ICAR AICE-JRF/SRF (PhD) — Environmental Sciences (subject 71) and Agricultural Meteorology (subject 60) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersHow organisms, populations, communities and ecosystems work: energy flow, productivity, nutrient cycles, succession and population dynamics. Every sustainability argument eventually rests on this subject.
In the exams: GATE ES Section 8 (ecology and ecosystems); ICAR AICE subject 71 Unit 1; UGC NET Environmental Sciences Unit 3 (environmental biology); GATE EY core
ICAR AICE-JRF/SRF (PhD) Environmental Sciences — Unit 1
Ecosystem structure and function, food chains and webs, pyramids, energy flow and the ten per cent law, productivity and its measurement, biogeochemical cycles, succession and climax theories, biomes, and agroecosystems.
How our questions for ICAR AICE-JRF/SRF spread across the units of Ecology & Ecosystem Science. Difficulty: 0 easy, 10 medium, 21 hard.
| Primary and secondary productivity | 5 | |
| Biogeochemical cycles: carbon, nitrogen, phosphorus, sulphur, water | 5 | |
| Agroecosystems compared with natural ecosystems | 5 | |
| Energy flow, ecological efficiency and ecological pyramids | 3 | |
| Population growth: exponential, logistic, r- and K-selection | 2 | |
| Species interactions: competition, predation, mutualism, parasitism | 2 | |
| Ecological succession: primary, secondary, climax concepts | 2 | |
| Ecosystem structure and function; trophic levels, food chains and webs | 2 | |
| Biomes of the world: forest, grassland, desert, tundra, aquatic | 2 | |
| Stability, resistance and resilience of ecosystems | 2 | |
| Levels of ecological organisation; autecology and synecology | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A fish stock follows logistic growth with r = 0.6 per year and K = 2000 tonnes. What is its maximum sustainable yield?
C. 300 tonnes per year
MSY = rK/4 = 0.6 × 2000 ÷ 4 = 300 t/yr, at a stock of K/2 = 1000 t. 1200 is rK; 600 is rK/2; 150 slips a factor of two.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Why is harvesting at the estimated maximum sustainable yield considered risky?
B. r and K are uncertain, so estimated-MSY harvests risk decline
Estimation errors and environmental variability mean MSY-based harvests have led to collapses; precautionary reference points are used instead.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Which approach introduces natural enemies from a pest's native range to control it in a new region?
C. Classical biological control
Classical biological control, such as the vedalia beetle against cottony cushion scale, imports natural enemies; conservation biocontrol protects existing ones.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Why does producing food from grain-fed livestock require far more land than producing plant foods for direct human consumption?
D. Energy is lost at the extra crop-to-animal step
Each trophic transfer passes on only a small fraction of energy, so feeding crops to animals multiplies the land needed per calorie.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
In a light–dark bottle experiment, initial dissolved oxygen is 8.0 mg/L, light bottle 9.5 mg/L and dark bottle 7.0 mg/L. What is gross primary productivity over the incubation?
A. 2.5 mg O₂/L
GPP = light − dark = 9.5 − 7.0 = 2.5. NPP = light − initial = 1.5; respiration = initial − dark = 1.0.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Global net primary productivity is about 105 Pg C per year. Roughly what share is marine?
A. About half
Field et al. (1998) estimated about 49 Pg C from oceans and 56 from land, roughly half each.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
What is net ecosystem productivity (NEP)?
A. NPP minus heterotrophic respiration
NEP = NPP − Rh; a positive NEP indicates a carbon sink.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Which traditional system retains many features of a natural ecosystem within agriculture?
B. Multistorey home gardens
Home gardens have high diversity, layered structure and nutrient recycling, resembling forests.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Ten here, 31 in the app. The Laisha app has every practice question we have written to ICAR AICE-JRF/SRF in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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