Notes For All Chapters Science Class 10 CBSE
1. Ecosystem – What are its Components?
Definition of Ecosystem:
An ecosystem is a system where all organisms (plants, animals, microorganisms, humans) interact with the physical surroundings.
It maintains a balance in nature.
It includes:
- Biotic components (living): plants, animals, microbes.
- Abiotic components (non-living): temperature, rainfall, soil, minerals, wind, light.
Types of Ecosystems:
- Natural ecosystems: Forests, ponds, lakes, rivers, seas, deserts.
- Artificial ecosystems: Gardens, crop fields, aquariums.
Example: Garden as an Ecosystem
- Plants: grasses, trees, rose, jasmine, sunflower.
- Animals: insects, birds, frogs.
- Abiotic factors: water, sunlight, soil nutrients.
- Interaction: Plants use sunlight → animals eat plants → decomposers recycle waste.
Aquarium as an Artificial Ecosystem
- Needs: water, oxygen (pump/aerator), food, space, aquatic plants.
- With plants + fish → becomes self-sustaining (plants produce oxygen & food, fish respire & release waste).
- But must be cleaned → unlike ponds/lakes which are naturally balanced.
2. Components of Ecosystem (Functional Groups)
Producers (Autotrophs):
- Green plants & certain bacteria.
- Produce food by photosynthesis.
- Convert solar energy → chemical energy (sugar, starch).
Consumers (Heterotrophs):
Depend on producers (directly/indirectly).
Types:
- Herbivores (primary consumers, e.g., cow, deer, grasshopper).
- Carnivores (secondary/tertiary consumers, e.g., tiger, frog).
- Omnivores (e.g., humans, crow).
- Parasites (e.g., lice, leech).
Decomposers:
- Bacteria, fungi.
- Break down dead organisms & waste.
- Convert complex organic matter → simple inorganic substances → absorbed by plants again.
- Essential for nutrient recycling.
- Without decomposers → garbage & dead bodies pile up, soil fertility decreases.
3. Food Chains and Food Webs
Food Chain:
- Sequence of organisms feeding on each other.
- Each step = trophic level.
Example (forest): Grass → Deer → Tiger
- Producers = 1st trophic level.
- Herbivores = 2nd.
- Small carnivores = 3rd.
- Large carnivores = 4th.
Flow of Energy:
Plants capture ~1% of sunlight energy.
Only 10% of energy passes to next trophic level (rest lost as heat, respiration, digestion).
Therefore:
- Food chains rarely exceed 3–4 levels.
- More individuals exist at lower trophic levels.
Food Web:
- Interconnected food chains in nature.
- Shows complex feeding relationships.
Characteristics of Energy Flow:
- Unidirectional – energy flows from sun → producers → consumers → decomposers, never back.
- Decreasing Availability – energy diminishes at each trophic level.
4. Biological Magnification
Pesticides & harmful chemicals used in crops → washed into soil & water → absorbed by plants → enter food chain.
Non-degradable → accumulate at each level.
Higher trophic levels have maximum concentration (humans at top suffer most).
Effects: presence of pesticide residues in grains, fruits, vegetables, meat.
5. How Do Our Activities Affect the Environment?
Ozone Layer and its Depletion
Ozone (O₃):
- Molecule of 3 oxygen atoms.
- Poisonous near ground, but in upper atmosphere protects life.
- Absorbs ultraviolet (UV) radiation from Sun.
- UV rays cause skin cancer, genetic damage.
Formation:
- O₂ + UV → O + O
- O + O₂ → O₃
Depletion:
- In 1980s ozone began declining.
- Main cause: CFCs (Chlorofluorocarbons) – used in refrigerators, fire extinguishers, aerosols.
- CFCs release chlorine atoms → destroy ozone.
Global Action:
- 1987 → UNEP (United Nations Environment Programme) → Montreal Protocol → freeze CFC production.
- Now → mandatory CFC-free appliances.
6. Managing Garbage We Produce
Waste Generation:
- Household waste: kitchen waste, plastic, wrappers, paper, bottles, clothes, footwear.
- Disposal: dumped in soil/water → environmental problem.
Biodegradable vs. Non-Biodegradable:
1. Biodegradable:
- Broken down by microbes.
- e.g., vegetable peels, paper, leftover food.
- Effect: add nutrients back to soil.
2. Non-Biodegradable:
- Cannot be broken down naturally.
- e.g., plastics, metals, glass.
- Persist for years, cause pollution.
- Harm organisms (choking, toxic leachates).
Problems of Waste:
- Rapid lifestyle changes → more disposable items.
- Excessive packaging → more plastic & non-biodegradable materials.
- Littering at tourist places.
- Sewage & industrial waste → pollute soil & water.
Examples:
- Earlier: plastic cups in trains → non-biodegradable.
- Later: clay cups (kulhads) → caused loss of fertile topsoil.
- Now: paper cups → better option.
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