Class 10 Science Notes Chapter 17 (Chapter 17) – Examplar Problems (English) Book

Alright class, let's get focused. You've asked for notes on Chapter 17 from the Class 10 Science Exemplar. Now, it seems there might be a slight mix-up with the chapter number. The current NCERT Class 10 Science syllabus, and therefore the Exemplar book, concludes with earlier chapters. Chapter 17 isn't part of the standard Class 10 curriculum anymore.

However, topics often covered towards the end of the syllabus, like 'Our Environment' or 'Management of Natural Resources' (which were Chapters 15 and 16 in older versions), are crucial for government exams. Let's concentrate on Chapter 15: Our Environment, as its concepts are fundamental and frequently tested. These notes are tailored for competitive exam preparation, focusing on key concepts and potential question areas.

Chapter 15: Our Environment - Detailed Notes for Exam Preparation

1. Ecosystem: What is it?

• Definition: An ecosystem is a self-sustaining functional unit comprising all interacting organisms (biotic components) in an area, along with the non-living physical components of the environment (abiotic components).
• Components:
  • Biotic Components: Living organisms.
    • Producers: Organisms that produce their own food using light energy (photosynthesis) or chemical energy. Examples: Green plants, blue-green algae (cyanobacteria). They form the base of the food chain.
    • Consumers: Organisms that obtain energy by feeding on other organisms.
      • Herbivores (Primary Consumers): Feed directly on producers (e.g., deer, grasshopper).
      • Carnivores (Secondary/Tertiary Consumers): Feed on other animals. Secondary consumers eat herbivores (e.g., frog eating grasshopper). Tertiary consumers eat other carnivores (e.g., snake eating frog).
      • Omnivores: Feed on both plants and animals (e.g., humans, bears).
      • Parasites: Live on or inside another organism (host) and derive nutrients from it (e.g., Cuscuta, ticks).
    • Decomposers: Organisms that break down dead organic matter (dead plants, animals, waste products) into simpler inorganic substances, returning nutrients to the soil. Examples: Bacteria, Fungi. Crucial role in nutrient cycling.
  • Abiotic Components: Non-living physical and chemical factors. Examples: Air, water, soil, sunlight, temperature, humidity, minerals. These factors influence the survival and distribution of organisms.
• Types of Ecosystems:
  • Natural Ecosystems: Operate under natural conditions without major human interference. Examples: Forests, grasslands, deserts, ponds, lakes, oceans.
  • Artificial (Man-made) Ecosystems: Created and maintained by humans. Examples: Crop fields, gardens, aquariums. These are often less diverse and require management.

2. Food Chains and Food Webs

• Food Chain: A sequence of organisms where each organism is eaten by the next organism in the chain, showing the flow of energy.
  • Example (Grassland): Grass (Producer) → Grasshopper (Primary Consumer) → Frog (Secondary Consumer) → Snake (Tertiary Consumer) → Eagle (Quaternary Consumer/Top Carnivore).
  • Trophic Levels: Each step or level in a food chain where energy transfer occurs.
    • 1st Trophic Level: Producers
    • 2nd Trophic Level: Primary Consumers
    • 3rd Trophic Level: Secondary Consumers
    • 4th Trophic Level: Tertiary Consumers
• Energy Flow:
  • Unidirectional: Energy flows from the sun to producers, then to consumers. It does not flow back from consumers to producers.
  • 10% Law (Lindeman's Law): Only about 10% of the energy available at one trophic level is transferred to the next trophic level. The remaining 90% is lost as heat during metabolic processes, used for life activities, or remains in uneaten parts/waste.
  • Consequence: Energy availability decreases significantly at higher trophic levels, limiting the number of trophic levels (usually 3-5).
• Food Web: A network of interconnected food chains within an ecosystem. It represents the multiple feeding relationships and provides more stability than a single food chain. If one food source becomes scarce, the consumer can often switch to another.

3. Biological Magnification (Biomagnification)

• Definition: The increasing concentration of certain non-biodegradable chemicals (like pesticides, heavy metals) in the tissues of organisms at successive higher levels in a food chain.
• Mechanism: These harmful substances are absorbed by organisms (e.g., pesticides in water absorbed by aquatic plants/plankton). When these organisms are eaten, the chemical accumulates in the consumer's body. Since the chemical is not easily metabolised or excreted, its concentration increases up the food chain.
• Example: DDT accumulation in aquatic food chains, leading to high concentrations in fish-eating birds, affecting their eggshell thickness.
• Consequence: Top carnivores (including humans) are most affected as they accumulate the highest concentrations.

4. Environmental Problems and Solutions

• A. Ozone Layer Depletion:
  • Ozone (O₃): A molecule formed from three atoms of oxygen.
  • Ozone Layer: A region in the Earth's stratosphere containing a high concentration of ozone.
  • Function: Absorbs most of the harmful ultraviolet (UV-B and UV-C) radiation from the sun, protecting life on Earth.
  • Depletion Cause: Primarily caused by human-made chemicals, especially Chlorofluorocarbons (CFCs), previously used in refrigerants, aerosols, and solvents. Halons, nitrogen oxides also contribute.
  • Mechanism: CFCs rise to the stratosphere, where UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can catalytically destroy thousands of ozone molecules.
  • Consequences of Depletion: Increased UV radiation reaching Earth's surface leads to:
    • Skin cancer (melanoma)
    • Cataracts and eye damage
    • Immune system suppression
    • Damage to plants and aquatic ecosystems (phytoplankton)
  • Mitigation: Montreal Protocol (1987) - An international treaty phasing out the production and use of ozone-depleting substances like CFCs. It's considered a successful environmental agreement.
• B. Waste Management:
  • Waste (Garbage): Unwanted or unusable materials.
  • Types of Waste:
    • Biodegradable Waste: Waste that can be broken down into simpler, harmless substances by the action of microorganisms (decomposers). Examples: Vegetable peels, food leftovers, paper, wood, cotton, sewage.
    • Non-biodegradable Waste: Waste that cannot be broken down by microorganisms or takes an extremely long time to decompose. Examples: Plastics, glass, metals, synthetic fibres, pesticides, radioactive waste.
  • Problems Caused by Waste Accumulation:
    • Soil and water pollution (leachate from landfills).
    • Air pollution (burning waste).
    • Spread of diseases (breeding ground for vectors like flies, mosquitoes).
    • Harm to wildlife (ingestion of plastics).
    • Aesthetic degradation.
  • Methods of Waste Disposal:
    • Landfills: Burying waste in low-lying areas, compacted and covered with soil. Issues: Leachate, methane gas production, land use.
    • Incineration: Burning waste at high temperatures to reduce volume. Issues: Air pollution (if not controlled properly), ash disposal. Often used for hazardous/biomedical waste. Energy recovery is possible.
    • Composting: Biological decomposition of organic biodegradable waste under controlled aerobic conditions to produce manure (compost).
    • Recycling: Processing waste materials to create new products. Examples: Paper, glass, metals, some plastics. Conserves resources and energy.
    • Reuse: Using items again for their original purpose or a new purpose (e.g., using jars for storage).
    • Sewage Treatment Plants (STPs): Treating wastewater from homes and industries before discharging it into water bodies.
  • The 3 R's (often expanded to 5 R's): A strategy for sustainable waste management.
    • Reduce: Minimize the amount of waste generated.
    • Reuse: Use items multiple times.
    • Recycle: Process waste to make new materials.
    • (Refuse): Avoid buying/using non-essential or environmentally harmful products.
    • (Repurpose): Use an item for a different function.

Multiple Choice Questions (MCQs)

1. Which of the following constitutes a food chain?
   a) Grass, Wheat and Mango
   b) Grass, Goat and Human
   c) Goat, Cow and Elephant
   d) Grass, Fish and Goat

2. In an ecosystem, the 10% energy available for transfer from one trophic level to the next is in the form of:
   a) Heat energy
   b) Light energy
   c) Chemical energy
   d) Mechanical energy

3. Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as:
   a) Eutrophication
   b) Pollution
   c) Biomagnification
   d) Accumulation

4. Which of the following limits the number of trophic levels in a food chain?
   a) Decrease in energy at higher trophic levels
   b) Deficient food supply
   c) Polluted air
   d) Water

5. Which of the statement is incorrect?
   a) All green plants and blue-green algae are producers
   b) Green plants get their food from organic compounds
   c) Producers prepare their own food from inorganic compounds
   d) Plants convert solar energy into chemical energy

6. The main cause of ozone layer depletion is the release of:
   a) Carbon dioxide
   b) Methane
   c) Chlorofluorocarbons (CFCs)
   d) Nitrogen oxides from vehicles

7. Which of the following is a non-biodegradable waste?
   a) Vegetable peels
   b) Waste paper
   c) Plastic bottles
   d) Cotton cloth

8. In the following groups of materials, which group(s) contains only non-biodegradable items?
   (i) Wood, paper, leather
   (ii) Polythene, detergent, PVC
   (iii) Plastic, detergent, grass
   (iv) Plastic, bakelite, DDT
   a) (iii)
   b) (iv)
   c) (i) and (iii)
   d) (ii) and (iv)

9. The decomposers in an ecosystem:
   a) Convert inorganic material to simpler forms
   b) Convert organic material to inorganic forms
   c) Convert inorganic material into organic compounds
   d) Do not break down organic compounds

10. An aquarium is an example of:
    a) A natural ecosystem
    b) An artificial ecosystem
    c) A community
    d) A biome

Answer Key for MCQs:

1. b) Grass, Goat and Human
2. c) Chemical energy
3. c) Biomagnification
4. a) Decrease in energy at higher trophic levels
5. b) Green plants get their food from organic compounds (They make organic compounds from inorganic ones)
6. c) Chlorofluorocarbons (CFCs)
7. c) Plastic bottles
8. d) (ii) and (iv)
9. b) Convert organic material to inorganic forms
10. b) An artificial ecosystem

Remember to study these concepts thoroughly. Pay special attention to the definitions, examples, the flow of energy, and the environmental problems discussed, as these are common areas for questions in government exams. Good luck with your preparation!