BA05 — Ecology & Environment

📖 BA05 · AFCAT General Awareness — Biology ★ Moderate + Current Affairs Relevance

Ecology connects biology to current affairs — AFCAT links ecosystem science with environmental policies. Questions about greenhouse gases, ozone depletion, and conservation are increasingly common.

✈ AFCAT Focus: Pyramid of energy ALWAYS upright (10% rule); numbers CAN be inverted; Rhizobium = nitrogen fixation in legume root nodules; in-situ = national park; ex-situ = zoo/seed bank; ozone destroyed by CFCs (Montreal 1987); global warming = CO₂, CH₄, N₂O; acid rain pH < 5.6.

1. Ecological Pyramids

🌿 Pyramid of Numbers

CAN be inverted — e.g. 1 tree → thousands of insects → few birds → 1 hawk
Usually upright: grassland, forest ecosystems
Represents number of organisms at each trophic level

⚡ Pyramid of Energy

ALWAYS upright — NEVER inverted
Only 10% energy passes to each next level; 90% lost as heat
Food chains rarely exceed 4–5 links (energy loss too great)
Biomass pyramid: CAN invert in aquatic ecosystems

2. Environmental Issues & Conservation

Issue	Cause	Effect	AFCAT Key Point
Global Warming	CO₂, CH₄, N₂O trap heat (greenhouse effect); deforestation; fossil fuels	Rising sea levels; extreme weather events; species extinction	Paris Agreement (2015)
Ozone Depletion	CFCs from ACs & fridges destroy stratospheric O₃ (ozone)	Increased UV-B radiation; skin cancer; cataracts	Montreal Protocol (1987)
Acid Rain	SO₂ + NO₂ (industry/vehicles) + water vapour → H₂SO₄ + HNO₃	Harms aquatic life; corrodes marble (Taj Mahal)	pH of acid rain < 5.6
Eutrophication	Excess N & P nutrients from fertilisers run into water bodies	Algal bloom; O₂ depletion; fish and aquatic life die	Water pollution problem
In-situ Conservation	Protect species in their NATURAL habitat	Species preserved in wild environment	National Parks, Sanctuaries, Biosphere Reserves
Ex-situ Conservation	Protect species OUTSIDE their natural habitat	Backup populations maintained	Zoos, Botanical Gardens, Seed Banks, Gene Banks

Nitrogen Cycle:
● Fixation: Rhizobium (legume root nodules) converts N₂ → NH₃. Also: Azotobacter (free-living), lightning.
● Nitrification: NH₃ → NO₂⁻ (Nitrosomonas) → NO₃⁻ (Nitrobacter). Nitrates = plant-usable form.
● Denitrification: NO₃⁻ → N₂ back to atmosphere. Cycle complete.

📝 AFCAT PYQs — Ecology

Q1. Which ecological pyramid is ALWAYS upright? AFCAT PYQ

(a) Numbers(b) Biomass(c) Energy(d) Numbers and Biomass

✔ (c) Pyramid of Energy

The pyramid of energy is always upright — energy is always lost as heat at each trophic level (10% rule) and can never increase going upward. Numbers and Biomass can both invert under certain conditions.

Q2. Montreal Protocol (1987) was signed to protect: AFCAT PYQ

(a) Forests from deforestation(b) Ozone layer from CFC damage(c) Biodiversity(d) Ocean from plastic

✔ (b) Ozone layer

CFCs from ACs and refrigerators destroy stratospheric ozone. Montreal Protocol (1987) phased out CFCs. Most successful environmental treaty. Contrast: Paris Agreement (2015) = climate change / CO₂.

🧠 Quick Memory Chart — BA05

🌿 Pyramids

Energy: ALWAYS upright; 10% rule
Numbers: CAN invert (tree → insects)
Biomass: CAN invert (aquatic)
90% energy lost as heat each step

⛛ Nitrogen

Rhizobium: N₂ fixation (legumes)
Azotobacter: free-living N₂ fixer
Nitrosomonas: NH₃ → NO₂⁻
Nitrobacter: NO₂⁻ → NO₃⁻ (usable)

🌎 Environment

Ozone: CFCs deplete; Montreal 1987
Global warming: CO₂ main GHG
Acid rain: SO₂+NO₂; pH < 5.6
In-situ: National Parks, Sanctuaries
Ex-situ: Zoo, Seed bank, Gene bank

📝 Mock Tests 🎯 Subject Quiz ✈️ Telegram