NCERT Science Notes - Class 10
Chapter 13 - Our Environment

Welcome to AJs Chalo Seekhen. This webpage is dedicated to Class 10 | Science | Chapter 13 | Our Environment. In this chapter, introduces students explore ecosystems and the impact of human activities on the environment. It discusses the importance of natural resources, the need for sustainable development, and the role of various factors in maintaining ecological balance. The chapter also covers pollution, its types, sources, and effects on living organisms. Students learn about the significance of biodiversity, conservation efforts, and practices to reduce environmental degradation, highlighting the need for responsible stewardship of our planet. This chapter is key to understanding the delicate balance of our environment and our role in preserving it.

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NOTES

13.0 - Introduction

Definition of Environment:
- The term "environment" refers to the surroundings or conditions in which a person, animal, or plant - lives or operates. It encompasses all living (biotic) and non-living (abiotic) elements that interact with one another.
Perceptions of Change:
- There is a common belief that the environment today is not what it used to be in the past. This sentiment is often expressed by older generations who may have observed significant changes in natural landscapes, climate, and biodiversity.
Healthy Environment:
- Discussions about a healthy environment are prevalent in various contexts, emphasizing the need for clean air, water, and sustainable ecosystems. A healthy environment contributes to the well-being of individuals and communities.
Global Environmental Issues:
- International summits and conferences are regularly held to address environmental challenges faced by both developed and developing countries. These discussions often focus on issues like climate change, pollution, deforestation, and biodiversity loss.
Components of the Environment:
- The environment consists of various components that interact with each other, including:
  - Atmosphere: The layer of gases surrounding the Earth, essential for weather and climate regulation.
  - Hydrosphere: All water bodies, including oceans, rivers, and lakes, which are vital for life.
  - Lithosphere: The Earth's crust and upper mantle, which provide minerals and resources.
  - Biosphere: The global sum of all ecosystems, encompassing all living organisms and their interactions.
Impact of Human Activities:
- Human activities significantly impact the environment through:
  - Pollution (air, water, soil)
  - Deforestation
  - Urbanization
  - Climate change
- Understanding these interactions is crucial for developing sustainable practices to mitigate negative impacts.
Conclusion:
- Studying the environment and its components helps us understand the delicate balance that sustains life on Earth. Recognizing our role and responsibility towards the environment is essential for ensuring a healthy planet for future generations.

13.1 - Ecosystem : What Are Its Components?

Definition of an Ecosystem:
- An ecosystem is a complex network comprising all living organisms (biotic components) and the non-living elements (abiotic components) of their environment, interacting as a system. This interaction helps maintain a balance in nature.
Components of an Ecosystem:
- Ecosystems are made up of two main types of components:
  - Biotic Components:
    - These include all living organisms within the ecosystem. Examples are:
      - Plants: Various types such as grasses, trees, and flowering plants (e.g., roses, jasmines, sunflowers).
      - Animals: Organisms such as frogs, insects, birds, and other wildlife that inhabit the ecosystem.
      - Microorganisms: Bacteria, fungi, and other microscopic life forms that play critical roles in nutrient cycling and decomposition.
  - Abiotic Components:
    - These are the non-living physical factors that affect the ecosystem. Examples include:
      - Temperature: Influences the metabolic rates of organisms and the types of species that can thrive in the ecosystem.
      - Rainfall: Affects water availability, impacting plant growth and animal habitats.
      - Wind: Influences temperature and humidity levels, which can affect plant and animal behavior.
      - Soil and Minerals: Provide nutrients essential for plant growth and thus support the entire food chain within the ecosystem.
Example of an Ecosystem:
- A garden serves as a practical example of an ecosystem, where:
  - Various plants (like grasses, trees, and flowering plants) provide habitat and food sources.
  - Animals (such as frogs, insects, and birds) interact with these plants and with each other.
  - The abiotic components, like soil quality, sunlight, and rainfall, significantly affect the growth and health of the plants and animals in the garden.
Types of Ecosystems:
- Natural Ecosystems: These include forests, ponds, lakes, and oceans, where interactions among organisms occur naturally without significant human influence.
- Human-made (Artificial) Ecosystems: Examples include gardens, parks, and agricultural fields, where humans play a crucial role in shaping and managing the environment.
Importance of Ecosystems:
- Ecosystems provide essential services such as food production, oxygen generation, climate regulation, and habitat for wildlife. Understanding the components and interactions within ecosystems is crucial for conservation efforts and sustainable management of natural resources.

Activity 13.1: Designing an Aquarium

Objective:
- To understand the components necessary for creating a balanced aquarium, which serves as a human-made ecosystem.
Components Needed for an Aquarium:
- Space: A sufficiently large container (such as a fish tank or a large jar) to provide ample space for the fish to swim.
- Water: Clean and treated water suitable for the fish species being kept.
- Oxygen: Essential for fish survival, which can be provided using an oxygen pump (aerator) that introduces air into the water.
- Food: Fish food, readily available in pet stores, to provide the necessary nutrients for the fish.
- Aquatic Plants: Adding plants helps oxygenate the water and provides hiding spaces and shelter for the fish.
- Aquatic Animals: Consider including a few compatible aquatic animals (like snails or shrimp) that can contribute to the ecosystem.
Self-sustaining System:
- An aquarium can become a self-sustaining ecosystem if designed properly. The aquatic plants produce oxygen through photosynthesis, which the fish use to breathe. In return, fish excrete waste that provides nutrients for the plants, creating a balanced cycle.
Maintenance of the Aquarium:
- Cleaning: The aquarium needs regular cleaning to remove algae, waste, and uneaten food, which can harm water quality. Over time, these substances can lead to toxic conditions for the fish.
- Water Changes: Periodic water changes are necessary to maintain optimal water quality and remove toxins that accumulate over time.
- Filter Maintenance: If a filtration system is used, it must be cleaned or replaced to ensure effective water circulation and removal of impurities.
Comparison with Natural Water Bodies:
- Ponds and Lakes: Unlike an aquarium, natural bodies of water like ponds and lakes have self-cleaning mechanisms. They have a diverse range of organisms, including bacteria and decomposers, which break down waste naturally.
- Natural Balance: In a natural ecosystem, the balance of organisms helps maintain water quality. For example, aquatic plants and microorganisms work together to filter and purify the water over time.
- Human Intervention: While natural water bodies do self-regulate, they can become polluted and may require human intervention (e.g., conservation efforts, clean-up initiatives) to restore their health and balance.
Questions to Consider:
- How do the interactions between fish, plants, and bacteria in an aquarium mirror those in natural ecosystems?
- Why is it important to monitor and maintain the conditions in an aquarium regularly compared to natural ecosystems?

Conclusion: Designing an aquarium helps illustrate the principles of ecosystems, showcasing the importance of balance and interaction among living organisms and their environment. Regular maintenance is crucial for the health of the aquarium, emphasizing the role of humans in managing ecosystems.

Organism Classification in Ecosystems

Producers:
- Definition: Organisms that can produce organic compounds like sugars and starches from inorganic substances using sunlight and chlorophyll through the process of photosynthesis.
- Examples:
  - Green Plants: Trees, shrubs, grasses.
  - Certain Bacteria: Cyanobacteria (blue-green algae) that can photosynthesize.
Consumers:
- Definition: Organisms that depend on producers either directly or indirectly for their sustenance by consuming food produced.
- Categories of Consumers:
  - Herbivores: Animals that primarily eat plants.
  - Carnivores: Animals that primarily eat other animals.
    - Examples: Lions, eagles, and sharks.
  - Omnivores: Animals that eat both plants and animals.
    - Examples: Humans, bears, and pigs.
  - Parasites: Organisms that live on or in a host organism and derive nutrients at the host's expense.
    - Examples: Tapeworms, lice, and fleas.
Decomposers:
- Definition: Microorganisms such as bacteria and fungi that break down dead organic matter and waste products, returning essential nutrients to the soil.
- Role in the Ecosystem: They convert complex organic substances into simple inorganic substances, enriching the soil and enabling plants to thrive. Without decomposers, the natural replenishment of soil nutrients would cease, leading to nutrient depletion and a disruption in the ecosystem.

Activity 13.2

Aquarium Care:
- When creating an aquarium, it is essential to ensure that the species selected do not prey on each other. If an aquatic animal that eats others is introduced, it could lead to a decrease in the fish population, disrupting the balance of the ecosystem.
Group Discussion:
- In small groups, discuss how producers, consumers, and decomposers depend on each other:
  - Producers: Provide energy and nutrients through photosynthesis.
  - Consumers: Rely on producers for food. Herbivores consume plants, carnivores eat herbivores or other carnivores, and omnivores eat both.
  - Decomposers: Break down dead organisms, returning nutrients to the soil, which producers use to grow.
Food Chain:
- Create a simple food chain using aquatic organisms. For example:
  - Plankton → Small Fish → Larger Fish.
- This chain demonstrates who eats whom and reflects the flow of energy through the ecosystem.
Importance of Organism Groups:
- Discuss whether any one group of organisms is of primary importance:
  - Producers: Considered crucial because they are the foundation of the food chain, converting solar energy into chemical energy.
  - Consumers: Important for transferring energy throughout the ecosystem.
  - Decomposers: Vital for nutrient recycling, enabling the ecosystem to function sustainably.
- Conclude that while all groups are interconnected and essential, producers play a primary role in initiating energy flow.

Conclusion: Understanding the interdependence of producers, consumers, and decomposers highlights the balance required in ecosystems. Each group plays a critical role in sustaining life, and maintaining this balance is essential for a healthy environment.

13.1.1 - Food Chains and Webs

Food Chain

Definition: A food chain is a linear sequence of organisms where each organism is eaten by the next in the series. It represents how energy and nutrients flow from one organism to another in an ecosystem.
Trophic Levels:
- First Trophic Level: Autotrophs or producers (e.g., green plants) that capture solar energy and convert it into chemical energy through photosynthesis.
- Second Trophic Level: Herbivores or primary consumers that feed on producers (e.g., rabbits, deer).
- Third Trophic Level: Small carnivores or secondary consumers that feed on primary consumers (e.g., snakes that eat rabbits).
- Fourth Trophic Level: Larger carnivores or tertiary consumers that feed on secondary consumers (e.g., hawks that eat snakes).

Energy Flow in Ecosystems

The energy flow in an ecosystem involves the transfer of energy through different trophic levels:
- Energy Capture: Green plants capture about 1% of the sunlight energy that falls on their leaves and convert it into food energy.
- Energy Loss: When primary consumers eat plants, much of the energy is lost as heat, used for digestion, or expended in activities. On average, only about 10% of the energy from the food consumed is converted into the consumer's body, making it available for the next trophic level.

Efficiency of Energy Transfer

Energy Transfer: Each step in the food chain typically sees about 90% of the energy lost, leading to a pattern where only 10% of the energy from one trophic level is passed to the next.
Trophic Level Limitations: Due to the significant energy loss, food chains usually consist of only three to four trophic levels. Beyond four levels, very little usable energy remains.
Population Distribution: Generally, there are more individuals at lower trophic levels (producers) compared to higher levels, with the highest number of organisms being producers.

Food Web

Definition: A food web is a complex network of interconnected food chains that illustrates the multiple feeding relationships among organisms in an ecosystem.
Complexity: Each organism may be part of several food chains, indicating that it can be eaten by multiple consumers while also preying on different organisms, leading to a branching representation of energy flow.

Energy Flow and Biological Magnification

Energy Flow

Unidirectional Flow:
- The flow of energy in an ecosystem is unidirectional; energy captured by autotrophs (producers) is not returned to them.
- Once energy moves to herbivores (primary consumers) and then to higher trophic levels (secondary and tertiary consumers), it does not revert back to the previous levels.
Progressive Diminishment:
- At each trophic level, energy availability diminishes due to loss of energy through heat, metabolic processes, and inefficiencies in energy transfer.
- This means that there is significantly less energy available to organisms at higher trophic levels.

Biological Magnification

Definition: Biological magnification refers to the accumulation of non-degradable harmful chemicals, such as pesticides, in organisms at successive trophic levels of a food chain.
Pathway of Chemicals:
- Chemicals from pesticides and pollutants enter the ecosystem, often through runoff into soil and water bodies.
- Plants absorb these chemicals along with nutrients, and aquatic organisms take them up from their environment.
- As animals consume these plants or other animals, the concentration of these chemicals increases at each trophic level.
Impact on Humans:
- As humans are typically at the top of the food chain, we are at the highest risk for accumulating these chemicals in our bodies, leading to potential health hazards.

Activity 13.3

Debate on Pesticide Bans:
- Group members can discuss the need for bans on products with high pesticide levels.
- Consider arguments about public health, environmental impacts, and economic implications for farmers and food producers.
Sources of Pesticides:
- Discuss potential sources of pesticides in food items, including agricultural practices, contaminated water sources, and use in food processing.
- Consider if pesticides could enter our bodies through other food products (e.g., processed foods containing vegetables or grains treated with pesticides).
Reducing Pesticide Intake:
- Discuss methods to minimize pesticide intake, such as:
  - Buying organic produce that uses fewer or no pesticides.
  - Washing fruits and vegetables thoroughly to remove surface residues.
  - Supporting local and sustainable farming practices that prioritize environmental health.
  - Advocating for stricter regulations on pesticide use and monitoring in agriculture.

13.2 - How Do Our Activities Affect the Environment?

Key Concepts

Human Impact on the Environment:
- Humans are an integral part of the environment, and our actions can lead to significant changes in our surroundings.
- Environmental pollution is one of the main consequences of human activities, which has been previously discussed.
Environmental Problems:
- This section focuses on two critical environmental issues: the depletion of the ozone layer and waste disposal.

13.2.1 - Ozone Layer and How it is Getting Depleted

Ozone (O₃):
- Ozone is a molecule composed of three oxygen atoms. While the more commonly known oxygen (O₂) is essential for aerobic life, ozone can be harmful at lower altitudes.
- In the upper atmosphere, however, ozone plays a crucial role in protecting the Earth by absorbing harmful ultraviolet (UV) radiation from the Sun, which can cause skin cancer and other health issues.
Formation of Ozone:
- Ozone is formed in the atmosphere when UV radiation splits molecular oxygen (O₂) into free oxygen atoms (O), which then combine with other oxygen molecules to create ozone (O₃).
Depletion of the Ozone Layer:
- The ozone layer began to significantly deplete in the 1980s due to synthetic chemicals, primarily chlorofluorocarbons (CFCs), commonly used in refrigeration and aerosol propellants.
- The depletion of ozone has serious implications for life on Earth due to increased exposure to UV radiation.
International Response:
- In response to the threat posed by CFCs, the United Nations Environment Programme (UNEP) initiated the Montreal Protocol in 1987, aiming to freeze CFC production at 1986 levels.
- Since then, there have been efforts worldwide to produce CFC-free products, particularly in refrigeration.

Activity 13.4

Research on Ozone-Depleting Chemicals:
- Investigate which specific chemicals are responsible for ozone layer depletion, focusing on CFCs, halons, and other ozone-depleting substances (ODS).
Evaluation of Regulatory Success:
- Assess whether regulations aimed at controlling the emission of these harmful chemicals have been effective.
- Look into scientific data regarding the size and condition of the ozone layer, particularly if there have been improvements or changes in the size of the ozone hole in recent years.

13.2.2 - Managing the Garbage We Produce

Key Concepts

Waste Generation:
- In our daily lives, we generate various types of waste materials, which include kitchen waste (spoiled food, vegetable peels, used tea leaves, milk packets, and empty cartons), waste paper, empty medicine bottles, old clothes, and broken footwear.
- After disposal, these waste materials undergo different processes based on their composition.
Understanding Waste Decomposition:
- The activity aims to help students observe how different materials decompose over time, leading to a better understanding of biodegradable and non-biodegradable substances.

Activity 13.5: Observing Waste Decomposition

Materials Collection:
- Gather various waste materials from home over the course of a day, including kitchen scraps, paper, plastic, and fabric.
Experimental Setup:
- Bury the collected waste in a pit in the school garden or in a container covered with at least 15 cm of soil.
- Keep the buried materials moist and observe them at 15-day intervals.
Observations to Make:
- Identify which materials remain unchanged over long periods.
- Determine which materials change their form and structure over time.
- Assess which of the changing materials decompose the fastest.

Understanding Biodegradability

Biodegradable Substances:
- These are materials that can be broken down by biological processes, mainly through the action of bacteria and other microorganisms. Examples include food scraps, paper, and natural fibers.
- Students should identify how many of the buried substances are biodegradable based on their observations.
Non-Biodegradable Substances:
- These materials do not decompose easily and persist in the environment, often causing pollution. Common examples include plastics, glass, and certain metals.
- Non-biodegradable substances may remain inert or may cause harm to ecosystems, disrupting the balance of the environment.

Biodegradable Substances: Materials that can be broken down by biological processes, such as the action of microorganisms, into simpler, non-toxic substances. Examples include food waste, paper, and natural fibers.
Non-Biodegradable Substances: Materials that do not decompose easily in the environment, often persisting for many years and potentially causing pollution. Common examples include plastics, glass, and metals.
Biodegradable Plastics: New types of plastics designed to break down more quickly than traditional plastics, usually through microbial action. They can be made from renewable sources and are intended to reduce the environmental impact of plastic waste.

Activity 13.6: Research on Waste

Research Biodegradable and Non-Biodegradable Substances:
- Use library or internet resources to gather information on both types of substances.
Lifespan of Non-Biodegradable Substances:
- Non-biodegradable substances can last in the environment for decades to centuries. For example:
  - Plastics: 100-1,000 years
  - Glass: Indefinitely (can take millions of years)
  - Aluminum cans: 80-200 years
  - Styrofoam: 500 years or more
Biodegradable Plastics:
- Investigate new biodegradable plastics, such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA). Determine their environmental impact and whether they truly degrade without causing harm.

Activity 13.7: Waste Management in Your Area

Household Waste Management:
- Investigate what happens to the waste generated at home and whether a waste collection system is in place.
Local Body Waste Management:
- Find out how the local municipal corporation or panchayat handles waste. Check if they separate biodegradable and non-biodegradable wastes.
Waste Generation Calculations:
- Calculate the daily waste generated at home and in the classroom, identifying how much of it is biodegradable.
Suggestions for Waste Management:
- Propose methods for managing waste effectively, such as:
  - Implementing composting for biodegradable waste.
  - Recycling non-biodegradable materials.
  - Reducing single-use plastics.

Activity 13.8: Sewage and Industrial Waste Treatment

Sewage Treatment:
- Research how sewage is treated in your locality and whether there are measures to prevent pollution of local water bodies.
Industrial Waste Management:
- Investigate how local industries handle their waste and whether there are mechanisms in place to protect soil and water from pollution.

Impact of Increased Waste Generation

Environmental Impact:
- Increased waste generation can lead to pollution, habitat destruction, and depletion of natural resources. The prevalence of disposable products contributes to the accumulation of non-biodegradable waste, affecting ecosystems and biodiversity.

Think It Over: Disposable Cups

Advantages of Disposable Paper Cups Over Plastic Cups:
- Biodegradable: Paper cups can break down more easily than plastic, reducing environmental impact.
- Less Harmful: Paper cups are generally less harmful to wildlife than plastic cups, which can cause choking and ingestion hazards.
- Renewable Resource: Paper is made from trees, a renewable resource, whereas plastic is made from petroleum, a non-renewable resource.

Activity 13.9: Hazardous Waste and Recycling

Hazardous Materials in Electronic Waste:
- Research the hazardous materials found in electronic items, such as lead, mercury, cadmium, and brominated flame retardants. Discuss how these materials can contaminate soil and water, posing risks to human health and the environment.
Plastics Recycling:
- Investigate the recycling process for plastics, including the steps involved and its impact on the environment. Recycling can reduce the need for new plastic production, but it can also consume energy and produce waste during the recycling process.

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

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

NOTES

13.0 - Introduction