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SSC CGL Environment & Ecology

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This page covers SSC CGL Environment & Ecology with complete concept notes, 30 graded practice MCQs, key points and exam-specific tips. Free to study.

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Concept Notes

Environment & Ecology— Rules & Concept

1.Core Concept

Read this first — the foundation of the topic
FOOD CHAIN

Transfer of energy from one organism to another. Always starts with a Producer (plants) → Herbivore → Carnivore → Top Carnivore. 2

FOOD WEB

Many food chains connected together. More realistic than a single food chain. 3

TROPHIC LEVELS

Each step in a food chain is called a Trophic Level. - Level 1 = Producers (Plants) - Level 2 = Primary Consumers (Herbivores) - Level 3 = Secondary Consumers (Small carnivores) - Level 4 = Tertiary Consumers (Top predators) 4

ECOLOGICAL PYRAMIDS

Graphical representation of trophic levels. - Pyramid of Numbers: Shows count of organisms at each level. - Pyramid of Biomass: Shows total mass of organisms. - Pyramid of Energy: ALWAYS upright. Never inverted. This is a top exam fact. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

2.Formula Block

Memorise — at least one formula appears in every paper
Formula: Energy at next level = Current level energy x 10 / 100
Example: If producers have 10,000 J → Herbivores get 1,000 J → Carnivores get 100 J → Top carnivores get 10 J.
Bioaccumulation = toxic substance builds up INSIDE one organism.
Biomagnification = toxic substance INCREASES at each higher trophic level.
Trick to remember: Bio-MAGNIFICATION = MAGNIFIES as you go UP the food chain.

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

SHORTCUT 1 — 10% Energy Law (Lindeman's Law):

Only 10% of energy transfers from one trophic level to the next.

SHORTCUT 2 — Bioaccumulation vs Biomagnification:

SHORTCUT 3 — Biodiversity Hotspot Rule:

India has 4 Biodiversity Hotspots:

1. Himalayas

2. Western Ghats + Sri Lanka

3. Indo-Burma

4. Sundaland (Nicobar Islands part)

Trick: Remember as H-W-I-S (Himalayas, Western Ghats, Indo-Burma, Sundaland)

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

3.Exam Patterns

What examiners ask — read before attempting PYQs

— WHAT GETS ASKED ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ SSC CGL frequently asks: - Which pyramid is always upright? (Answer: Energy pyramid) - What is the 10% energy law called? (Answer: Lindeman's Law) - Which gas causes greenhouse effect? (CO2 is primary, but methane is 25x more potent) - Full form of IUCN, WWF, CITES - Red Data Book — maintained by IUCN - Project Tiger started in which year? (1973) - Which is the largest ecosystem? (Ocean/Marine ecosystem) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

4.Worked Example

Solve this step-by-step before moving on
1
Step 1

Identify the trophic levels. Producers (Level 1) → Primary Consumers (Level 2) → Secondary Consumers (Level 3)

2
Step 2

Apply 10% Law. Energy at Level 2 = 1,00,000 x 10% = 10,000 J Energy at Level 3 = 10,000 x 10% = 1,000 J Answer: 1,000 J is available to secondary consumers. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ WORKED EXAMPLE 2 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Question: DDT is sprayed on a lake. Small fish eat plankton, big fish eat small fish, birds eat big fish. Where is DDT concentration highest?

1
Step 1

Identify the food chain. Plankton → Small fish → Big fish → Birds

2
Step 2

Apply Biomagnification rule. DDT does NOT break down. It accumulates. Each level eats MANY organisms of the level below. So DDT multiplies at each level.

3
Step 3

Highest level = highest concentration. Answer: Birds (top trophic level) have the HIGHEST DDT concentration. This is biomagnification. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ NUMBER 1 COMMON TRAP — DO NOT FALL FOR THIS ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ TRAP: Students think the Pyramid of Biomass is always upright. REALITY: Pyramid of Biomass CAN be inverted (example: in ocean ecosystems, phytoplankton biomass is less than zooplankton at certain times). But Pyramid of ENERGY is ALWAYS upright — no exception. SSC has asked this multiple times to trick students.

Key Points to Remember

  • Ecology = study of interaction between organisms and their environment; Ecosystem = biotic + abiotic components working together.
  • Food chain always starts with Producers (green plants) — they are the only organisms that make their own food via photosynthesis.
  • Trophic Level 1 = Producers, Level 2 = Herbivores, Level 3 = Secondary Consumers, Level 4 = Tertiary Consumers.
  • FORMULA: Lindeman's 10% Law — only 10% energy transfers to the next trophic level; 90% is lost as heat.
  • Pyramid of Energy is ALWAYS upright — this is an absolute rule with no exceptions in any ecosystem.
  • SHORTCUT — Biomagnification: toxic substances like DDT, mercury INCREASE in concentration as you go HIGHER in the food chain.
  • India has exactly 4 Biodiversity Hotspots: Himalayas, Western Ghats, Indo-Burma, and Sundaland — remember H-W-I-S.
  • Red Data Book is maintained by IUCN and lists threatened and endangered species of plants and animals globally.
  • FORMULA — Greenhouse Gas Potency: Methane (CH4) is 25x more potent than CO2; Nitrous Oxide (N2O) is 298x more potent than CO2 over 100 years.
  • Project Tiger was launched in India in 1973; Project Elephant was launched in 1992 — both are Government of India flagship programs.

Exam-Specific Tips

  • Lindeman's 10% Law (1942): Only 10% of energy at one trophic level is passed to the next; this law was given by Raymond Lindeman.
  • IUCN = International Union for Conservation of Nature, headquartered in Gland, Switzerland — it publishes the Red Data Book.
  • CITES = Convention on International Trade in Endangered Species of Wild Fauna and Flora — came into force in 1975.
  • Project Tiger was launched on 1st April 1973 in India; Jim Corbett National Park was the first Tiger Reserve under this project.
  • The largest ecosystem on Earth is the Marine (Ocean) ecosystem, covering over 70% of the Earth's surface.
  • Pyramid of Energy is ALWAYS upright in ALL ecosystems — Pyramid of Numbers and Pyramid of Biomass can be inverted.
  • India's 4 Biodiversity Hotspots: Himalayas, Western Ghats & Sri Lanka, Indo-Burma, and Sundaland (includes Andaman & Nicobar).
  • Ozone layer is located in the Stratosphere at 15–35 km altitude; it absorbs harmful UV-B and UV-C radiation from the Sun.
Practice MCQs

Environment & Ecology — Practice Questions

30graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 30

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Practice 1easy

The process by which plants convert sunlight into chemical energy stored in glucose is called:

Practice 2easy

Which of the following is the primary greenhouse gas responsible for climate change, and what is its approximate concentration in the atmosphere as of 2024?

Practice 3easy

Which of the following is an example of a renewable energy source?

Practice 4easy

Which of the following is a biodegradable pollutant?

Practice 5easy

The layer of the atmosphere closest to the Earth's surface where weather occurs is called:

Practice 6easy

What is the primary cause of acid rain in industrial regions?

Practice 7easy

Which of the following ecosystems has the highest biodiversity on Earth?

Practice 8easy

Which of the following is a biodegradable waste material?

Practice 9easy

Which of the following gases is primarily responsible for the depletion of the ozone layer in the Earth's stratosphere?

Practice 10easy

Which of the following gases is primarily responsible for the greenhouse effect and is released through burning of fossil fuels?

Practice 11easy

Which of the following is an example of a renewable source of energy?

Practice 12medium

The Montreal Protocol, signed in 1987, was primarily designed to address which environmental problem?

Practice 13medium

The process by which water changes from a liquid state to a gaseous state due to heat energy is called:

Practice 14medium

Which of the following is the correct definition of 'biodiversity hotspot' as per conservation biology?

Practice 15medium

Which of the following gases is primarily responsible for the 'Greenhouse Effect' on Earth?

Practice 16medium

The 'carbon footprint' of a product or activity is primarily measured in terms of which unit?

Practice 17medium

Which of the following is NOT a renewable energy source?

Practice 18medium

Which of the following best describes the process of 'eutrophication' in aquatic ecosystems?

Practice 19medium

The Montreal Protocol (1987) was primarily designed to address which environmental problem?

Practice 20medium

Which of the following ecosystems is characterized by the highest biodiversity per unit area and covers approximately 6–7% of Earth's land surface?

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60-Second Revision — Environment & Ecology

  • Remember: 10% Law (Lindeman) — energy halves drastically each level. Formula: Next Level Energy = Current Energy × 10%. If producers = 10,000 J, top carnivore gets only 10 J.
  • Formula: Trophic Levels — P → H → SC → TC (Producers → Herbivores → Secondary Consumers → Tertiary Consumers). Always 4 main levels.
  • Trap: Pyramid of BIOMASS can be inverted (ocean ecosystems) but Pyramid of ENERGY is ALWAYS upright — never write inverted for energy pyramid.
  • Remember: Biomagnification = DDT/Mercury concentration INCREASES going UP the food chain. Top predators (birds, humans) are most affected.
  • Remember: India's 4 Hotspots = H-W-I-S (Himalayas, Western Ghats, Indo-Burma, Sundaland). Project Tiger = 1973, Project Elephant = 1992.
  • Trap: Students confuse Bioaccumulation (within one organism) with Biomagnification (across trophic levels). Magnification = across levels.
  • Remember: IUCN maintains Red Data Book. CITES = trade of endangered species (1975). Ozone = Stratosphere, 15–35 km altitude.
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