8 public questions tagged with this topic.
Immigration refers to the movement of individuals into a population, increasing its size.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
High birth rates contribute to population growth, whereas emigration, mortality, and lack of resources lead to population decline.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
If birth rate and immigration exceed death rate and emigration, the population size will increase.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
Birth rate and death rate are key factors that regulate population growth and size.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
Carrying capacity is not constant; it varies based on environmental conditions and resource availability.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
“Island distance” for isolation-controlled immigration is affected by. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. The remaining alternatives—“Island size”, “Island vegetation”, “Island shape”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: The Theory of Island Biogeography, MacArthur & Wilson, Ch. 2-4
“Core-satellite metapopulation” for a population that persists due to immigration despite high local extinction rates exemplifies. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. The remaining alternatives—“Classical metapopulation”, “Nonequilibrium metapopulation”, “Continuous population”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
“Rescue effect” for immigration prevents extinction in a patch; this phenomenon is called. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. The remaining alternatives—“Founder effect”, “Genetic drift”, “Colonization effect”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. 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
