8 public questions tagged with this topic.
r-selected species focus on rapid reproduction and minimal parental care, unlike K-selected species.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Interactions - Parasitism and Commensalism
Parallel evolution occurs when species in different geographical areas evolve similar traits independently.
Ref: NCERT Class 12 Biology Chapter 6: Evolution Adaptive Radiation and Biological Evolution
The keyed exception is “Less likely to invade species-rich ecosystems.” In the context of characteristic generally not true for invasive species, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Species management must identify the demographic stage and ecological process that most strongly limits population growth. Prevention, early detection, removal, habitat manipulation, and biological control act at different points in an invasion or recovery trajectory. The remaining alternatives—“Greater phenotypic plasticity”, “High dispersal ability”, “High competitive ability”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Effective control reduces propagule pressure or population growth without causing unacceptable non-target effects. Repeated monitoring is necessary because seed banks, dormant stages, recolonization, and density-dependent compensation can reverse short-term gains. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 21
“Invasive” for high dispersal ability and competitive ability species likely become. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Species management must identify the demographic stage and ecological process that most strongly limits population growth. Prevention, early detection, removal, habitat manipulation, and biological control act at different points in an invasion or recovery trajectory. The remaining alternatives—“Endangered”, “Dominant”, “Specialist”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Effective control reduces propagule pressure or population growth without causing unacceptable non-target effects. Repeated monitoring is necessary because seed banks, dormant stages, recolonization, and density-dependent compensation can reverse short-term gains. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 21
Generalists have broad niches: they can use many resource types, occupy varied habitats, or tolerate a wide range of environmental conditions. This flexibility buffers them against fluctuations in any single resource and often helps them colonize disturbed or novel environments. Examples include omnivores with diverse diets and plants capable of growing across broad soil or light conditions. A broad niche does not mean equal performance everywhere; generalists may still have optimal conditions and may trade peak efficiency for flexibility. Specialists use a narrower set of conditions or resources and can outperform generalists within that restricted domain, but they are often more sensitive to environmental change. Reduced adaptability and limited habitat preferences therefore characterize specialization more closely, although evolutionary potential is not determined by niche breadth alone. Niche width can also differ across dimensions: an organism may be a dietary generalist but a climatic specialist. The generalist–specialist continuum is useful for predicting invasion success, extinction risk, responses to disturbance, and the degree of resource overlap with other species.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 13
“Less extinction prone” for an organism with low variability in population size is. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. The mechanism should be evaluated across both local and global scales. Local disappearance can be reversed by recolonization, whereas global extinction is irreversible and requires the loss of every surviving population. The remaining alternatives—“Highly extinction prone”, “Genetically unstable”, “Unable to adapt”—refer to different states, processes, or scales and therefore do not express the same causal relationship. 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. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7
“Narrow habitat range” for which species trait increases susceptibility to extinction. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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—“Generalized diet”, “High reproductive rate”, “High dispersal ability”—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. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.
Ref: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7
High fecundity is characteristic of many r-selected species that dominate early succession. Disturbed habitats are open, temporary, and unpredictable, so natural selection favours organisms that reproduce quickly and produce many offspring capable of reaching new patches. Seeds or propagules are often small, dispersive, and short-generation, allowing rapid population increase when light and nutrients are abundant. Investment in numerous offspring usually trades off against large body size, prolonged parental care, durable tissues, and late reproduction. Long life span and slow maturation are more often associated with species in stable, competitive later stages, although real organisms fall along continua rather than into two fixed categories. Early colonists also tend to grow fast and tolerate physical stress but may be poor competitors under shade. The “r” refers to the intrinsic rate of population increase in population models. Producing many offspring raises that potential rate, explaining mechanistically why high fecundity fits the opportunities and risks of newly disturbed successional environments.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 20
