Our Environment
Overview: Ecosystem, Food Chain & Web, 10% Law, Biomagnification, Ozone Layer, Garbage.
1. Ecosystem
Interaction of living (biotic) and non-living (abiotic) components.
- Producers: Make food (Plants).
- Consumers: Eat others (Herbivores, Carnivores, Omnivores).
- Decomposers: Break down dead matter (Bacteria, Fungi).
2. Food Chain
Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer.
10% Law: Only 10% energy is transferred to next level. 90% lost as heat.
Biomagnification: Accumulation of harmful chemicals (pesticides) increases at each trophic level. Max in humans.
3. Environmental Problems
Ozone Depletion: O3 protects from UV rays. Depleted by CFCs (Chlorofluorocarbons).
Garbage Management:
- Biodegradable: Decomposed by microbes (Paper, Peels).
- Non-biodegradable: Cannot be decomposed (Plastic, Glass).
NCERT In-Text Questions (Solved)
Page 257
Q1. What are trophic levels? Example.
Each step/level of a food chain where transfer of energy takes place is a trophic
level.
Example: Grass (1st) → Deer (2nd) → Lion (3rd).
Example: Grass (1st) → Deer (2nd) → Lion (3rd).
Q2. Role of decomposers in ecosystem?
They break down complex organic matter from dead plants/animals into simple inorganic
substances that go into soil. They act as natural cleaning agents and replenish soil nutrients.
Page 261
Q1. Why are some substances biodegradable and some non-biodegradable?
Decomposition is specific. Enzymes released by bacteria can only break down natural
organic bonds (Biodegradable). They cannot break artificial strong bonds of plastics
(Non-biodegradable).
Q2. Ways in which biodegradable substances affect environment?
1. Foul smell during decomposition.
2. Breeding ground for flies/mosquitoes (disease).
3. Produces greenhouse gases (Methane).
2. Breeding ground for flies/mosquitoes (disease).
3. Produces greenhouse gases (Methane).
Q3. Ways in which non-biodegradable substances affect environment?
1. Clog drains/Soil pollution.
2. Harm animals (cows eat plastic).
3. Biomagnification in food chain.
2. Harm animals (cows eat plastic).
3. Biomagnification in food chain.
Page 264
Q1. What is Ozone? How does it affect ecosystem?
Ozone is O3. At ground level, it is deadly poison. But in stratosphere, it
shields earth from harmful UV radiation of Sun. UV causes skin cancer in humans.
Q2. Steps to limit damage to ozone layer?
1. Banning CFCs (in ACs/Fridges).
2. UNEP agreement (Montreal Protocol) to freeze CFC production.
2. UNEP agreement (Montreal Protocol) to freeze CFC production.
NCERT Exercise Questions
Complete solutions for Chapter 13 exercises.
Q1. Which group contains only biodegradable items?
(a) Grass, flowers, leather (Yes).
(c) Fruit peels, cake, lime juice (Yes).
(d) Cake, wood, grass (Yes).
(a), (c) and (d) contain only biodegradable items. (b) contains plastic.
(c) Fruit peels, cake, lime juice (Yes).
(d) Cake, wood, grass (Yes).
(a), (c) and (d) contain only biodegradable items. (b) contains plastic.
Q2. Which constitutes a food chain?
(b) Grass, Goat, Human. (Producer -> Herbivore -> Omnivore).
Q3. Which are environment-friendly practices?
(d) All of the above. (Carrying cloth bag, Switching off lights, Walking to school).
Q4. Consequences if we kill all organisms in one trophic level?
Imbalance in ecosystem.
1. Population of lower level will increase explode (no predator).
2. Population of higher level will die (no food).
E.g., Killing all deer -> Grass grows unchecked, Lions die.
1. Population of lower level will increase explode (no predator).
2. Population of higher level will die (no food).
E.g., Killing all deer -> Grass grows unchecked, Lions die.
Q5. Will impact of removing all organisms be different for different levels?
Yes, but all are damaging. Removing Producers (Plants) is most severe as all life depends on them.
Removing top carnivores is less immediate but leads to overpopulation of herbivores. Ecosystem needs
balance.
Q6. What is biological magnification? Will levels be different?
Increase in concentration of harmful non-biodegradable chemicals (pesticides) at successive trophic
levels.
Yes, levels are different. It is maximum at the top level (Humans) because they eat maximum amount of food accumulated from lower levels.
Yes, levels are different. It is maximum at the top level (Humans) because they eat maximum amount of food accumulated from lower levels.
Q7. Solutions for waste disposal problem?
1. Segregation: Separate bio and non-bio waste.
2. Composting: Convert kitchen waste to manure.
3. Recycling: Plastic/Paper/Glass.
4. Reduce usage of single-use items.
2. Composting: Convert kitchen waste to manure.
3. Recycling: Plastic/Paper/Glass.
4. Reduce usage of single-use items.
Q8. If all waste we generate is biodegradable, will it have no impact?
It will still have impact if generated in huge excess. Decomposers take time to break it down. Huge
piles will smell, breed diseases, and block drains before they decompose.
Q9. Why is damage to ozone layer a cause for concern? Steps?
Ozone hole allows harmful UV radiation to reach earth, causing skin cancer, cataracts, and damage to
crops/immune system.
Steps: Montreal Protocol (1987) reduced use of CFCs. Now HFCs are used which don't damage ozone.
Steps: Montreal Protocol (1987) reduced use of CFCs. Now HFCs are used which don't damage ozone.
Key Rules & Facts
Energy flow and environmental terms.
Important Principles
10% Law
Energy Transfer
Solar Energy Capture
1% by Plants
Biomagnification
Max in Top Level
Ozone
O3 Molecule
UNE
United Nations Environment
50 Important Facts
1. Ecosystem: Interaction of biotic and abiotic.
2. Biotic components: Living (Plants, Animals).
3. Abiotic components: Non-living (Soil, Air, Temp).
4. Garden is an artificial ecosystem.
5. Forest is a natural ecosystem.
6. Pond is a natural ecosystem.
7. Producers prepare their own food (Green plants).
8. Consumers depend on producers.
9. Herbivores eat plants.
10. Carnivores eat animals.
11. Omnivores eat both.
12. Parasites live on host (Lice, Cuscuta).
13. Decomposers break down dead organic matter.
14. Bacteria and Fungi are decomposers.
15. Food Chain: Who eats whom.
16. Food chain is unidirectional.
17. Trophic levels are steps in a food chain.
18. Producers are at first trophic level.
19. Primary consumers (Herbivores) are second.
20. 10% Law given by Lindeman.
21. 90% energy is lost as heat/metabolism.
22. Food Web: Interconnected food chains.
23. Plants capture 1% of sunlight.
24. Energy flow is Unidirectional.
25. Nutrients flow is Cyclic.
26. Biological Magnification: Chemical accumulation.
27. DDT is non-biodegradable.
28. Max concentration in humans (Top carnivore).
29. Ozone (O3) is a deadly poison.
30. Ozone layer in Stratosphere is beneficial.
31. UV rays cause skin cancer.
32. UV rays can damage crops.
33. CFCs (Chlorofluorocarbons) deplete ozone.
34. Montreal Protocol (1987) to freeze CFC
production.
35. Biodegradable waste rots naturally.
36. Non-biodegradable waste persists.
37. Plastic is non-biodegradable.
38. Glass and metals are non-biodegradable.
39. Composting: Recycling organic waste.
40. Vermicomposting uses earthworms.
41. Incineration: Burning waste at high temp.
42. Landfills: Dumping waste in low lying areas.
43. 3R: Reduce, Reuse, Recycle.
44. Reuse is better than Recycle (Saves energy).
45. Kulhads (Clay cups) are biodegradable.
46. Paper cups are biodegradable.
47. Plastic cups create pollution.
48. Biogas can be produced from biodegradable waste.
49. Aquarium needs cleaning (No decomposers).
50. Ponds don't need cleaning (Natural decomposers).
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