‘रचना-प्रयोग’ का मुख्य उद्देश्य क्या है?

व्याकरण का व्यावहारिक प्रयोग सिखाना

‘द्वितीयः’ किस प्रकार की संख्या है?

क्रमवाचक (दूसरा)

Why are food chains usually limited to three or four trophic levels?

Only about 10% of energy passes to the next level, so too little energy remains to support many levels.

Why is the depletion of the ozone layer a cause for concern?

Ozone absorbs harmful ultraviolet radiation; its depletion lets more UV reach Earth, causing skin cancer, cataracts and ecological damage.

What is an ecosystem? Name its two components.

A community of interacting organisms together with their physical environment; its two components are the biotic (living) and abiotic (non-living) components.

What are producers, consumers and decomposers?

Producers (green plants) make food by photosynthesis; consumers eat other organisms; decomposers (bacteria and fungi) break down dead matter and recycle nutrients.

What is a food chain and a trophic level?

A food chain is a series of organisms showing who eats whom and how energy flows; each step or feeding level in it is called a trophic level.

State the ten per cent law of energy flow.

Only about 10% of the energy at one trophic level is passed on to the next; the rest is lost as heat, which limits food chains to three or four levels.

Differentiate between biodegradable and non-biodegradable substances with examples.

Biodegradable substances are broken down by natural processes (e.g. paper, vegetable peels), while non-biodegradable substances are not (e.g. plastics, DDT) and cause pollution.

Why is the ozone layer important, and what damages it?

The ozone layer absorbs the sun’s harmful ultraviolet radiation; chemicals such as CFCs (chlorofluorocarbons) deplete it, increasing the risk of skin cancer and cataracts.

Why are food chains usually not very long?

Because only about 10% of the energy passes to each higher level, too little energy is left to support many trophic levels.

How can the problems caused by non-biodegradable waste be reduced?

By reducing their use, reusing and recycling materials, segregating waste, and using eco-friendly biodegradable alternatives.

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CBSE Class 10 — Notes, Chapters & Practice Quizzes

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Chapter 13: Our EnvironmentClass 10 Science — summary, notes, extra questions & NCERT solutions

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A series showing the flow of energy from one organism to the next is a:

Summary

The environment is a system in which living organisms interact with one another and with their non-living surroundings, forming ecosystems. Energy from the sun flows through ecosystems along food chains and food webs, passing from producers to consumers across trophic levels; only about 10% of the energy is transferred at each level, which limits the length of food chains. Materials, by contrast, are cycled and reused. Human activity affects the environment in major ways: the build-up of biodegradable and non-biodegradable wastes creates disposal problems, and the depletion of the ozone layer by chemicals like CFCs increases harmful ultraviolet radiation reaching the Earth. Understanding these links helps explain why pollution and waste management matter, and why protecting natural balances is essential for the health of all organisms, including humans.

Ecosystem and its componentsFood chains and food websFlow of energy and the 10% lawBiodegradable and non-biodegradable wastesOzone layer and waste management

Key terms

Ecosystem

A community of organisms interacting with their physical environment.

Food chain

A sequence showing the flow of energy from one organism to the next.

Trophic level

A step or feeding level in a food chain.

Biodegradable waste

Waste that can be broken down by natural processes.

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A community of organisms interacting with their physical environment.

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Chapter 13: Our EnvironmentClass 10 Science — summary, notes, extra questions & NCERT solutions

Summary

Key terms

Extra questions & answers

Activity 13.1

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