Class 10 Science Chapter 13 Our Environment

Key Concept: CFCs Impact

c) They deplete the ozone layer
[Solution Description] Chlorofluorocarbons (CFCs) are synthetic chemicals that contribute to the depletion of the ozone layer by releasing chlorine atoms in the stratosphere, which break down ozone molecules.

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Key Concept: UV Radiation Effect

c) It splits $O_2$ into free oxygen atoms.
[Solution Description] Ultraviolet (UV) radiation splits molecular oxygen $(O_2)$ into free oxygen atoms (O). These free oxygen atoms then combine with other $(O_2)$ molecules to form ozone $(O_3)$. Thus, UV radiation is essential for the initial splitting process.

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Key Concept: Human Impact, Energy Flow Impact

a) Reduction by 30 units
[Solution Description] Initial biomass of producers is reduced from 8000 kg to 5000 kg due to deforestation. Assuming proportional energy loss and a 10% transfer efficiency:

Initial energy to Secondary Consumers from 8000 kg:
$E_{\text{initial\_primary}} = 0.1 \times 8000 = 800 \text{ units}$
$E_{\text{initial\_secondary}} = 0.1 \times 800 = 80 \text{ units}$

Reduced energy to Secondary Consumers from 5000 kg:
$E_{\text{reduced\_primary}} = 0.1 \times 5000 = 500 \text{ units}$
$E_{\text{reduced\_secondary}} = 0.1 \times 500 = 50 \text{ units}$

The impact is a reduction of 30 energy units for secondary consumers.

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Key Concept: International Efforts

c) United Nations Environment Programme (UNEP)
[Solution Description] The United Nations Environment Programme (UNEP) was instrumental in coordinating international efforts to address the issue of CFC emissions. UNEP facilitated the development and implementation of agreements such as the Montreal Protocol, which aimed at reducing and eventually phasing out the use of substances that harm the ozone layer.

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Key Concept: Consumer Dependency

c) Tertiary consumers
[Solution Description] Tertiary consumers typically feed on secondary consumers, who are often carnivores themselves. Therefore, tertiary consumers rely on carnivores for energy.

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Key Concept: Simple Recall

c) Burning waste
[Solution Description] Burning waste contributes to air pollution because it emits harmful gases and particulates.

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Key Concept: Role of Individuals

c) Turning off unnecessary lights and appliances
[Solution Description] By turning off lights and appliances when not needed, individuals can conserve a significant amount of energy, reducing their carbon footprint.

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Key Concept: Scenario Evaluation, Advanced Cause and Effect

c) High incidence of neurological disorders
[Solution Description] Mercury can accumulate in water bodies due to industrial discharge. As it enters the aquatic food chain, it becomes concentrated at higher trophic levels through biological magnification. Birds that feed on fish are top predators in this chain and would consume fish with high mercury content. Increased mercury intake can lead to severe health issues such as neurological damage or reproductive failure in birds.

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Key Concept: Simple Duration

d) Indefinitely
[Solution Description] Non-biodegradable substances like plastics can last in the environment indefinitely, often taking hundreds to thousands of years to break down completely.

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Key Concept: Advanced Environmental Impact Evaluation, Integration of Waste Management Systems

c) Combining recycling and incineration with energy recovery
[Solution Description] To effectively minimize the environmental impact of non-biodegradable waste, a combination approach is often necessary. Recycling helps to reduce the need for new raw materials and can decrease energy use and pollution. Incineration with energy recovery can reduce the volume of waste and produce energy, but it must be carefully managed to avoid air pollution. Landfilling should be minimized due to long-term land use and potential leachate problems.

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Key Concept: Biodegradable Substances

c) Vegetable peels
[Solution Description] Vegetable peels are organic and can be broken down by microorganisms, making them biodegradable.

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Key Concept: Energy Loss

c) 10%
[Solution Description] According to the 10% rule of energy transfer, only about 10% of the energy at any trophic level is transferred to the next level. This occurs because most of the energy is used for metabolic processes or lost as heat.

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Key Concept: Complex Cause and Effect, Trophic Level Dynamics

d) Top-level predators like large fish or birds will have the highest pesticide concentration.

[Solution Description] As pesticides enter the water body, they are absorbed by aquatic plants and phytoplankton (primary producers). Small fish feed on these plants, accumulating more pesticide residue than the concentration found in the plants. Larger predatory fish then consume multiple small fish, leading to higher concentrations of pesticides in their bodies compared to both the small fish and the primary producers. Biological magnification results in top predators having the highest pesticide concentrations.

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Key Concept: Trophic Level Identification

c) Fox
[Solution Description] The third trophic level typically consists of secondary consumers, which feed on primary consumers. In a grassland ecosystem, primary consumers are usually herbivores like rabbits or deer that eat plants. Secondary consumers could be predators such as foxes or snakes that prey on these herbivores.

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Key Concept: Food Web Complexity

c) They allow for multiple pathways of energy transfer.
[Solution Description] Food webs consist of multiple interconnected food chains, providing alternative feeding options and pathways for energy flow, which distributes the impact if one species is removed or reduced.

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Key Concept: Biodegradable Process

c) Biological processes
[Solution Description] Biodegradable substances are decomposed by biological processes involving microorganisms like bacteria and fungi that break down organic matter.

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Key Concept: Comparative Analysis, Advanced Reasoning

c) Chlorine-induced reactions are repetitive, depleting ozone faster than natural factors

[Solution Description] Naturally occurring factors like solar cycles and atmospheric patterns affect ozone levels but tend to maintain an equilibrium. Chlorine atoms, primarily from synthetic sources like CFCs, disrupt this balance by continuously destroying ozone molecules $(O_3)$ through catalytic cycles. Unlike natural fluctuations, chlorine’s impact has been profound and prolonged, leading to significant concerns about human-induced ozone depletion since the industrial revolution.

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Key Concept: Role of Local Bodies

c) Collecting and managing waste
[Solution Description] Local municipal bodies are responsible for organizing waste collection, treatment, and disposal services in their respective areas to ensure environmental cleanliness and public health.

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Key Concept: Conceptual Link

d) It results in increased toxin concentration at higher levels.
[Solution Description] Trophic levels represent different stages in a food chain, starting from producers to top predators. Biological magnification involves non-degradable substances accumulating at higher concentrations at successive trophic levels, particularly affecting those at the top.

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Key Concept: Environmental Solutions

d) Recycling materials like plastics and glass.
[Solution Description] Recycling involves reprocessing materials into new products, thus reducing reliance on raw materials, energy usage, pollution, and waste sent to landfills.

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Key Concept: Ecosystem Complexity

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.
[Solution Description]
The assertion that food webs are more complex than food chains is true as food webs show the interconnectedness of various organisms, indicating multiple interaction pathways. The reason provided is also true since food webs exhibit energy flow across various paths through different trophic levels, representing an intricate and multi-directional network. However, while both statements are true, the complexity of food webs is primarily due to the numerous feeding relationships rather than just the directionality of energy flow.

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Key Concept: Producers’ Energy Capture

a) 1%
[Solution Description] Producers, such as green plants, capture about 1% of the solar energy that falls on their leaves and convert it into chemical energy through photosynthesis.

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Key Concept: Human Impact

c) Through contaminated water and soil
[Solution Description] Pesticides often enter food chains through absorption by plants from contaminated water and soil. These chemicals then move up the food chain as they are ingested by animals feeding on those plants, affecting higher trophic levels due to accumulation over time.

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Key Concept: Ecosystem Components

c) Water
[Solution Description] Abiotic components are non-living elements of an ecosystem that influence living organisms. In a pond ecosystem, water is an example of an abiotic factor, as it affects the habitat and survival of aquatic life.

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Key Concept: CFC Alternatives

d) Ammonia
[Solution Description] Ammonia is widely used as an alternative refrigerant instead of CFCs in industrial applications. It is non-ozone-depleting and has been adopted due to its efficiency and low environmental impact compared to CFCs.

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Key Concept: Sustainable Practices

c) Composting organic kitchen waste
[Solution Description] Composting is a sustainable practice where organic kitchen waste is broken down naturally into nutrient-rich compost. This process not only reduces the amount of waste sent to landfills but also benefits home gardening by enriching the soil.

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Key Concept: Maintenance Requirement

b) To remove algae
[Solution Description] Regular cleaning of a garden pond is important to remove algae and other debris that can accumulate over time. This helps maintain water quality and prevents harmful conditions for the organisms living there.

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Key Concept: Non-biodegradable Impact

c) They remain unchanged and may harm ecosystems
[Solution Description] Non-biodegradable substances persist in the environment, often accumulating and potentially causing harm to ecosystems, as they cannot be easily broken down by natural processes.

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Key Concept: Producer Identification

b) Grass
[Solution Description] Producers are organisms that produce their own food through photosynthesis. Green plants are typical examples of producers.

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Key Concept: UV Radiation Effects

c) Decreased crop yield
[Solution Description] Increased UV radiation can lead to reduced crop yields as it negatively affects plant growth and photosynthesis. Many plants are sensitive to UV exposure, which leads to stunted growth and lower productivity.

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Key Concept: Energy Flow Analysis, Ecosystem Dynamics

c) Biomass decreases as you move up trophic levels.
[Solution Description] The unidirectional flow of energy implies that as energy is transferred from producers to tertiary consumers, it diminishes significantly due to metabolic processes and heat loss. According to the 10% rule, only about 10% of energy is passed on to the next level. This results in a pyramid-shaped biomass distribution where producers have the most biomass, followed by primary, secondary, and tertiary consumers having progressively less biomass.

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Key Concept: Dependency Recognition

c) Both producers and consumers
[Solution Description] Both producers (plants) and consumers rely on decomposers for recycling nutrients back into the soil to maintain nutrient balance.

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Key Concept: Real-world Waste Management, Industrial Waste Treatment

b) 130 tons

[Solution Description]

First, calculate the amount of waste aimed for treatment: 60% of 250 tons is $\frac{60}{100} \times 250 = 150$ tons. Due to errors, only 80% of this waste is successfully treated: $\frac{80}{100} \times 150 = 120$ tons. Therefore, the untreated amount from the attempted treatment is $150 – 120 = 30$ tons. The total initial non-biodegradable waste is $250 – 150 = 100$ tons, thus the remaining untreated non-biodegradable waste becomes $100 + 30 = 130$ tons.

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Key Concept: Interaction Understanding

c) It aids in seed dispersal and pollination
[Solution Description] Wind affects plant growth by influencing transpiration rates and pollination. High wind speeds can increase water loss through transpiration, which may lead to water stress if not compensated by adequate water supply. Additionally, wind aids in the dispersal of seeds and pollen, facilitating reproduction.

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Key Concept: Interaction Understanding

c) They determine the survival and reproduction of organisms
[Solution Description] Abiotic factors like temperature, rainfall, and soil quality are crucial for determining the types of organisms that can survive and reproduce in an environment. These non-living components affect the availability of resources and create conditions that either support or limit life.

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Key Concept: Energy Loss

c) 5 units

[Solution Description]

According to the 10% energy transfer rule, each trophic level receives approximately 10% of the energy from the previous level. Starting with 5000 units at the producer level:

Primary Consumers: $\frac{10}{100} \times 5000 = 500$ units.

Secondary Consumers: $\frac{10}{100} \times 500 = 50$ units.

Tertiary Consumers: $\frac{10}{100} \times 50 = 5$ units.

Therefore, 5 units of energy are available to tertiary consumers.

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Key Concept: Factor Prioritization, Integrated Analysis

c) Rainfall pattern preservation
[Solution Description] In a tropical rainforest, rainfall directly influences water availability and indirectly affects soil erosion, nutrient cycling, and plant growth. Thus, conserving rainfall patterns should be prioritized as it supports multiple interconnected ecological processes that maintain biodiversity.

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Key Concept: Long-term Environmental Effects, Industrial Waste Management

b) Contamination of water bodies leading to loss of species diversity.
[Solution Description] Improper management of industrial chemical waste leads to the accumulation of toxic substances in aquatic ecosystems. These chemicals can cause eutrophication, leading to oxygen depletion and harming aquatic life. They may also contaminate water sources, affecting both human and animal health. Long-term exposure can result in bioaccumulation in the food chain, potentially leading to ecosystem collapse. Awareness and enforcement of strict regulations are necessary to mitigate these impacts.

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Key Concept: Concept of Biological Magnification, Energy Flow Analysis

d) 10% energy retained at each step, with increasing pollutant concentration at top levels
[Solution Description] The 10% energy transfer rule states that only about 10% of the energy is transferred from one trophic level to the next. Simultaneously, pollutants like DDT amplify at higher trophic levels due to biological magnification, impacting organisms such as tertiary consumers significantly.

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Key Concept: Simple Cause and Effect

b) Decreases
[Solution Description] Insufficient rainfall results in less water availability for plants, leading to decreased plant growth due to the lack of necessary hydration.

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Key Concept: Energy Flow

b) Producers to Herbivores
[Solution Description]
Energy flow in a food chain begins with autotrophs or producers who capture solar energy and convert it into chemical energy. This energy then moves to primary consumers, which are generally herbivores that consume the producers. Therefore, energy flows from producers to herbivores.

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