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Practice population-ecology with 20 free MCQ questions covering environment-and-ecology. Detailed explanations in English and Hindi, perfect for UPSC, SSC, and competitive exam preparation.
Attempt the quiz above first, then review every question with its correct answer and a short explanation below.
Q1.Which of the following processes leads to an increase in population density?
Explanation: NCERT Class 12 Biology Chapter 13 states: 'Natality (B) and Immigration (I) contribute to an increase in population density, while Mortality (D) and Emigration (E) contribute to a decrease.'
Q2.If a new habitat is just being colonized, which of the following processes may contribute more significantly to population growth than birth rates?
Explanation: NCERT notes: 'Under normal conditions, births and deaths are the most important factors influencing population density... But if a new habitat is just being colonized, immigration may contribute more significantly to population growth than birth rates.'
Q3.Under unlimited resource conditions, a population exhibits which type of growth curve?
Explanation: When resources (food and space) in the habitat are unlimited, each species has the ability to realize fully its innate potential to grow in number, leading to exponential or geometric growth, resulting in a J-shaped curve (NCERT Chapter 13).
Q4.Which of the following equations represents the exponential growth model of a population?
Explanation: As per NCERT, the differential equation for exponential growth is dN/dt = (b - d)N. If (b - d) is substituted as 'r' (intrinsic rate of natural increase), the equation becomes dN/dt = rN.
Q5.In the exponential growth equation, what does the parameter 'r' represent, which is a key measure of the biotic potential of a species?
Explanation: NCERT Class 12 Biology states that 'r' is called the 'intrinsic rate of natural increase' and is a very important parameter chosen for assessing impacts of any biotic or abiotic factor on population growth.
Q6.Which of the following is the correct integral form of the exponential growth equation?
Explanation: NCERT Chapter 13 defines the integral form of exponential growth as: Nt = N0 * e^(rt), where Nt = population density at time t, N0 = population density at time zero, r = intrinsic rate of natural increase, and e = base of natural logarithms (2.71828).
Q7.Match the following historical 'r' values (intrinsic rate of natural increase) documented in NCERT Class 12 Biology with their correct organisms:
Explanation: NCERT Chapter 13 provides these values: 'For the Norway rat the r is 0.015, and for the flour beetle it is 0.12.' For the human population in India in 1981, it was 0.0205.
Q8.A population growing in a habitat with limited resources exhibits a Sigmoid (S-shaped) curve. This model of growth is known as:
Explanation: NCERT Class 12 Biology states that population growth in a limited resource environment is described by the Verhulst-Pearl Logistic Growth model, which yields a sigmoid (S-shaped) curve due to resource limitations restricting growth as density approaches carrying capacity.
Q9.The maximum population size of a species that a given environment can sustain indefinitely, given the food, habitat, water, and other necessities, is called its:
Explanation: Carrying capacity (K) represents the maximum number of individuals of a species that a habitat can support with its available resources. Beyond K, no further growth is possible because resources become limiting (NCERT).
Q10.Which of the following equations represents the Verhulst-Pearl Logistic Growth model?
Explanation: The logistic growth equation is dN/dt = rN * [(K - N)/K], where N = population density at time t, r = intrinsic rate of natural increase, and K = carrying capacity (NCERT Chapter 13).
Q11.In a logistic population growth curve (S-shaped), what is the term for the final phase where the growth rate stabilizes as the population size reaches Carrying Capacity?
Explanation: NCERT Class 12 Biology defines the phases of logistic growth: lag phase, acceleration phase, deceleration phase, and finally an asymptote, when the population density reaches the carrying capacity (N = K).
Q12.Why is the logistic growth model considered more realistic than the exponential growth model in nature?
Explanation: NCERT notes: 'Since resources for growth for most animal populations are finite and become limiting sooner or later, the logistic growth model is considered a more realistic one.' Unlimited resources are rarely present in nature.
Q13.When a population size exceeds its carrying capacity due to temporary factors, it often experiences a rapid and steep collapse. This ecological event is called a:
Explanation: A population crash occurs when a population growing exponentially shoots past its carrying capacity, leading to severe resource depletion, starvation, or disease, causing a rapid collapse of the population (often seen in seasonal insects or algal blooms).
Q14.Species that produce large numbers of small-sized offspring, have short life spans, and show rapid development (like oysters and insects) are classified as:
Explanation: r-selected species are adapted to maximize growth rates. They produce many small offspring, provide little to no parental care, and exhibit high growth rates under unstable or temporary conditions. In contrast, K-selected species (like elephants, humans) produce few large offspring with high parental care in stable environments.
Q15.Under the rules of natural selection, organisms evolve to maximize their reproductive fitness, also known as:
Explanation: NCERT Class 12 Biology states: 'Organisms behave in this way to maximise their reproductive fitness, also called Darwinian fitness (high r value), in the habitat in which they live.'
Q16.Which of the following organisms breeds only once in its lifetime (semelparous) and then dies, as part of its life history strategy?
Explanation: NCERT documents life history variations: 'Some organisms breed only once in their lifetime (Pacific salmon fish, bamboo) while others breed many times during their lifetime (most birds and mammals).'
Q17.Which pairing correctly matches the reproductive strategy of producing small offspring in large numbers with the organism?
Explanation: NCERT states: 'Some produce a large number of small-sized offspring (oysters, pelagic fishes) while others produce a small number of large-sized offspring (birds, mammals).'
Q18.The sum of all limiting factors (such as food shortages, space limits, disease, predation) that prevent a population from growing exponentially is called:
Explanation: Environmental resistance consists of all the abiotic and biotic limiting factors that prevent a population from achieving its maximum potential growth (biotic potential). It is mathematically represented in the logistic growth equation as the term (K-N)/K.
Q19.When N is very small compared to K, the term [(K-N)/K] is close to 1, meaning that the population growth is:
Explanation: In the logistic equation dN/dt = rN * [(K-N)/K], if N is very small, then (K-N)/K is approximately (K/K) = 1. Thus, the equation simplifies to dN/dt = rN, which is the equation for exponential growth.
Q20.If a population density (N) reaches exactly carrying capacity (K), what will be the rate of population change (dN/dt)?
Explanation: In the logistic equation, if N = K, then the term [(K-N)/K] becomes [(K-K)/K] = 0. Therefore, dN/dt = rN * 0 = 0. The population size stops changing and remains stable (at the asymptote phase).
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