Our Environment - long answer Questions

Q: (a) How is ozone formed? (b) What is its importance? (c) What chemicals cause its depletion? (d) What is the 'ozone hole'? (e) Name the treaty to control this.

1. Formation: UV splits O₂ into O; O + O₂ -> O₃. 2. Importance: Absorbs harmful UV-B radiation. 3. Chemicals: Chlorofluorocarbons (CFCs). 4. Ozone Hole: Thinning of the ozone layer, especially over Antarctica. 5. Treaty: The Montreal Protocol (1987).

Q: (a) State the 10% energy law. (b) Why do food chains have only 3-4 trophic levels? (c) If producers have 50,000 J, how much energy will tertiary consumers have?

(a) Only 10% of energy is transferred to the next trophic level; 90% is lost as heat. (b) Due to the 90% energy loss, the energy remaining at the 4th or 5th level is too small to support life. (c) T1=50,000J -> T2=5,000J -> T3=500J -> T4 (Tertiary Consumers)=50J.

Q: (a) Define biomagnification. (b) Why do these substances get biomagnified? (c) Explain its effect on the food chain.

(a) The increase in concentration of harmful, non-biodegradable chemicals up the food chain. (b) Because they are non-biodegradable and fat-soluble (they accumulate in the body). (c) The concentration increases at each level, reaching toxic levels in top consumers like birds and humans, causing disease or death.

Q: (a) List two problems from improper garbage disposal. (b) State and explain the '3 Rs'. (c) Which 'R' is the best and why?

(a) Land/Water pollution and spread of diseases. (b) Reduce (use less), Reuse (use again), Recycle (make new products). (c) 'Reduce' is the best because it stops waste generation at the source, saving resources and energy.

Q: Differentiate between the flow of energy and the flow of nutrients in an ecosystem.

Energy flow is unidirectional (one-way). It enters from the sun, flows up the food chain, and is lost as heat. It is not recycled. Nutrient flow is cyclic. Decomposers return nutrients from dead organisms back to the soil, where they are reused by plants.

Q: (a) Difference between food chain and food web? (b) Why is a food web more stable? (c) What happens if all lions are removed?

(a) A food chain is a single line (Grass->Deer->Lion). A food web is a network of many food chains. (b) A food web is more stable because it provides alternative food sources. (c) If lions are removed, the deer population will increase, they will eat all the grass, and then the deer population will crash.

Q: (a) What are decomposers? (b) List three roles. (c) What if they were absent?

(a) Microorganisms (bacteria, fungi) that break down dead organic matter. (b) Roles: Cleaning the environment, recycling nutrients, improving soil fertility. (c) If absent, dead bodies would pile up, and nutrients would not be recycled, causing the ecosystem to collapse.

Q: (a) What is an ecosystem? (b) What are its two main components? (c) Differentiate producers and consumers.

(a) A self-sustaining unit of biotic (living) and abiotic (non-living) components. (b) Biotic (plants, animals) and Abiotic (sunlight, water). (c) Producers (plants) make their own food. Consumers (animals) eat other organisms.

Q: (a) Differentiate biodegradable and non-biodegradable waste. (b) Give household examples. (c) Explain two disposal methods.

(a) Biodegradable waste can be decomposed by microbes (e.g., vegetable peels). Non-biodegradable cannot (e.g., plastic). (b) Bio: Leftover food. Non-Bio: Plastic wrappers. (c) Composting (for biodegradable) and Recycling (for non-biodegradable).

Q: (a) What are trophic levels? (b) Draw a pyramid of energy. (c) Why is it always upright? (d) Differentiate consumers.

(a) The steps in a food chain. (b) A pyramid shape with producers (T1) at the base and top carnivores (T4) at the apex. (c) It's upright due to the 10% energy law; energy is maximum at the base (T1) and minimum at the top. (d) Primary (herbivores), Secondary (eat herbivores), Tertiary (eat carnivores).

Question

(a) How is ozone formed in the upper atmosphere?
(b) What is its importance?
(c) What are the main chemicals responsible for its depletion?
(d) What is the "ozone hole"?
(e) Name the international treaty signed to control this problem.

Answer 1

Answer:

(a) Formation: Ozone (O₃) is formed when high-energy UV radiation splits molecular oxygen (O₂) into free oxygen (O) atoms. These free (O) atoms then combine with other oxygen (O₂) molecules to form ozone (O₃).
(b) Importance: The ozone layer acts as a protective shield, absorbing the sun's harmful ultraviolet (UV-B) radiation and preventing it from reaching the Earth, thus protecting organisms from skin cancer, cataracts, and immune system damage.
(c) Depleting Chemicals: The main chemicals are Chlorofluorocarbons (CFCs), which were widely used in refrigerants, air conditioners, and aerosol sprays.
(d) Ozone Hole: This refers to the drastic thinning (depletion) of the ozone layer in the stratosphere, first observed over Antarctica.
(e) International Treaty: The **Montreal Protocol** (signed in 1987) is the international agreement that successfully phased out the production and consumption of ozone-depleting substances like CFCs.

Answer 2

Answer:

(a) 10% Law: This law, given by Lindemann, states that during the transfer of energy from one trophic level to the next, only about 10% of the energy is stored in the biomass of the next level. The remaining 90% is lost to the environment as heat through metabolic processes (like respiration, digestion).
(b) Limited Trophic Levels: Due to this 90% energy loss at each step, the energy available to higher trophic levels becomes progressively smaller. By the 4th or 5th level, the amount of energy remaining is so minuscule that it cannot sustain a viable population of organisms.
(c) Calculation:
- Energy at T1 (Producers): 50,000 J
- Energy at T2 (Primary Consumers): 10% of 50,000 J = 5,000 J
- Energy at T3 (Secondary Consumers): 10% of 5,000 J = 500 J
- Energy at T4 (Tertiary Consumers): 10% of 500 J = 50 J

Answer 3

Answer:

(a) Definition: Biomagnification (or biological magnification) is the process by which the concentration of certain harmful, non-biodegradable chemical substances (like pesticides) increases as they move up the food chain from one trophic level to the next.
(b) Reason for Magnification: These substances (like DDT or mercury) get biomagnified because they are:
- Non-biodegradable: They cannot be broken down by microorganisms.
- Fat-soluble: They accumulate in the body fat of organisms instead of being excreted.
(c) Effect on Food Chain: When these chemicals enter the food chain (e.g., from water into plankton), they are passed on to small fish, then large fish, and finally to birds or humans. At each level, the chemical is not broken down but accumulates. This results in the top consumers (like birds or humans) having the highest, often toxic, concentration of the chemical, which can cause diseases, birth defects, and even death.

Answer 4

Answer:

(a) Problems:
- Land and Water Pollution: Garbage dumps (landfills) leak toxic chemicals (leachate) that pollute underground water and soil.
- Spread of Diseases: Garbage dumps become breeding grounds for disease-carrying vectors like flies, mosquitoes, and rats.
(b) The 3 Rs:
- Reduce: This means using less. E.g., not buying unnecessary items, avoiding single-use plastics.
- Reuse: This means using items again and again. E.g., using a cloth bag for shopping, refilling water bottles.
- Recycle: This means converting waste materials into new products. E.g., recycling paper, plastic, and glass.
(c) Best 'R': Reduce is considered the best method because it stops the problem at the source. It prevents waste from being generated in the first place, thereby saving raw materials, energy, and reducing pollution from manufacturing and disposal.

Answer 5

Answer:

Energy Flow (Unidirectional):
- Energy flows in only one direction, from the sun to producers, and then to consumers.
- At each trophic level, 90% of the energy is lost as heat to the environment.
- This energy does not return to the sun or to the lower trophic levels. It is eventually all lost and must be constantly replenished by the sun. This is why it is called unidirectional (one-way).
Nutrient Flow (Cyclic):
- Nutrients (like carbon, nitrogen, water) are never "lost" or "used up."
- Producers take nutrients from the abiotic environment (soil, air).
- These nutrients are passed to consumers.
- When organisms die, decomposers break them down and return these nutrients to the soil and air.
- The nutrients are then ready to be used by producers again. This creates a continuous cycle.

Answer 6

Answer:

(a) Difference: A food chain is a single, linear pathway showing how energy is transferred (e.g., Grass -> Deer -> Lion). A food web is a complex network of many interconnected food chains, showing all the different feeding relationships in an ecosystem.
(b) Stability: A food web is more stable because it provides alternative pathways for energy flow. If one species (e.g., rabbits) is removed, the predators (e.g., foxes) have other food sources (e.g., rats, birds) and will not starve. This maintains the ecosystem's balance.
(c) Impact of Removing Lions: Lions are top carnivores. If they are removed, the population of their prey (e.g., deer) will increase dramatically. The increased deer population will overgraze, consuming all the grass (producers). This will lead to a scarcity of food, causing the deer population to crash and the ecosystem to become unstable.

Answer 7

Answer:

(a) Definition: Decomposers are microorganisms that get their energy by breaking down the complex organic compounds in dead organisms and waste products. Examples: Bacteria and Fungi.
(b) Three Roles:
- Cleaning Agents: They decompose dead bodies, preventing the environment from being filled with waste.
- Nutrient Recycling: They break down complex organic matter into simple inorganic nutrients (like nitrogen, phosphorus) and return them to the soil, making them available for producers.
- Soil Fertility: Their action produces humus, which improves soil structure and fertility.
(c) Consequence of Absence: If there were no decomposers, dead organisms and waste would pile up, polluting the environment. More importantly, the flow of nutrients would stop. Nutrients would be locked in dead bodies, the soil would become infertile, and producers (plants) would not be able to grow, causing the entire ecosystem to collapse.

Answer 8

Answer:

(a) Ecosystem: An ecosystem is a self-sustaining functional unit consisting of all living organisms (biotic components) in an area, interacting with each other and with their non-living (abiotic) physical environment.
(b) Components:
- Biotic (Living) Components: Examples: Plants, Animals, Bacteria, Fungi.
- Abiotic (Non-Living) Components: Examples: Sunlight, Water, Air, Soil, Temperature.
(c) Difference:
- Producers (Autotrophs): Organisms that can produce their own food from simple inorganic substances using sunlight (photosynthesis). Example: Green plants.
- Consumers (Heterotrophs): Organisms that cannot make their own food and must obtain energy by eating other organisms. Example: Deer, Lion.

Answer 9

Answer:

(a) Difference:
- Biodegradable: Wastes that can be broken down by microorganisms into harmless substances.
- Non-Biodegradable: Wastes that cannot be broken down by microorganisms and persist in the environment.
(b) Examples:
- Biodegradable: Vegetable peels, leftover food, paper.
- Non-Biodegradable: Plastic wrappers, glass bottles, metal foil.
(c) Disposal Methods:
- Composting: Biodegradable waste (like kitchen scraps) can be put in a compost pit. Microorganisms will decompose it into manure, which can be used for plants.
- Recycling: Non-biodegradable waste (like paper, plastic, glass) should be segregated and given to rag-pickers or waste collectors so it can be sent to recycling plants to make new items.

Answer 10

Answer:

(a) Trophic Levels: The various steps or levels in a food chain at which the transfer of energy occurs.

(b) Pyramid of Energy:

    T4 (Top Carnivore) - [e.g., Hawk - 1 J]
    T3 (Carnivore)    - [e.g., Snake - 10 J]
    T2 (Herbivore)    - [e.g., Rabbit - 100 J]
    T1 (Producer)     - [e.g., Grass - 1000 J]

(Note: Students should draw a pyramid shape with these levels).

(c) Always Upright: The pyramid of energy is always upright because of the 10% energy law. There is a progressive loss of energy (90%) at each level. Therefore, the energy at the producer level (base) is always the maximum, and the energy at the top carnivore level (apex) is always the minimum.
(d) Consumers:
- Primary Consumers (Herbivores): Feed directly on producers (plants). E.g., Deer.
- Secondary Consumers (Carnivores): Feed on primary consumers. E.g., Wolf.
- Tertiary Consumers (Top Carnivores): Feed on secondary consumers. E.g., Lion.

Answer 11

Answer:

(a) Artificial Ecosystem: A man-made, managed ecosystem that is not self-sustaining and requires human input to function. Examples: Aquarium, Crop field, Garden.
(b) Cleaning: A natural pond is a complete, self-sustaining ecosystem. It contains decomposers (bacteria, fungi) that break down the waste (dead fish, excreta) and recycle nutrients. An aquarium is an incomplete ecosystem and usually lacks a significant population of decomposers. Therefore, toxic waste (like ammonia) builds up and must be manually removed by cleaning.
(c) Components of an Aquarium:
- Biotic: Fish, aquatic plants, snails.
- Abiotic: Water, oxygen (from a pump), light (from a lamp), gravel, temperature.

Answer 12

Answer:

(a) Reason for Ban: The government is banning single-use plastics because they are non-biodegradable, a major source of pollution, fill up landfills, clog drains (causing floods), and harm animals that ingest them.
(b) Consequence: Plastic persists in the environment for hundreds of years. It breaks down into microplastics, which enter our food chain (biomagnification) and soil, causing widespread land and water pollution.
(c) Alternatives:
- Cloth bags (made of cotton or recycled fabric)
- Jute bags
- Recycled paper bags

Answer 13

Answer:

(a) Energy for Goats (T2): 10% of 100,000 J = 10,000 J
(b) Energy for Tigers (T3): 10% of 10,000 J = 1,000 J
(c) Energy Lost: The energy available to goats was 10,000 J. Only 1,000 J was transferred to tigers. The energy lost (as heat, metabolism) is 10,000 J - 1,000 J = 9,000 J (which is 90% of the goat's energy).
(d) Law: The 10% Energy Law.

Answer 14

Answer: The accumulation of non-biodegradable waste, especially chemicals like pesticides (DDT), causes several problems:

Persistence: Since they cannot be broken down by decomposers, they remain in the soil and water for many years, continuously causing pollution.
Biomagnification: These chemicals are absorbed by producers (plants) from the soil. They then enter the food chain. At each trophic level, their concentration increases.
Harm to Top Consumers: The highest concentration is found in top consumers. In birds, for example, high levels of DDT caused their eggshells to become thin, leading to the death of chicks and a decline in the bird population. In humans, these chemicals can cause cancer and other serious diseases.
Water Pollution: When these chemicals wash off from fields into rivers and lakes (eutrophication is a separate issue, but pesticides add to water toxicity), they kill aquatic life like fish.

Answer 15

Answer:

(a) Food Chain: A food chain is a linear sequence of organisms where each organism is eaten by the next organism in the chain, showing the flow of energy.
(b) Example Food Chain: Grass -> Grasshopper -> Frog -> Snake
(c) Identification:
- Producer (T1): Grass
- Primary Consumer (T2): Grasshopper
- Secondary Consumer (T3): Frog
- Tertiary Consumer (T4): Snake

Answer 16

Answer:

Justification: Humans are omnivores.
- When humans eat plants (vegetables, fruits), they are at the T2 level (Primary Consumers).
- When humans eat herbivores (like goat or chicken), they are at the T3 level (Secondary Consumers).
- When humans eat carnivores (like a large fish that ate smaller fish), they can even be at the T4 level (Tertiary Consumers).
Energy Impact: According to the 10% law, energy decreases at each level.
- Eating plants (T1) gives us the most energy (10% of producer's energy).
- Eating a goat (T2) gives us only 10% of the goat's energy, which is just 1% of the plant's original energy.
Energy-Efficient Diet: A vegetarian diet is far more energy-efficient. More food energy is available to humans at the T2 level (as primary consumers) than at higher levels.

Answer 17

Answer:

(a) Necessity of Segregation: It is necessary because different types of waste require different disposal methods. If they are mixed, it becomes difficult or impossible to dispose of them properly, and the entire mixture often ends up in a landfill.
(b) Two Bins:
- Green Bin: For Biodegradable waste (e.g., food scraps, paper, leaves).
- Blue Bin: For Non-Biodegradable waste (e.g., plastic wrappers, bottles, pens, foil).
(c) Waste Destination:
- Green Bin (Biodegradable): This waste can be sent for **composting** (or to a biogas plant). Microorganisms will decompose it into nutrient-rich manure.
- Blue Bin (Non-Biodegradable): This waste is sent for **recycling**. Plastics, glass, and metals are melted and used to create new products.

Answer 18

Answer:

Ecosystem: An ecosystem is a self-sustaining functional unit of living organisms (biotic) interacting with their non-living (abiotic) environment.
If all Producers are removed: Producers (plants) are the only organisms that can convert solar energy into food. If they are removed, the entire food chain will collapse. All primary consumers (herbivores) will starve and die, which will subsequently lead to the death of all secondary and tertiary consumers. The ecosystem will be destroyed.
If all Consumers are removed: If all consumers (herbivores, carnivores) are removed, the producers (plants) would initially flourish. However, decomposers would still be present. If *all* consumers *and* decomposers were removed, the producers would eventually die, and the nutrients locked in their dead bodies would not be recycled, leading to a sterile environment where new life cannot grow.

Answer 19

Answer:

Problem: Global Warming (due to excess CO₂ from burning fossil fuels).
Solution: Reduce dependence on fossil fuels and switch to renewable energy sources (solar, wind).
Problem: Ozone Layer Depletion (due to CFCs).
Solution: Adhere to the Montreal Protocol and find non-CFC alternatives for refrigerants.
Problem: Deforestation (clearing forests for land).
Solution: Reforestation and Afforestation (planting new trees) and practicing sustainable agriculture.
Problem: Plastic Pollution (accumulation of non-biodegradable waste).
Solution: Banning single-use plastics and promoting the use of biodegradable alternatives (jute, cloth bags).
Problem: Water Pollution (dumping industrial/sewage waste).
Solution: Mandatory treatment of sewage and industrial effluents in ETPs (Effluent Treatment Plants) before release into rivers.

Answer 20

Answer:

(a) UV Radiation: Ultraviolet radiation is a form of high-energy electromagnetic radiation from the sun, which is harmful to living organisms.
(b) Harms:
- In Humans: Causes skin cancer, eye cataracts, and weakens the immune system.
- In Plants: Reduces the rate of photosynthesis, leading to lower crop yields.
- In Aquatic Life: Kills phytoplankton and zooplankton, disrupting the entire aquatic food web.
(c) Substance: Chlorofluorocarbons (CFCs).

Answer 21

Answer:

(a) Percentage Captured: Producers (like green plants) capture only about 1% of the total solar energy that falls on their leaves.
(b) Rest of the Energy: The remaining 99% of the solar energy is reflected back into space, passes through the leaves without being absorbed, or is lost as heat.
(c) Transfer to Next Level: When producers are eaten by primary consumers (herbivores), the 10% energy law applies. Only 10% of the energy stored in the producers (the 1% they captured) is transferred to the primary consumers. The other 90% is lost by the producer during its own life processes (respiration, etc.) as heat.

Answer 22

Answer:

(a) Sustainable Management: It means using our natural resources in a way that meets our current needs without compromising the ability of future generations to meet their own needs. It focuses on conservation and judicious use.
(b) Individual Contribution:
- Save Water: Turn off taps while brushing; fix leaking taps.
- Save Electricity: Switch off lights and fans when leaving a room; use LED bulbs.
- Reduce Waste: Follow the 3 Rs (Reduce, Reuse, Recycle). Carry a cloth bag for shopping to "Reduce" plastic use.
- Sustainable Transport: Use public transport, walk, or cycle for short distances instead of using a personal car, to "Reduce" fossil fuel consumption.

Answer 23

Answer:

(a) Consequence: The toxic chemical (if non-biodegradable) will enter the food chain through the algae.
(b) Maximum Concentration: The Bird (T4) will have the maximum concentration. This phenomenon is called Biomagnification.
(c) Impact of Removing Large Fish:
- The population of Small Fish (T2) will increase, as their predator is gone.
- The population of Birds (T4) will decrease due to a lack of food.
- The increased population of Small Fish will lead to a decrease in Algae (T1) due to overconsumption.

Answer 24

Answer: Abiotic factors determine the type of organisms that can survive in an ecosystem.

Temperature: Temperature affects the survival of organisms. For example, a polar bear (adapted for cold) cannot survive in a hot desert, and a camel (adapted for heat) cannot survive in the arctic. It dictates the entire ecosystem type (e.g., tundra, desert, rainforest).
Water: The availability of water is essential for all life. Areas with high rainfall (like rainforests) support a vast diversity of plants and animals. Areas with very little water (deserts) can only support organisms that have special adaptations to conserve water (e.g., cacti, camels).
(Extra) Soil: The type of soil (sandy, clay, loamy) and its nutrient content determine the types of plants (producers) that can grow, which in turn determines the types of animals (consumers) that can live there.

Answer 25

Answer:

(a) Components:
- Biotic Components: All the living organisms (e.g., plants, animals, microorganisms).
- Abiotic Components: All the non-living physical factors (e.g., sunlight, air, water, temperature, soil).
(b) Grassland Ecosystem:
- Producers: Grass, Small shrubs
- Primary Consumers: Rabbit, Deer, Grasshopper
- Secondary Consumers: Fox, Snake, Frog
- Decomposers: Bacteria, Fungi

Our Environment - long answer Questions

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NCERT Science Textbook Class 10

S. Chand Physics for Class 10

S. Chand Biology for Class 10

S. Chand Chemistry for Class 10

NCERT Exemplar Problems Science Class 10

Top 25 LA Questions - Our Environment

Question 1: Ozone Layer (Full)

Question 2: 10% Energy Law (Full)

Question 3: Biomagnification (Full)

Question 4: Waste Management (3 Rs)

Question 5: Energy vs. Nutrient Flow

Question 6: Food Web vs. Food Chain

Question 7: Role of Decomposers

Question 8: Ecosystem Components

Question 9: Household Waste

Question 10: Trophic Levels (Full)

Question 11: Artificial Ecosystem

Question 12: Plastic & Alternatives

Question 13: Energy Loss Calculation

Question 14: Impact of Waste

Question 15: Food Chain Components

Question 16: Human Trophic Levels

Question 17: Waste Segregation

Question 18: Ecosystem Balance

Question 19: Environmental Problems

Question 20: UV Radiation

Question 21: Energy Transfer

Question 22: Sustainable Management

Question 23: Trophic Level Impact

Question 24: Abiotic Impact

Question 25: Components of Ecosystem

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