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English · हिन्दी · తెలుగు · தமிழ் · മലയാളം · मराठी · ಕನ್ನಡ

Quick recap: Ecology basics on one page

ಕನ್ನಡದಲ್ಲಿ ವಿವರಣೆ

Ecology basics · Quick recap · Fact-checked on · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

Both parts of Ecology basics condensed for quick revision: ecosystem structure, energy flow, pyramids and biomagnification; succession, interactions, special species roles and ecotones; the biogeochemical cycles; a one-table overview and eight mixed questions.

Each idea is explained first in Kannada (ಕನ್ನಡ), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Kannada and revise it in English.

ಈ ಅಧ್ಯಾಯಕ್ಕೆ ಎರಡು ಭಾಗಗಳು: ಪರಿಸರ ವ್ಯವಸ್ಥೆ ಹೇಗೆ ರಚನೆಯಾಗಿದೆ, ಶಕ್ತಿ ಹೇಗೆ ಹರಿಯುತ್ತದೆ; ನಂತರ ಬದಲಾವಣೆ, ಜೀವಿಗಳ ಸಂಬಂಧ, ವಸ್ತುಗಳ ಚಕ್ರಗಳು. ಶಕ್ತಿ ಒಮ್ಮೆ ಮಾತ್ರ ಹಾದುಹೋಗುತ್ತದೆ, ಪೋಷಕಾಂಶಗಳು ಸುತ್ತುತ್ತವೆ, ಇದೇ ಎರಡನ್ನೂ ಜೋಡಿಸುವ ದಾರ. (→ English: ecosystem · हिन्दी: पारिस्थितिकी तंत्र)

In exam EnglishEcology basics has two parts. Part 1 shows how an ecosystem is built and how energy moves through it; Part 2 shows how ecosystems change, how species affect one another and how matter is recycled. One line joins them: energy flows through once and leaves as heat, while nutrients go round in cycles. This recap gathers the facts most often tested.

ಆವಾಸ ಎಂದರೆ ಜೀವಿ ಇರುವ ಜಾಗ, ಗೂಡು ಎಂದರೆ ಅಲ್ಲಿ ಅದರ ಕೆಲಸ. ಉತ್ಪಾದಕರು ಆಹಾರ ತಯಾರಿಸುತ್ತಾರೆ, ಗ್ರಾಹಕರು ಇತರರನ್ನು ತಿನ್ನುತ್ತಾರೆ, ಬ್ಯಾಕ್ಟೀರಿಯಾ, ಶಿಲೀಂಧ್ರಗಳು ಸತ್ತವನ್ನು ಕೊಳೆಸುತ್ತವೆ, ಎರೆಹುಳು ಅವನ್ನು ತಿನ್ನುತ್ತದೆ. ಜೀವಂತ ಸಸ್ಯದಿಂದ ಶುರುವಾಗುವ ಆಹಾರ ಸರಪಳಿ ಒಂದು, ಕೊಳೆತ ವಸ್ತುವಿನಿಂದ ಶುರುವಾಗುವುದು ಇನ್ನೊಂದು. (→ English: habitat; niche; food chain · हिन्दी: आवास; निकेत; खाद्य श्रृंखला)

In exam EnglishHaeckel coined the word ecology in 1866 and Tansley the word ecosystem in 1935. A habitat is where a species lives; its niche is the role it plays there. Producers make food, mostly by photosynthesis, though bacteria at deep-sea vents use chemical energy; consumers eat others; decomposers such as bacteria and fungi break dead matter down chemically, while detritivores such as earthworms eat it. A grazing food chain starts with living plants and a detritus chain with dead matter, and chains interlock into food webs.

ಶಕ್ತಿ ಒಂದೇ ದಿಕ್ಕಿನಲ್ಲಿ ಹೋಗುತ್ತದೆ, ಪ್ರತಿ ಮೆಟ್ಟಿಲಿಗೆ ಸುಮಾರು ಹತ್ತನೇ ಒಂದು ಭಾಗ ಮಾತ್ರ ಮೇಲೆ ತಲುಪುತ್ತದೆ, ಅದಕ್ಕೇ ಹುಲಿಗಳು ಕಡಿಮೆ. ಶಕ್ತಿಯ ಪಿರಮಿಡ್ ಎಂದೂ ತಲೆಕೆಳಗಾಗುವುದಿಲ್ಲ. ಡಿಡಿಟಿಯಂತಹ ವಿಷಗಳು ಸರಪಳಿಯಲ್ಲಿ ಮೇಲೆ ಹೋದಂತೆ ಹೆಚ್ಚುತ್ತವೆ, ಅದೇ ಜೈವಿಕ ವರ್ಧನೆ; ಕೆರೆಯ ಸಣ್ಣ ಮೀನಿನಲ್ಲಿ ಸ್ವಲ್ಪ, ಅದನ್ನು ತಿನ್ನುವ ಕೊಕ್ಕರೆಯಲ್ಲಿ ತುಂಬಾ ಹೆಚ್ಚು. (→ English: ten per cent law; biomagnification · हिन्दी: दस प्रतिशत नियम; जैव आवर्धन)

In exam EnglishEnergy flows one way, and on average only about a tenth of it passes from one trophic level to the next, the ten per cent law described by Lindeman in 1942; that is why chains are short and top predators few. Net primary productivity is gross productivity minus the producers' respiration; rainforests, reefs and estuaries are the most productive per unit area. Of Elton's three pyramids, those of number and biomass can be inverted but that of energy never is. Persistent, fat-soluble poisons such as DDT and mercury undergo biomagnification, reaching their highest levels in top predators.

ಪರಿಸರ ಅನುಕ್ರಮ ಎಂದರೆ ಒಂದೇ ಜಾಗದಲ್ಲಿ ಜೀವ ಸಮುದಾಯಗಳು ಕ್ರಮವಾಗಿ ಬದಲಾಗುವುದು. ಮಣ್ಣಿಲ್ಲದ ಕಡೆ ಶುರುವಾದರೆ ನಿಧಾನ, ಮಣ್ಣಿರುವ ಕಡೆ ವೇಗ. ಬಂಡೆಯ ಮೇಲೆ ಕಲ್ಲುಹೂ, ಕೆರೆಯಲ್ಲಿ ನೀರಿನ ಪಾಚಿ ಮೊದಲು ಬರುತ್ತವೆ; ಕೊನೆಗೆ ಹವಾಮಾನಕ್ಕೆ ಹೊಂದುವ ಪರಾಕಾಷ್ಠೆ ಸಮುದಾಯ ನೆಲೆಗೊಳ್ಳುತ್ತದೆ. (→ English: ecological succession; climax community · हिन्दी: पारिस्थितिक अनुक्रमण; चरम समुदाय)

In exam Englishecological succession is the orderly replacement of communities in one place. Primary succession starts where there is no soil and is slow; secondary succession starts where soil survives and is faster. Lichens are the usual pioneers on rock (a xerosere) and floating algae in a pond (a hydrosere), and the series ends in a climax community in balance with the climate.

ಜೀವಿಗಳ ಸಂಬಂಧಗಳು ಲಾಭ-ನಷ್ಟದಿಂದ: ಎರಡಕ್ಕೂ ಲಾಭ ಪರಸ್ಪರ ಸಹಾಯ ಜೀವನ (ಅತ್ತಿ, ಕಣಜ), ಒಂದಕ್ಕೆ ಲಾಭ ಇನ್ನೊಂದಕ್ಕೆ ಏನೂ ಇಲ್ಲ (ಮಾವಿನ ಮೇಲಿನ ಆರ್ಕಿಡ್), ಪರಾವಲಂಬನೆ, ಬೇಟೆ, ಪೈಪೋಟಿ. ಕೀಸ್ಟೋನ್ ಪ್ರಭೇದ ಚಿಕ್ಕದಾದರೂ ದೊಡ್ಡ ಪರಿಣಾಮ ಬೀರುತ್ತದೆ; ಅಂತರಗಂಗೆ, ಲಂಟಾನ ನಮ್ಮಲ್ಲಿ ಆಕ್ರಮಣಕಾರಿ ಪ್ರಭೇದ. ಎರಡು ಸಮುದಾಯಗಳು ಸೇರುವ ಪರಿಸರ ಸಂಕ್ರಮಣ ವಲಯದಲ್ಲಿ, ಗಡಿಯ ಸಂತೆಯಂತೆ, ಬಗೆಗಳು ಹೆಚ್ಚು. (→ English: mutualism; keystone species; invasive species; ecotone · हिन्दी: सहोपकारिता; कीस्टोन प्रजाति; आक्रामक प्रजाति; इकोटोन)

In exam EnglishInteractions are sorted by gain and loss: mutualism (+/+, fig and fig wasp, lichens), commensalism (+/0, an orchid on a mango tree), parasitism and predation (+/−), competition (−/−, which Gause showed can drive one species out) and amensalism (0/−, Penicillium and bacteria). A keystone species has an effect far beyond its numbers; the tiger is both a flagship and an umbrella species; lichens indicate clean air; water hyacinth, Lantana and Parthenium are invasive species in India. An ecotone such as a mangrove belt often holds more species than either neighbouring community, the edge effect.

ಜೈವಿಕ ಭೂರಾಸಾಯನಿಕ ಚಕ್ರ ಎರಡು ಬಗೆ: ಗಾಳಿಯಲ್ಲಿ ಸಂಗ್ರಹ ಇರುವವು (ಕಾರ್ಬನ್, ಸಾರಜನಕ), ಬಂಡೆಯಲ್ಲಿ ಸಂಗ್ರಹ ಇರುವವು (ರಂಜಕ, ಗಂಧಕ). ದ್ವಿದಳ ಬೆಳೆಗಳ ಬೇರುಗಳು ಸಾರಜನಕ ಹಿಡಿಯುತ್ತವೆ. ಗೊಬ್ಬರದ ನೀರು ಕೆರೆ ಸೇರಿದರೆ ಪೋಷಕಾಂಶ ಅತಿಶಯ ಉಂಟಾಗಿ ಮೀನು ಸಾಯುತ್ತವೆ; ಕಲ್ಲಿದ್ದಲಿನ ಹೊಗೆ ಆಮ್ಲ ಮಳೆ ತರುತ್ತದೆ. ಜಲಚಕ್ರ ಎಲ್ಲವನ್ನೂ ಜೋಡಿಸುತ್ತದೆ. (→ English: biogeochemical cycle; eutrophication · हिन्दी: जैव भू-रासायनिक चक्र; सुपोषण)

In exam EnglishEach biogeochemical cycle is either gaseous, with its main store in the air or ocean (carbon, nitrogen), or sedimentary, with its main store in rocks (phosphorus, which has no significant gas phase, and sulphur, which does). Photosynthesis takes carbon out of the air and respiration returns it; burning fossil fuels and clearing forests add more than sinks absorb. Nitrogen is fixed by Rhizobium, Azotobacter, cyanobacteria, lightning and industry, then passes through ammonification, nitrification by Nitrosomonas and Nitrobacter, assimilation and denitrification. Excess nitrogen and phosphorus cause eutrophication; sulphur dioxide causes acid rain; the sun-driven water cycle links them all.
Ecology basics at a glance
IdeaKey pointName or example
Energy flowOne way; about 10% passes up each levelLindeman, 1942
PyramidsEnergy never inverted; number and biomass can beElton, 1927
BiomagnificationHighest at the top of the chainDDT, mercury (Minamata)
SuccessionPrimary slow (no soil), secondary fasterLichens on rock; climax community
Interactions+/+, +/0, +/−, −/−, 0/−Fig and wasp; orchid; Cuscuta; Penicillium
Species rolesKeystone, flagship, umbrella, indicator, invasiveSea otter; tiger; lichens; water hyacinth
CyclesGaseous (C, N) vs sedimentary (P, S)Phosphorus has no gas phase

Exam traps

Recap

Practice questions

Q1. Which one of the following is a detritivore rather than a decomposer?

  1. Bacteria
  2. Fungi
  3. Earthworm
  4. Actinomycetes
Show answer

Answer: C. Earthworm

The earthworm eats dead matter and breaks it into pieces, so it is a detritivore. Bacteria, fungi and actinomycetes are microbes that break dead matter down chemically, so they are decomposers.

Q2. Consider the following statements:
1. The pyramid of energy can be inverted in an open-sea ecosystem.
2. The pyramid of number can be inverted when one tree supports many insects.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: B. 2 only

Statement 1 is wrong: the energy pyramid is always upright (the open sea inverts the biomass pyramid). Statement 2 is correct. So '1 only', 'both' and 'neither' are wrong.

Q3. If the producers of an ecosystem fix 20,000 units of energy, about how much will reach the second carnivores according to the ten per cent law?

  1. 2,000 units
  2. 200 units
  3. 20 units
  4. 2 units
Show answer

Answer: C. 20 units

Herbivores get about 2,000, first carnivores about 200 and second carnivores about 20. 2,000 and 200 stop too early in the chain, and 2 is one step too far.

Q4. Which one of the following is most likely to show the highest concentration of DDT in a lake ecosystem?

  1. Phytoplankton
  2. Zooplankton
  3. Small fish
  4. Fish-eating birds
Show answer

Answer: D. Fish-eating birds

DDT builds up at each step of the chain, so the top predator, the fish-eating bird, carries the most. Phytoplankton, zooplankton and small fish sit lower in the chain and hold less.

Q5. Consider the following statements:
1. Secondary succession is generally faster than primary succession.
2. The climax community is the first community to colonise a bare area.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct because soil already exists. Statement 2 is wrong: the first colonisers are pioneers; the climax is the final, stable stage. So '2 only', 'both' and 'neither' are wrong.

Q6. Match the species roles with the examples:
A. Keystone 1. Lichens in clean air
B. Indicator 2. Water hyacinth
C. Invasive 3. Sea otter
Select the correct answer using the code given below:

  1. A-3, B-1, C-2
  2. A-1, B-3, C-2
  3. A-3, B-2, C-1
  4. A-2, B-1, C-3
Show answer

Answer: A. A-3, B-1, C-2

The sea otter is the classic keystone, lichens indicate air quality, and water hyacinth is invasive. The other codes swap keystone with indicator, indicator with invasive, or keystone with invasive.

Q7. Consider the following statements:
1. The carbon cycle is a gaseous cycle.
2. The phosphorus cycle is a sedimentary cycle.
3. The sulphur cycle has no gaseous stage.
Which of the statements given above is/are correct?

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3
Show answer

Answer: A. 1 and 2 only

Statements 1 and 2 are correct. Statement 3 is wrong: sulphur enters the air as sulphur dioxide and hydrogen sulphide. So every option containing 3 is wrong.

Q8. The conversion of nitrate back into nitrogen gas, which occurs mainly in waterlogged soils, is called

  1. nitrification
  2. ammonification
  3. denitrification
  4. nitrogen fixation
Show answer

Answer: C. denitrification

Denitrification returns nitrate to the air as N2. Nitrification makes nitrate from ammonia, ammonification makes ammonia from dead matter, and fixation turns N2 into usable compounds, the opposite direction.

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