UGC NET — Environmental Sciences (subject code 89) · India · National Testing Agency for the University Grants Commission
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
UGC NET Environmental Sciences — Unit 3 (environmental biology)
Ecological concepts and principles (niche, competitive exclusion, laws of limiting factors), population and community ecology, IVI and diversity indices, succession, nutrient cycles and biomes, often as matching and assertion–reason items.
How our questions for UGC NET spread across the units of Ecology & Ecosystem Science. Difficulty: 0 easy, 42 medium, 32 hard.
| Community structure, diversity and dominance | 7 | |
| Energy flow, ecological efficiency and ecological pyramids | 7 | |
| Habitat, niche and the competitive exclusion principle | 6 | |
| Species interactions: competition, predation, mutualism, parasitism | 6 | |
| Ecological succession: primary, secondary, climax concepts | 6 | |
| Primary and secondary productivity | 6 | |
| Stability, resistance and resilience of ecosystems | 6 | |
| Population characteristics: density, natality, mortality, age structure | 5 | |
| Ecosystem structure and function; trophic levels, food chains and webs | 5 | |
| Biogeochemical cycles: carbon, nitrogen, phosphorus, sulphur, water | 5 | |
| Biomes of the world: forest, grassland, desert, tundra, aquatic | 5 | |
| Levels of ecological organisation; autecology and synecology | 4 | |
| Population growth: exponential, logistic, r- and K-selection | 4 | |
| Agroecosystems compared with natural ecosystems | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
In the logistic model, at what population size is the growth rate (dN/dt) greatest?
B. At K/2
dN/dt = rN(1 − N/K) peaks at N = K/2, the basis of maximum sustainable yield.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Mycorrhizal associations benefit plants chiefly by
D. better phosphorus and water uptake for plant sugars
Mycorrhizal fungi extend root reach, especially for phosphorus and water; nitrogen fixation is by rhizobia and others.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
The importance value index (IVI) of a species in a forest is calculated as
D. relative density + frequency + dominance
IVI sums three relative measures, so all species' IVIs total 300.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Which mechanism of succession, in Connell and Slatyer's (1977) models, involves early species making conditions more suitable for later species?
C. Facilitation
In facilitation early colonists modify the environment (for example building soil) to aid later species; tolerance and inhibition work differently.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
According to the Millennium Ecosystem Assessment (2005), pollination and water purification are
C. regulating services
Regulating services include pollination, climate and flood regulation and water purification; provisioning covers food and water.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
A single large tree supporting thousands of insects gives which type of pyramid of numbers?
B. Inverted
One producer supports many herbivores, so the number pyramid is inverted at its base.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Which nutrient most commonly limits productivity in freshwater lakes?
B. Phosphorus
Phosphorus is typically limiting in freshwater; nitrogen more often in marine systems.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
In a stratified temperate lake in summer, the layer where temperature falls rapidly with depth is the
A. thermocline, or metalimnion
The epilimnion is the warm upper layer, the hypolimnion the cold bottom layer, and the thermocline between them.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
What did David Tilman's Cedar Creek grassland experiments show?
A. Diverse plots had steadier biomass and resisted drought
Higher diversity stabilised community biomass and improved drought resistance, consistent with the insurance hypothesis.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
What does the insurance hypothesis propose?
C. Species respond differently, so diversity sustains function
Functional redundancy and response diversity buffer ecosystems against fluctuations.
Further reading: See the manual sources: standard ecology textbooks (Odum, Begon et al., Krebs) and the original studies named in the explanation
Ten here, 74 in the app. The Laisha app has every practice question we have written to UGC NET 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.
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