📘 Class 9 Science Notes
🌎 1. Earth as a System
Earth is a closed system for matter and an open system for energy.
- Matter is recycled within Earth
- Energy mainly comes from the Sun
☀️ 2. Energy in Earth System
🔹 Main source of energy:
- Sun
🔹 Forms of energy on Earth:
- Solar energy
- Heat energy
- Wind energy
- Chemical energy (food, fuels)
👉 Energy flows in one direction, not recycled like matter.
🔄 3. Matter Cycles
Matter is continuously recycled through natural cycles:
🌿 (A) Water Cycle
Evaporation → Condensation → Precipitation → Collection
🌱 (B) Carbon Cycle
- CO₂ used by plants (photosynthesis)
- Released by respiration and burning
🌬️ (C) Nitrogen Cycle
- Nitrogen fixation → plants absorb → animals consume → return to atmosphere
🌱 4. Life and Earth Systems
Life depends on interaction between:
- Atmosphere (air)
- Hydrosphere (water)
- Lithosphere (land)
- Biosphere (living organisms)
🌡️ 5. Energy Flow in Ecosystem
Food chain example:
Sun → Plants → Herbivores → Carnivores
👉 Energy decreases at each level
Questions
🌍 Earth as a System
1. Earth is a closed system for:
A) Energy
B) Matter
C) Light
D) Heat
Answer: B
2. Earth is an open system for:
A) Matter
B) Energy
C) Soil
D) Water
Answer: B
3. Main source of energy for Earth is:
A) Moon
B) Sun
C) Wind
D) Ocean
Answer: B
4. Energy flow in ecosystem is:
A) Cyclic
B) Two-way
C) One-way
D) Random
Answer: C
🌿 Matter Cycles
5. Water cycle is driven mainly by:
A) Wind
B) Sun
C) Gravity
D) Soil
Answer: B
6. Evaporation means conversion of:
A) Gas to liquid
B) Liquid to gas
C) Solid to liquid
D) Gas to solid
Answer: B
7. Condensation means conversion of:
A) Gas to liquid
B) Liquid to gas
C) Solid to gas
D) Liquid to solid
Answer: A
8. Precipitation is related to:
A) Wind
B) Rainfall
C) Evaporation
D) Photosynthesis
Answer: B
🌱 Carbon & Nitrogen Cycle
9. Carbon cycle involves:
A) Oxygen only
B) CO₂ exchange
C) Nitrogen only
D) Water only
Answer: B
10. Plants absorb CO₂ during:
A) Respiration
B) Photosynthesis
C) Digestion
D) Transpiration
Answer: B
11. Nitrogen is mainly present in:
A) Soil
B) Water
C) Atmosphere
D) Plants
Answer: C
12. Nitrogen fixation converts nitrogen into:
A) Oxygen
B) Proteins directly
C) Usable compounds
D) Water
Answer: C
🌍 Ecosystem & Life
13. Biosphere includes:
A) Rocks
B) Water only
C) Living organisms
D) Air only
Answer: C
14. Hydrosphere refers to:
A) Air
B) Land
C) Water bodies
D) Life
Answer: C
15. Lithosphere refers to:
A) Water
B) Air
C) Land
D) Clouds
Answer: C
16. Producers in ecosystem are:
A) Animals
B) Plants
C) Fungi
D) Bacteria only
Answer: B
17. Consumers depend on:
A) Sun
B) Plants or animals
C) Rocks
D) Air
Answer: B
18. Decomposers break down:
A) Sunlight
B) Dead matter
C) Water
D) Oxygen
Answer: B
⚡ Energy Flow
19. Energy in food chain:
A) Increases
B) Decreases
C) Remains same
D) Disappears
Answer: B
20. Energy transfer between trophic levels is about:
A) 1%
B) 10%
C) 50%
D) 100%
Answer: B
🧠 Key Concept MCQs
21. Matter in Earth system is:
A) Destroyed
B) Created
C) Recycled
D) Lost
Answer: C
22. Energy in ecosystem is:
A) Recycled
B) Lost
C) One-way flow
D) Stored permanently
Answer: C
23. Ecosystem means interaction of:
A) Plants only
B) Animals only
C) Organisms and environment
D) Water and air only
Answer: C
24. Photosynthesis produces:
A) CO₂
B) Oxygen
C) Nitrogen
D) Soil
Answer: B
25. Respiration releases:
A) Oxygen
B) CO₂
C) Sunlight
D) Water only
Answer: B
Assertion–Reason (10 Questions)
- A: Earth is a closed system for matter
R: Matter is recycled within Earth
👉 A - A: Energy is recycled in ecosystem
R: Energy flows one-way
👉 D - A: Sun is main energy source
R: It drives all cycles
👉 A - A: Carbon cycle involves CO₂
R: Plants absorb CO₂
👉 A - A: Nitrogen is directly usable by plants
R: It must be fixed first
👉 C
📊 Numericals (Basic Concept Based)
- If 1000 J energy enters food chain and 10% is transferred → next level?
👉 100 J - Energy decreases by 90% per trophic level → remaining after 2 levels?
👉 1% of original - If Sun gives 5000 J, plant stores 1% → energy stored?
👉 50 J - If ecosystem has 4 levels, energy flow?
👉 Decreasing stepwise - If 200 J enters, 10% transfer → third level energy?
👉 2 J
📄 Fill in the Blanks (Compact Revision)
- Earth is a ________ system for matter → closed
- Earth is an ________ system for energy → open
- Main energy source → ________ → Sun
- Matter is ________ → recycled
- Energy is ________ → one-way
- Water cycle is driven by ________ → Sun
- CO₂ is used in ________ → photosynthesis
- Oxygen is released by ________ → plants
- Atmosphere is layer of ________ → gases
- Biosphere contains ________ → life