Short notes and key points of class 9 biology chapter-Natural Resources
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Short notes and key points of class 9 biology chapter-Natural Resources
May 13, 2022, 16:45 IST
Class-9 biology chapter-Natural Resources
The word ‘resource’ is used for means of supplying a material generally held in reserve .
Components of atmosphere -:
| Component | Volume |
| Nitrogen (N 2 ) | 78.08 % |
| Oxygen (O 2 ) | 20.92 % |
| Carbon dioxide (CO 2 ) | 0.03 % |
| Argon | 0.93 % |
| Trace components* | 0.4 % |
Lower part of troposphere is the reservoir of gases that are essential for life, e.g., oxygen and carbon dioxide. Stratosphere has protective ozone shield (ozonosphere) that protects us from harmful UV radiations.
Air pollution
Air pollution is defined as an undesirable change in the physical, chemical or biological characteristics of air making it harmful for organisms (including man). The agents or substances that pollute the air are called air pollutants . There are two main sources of air pollution
- natural , and
- man-made .
Air pollution causes numerous harmful effects. These include:
- Respiratory problems in humans (bronchitis, asthma, lung cancer etc.).
- Carbon monoxide poisoning,
- Acid rain
- Depletion of ozone layer thereby increasing risks of skin cancer, damage to eyes and immune system,
- Global warming due to green house effect , and
- Serious
NCERT solutions for class 9 Science is prepared by Physics Wallah and consist of solution of all questions asked in NCERT text book.
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