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100 questions in this collection · Page 1 of 10
Question 1 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding Prof. Ramdeo Misra:
I. He obtained his Ph.D. in Ecology from Leeds University in the UK under Prof. W. H. Pearsall. II. He established ecology teaching and research at the Department of Botany of the Banaras Hindu University, Varanasi. III. His research laid the foundations for understanding tropical communities and their succession, environmental responses of plant populations, and productivity and nutrient cycling. IV. He was instrumental in establishing the National Committee for Environmental Planning and Coordination in 1972, which later paved the way for the establishment of the Ministry of Environment and Forests in 1984.
Which of the statements given above are correct?
All four statements are correct. Prof. Ramdeo Misra is regarded as the Father of Ecology in India. He completed his Ph.D. under Prof. W. H. Pearsall, established ecology teaching and research at BHU, contributed significantly to tropical ecology, and played an important role in establishing the National Committee for Environmental Planning and Coordination (1972), which later paved the way for the Ministry of Environment and Forests (1984).
Question 2 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements about biological organization and ecology:
I. Ecology is basically concerned with four levels of biological organization: macromolecules, cells, tissues, and organs. II. Although an individual organism has to cope with a changed environment, it is at the population level that natural selection operates to evolve desired traits. III. All organisms, while remaining individuals, interact with other organisms and physical habitats as a group and behave like organized wholes. IV. Biomes represent a level of biological organization with which ecology is basically concerned.
Which of the statements given above are correct?
Statement I is incorrect because ecology is basically concerned with four levels of biological organization: organisms, populations, communities, and biomes. Statements II, III, and IV are correct.
Question 3 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding population attributes:
I. An individual is characterized by births and deaths, whereas a population is characterized by birth rates and death rates. II. In a population, birth and death rates refer to per capita births and deaths. III. If 4 fruit flies in a laboratory population of 40 died during a week, the death rate is 0.1 individuals per fruit fly per week. IV. If a pond had 20 lotus plants last year and 8 new plants are added through reproduction, the birth rate is 0.4 offspring per lotus per year.
Which of the statements given above are correct?
All statements are correct. Population attributes such as birth rate and death rate are measured on a per capita basis. The calculated death rate is 4/40 = 0.1 individuals per fruit fly per week, and the birth rate is 8/20 = 0.4 offspring per lotus per year.
Question 4 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements concerning sex ratio and age pyramids:
I. An individual organism has a sex ratio, while a population can only be male or female. II. For the human population, age pyramids generally show the age distribution of males and females in a single diagram. III. The shape of the age pyramid reflects the growth status of the population, indicating whether it is growing, stable, or declining. IV. A declining human population pyramid is typically characterized by a very broad base of pre-reproductive individuals.
Which of the statements given above are correct?
Statement I is incorrect because an individual is either male or female, whereas a population has a sex ratio. Statement IV is incorrect because a broad base of pre-reproductive individuals indicates a growing population, not a declining one.
Question 5 of 100
📘 CLASS XII
Organisms And Populations
Consider the statements regarding population density (N):
I. Total number of individuals is always the most easily adoptable and meaningful measure of population size in nature. II. In an area with 200 carrot grass (Parthenium hysterophorus) plants and a single huge banyan tree, the percent cover or biomass is a more meaningful measure of population size. III. For certain ecological investigations, relative densities (like the number of fish caught per trap) serve the purpose equally well as absolute densities. IV. The tiger census in national parks and tiger reserves is often based on indirect estimations such as pug marks and fecal pellets.
Which of the statements given above are correct?
Statement I is incorrect because the total number of individuals is not always the most meaningful measure. In many situations, biomass, percent cover, or relative density provide better estimates of population size. Statements II, III, and IV are correct.
Question 6 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding the factors influencing population growth:
I. The density of a population in a given habitat fluctuates due to changes in four basic processes: natality, mortality, immigration, and emigration. II. Under normal conditions, immigration and emigration are the most important factors influencing population density. III. If a new habitat is just being colonized, immigration may contribute more significantly to population growth than birth rates. IV. The equation Nt+1 = Nt + [(B + I) - (D + E)] represents the population density at time t+1.
Which of the statements given above are correct?
Statement II is incorrect because under normal conditions, natality and mortality are the most important factors affecting population density. Immigration and emigration become important under special situations such as colonization.
Question 7 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding exponential growth:
I. Exponential or geometric growth occurs when resources (food and space) in the habitat are unlimited. II. In the exponential growth equation, r represents the intrinsic rate of natural increase. III. The r value for the Norway rat is 0.12, and for the flour beetle it is 0.015. IV. In 1981, the r value for the human population in India was 0.0205.
Which of the statements given above are correct?
Statement III is incorrect because the values are reversed. The intrinsic rate of natural increase (r) is 0.015 for the Norway rat and 0.12 for the flour beetle. Statements I, II, and IV are correct.
Question 8 of 100
📘 CLASS XII
Organisms And Populations
Read the following mathematical statements describing exponential growth:
I. The change in population size N during a unit time period t is expressed as dN/dt = (b - d) × N. II. If (b - d) = r, the equation becomes dN/dt = rN. III. The integral form of the exponential growth equation is Nt = N0ert. IV. Plotting N in relation to time t for exponential growth results in a sigmoid (S-shaped) curve.
Which of the statements given above are correct?
Statement IV is incorrect because exponential growth results in a J-shaped curve, whereas a sigmoid (S-shaped) curve is characteristic of logistic growth. Statements I, II, and III are correct.
Question 9 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding carrying capacity:
I. No population in nature has unlimited resources to permit exponential growth indefinitely, leading to competition for limited resources. II. A given habitat has enough resources to support a maximum possible number of individuals of a species, beyond which no further growth is possible. III. This limit of resources is called nature's carrying capacity (K) for that species in that habitat. IV. In a habitat at carrying capacity, the population growth rate (dN/dt) reaches its maximum positive value.
Which of the statements given above are correct?
Statement IV is incorrect because when population density (N) reaches the carrying capacity (K), the population growth rate dN/dt becomes zero, not maximum. Statements I, II, and III are correct.
Question 10 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding logistic growth:
I. Verhulst-Pearl Logistic Growth is described by the equation dN/dt = rN[(K - N)/K]. II. A population growing in a habitat with limited resources shows an initial lag phase, followed by phases of acceleration and deceleration, and finally an asymptote. III. The logistic growth model is considered more realistic because resources for growth for most animal populations are finite and become limiting sooner or later. IV. A plot of N in relation to time t under resource limitation results in a J-shaped curve.
Which of the statements given above are correct?
Statement IV is incorrect because logistic growth results in a sigmoid (S-shaped) curve, whereas a J-shaped curve is characteristic of exponential growth. Statements I, II, and III are correct.