Unit 6 Nature and Environment
Class 10 Science Notes
Table of Contents (Unit 6 Nature and Environment)
1. Summary: Nature and Environment
1.1 Important Terms & Definitions
Biodiversity
Definition: The variety of living organisms (plants, animals, and microorganisms) found in a particular area or on Earth as a whole.
Climate Change
Definition: Significant and lasting changes in the statistical distribution of weather patterns (such as temperature and rainfall) over periods ranging from decades to millions of years.
Rare Species
Definition: Species that have a small population and are often found in limited geographical areas, making them vulnerable to extinction.
Endangered Species
Definition: Species that are at a very high risk of extinction in the wild in the near future.
Extinct Species
Definition: Species that no longer exist anywhere on Earth.
Indigenous Species
Definition: Plants or animals that naturally occur in a specific place or region (native species).
Medicinal Plants
Definition: Plants that possess therapeutic properties and are used in traditional or modern medicine to treat various ailments.
Conservation
Definition: The protection, preservation, management, or restoration of wildlife and of natural resources such as forests, soil, and water.
Environmental Pollution
Definition: The contamination of the physical and biological components of the earth/atmosphere system to such an extent that normal environmental processes are adversely affected.
1.2 Key Principles & Concepts
A. Factors Affecting Biodiversity
The chapter identifies several key factors responsible for the decline in plant and animal populations:
• Climate Change: Alterations in weather patterns affect the distribution and survival of sensitive species.
• Habitat Loss: Modernization, industrialization, and uncontrolled land use destroy the natural homes of organisms.
• Invasive Species: Growing new species without research can displace indigenous plants. Similarly, rearing new animal species can displace local animals.
• Over-exploitation: Uncontrolled use of biological resources (e.g., over-harvesting herbs, poaching) leads to a rapid decline in numbers.
• Pollution: Increasing environmental pollution degrades air, water, and soil quality, making survival difficult for many species.
B. The Importance of Herbal Medicine
The chapter highlights the relevance of traditional herbal medicine in the modern age.
It emphasizes the need to preserve knowledge about local medicinal plants for future generations.
C. Conservation Responsibility
Conservation is not just about saving animals; it is about maintaining the balance of the entire ecosystem.
It is a collective responsibility to protect rare species so future generations can learn about and utilize them.
1.3 Quick Review (Key Takeaways)
• This chapter, Nature and Environment, focuses on the delicate relationship between living organisms and their surroundings.
• The Earth is home to a vast variety of flora and fauna, but their existence is currently under threat.
• Human activities—specifically industrialization and modernization—have accelerated climate change, leading to rising temperatures and melting snow on mountains.
• Climate change directly impacts the habitats of plants and animals, forcing them to migrate or face extinction.
• Many indigenous plants and animals in Nepal are becoming rare or extinct due to factors like habitat destruction, introduction of invasive species, and environmental pollution.
• The chapter emphasizes the value of medicinal plants and urges the preservation of traditional herbal knowledge.
• Protecting biodiversity is essential for our own survival, and we must adopt sustainable practices to ensure these resources remain available for future generations.
2.1 Choose the correct options for the following questions:
(a) Nowadays, sometimes there is low rainfall and sometimes heavy rainfall, which has affected agricultural production. What may be the reason for this?
(b) What is the reason for the increase in the volume of sea level?
(c) Which of the following groups is a group of endangered animals?
(d) In which group of plants does Tulsi belong?
(e) The union of a type of caterpillar with a specific fungus forms Yarsagumba. In this, what is the relation between the caterpillar and fungi?
(f) In chickenpox, neem powder paste is applied to the affected parts, and neem leaves are spread on the bed. It helps to heal chickenpox. What property in neem helps to do so?
(g) Which part of Bojo is used for medicinal purposes?
(h) Rama has been coughing for a long time. For this, which medicinal plant helps to get relief from cough?
(i) What is the reason for the natural disaster shown in the given picture?
Natural disaster caused by climate change
2.2 Write the differences:
(a) Weather change and Climate change
| S.N. | Weather Change | Climate Change |
|---|---|---|
| 1. | It refers to the short-term fluctuation in atmospheric conditions. | It refers to the long-term shift in average weather patterns globally or regionally. |
| 2. | It changes from hour to hour or day to day. | It takes decades or centuries to show significant changes. |
| 3. | It applies to a small, specific area (e.g., a city or village). | It applies to a large geographical area or the entire planet. |
| 4. | Examples include sunny, rainy, cloudy, or windy days. | Examples include global warming, rising sea levels, and melting glaciers. |
| 5. | It is studied by meteorologists. | It is studied by climatologists. |
(b) Endangered plants and Medicinal plants
| S.N. | Endangered Plants | Medicinal Plants |
|---|---|---|
| 1. | These are plants that are at a high risk of extinction from the wild. | These are plants that possess therapeutic properties used to treat diseases. |
| 2. | Their population has declined significantly due to habitat loss or over-harvesting. | They may or may not be rare; many are commonly found (like Tulsi), though some are also endangered. |
| 3. | They require strict legal protection and conservation efforts to survive. | They require sustainable management and proper knowledge for utilization. |
| 4. | Examples: Spikenard (Jatamasi), Serpentina (Sarpagandha), Golden Michelia (Champ). | Examples: Neem, Tulsi, Aloe Vera, Bojo. |
| 5. | The primary focus is on their survival and preventing extinction. | The primary focus is on their utility for health and pharmaceutical value. |
(c) Greenhouse effect and Climate change
| S.N. | Greenhouse Effect | Climate Change |
|---|---|---|
| 1. | It is the natural process where atmospheric gases trap heat from the sun to warm the Earth. | It is the alteration of the Earth’s climate systems, often resulting from an enhanced greenhouse effect. |
| 2. | It is a cause or mechanism. | It is an effect or consequence. |
| 3. | Ideally, it is beneficial as it maintains a habitable temperature on Earth. | It is generally harmful, leading to extreme weather, ice melt, and habitat destruction. |
| 4. | The main components are greenhouse gases like $CO_2$, Methane, and Water Vapor. | The main indicators are rising global temperatures, shifting rainfall patterns, and sea-level rise. |
| 5. | Without it, Earth would be too cold for life. | Unchecked, it threatens the survival of many species and human civilization. |
2.3 Give reason:
(a) The main causative factor of non-seasonal rainfall is climate change.
Reason: Climate change disturbs the natural thermal balance of the Earth. As the Earth warms, evaporation rates increase, and atmospheric circulation patterns shift. This disruption leads to clouds forming and precipitating at unexpected times, causing rainfall during seasons when it typically does not rain (non-seasonal rainfall).
(b) Sea level rises due to climate change.
Reason: Climate change causes global warming, which leads to the rise in sea level in two main ways: first, the melting of polar ice caps and glaciers adds more water to the oceans; second, as ocean water warms up, it expands (thermal expansion), increasing its volume and causing the level to rise.
(c) Climate change also causes the extinction of animals.
Reason: Rapid climate change alters habitats faster than many species can adapt. It causes loss of food sources, destruction of breeding grounds (like melting ice for polar bears), and extreme weather events. Animals that cannot migrate or adapt to these new harsh conditions die out, leading to extinction.
(d) Endangered animals can be protected by conserving their natural habitat.
Reason: The primary reason for animal endangerment is the loss of their home (habitat) due to deforestation and human encroachment. By conserving their natural habitat, we ensure they have adequate food, shelter, and breeding space, which allows their populations to recover and thrive naturally without stress.
(e) The use of medicinal plants is beneficial for human health.
Reason: Medicinal plants contain natural chemical compounds that can treat various ailments with fewer side effects compared to some synthetic drugs. They boost immunity, cure diseases naturally, and have been tested over centuries in traditional medicine systems like Ayurveda.
(f) Tulsi is called a life-giving plant.
Reason: Tulsi is called a life-giving plant because of its immense medicinal value. It produces oxygen for 20 hours a day and purifies the air. Its leaves, stem, and seeds are used to cure common ailments like cold, cough, fever, and respiratory disorders, effectively acting as a natural “sanctuary” for health.
(g) Neem is a multipurpose medicinal plant.
Reason: Neem is considered multipurpose because every part of the tree—leaves, bark, fruit, seeds, and oil—has medicinal value. It treats skin diseases, dental problems, and infections, acts as a biopesticide in agriculture, and purifies the air, serving medicinal, agricultural, and environmental purposes.
(h) Yarsagumba is used as an energy-booster herbal medicine.
Reason: Yarsagumba contains active compounds (like cordycepin) that improve the body’s production of ATP (energy molecules). It increases oxygen uptake, reduces fatigue, and boosts physical stamina and vitality, which is why it is renowned as a Himalayan energy booster or tonic.
2.4 Answer the following questions:
(a) What is climate change?
Answer: Climate change refers to the long-term alteration in the Earth’s average weather patterns, including significant shifts in temperature, precipitation, and wind patterns that last for an extended period (decades or longer). It is currently largely driven by human activities that emit greenhouse gases.
(b) Write the main reasons for climate change.
Answer: The main reasons for climate change are:
• Burning Fossil Fuels: Excessive use of coal, oil, and petrol releases massive amounts of carbon dioxide ($CO_2$).
• Deforestation: Cutting down trees reduces the Earth’s capacity to absorb $CO_2$.
• Industrialization: Factories release harmful greenhouse gases like methane and nitrous oxide.
• Urbanization: Expanding concrete cities trap heat (Urban Heat Island effect).
• Use of Chemical Fertilizers: Releases nitrous oxide into the atmosphere.
(c) Describe the effects of climate change.
Answer: The effects of climate change include:
• Global Warming: Increase in the average temperature of the Earth.
• Melting of Ice: Glaciers and polar ice caps are melting, threatening fresh water supplies.
• Sea Level Rise: Causing flooding of coastal areas and islands.
• Extreme Weather: Increased frequency of droughts, floods, storms, and non-seasonal rain.
• Biodiversity Loss: Extinction of plant and animal species that cannot adapt to temperature changes.
• Health Risks: Spread of tropical diseases and heat-related illnesses in humans.
(d) What types of animals are called rare animals?
Answer: Rare animals are those species that have a very small population and are found in limited geographical areas. They are not necessarily in immediate danger of extinction yet but are at risk due to their low numbers and specific habitat requirements (e.g., Red Panda, One-horned Rhino).
(e) What measures can be adopted to protect rare animals?
Answer: The following measures can be adopted to protect rare animals:
• Habitat Conservation: Establishing national parks and wildlife reserves to protect their natural homes.
• Strict Laws: Enforcing strict bans on poaching, hunting, and illegal trade of animal parts.
• Public Awareness: Educating local communities about the importance of wildlife.
• Afforestation: Planting trees to restore destroyed habitats.
• Breeding Centers: Establishing conservation breeding centers to increase their population.
(f) Many plants are being extinct in Nepal due to climate change. What role can you play to protect such plants? Describe in brief.
Answer: To protect plants from extinction due to climate change, I can play the following roles:
• Plantation: I can actively participate in afforestation programs and plant indigenous species in my locality.
• Awareness: I can educate my friends and family about the importance of protecting rare plants and the dangers of climate change.
• Sustainable Use: I can encourage the sustainable harvesting of medicinal herbs rather than uprooting them completely.
• Reduce Pollution: I can adopt an eco-friendly lifestyle to help reduce the overall impact of climate change.
(g) In order to protect and promote the medicinal herbs found in Nepal, it is essential to train the local people on the processing of herbs and their use. Explain your opinions.
Answer: Local people are the primary guardians of medicinal herbs. Training them is essential because:
• Sustainable Harvesting: They need to know how to harvest herbs without killing the plant (e.g., taking leaves but leaving roots).
• Economic Benefit: If locals can process herbs into finished products, they can earn more, motivating them to conserve the resource rather than selling raw herbs cheaply.
• Traditional Knowledge: It helps preserve ancient healing knowledge combined with modern scientific processing methods.
• Conservation: When locals understand the true value of these herbs, they will actively protect the forests from smugglers and destruction.
(h) By protecting Yarsagumba and increasing its production, the economy of the country can also improve. Explain this statement.
Answer: Yarsagumba is known as “Himalayan Gold” due to its extremely high value in the international market.
• High Export Value: It is one of Nepal’s most expensive export items. Increasing production means more foreign currency earnings.
• Employment: Collection and trade provide income for thousands of people in remote Himalayan districts.
• Revenue: The government collects significant tax revenue from its trade.
Therefore, sustainable management and protection of Yarsagumba directly boost both the local standard of living and the national economy.
(i) Study the concept map and complete it.
Climate Change Concept Map
- Reason:
- Man-made: Pollution, deforestation, burning of fossil fuels
- Natural: Volcanic eruptions, solar variations
- Effect: Global warming / melting of ice / extreme weather conditions
- Management: Solar radiation management, emphasize carbon storage to reduce carbon emission
Answer: The completed concept map includes:
• Man-made causes: Pollution, deforestation, burning of fossil fuels
• Natural causes: Volcanic eruptions, solar variations
• Effects of climate change: Global warming, melting of ice, extreme weather conditions
• Climate change management strategies: Solar radiation management, emphasize carbon storage to reduce carbon emission
(j) Analyse the differences between part A and part B by observing the given picture.
Earth with water (Part A) and without water (Part B)
Answer:
Part A:
• Shows a clean, healthy, and green environment.
• Fresh air, blue sky, and healthy biosphere.
• Symbolizes a sustainable and protected planet.
• Represents positive human activities such as conservation, tree planting, and pollution control.
Part B:
• Shows a damaged, polluted, and overheated environment.
• The Earth looks dry, cracked, and burning.
• Symbolizes environmental destruction and climate crisis.
• Represents negative human activities like pollution, deforestation, and excessive carbon emissions.
Main Difference: Part A depicts a healthy Earth, whereas Part B shows a polluted and climate-affected Earth.
(k) Look at the picture thoroughly and explain its role in climate change.
Pollution contributing to climate change
Answer: The picture shows a person walking over a large pile of burning or decomposing waste. Such waste sites play a major role in climate change because:
• Burning of waste releases greenhouse gases like carbon dioxide and methane.
• Decomposing organic waste emits methane, a gas 25 times more harmful than CO₂.
• Plastic pollution releases toxic fumes when burned, contributing to air pollution.
• Unmanaged waste increases land pollution, destroying soil quality and ecosystems.
• The smoke and gases contribute to global warming, air pollution, and health problems.
(l) The one-horned rhinoceros is on the verge of extinction. What can be done to protect it? Write in brief.
Answer: To protect the one-horned rhinoceros:
• Anti-Poaching Patrols: Strengthen security in national parks (like Chitwan and Bardia) to stop poachers who kill rhinos for their horns.
• Habitat Restoration: Protect grasslands and wetlands which are the natural habitat of rhinos.
• Translocation: Move some rhinos to other suitable reserves to create new breeding populations and reduce overcrowding or disease risk.
• Community Engagement: Involve local buffer-zone communities in tourism so they benefit from protecting rhinos rather than harming them.
(m) We can find different types of medicinal herbs in our locality. But we depend on others for the treatment of common ailments. Identify the main reason for this and write about what can be done to maximize the use of local medicinal herbs.
Answer:
Main Reason: The main reason we depend on others (modern medicine) is the lack of knowledge and transfer of traditional skills. The younger generation is often unaware of the identification and specific uses of local herbs, and there is a preference for “quick-fix” allopathic medicines.
Measures to maximize use:
• Education: Include practical identification of herbs in school curriculums.
• Documentation: Elders should document their knowledge of herbal remedies before it is lost.
• Home Gardens: Encourage every household to maintain a small herbal garden (e.g., Tulsi, Neem, Aloe Vera).
• Scientific Validation: Promote research to scientifically validate local herbs, increasing public trust in their efficacy.