is labelled 'brown' if the manufacturing process releases both carbon dioxide and carbon monoxide to the air. In what way is the manufacturing process of brown hydrogen WORSE than that of grey hydrogen for the environment?

a. It releases into the atmosphere a gas that directly causes a greenhouse effect.

b. It releases into the atmosphere carbon which was stored for millions of years.

c. It releases into the atmosphere a gas that is toxic to human beings.

d. It releases into the atmosphere gases that cause acid rain.

Answer: 

(a) It releases into the atmosphere a gas that directly causes a greenhouse effect.

Explanation:

The manufacturing process of brown hydrogen is worse than grey hydrogen for the environment because it releases both carbon dioxide (CO₂) and carbon monoxide (CO) into the atmosphere. While CO₂ is a well-known greenhouse gas that contributes to global warming, carbon monoxide (CO) is also a harmful gas. Carbon monoxide is toxic to humans and animals in high concentrations, but more importantly, it can also contribute to the greenhouse effect by indirectly increasing the presence of other greenhouse gases like methane.

Therefore, releasing both CO₂ and CO makes the environmental impact worse compared to grey hydrogen, where only CO₂ is released without the additional toxic or indirect effects of carbon monoxide.

(ii) What is the ratio of average amount of energy absorbed by producers to the average amount of energy absorbed by the primary consumers?

a. 1:2

b. 2:1

c. 1:10

d. 10:1

Answer: 

(d) 10:1

Explanation:

In an ecosystem, energy flow follows the 10% law, which states that only about 10% of the energy available at one trophic level is transferred to the next trophic level, while the rest is lost as heat or used in metabolic processes.

Producers (plants, algae, etc.) absorb energy from the sun through photosynthesis, and primary consumers (herbivores) obtain their energy by consuming producers. On average, the energy transferred from producers to primary consumers is about 10% of the energy producers absorb. Therefore, the ratio of the energy absorbed by producers to that absorbed by primary consumers is approximately 10:1.

(iii) Which of the following describes the flow of energy and nutrients, respectively, through the ecosystem?

a. bidirectional and cyclic

b. unidirectional and cyclic

c. cyclic and bidirectional

d. cyclic and unidirectional

Answer: 

(b) unidirectional and cyclic

Explanation:

Energy flow in an ecosystem is unidirectional: Energy flows in a single direction, starting from the sun to producers (plants), then to consumers (herbivores, carnivores), and finally to decomposers. At each trophic level, a significant amount of energy is lost as heat, and it does not return to its original source.

Nutrient flow in an ecosystem is cyclic: Nutrients such as carbon, nitrogen, phosphorus, and others are recycled through the ecosystem in biogeochemical cycles. For example, carbon cycles between the atmosphere, organisms, and soil, while nitrogen cycles through nitrogen fixation, assimilation, and decomposition. Nutrients are reused within the ecosystem.

2. Lions have no known natural predators.

Based on energy transfer in a food chain, what could be the most likely reason for the above statement?

Answer:

The most likely reason lions have no known natural predators is due to the low energy transfer across trophic levels in the food chain.

1. Energy transfer inefficiency: According to the 10% law, only about 10% of the energy at one trophic level is transferred to the next. Lions are apex predators at the top of the food chain, meaning they are at the highest trophic level. By the time energy reaches this level, it is minimal, making it inefficient for another predator to evolve that exclusively hunts lions.
2. Ecological balance: Lions are keystone species and play a vital role in maintaining the balance of their ecosystems. Predators at the apex level are typically not hunted by others because the energy dynamics of the ecosystem do not support another trophic level above them.
3. Behavior and physical attributes: In addition to energy considerations, lions' physical dominance, strength, and social hunting behavior (in prides) make them formidable and unattractive prey, further ensuring their status as apex predators.

Thus, their position in the food chain and the principles of energy transfer explain why lions have no natural predators.

3. The stratosphere is very dry and rarely allows clouds to form. In the extreme cold of the polar winter, however, stratospheric clouds of different types may form. These clouds are called Polar Stratospheric Clouds (PSCs).

Scientists recently discovered that polar stratospheric clouds, long known to play an important role in Antarctic ozone destruction, are occurring with increasing frequency in the Arctic. These high-altitude clouds form only at very low temperatures help destroy ozone in two ways:

(1) They provide a surface which converts benign forms of chlorine into reactive, ozone-destroying forms, and

(2) they remove nitrogen compounds that moderate the destructive impact of chlorine. In recent years, the atmosphere above the Arctic has been colder than usual, and polar stratospheric clouds have lasted into the spring. As a result, ozone levels have been decreasing.(Information credit: NASA)

(a) How is ozone formed in the outer atmosphere?

(b) Ozone is being continuously destroyed due to extreme low temperatures. However, ozone formation is also a continuous process. Why is there a depletion in the ozone layer still?

(c) What can be a positive effect of global warming on the depletion of the ozone layer?

(d) How does ozone layer depletion impact human health?

Answer:

(a) Ozone is formed in the stratosphere by a process known as the ozone-oxygen cycle. Ultraviolet (UV) radiation from the Sun splits molecular oxygen (O₂) into two oxygen atoms (O). These oxygen atoms then react with other oxygen molecules to form ozone (O₃). This reaction is represented as:
O₂+UV radiation→2O

O+O₂→O₃

(b) Ozone formation is a continuous process, but the rate of ozone destruction has increased due to human activities and natural factors. Key reasons include:

1. Polar Stratospheric Clouds (PSCs): These clouds facilitate chemical reactions that convert benign forms of chlorine (like CFCs and HCFCs) into reactive chlorine compounds, which destroy ozone.
2. Chlorofluorocarbons (CFCs): Human-made chemicals released into the atmosphere break down under UV light, releasing chlorine atoms that destroy ozone molecules.
3. Nitrogen compound removal: PSCs remove nitrogen compounds that would otherwise moderate the destructive effects of chlorine.
4. Extreme low temperatures: Colder temperatures in the polar stratosphere increase the frequency and persistence of PSCs, accelerating ozone destruction.

Despite ongoing ozone formation, these accelerated destruction processes outweigh the natural replenishment rate, leading to net depletion.

(c) Global warming primarily affects the troposphere, causing it to warm, but it can lead to cooling in the stratosphere. Warmer surface temperatures increase greenhouse gas concentrations, which trap heat in the troposphere and reduce the amount reaching the stratosphere. Cooler stratospheric temperatures may decrease the frequency of Polar Stratospheric Clouds (PSCs), thereby reducing the conditions that promote ozone destruction.

(d) Ozone layer depletion allows more harmful UV-B radiation to reach the Earth's surface, leading to:

1. Increased risk of skin cancer, particularly melanoma and non-melanoma types.
2. Eye damage, including cataracts and photokeratitis (snow blindness).
3. Weakened immune system, reducing the body’s ability to fight infections and diseases.
4. Harmful effects on ecosystems, indirectly affecting human health through impacts on agriculture, marine life, and biodiversity.

4. Answer the following questions about transfer of materials in the ecosystem.

(a) Mention TWO ways by which energy is lost from the trophic levels in the ecosystem.

(b) A lot of harmful chemicals enter our body through different sources like food. Since human beings are at the top of the food chain/trophic structure, maximum concentration of such chemicals is found in human beings. What is this phenomenon known as?

Answer:

(a) 

1. Heat loss during metabolic activities: A significant amount of energy is lost as heat during cellular respiration and other metabolic processes. This energy is used for maintaining body temperature, movement, and other physiological activities.
2. Energy loss in undigested material and excretion: Not all energy from consumed food is assimilated by organisms. A portion of the energy is lost in undigested materials (e.g., plant fibers) and through excretory products like feces and urine.

(b) This phenomenon is known as biomagnification (or biological magnification).

Biomagnification refers to the progressive increase in the concentration of harmful chemicals (such as pesticides, heavy metals, or pollutants like DDT and mercury) as they move up the food chain. Since human beings occupy the top trophic level, they accumulate the highest concentration of these toxic substances, leading to potential health risks.

5. Arrange the four objects given above according to the time they take to get biodegraded (LEAST time TO MOST time).

Answer:

Living organisms rely on numerous essential resources, many of which eventually become waste after serving their purpose. This waste can be classified into organic, biodegradable, and non-biodegradable categories. Solid waste can be segregated accordingly, with recyclable and reusable materials undergoing appropriate processes. Waste that holds no further value is disposed of and managed by municipal authorities. Globally, over 380 million tonnes of plastic are produced annually, a significant portion of which may become pollutants, infiltrating the environment and posing a serious global ecological threat. On the other hand, materials like bone, being biodegradable, decompose relatively quickly.

Bone→Paper sheet→Metal can→Plastic bottle

6. Answer the two following questions based on the information given below.

Shown here is the extent to which two different animals can see in either direction without turning their heads. In animal 1, the eyes are placed towards the front of the head and in animal 2, the eyes are placed on either side of the head.

Since the placement of eyes in the two animals is different, their vision is also slightly different.

In the figures above, the grey part represents the parts that can be seen by both eyes at a time, whereas the white parts represent those parts that can be seen only by one eye at a time.

Animal 2 can see a broader area at any time compared to animal 1. Animal 1 can distinguish depths better compared to animal 2.

Based on this, which of the two animals is most likely to be a predator and why?

Answer:

A food web represents the interconnected food chains within a single ecosystem. Every organism in the ecosystem participates in multiple food chains, with each chain illustrating a potential pathway for the flow of energy and nutrients. Predators typically have forward-facing eyes, enabling them to focus on and target prey effectively. In contrast, prey animals usually have eyes positioned on the sides of their skulls, providing a broader field of vision to detect predators. Based on this distinction, animals in the food web can be categorized into two groups:

Group 1 (Carnivores): Lion, wild cat, jackal, kite, and owl.
Group 2 (Herbivores): Mouse, goat, and rabbit.

7. Observe the following food web. Classify the animals into two groups - one that would need to have vision as Animal 1 and another as Animal 2 in the diagram above.

Answer:

To classify the animals based on their need for vision in the given food web:

Animal 1: Vision-dependent predators

These animals rely heavily on their vision for hunting and capturing prey.

• Lion
• Kite
• Owl
• Wild cat

Animal 2: Less vision-dependent animals (herbivores/prey)

These animals rely more on other senses or are prey that don't need sharp vision for survival.

• Goat
• Rabbit
• Mouse

Important Concepts in Chapter 13: Our Environment, Class 10

Learning the basic concepts in Our Environment helps students appreciate the delicate balance of natural systems and the human role in maintaining this balance. Below are the detailed important-to-know concepts:

Ecosystem

An ecosystem is a functional unit where living organisms (biotic factors) and non-living elements (abiotic factors) interact to sustain life and processes.

Components of an Ecosystem:

Producers: Green plants and some algae that use sunlight to produce food through photosynthesis. These are the foundation of the food chain, as they generate energy for all other organisms.

Consumers: Animals that depend on producers or other animals for food. These are categorised as:

• Herbivores: Plant-eaters like cows, deer, and caterpillars.
• Carnivores: Meat-eaters such as lions, tigers, and hawks.
• Omnivores: Organisms that eat both plants and animals, such as humans and bears.

Decomposers: Microorganisms like fungi and bacteria that break down dead organisms and organic waste into simpler substances, recycling nutrients back into the ecosystem.

Food Chains and Food Webs

• Food Chain: Represents the linear flow of energy from one organism to another. Example:
  Grass → Grasshopper → Frog → Snake → Hawk.
• Food Web: A more complex structure showing multiple interconnected food chains within an ecosystem, illustrating the dependency of organisms on various sources of food.

Energy Flow in an Ecosystem

• Unidirectional Energy Flow: Energy in an ecosystem flows in one direction—from the Sun to producers and then to various levels of consumers.
• 10% Law: Only 10% of energy is passed to the next trophic level, while the remaining 90% is lost as heat during metabolic processes. This explains why energy decreases at higher trophic levels and limits the length of food chains.

Biodegradable and Non-Biodegradable Substances

• Biodegradable Substances: These break down naturally by decomposers, reducing environmental pollution. Examples: vegetable peels, paper, and leaves.
• Non-Biodegradable Substances: These persist in the environment for decades, posing a threat to ecosystems. Examples: plastic, glass, and synthetic chemicals. Their accumulation leads to long-term environmental damage, such as soil and water pollution.

Environmental Problems

• Ozone Depletion: Caused by the excessive release of chlorofluorocarbons (CFCs) from refrigerators, air conditioners, and aerosols. Leads to the thinning of the ozone layer, allowing harmful ultraviolet (UV) rays to reach Earth, causing skin cancer and other health issues.
• Waste Management: Inadequate waste disposal contributes to water, soil, and air pollution. Segregation of waste into biodegradable and non-biodegradable categories is crucial for effective recycling and disposal.

Steps Toward Sustainability

Promote the 3Rs:

• Reduce: Minimize waste generation by avoiding unnecessary consumption.
• Reuse: Utilise items like bottles and containers multiple times to reduce waste.
• Recycle: Process used materials into new products to save resources and reduce pollution.

Afforestation: Planting more trees to enhance biodiversity and combat deforestation.

Conservation of Resources: Use water, fossil fuels, and minerals judiciously to ensure their availability for future generations.

Renewable Energy: Shift to clean energy sources like solar, wind, and hydropower to reduce reliance on non-renewable resources.

By comprehending these principles, students not only excel in exams but also develop a sense of responsibility toward environmental preservation.

Tips for Preparing Chapter 13 CBSE Class 10 

To prepare effectively for Our Environment, it is important to focus on understanding concepts, practicing diagrams, and solving application-based questions. Below are detailed tips to make sure of thorough preparation:

Understand Ecosystem Dynamics

• Familiarise yourself with the structure and functions of ecosystems.
• Focus on the roles of producers, consumers, and decomposers and how they interact to maintain ecological balance.
• Study examples of food chains (e.g., Grass → Grasshopper → Frog → Snake) and food webs to hold firmly the complexity of ecosystems.

Focus on Energy Flow

• Learn the 10% Law of energy transfer between trophic levels.
• Understand why energy diminishes as it moves from producers to higher-level consumers, limiting the length of food chains.

Differentiate Substances

Clearly distinguish between:

• Biodegradable Substances: Decompose naturally (e.g., food scraps, paper).
• Non-Biodegradable Substances: Persist in the environment and cause pollution (e.g., plastics, metals).

Practice Diagrams

Draw and label key diagrams such as:

• Food chains and food webs.
• Energy flow in ecosystems.

Ensure accuracy and neatness in your diagrams, as they often fetch easy marks in exams.

Study Environmental Issues

Focus on pressing environmental problems, such as:

• Ozone Layer Depletion: Causes (CFCs), effects (UV radiation exposure), and preventive measures (reducing CFC use).
• Waste Management: Importance of waste segregation into biodegradable and non-biodegradable categories.

Understand sustainable practices like the 3Rs (Reduce, Reuse, Recycle) and their significance in minimising environmental damage.

Solve Application-Based Questions

Practice real-life problem-solving questions, such as those involving:

• Waste segregation techniques.
• Energy conservation methods in households and industries.

Work on numerical problems and case studies to strengthen your ability to apply theoretical concepts to practical situations.

By focusing on these tips, you will not only grow your knowledge of the chapter but also improve your ability to answer exam questions effectively. Regular revision and consistent practice are literally so important to know the Ch 13 Our Environment CBSE Class 10 better.

Chapter 13 provides students with the knowledge to recognise and address environmental challenges. By understanding ecosystems, energy flow, and sustainability practices, students can contribute to creating a healthier planet. Additionally, this chapter often includes straightforward questions in exams, making it a scoring opportunity for well-prepared students. 

We hope that you practise the above Our Environment Class 10 Important Questions And Answers and achieve your dream marks.

All the best!