Our Environment Class 10 Science Chapter 13 Notes are available here. These notes are prepared by the subject experts of our team.
Our Environment Class 10 Science Chapter 13 Notes
Ecosystem – What are its components?
1. Interdependence in Nature: All organisms, including plants, animals, microorganisms, and humans, interact with each other and their physical surroundings to maintain a balance in nature.
2. Definition of Ecosystem: An ecosystem consists of interacting organisms (biotic components) and non-living constituents (abiotic components) of the environment.
3. Components of an Ecosystem:
- Biotic Components: Living organisms such as plants, animals, and microorganisms.
- Abiotic Components: Physical factors like temperature, rainfall, wind, soil, and minerals.
4. Example of an Ecosystem: A garden is an example of an ecosystem where various plants and animals interact with each other and are influenced by abiotic factors.
5. Types of Ecosystems:
- Natural Ecosystems: Forests, ponds, and lakes.
- Artificial Ecosystems: Gardens and crop fields, which are human-made.
6. Classification of Organisms: Organisms are grouped into producers, consumers, and decomposers based on how they obtain sustenance from the environment.
7. Producers:
- Green plants and certain bacteria can produce organic compounds like sugar and starch from inorganic substances using the Sun’s radiant energy in the presence of chlorophyll through photosynthesis.
- Producers create food that sustains other organisms.
8. Consumers:
- Depend on producers either directly or indirectly for sustenance.
- Consume food produced by producers or by feeding on other consumers.
- Classified into herbivores, carnivores, omnivores, and parasites.
9. Decomposers:
- Microorganisms such as bacteria and fungi that break down dead organisms and waste products.
- Convert complex organic substances into simple inorganic substances that return to the soil, aiding plant growth.
- Essential for the natural replenishment of soil.
10. Importance of Decomposers: Without decomposers, garbage, dead animals, and plants would not be broken down, disrupting the natural cycle of nutrient replenishment in the soil.
Food Chains and Webs
1. Food Chains:
- A food chain is a series of organisms feeding on one another, forming various biotic levels.
2. Trophic Levels:
- Each step or level of a food chain is called a trophic level.
- Producers (Autotrophs): Form the first trophic level by fixing solar energy and making it available for consumers (heterotrophs).
- Primary Consumers (Herbivores): Occupy the second trophic level.
- Secondary Consumers (Small Carnivores): Occupy the third trophic level.
- Tertiary Consumers (Larger Carnivores): Form the fourth trophic level.
3. Energy Flow:
- Food acts as fuel, providing energy for work, illustrating the flow of energy among various environmental components.
- Autotrophs capture solar energy and convert it into chemical energy, supporting all activities of the living world.
- Energy flows from autotrophs to heterotrophs and decomposers.
4. Energy Loss:
- During energy conversion from one form to another, some energy is lost to the environment in unusable forms.
5. Energy Capture by Green Plants:
- Green plants in terrestrial ecosystems capture about 1% of the sunlight energy that falls on their leaves and convert it into food energy.
6. Energy Loss in Primary Consumers:
- When green plants are consumed by primary consumers, a significant amount of energy is lost as heat.
- Some energy is used for digestion and work, while the rest is used for growth and reproduction.
- On average, only 10% of the food eaten by a consumer is converted into its own body mass and is available for the next level of consumers.
7. 10% Energy Transfer Rule:
- Approximately 10% of the organic matter at each trophic level is passed to the next level of consumers.
8. Limited Food Chain Length:
- Due to significant energy loss at each trophic level, food chains typically consist of only three or four steps.
- Very little usable energy remains after four trophic levels.
9. Trophic Level Population:
- There are generally more individuals at the lower trophic levels, with the greatest number being producers.
10. Food Chains and Food Webs:
- Food chains vary in length and complexity.
- Each organism is typically eaten by multiple other organisms, forming a series of branching lines known as a food web instead of a simple straight-line food chain.
11. Unidirectional Energy Flow:
- Energy flow in an ecosystem is unidirectional.
- Energy captured by autotrophs does not return to the solar input, and energy passed to herbivores does not revert to autotrophs.
12. Diminishing Energy Across Trophic Levels:
- The energy available at each trophic level decreases progressively due to energy loss at each level.
13. Chemical Entry into the Food Chain:
- Harmful chemicals enter the food chain through pollution and the use of pesticides and chemicals in agriculture.
- These chemicals are absorbed by plants from soil and water, and by aquatic plants and animals from water bodies.
14. Non-degradable Chemical Accumulation:
- Non-degradable chemicals accumulate at each trophic level.
- Human beings, occupying the top level in any food chain, accumulate the maximum concentration of these chemicals.
15. Biological Magnification:
- The phenomenon of increasing concentration of non-degradable chemicals in organisms at higher trophic levels is known as biological magnification.
- Pesticide residues can be found in food grains, vegetables, fruits, and meat, and cannot always be removed by washing or other methods.
Ozone Layer and How it is Getting Depleted
1. Ozone Composition:
- Ozone (O₃) is a molecule made up of three oxygen atoms.
- While O₂ (oxygen) is essential for aerobic life, ozone is a deadly poison at ground level.
2. Protective Role of Ozone:
- At higher atmospheric levels, ozone plays an essential role by shielding the Earth’s surface from harmful ultraviolet (UV) radiation from the Sun, which can cause skin cancer in humans.
3. Formation of Ozone:
- Ozone is formed in the atmosphere when UV radiation acts on oxygen molecules (O₂).
- The process involves splitting oxygen molecules into free oxygen atoms, which then combine with molecular oxygen to form ozone.
4. Decline in Atmospheric Ozone:
- The amount of atmospheric ozone began to decline sharply in the 1980s.
- This decrease is linked to synthetic chemicals like chlorofluorocarbons (CFCs), used in refrigerants and fire extinguishers.
5. Global Response:
- In 1987, the United Nations Environment Programme (UNEP) secured an agreement to freeze CFC production at 1986 levels.
- It is now mandatory for manufacturers worldwide to produce CFC-free refrigerators.
Managing the Garbage we Produce
1. Waste Generation:
- Daily activities generate a significant amount of waste material.
- Common waste includes human-made materials like plastics, which are difficult to break down.
2. Enzymes and Material Breakdown:
- Enzymes are specific in their action, requiring particular enzymes to break down specific substances.
- Human-made materials like plastics are not easily broken down by bacteria or other saprophytes and persist in the environment.
3. Biodegradable vs. Non-Biodegradable:
- Biodegradable substances can be broken down by biological processes.
- Non-biodegradable substances cannot be broken down this way and persist in the environment, potentially causing harm to ecosystems.
4. Garbage Problem:
- Garbage accumulation is common in towns, cities, and tourist areas, often consisting of non-biodegradable materials like empty food wrappers.
- The increase in disposable items and non-biodegradable packaging contributes to waste generation.
5. Impact of Lifestyle and Attitude:
- Improved lifestyles and changes in attitudes have led to increased waste generation.
- The shift toward disposable items and non-biodegradable packaging impacts the environment negatively.