5 public questions tagged with this topic.
Birth rates are influenced by resource availability, as sufficient food and shelter support higher reproduction.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Interactions - Predation and Herbivory
Hurricanes and other natural disasters affect populations regardless of their density, making them density-independent factors.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Interactions - Predation and Herbivory
Emigration reduces population density as individuals leave the habitat, while natality and immigration increase it.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Life History Variations and Population Interactions - Overview
Population size changes through four demographic flows summarized by the BIDE accounting identity: births and immigration add individuals, whereas deaths and emigration remove them. Thus, population change over an interval is ΔN = B + I − D − E. Births recruit newly produced organisms into the population, while immigration transfers organisms into the defined study area from elsewhere. Both processes increase the census count even though only birth increases the total number of organisms in a closed regional system. Mortality and disease-associated deaths reduce abundance, and emigration is a loss from the focal population despite the emigrants remaining alive outside it. This distinction depends on the spatial boundary chosen by the investigator: movement into one local population may be emigration from another. In a genuinely closed population, immigration and emigration are absent, leaving births and deaths as the only drivers. Recognizing these signs is essential when estimating growth rate, constructing life tables, or separating local demographic performance from movement among habitat patches.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 11
The keyed exception is “Broad geographic distribution.” In the context of which of the following does not increase extinction probability, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Human-driven habitat conversion, exploitation, introduced enemies, pollution, and climate change often interact rather than acting independently. Traits such as slow reproduction or ecological specialization can magnify vulnerability. The remaining alternatives—“High degree of specialization”, “High trophic status”, “Small population size”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Extinction risk rises when abundance, geographic range, or genetic variation becomes small because demographic chance, environmental fluctuations, inbreeding, and rare catastrophes then have disproportionate effects. Correlated losses among subpopulations further weaken regional persistence. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7
