8 public questions tagged with this topic.
K-selected species invest in high parental care, ensuring the survival of fewer but more competitive offspring.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Interactions - Competition - Competitive Exclusion
K-selected species produce fewer offspring, invest in parental care, and have longer lifespans.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Life History Variations and Population Interactions - Overview
Agave is a classic semelparous plant: it grows vegetatively for years, stores resources, produces one exceptionally large flowering stalk, sets seed, and then the reproductive rosette dies. The defining feature is the single reproductive event. Stable resources or repeated seasonal flowering would instead support continued maintenance and iteroparity, while juvenile care is not the relevant mechanism in this plant. The r/K framework is best treated as a continuum. At one end, rapid development and many inexpensive offspring suit transient opportunities; at the other, slower development and greater investment per offspring can improve success near environmental limits. Modern life-history theory tests the underlying trade-offs directly rather than assigning every species to a fixed box. The key idea is the direction of the trade-off or feedback, because that direction determines the population-level outcome. Field evidence should therefore be compared with the model assumptions before extending the conclusion to every species, habitat, or time period.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 12
Altricial young hatch or are born in an underdeveloped condition. They may be blind, poorly insulated, weakly mobile, or unable to feed independently, so parents must provide warmth, food, defense, or transport. Precocial young are comparatively mature and mobile soon after birth. Altriciality concerns developmental state and dependence, not whether adults reproduce once or repeatedly. The r/K framework is best treated as a continuum. At one end, rapid development and many inexpensive offspring suit transient opportunities; at the other, slower development and greater investment per offspring can improve success near environmental limits. Modern life-history theory tests the underlying trade-offs directly rather than assigning every species to a fixed box. The conclusion follows from tracking how density or age changes the rates experienced by individual organisms. Field evidence should therefore be compared with the model assumptions before extending the conclusion to every species, habitat, or time period. Interpreting the example at the appropriate population scale keeps the causal mechanism distinct from a simple correlation or an absolute rule.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 12
“High fecundity reduces lifespan” for the trade-off between fecundity and survival suggests. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Survivorship curves summarize age-specific mortality: Type I concentrates loss late in life, Type II approximates a constant hazard, and Type III concentrates loss early. They are empirical patterns, not rigid taxonomic rules. The remaining alternatives—“High reproduction = long life”, “More survival = less reproduction”, “Long life increases fecundity”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Selection favors the schedule that increases lifetime reproductive success under local mortality and resource conditions. Body size, development time, fecundity, parental investment, and generation length consequently tend to covary. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Plant Strategies and Vegetation Processes, Grime, 2nd Ed.
“More number = smaller size” for in trade-off between offspring number and size. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Survivorship curves summarize age-specific mortality: Type I concentrates loss late in life, Type II approximates a constant hazard, and Type III concentrates loss early. They are empirical patterns, not rigid taxonomic rules. The remaining alternatives—“Large number = larger size”, “Small number = smaller size”, “They are unrelated”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Selection favors the schedule that increases lifetime reproductive success under local mortality and resource conditions. Body size, development time, fecundity, parental investment, and generation length consequently tend to covary. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Plant Strategies and Vegetation Processes, Grime, 2nd Ed.
“Fecundity vs. parental care” for which of the following is a trade-off pair. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Life-history traits reflect allocation among growth, maintenance, survival, and reproduction. Energy invested in many offspring cannot simultaneously be invested in large offspring, prolonged care, or future breeding, creating measurable trade-offs. The remaining alternatives—“Growth vs. temperature”, “Longevity vs. competition”, “Dispersal vs. territory”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Survivorship curves summarize age-specific mortality: Type I concentrates loss late in life, Type II approximates a constant hazard, and Type III concentrates loss early. They are empirical patterns, not rigid taxonomic rules. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Plant Strategies and Vegetation Processes, Grime, 2nd Ed.
The keyed exception is “Show early semelparity.” In the context of which of the following is false regarding k-selected species, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Mechanistic support comes from showing how resource limitation, enemies, mate availability, or physiological stress changes demographic performance. A descriptive association alone does not establish regulation or causation. The remaining alternatives—“Low reproductive rate”, “High parental investment”, “Thrive in stable environments”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Population ecology links individual births, deaths, immigration, and emigration to changes in abundance. Per-capita rates determine the direction of change, while density dependence creates feedback when crowding alters survival or reproduction. 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: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
