Our Environment Class 10 || Science|| Chapter 13 Notes

Our Environment Class 10 ||Science|| Chapter 13 Notes

1. Introduction

The environment consists of everything that surrounds us, including living organisms, physical components (like air, water, and soil), and the interactions between them. Human activities have significantly impacted the environment, leading to issues like pollution, loss of biodiversity, and climate change.

2. Ecosystem

An ecosystem is a self-contained unit of living organisms (plants, animals, and microorganisms) and their physical environment (soil, air, water) interacting with each other. Ecosystems can be:

  • Natural Ecosystems: Forests, rivers, lakes, oceans, etc.
  • Artificial Ecosystems: Gardens, crop fields, aquariums, etc.

Components of an Ecosystem:

  • Biotic Components: The living organisms in an ecosystem (plants, animals, microorganisms).
  • Abiotic Components: The non-living factors like air, water, soil, and temperature.

Trophic Levels:

  • The trophic level refers to the position an organism occupies in the food chain:
    1. Producers (Autotrophs): Plants and other organisms that produce their own food through photosynthesis.
    2. Primary Consumers (Herbivores): Organisms that feed on producers (e.g., cows, deer).
    3. Secondary Consumers (Carnivores): Organisms that feed on primary consumers (e.g., lions, tigers).
    4. Tertiary Consumers: Top carnivores that feed on secondary consumers (e.g., eagles, sharks).
    5. Decomposers (Detritivores): Organisms like bacteria and fungi that break down dead matter, returning nutrients to the ecosystem.

3. Food Chain and Food Web

Food Chain:

  • A food chain is a linear sequence of organisms where one organism is eaten by the next in the chain. For example:
    • Grass → Deer → Lion.

Food Web:

  • A food web is a complex network of interconnected food chains in an ecosystem. It shows how different food chains are interlinked, offering a more accurate representation of energy flow.

Energy Flow:

  • Energy flows through ecosystems in one direction, from producers to various levels of consumers.
  • The 10% law: Only about 10% of the energy at one trophic level is transferred to the next trophic level; the rest is lost as heat.

4. Biodegradable and Non-Biodegradable Substances

  • Biodegradable Substances: These are materials that can be broken down by microorganisms into simpler substances (e.g., vegetable peels, paper, dead plants, and animals).
  • Non-Biodegradable Substances: These are materials that cannot be broken down by natural decomposers and persist in the environment for long periods (e.g., plastic, glass, metals).

5. Ozone Layer and Its Depletion

  • The ozone layer is a protective layer in the Earth’s atmosphere that absorbs most of the Sun’s harmful ultraviolet (UV) radiation.
  • Ozone Depletion: Human-made chemicals like chlorofluorocarbons (CFCs), used in refrigeration and aerosol sprays, are responsible for depleting the ozone layer.
    • When CFCs reach the stratosphere, they release chlorine atoms, which break down ozone molecules.
    • Ozone depletion leads to an increase in UV radiation reaching the Earth’s surface, which can cause skin cancer, cataracts, and harm to marine life.

Efforts to Protect the Ozone Layer:

  • The Montreal Protocol (1987) is an international treaty aimed at phasing out the production of ozone-depleting substances like CFCs.

6. Waste Management

Proper management of waste is essential to minimize its impact on the environment. There are different methods of waste management:

  1. Segregation of Waste:

    • Biodegradable Waste: Should be composted or processed through biological treatment.
    • Non-Biodegradable Waste: Should be recycled, reused, or safely disposed of.

  2. Methods of Waste Disposal:

    • Landfills: Burying waste in designated areas, though this requires large amounts of land and can cause soil and groundwater pollution.
    • Incineration: Burning waste at high temperatures. This method reduces the volume of waste but releases harmful gases into the atmosphere.
    • Recycling: Converting waste materials into reusable materials. It helps reduce the need for raw materials and conserves resources.

7. Harmful Effects of Human Activities

Human activities have led to a number of environmental issues, including:

  1. Deforestation: Large-scale cutting down of forests for timber and agriculture reduces biodiversity and disrupts ecosystems.
  2. Pollution: Human activities like industrial processes, agricultural practices, and improper waste disposal contribute to air, water, and soil pollution.
  3. Greenhouse Effect and Global Warming: The excessive release of greenhouse gases (like carbon dioxide) from burning fossil fuels traps heat in the Earth's atmosphere, leading to global warming.
  4. Loss of Biodiversity: Habitat destruction, pollution, and over-exploitation of natural resources are causing the extinction of many species.

8. Sustainable Development

To ensure a balance between economic development and environmental protection, the concept of sustainable development has been introduced. It focuses on:

  • Using natural resources wisely.
  • Minimizing environmental impact.
  • Ensuring that future generations also have access to the same resources.

Summary:

  • An ecosystem consists of living organisms and their interactions with the environment.
  • Energy flows through food chains and food webs, with only 10% of energy being transferred from one trophic level to the next.
  • Biodegradable substances can be broken down by natural processes, while non-biodegradable substances persist in the environment and cause pollution.
  • The ozone layer protects the Earth from harmful UV radiation, but it is being depleted by chemicals like CFCs.
  • Waste management strategies such as recycling and composting can help reduce environmental damage.
  • Human activities like deforestation and pollution are causing severe environmental problems, and there is a need for sustainable development to protect the environment for future generations.

This chapter emphasizes the importance of protecting the environment through responsible behavior and sustainable practices.