101. Which type of population growth is considered more realistic in natural habitats where resources are limited?
ⓐ. Logistic growth
ⓑ. Exponential growth
ⓒ. Geometric growth
ⓓ. Linear growth
Correct Answer: Logistic growth
Explanation: Natural populations usually do not grow indefinitely because food, space, and other resources become limiting. Logistic growth takes this environmental resistance into account and therefore gives a more realistic picture of population increase. It assumes that growth slows as the population approaches the maximum supportable size.
102. Carrying capacity of a habitat refers to
ⓐ. the minimum number of individuals needed for reproduction
ⓑ. the number of immigrants entering a population each year
ⓒ. the maximum population size that the habitat can support
ⓓ. the number of individuals added during the reproductive season
Correct Answer: the maximum population size that the habitat can support
Explanation: Carrying capacity is represented by $K$ and describes the upper limit of population size that available resources can sustain. It is not the same as the present population size or the growth rate. As a population nears this limit, further increase becomes progressively more difficult.
103. Which equation correctly represents logistic population growth?
ⓐ. $\dfrac{dN}{dt} = rN$
ⓑ. $\dfrac{dN}{dt} = K-N$
ⓒ. $\dfrac{dN}{dt} = \dfrac{r}{N}$
ⓓ. $\dfrac{dN}{dt} = rN\left(\dfrac{K-N}{K}\right)$
Correct Answer: $\dfrac{dN}{dt} = rN\left(\dfrac{K-N}{K}\right)$
Explanation: Logistic growth includes both the growth potential of the population and the limiting effect of available resources. The term $\left(\dfrac{K-N}{K}\right)$ reduces growth as population size $N$ approaches carrying capacity $K$. When the population is much smaller than $K$, growth can still be rapid.
104. Which symbol is used for carrying capacity in population ecology?
ⓐ. $N$
ⓑ. $K$
ⓒ. $r$
ⓓ. $e$
Correct Answer: $K$
Explanation: The symbol $K$ is used to denote carrying capacity, the maximum number of individuals a habitat can sustain over time. It is different from $N$, which represents population size or density, and from $r$, which represents intrinsic rate of natural increase. Using a separate symbol helps distinguish the present size from the environmental limit.
105. Which curve shape is characteristically produced by logistic growth?
ⓐ. S-shaped curve
ⓑ. J-shaped curve
ⓒ. Bell-shaped curve
ⓓ. Rectangular curve
Correct Answer: S-shaped curve
Explanation: Logistic growth gives a sigmoid or S-shaped curve because population increase does not remain rapid throughout. It begins slowly, then accelerates, and later slows again as the population approaches carrying capacity. This produces a smooth curve with an upper leveling trend.
106. In the logistic growth model, growth slows down mainly because
ⓐ. intrinsic rate of increase becomes equal to zero from the beginning
ⓑ. immigration always becomes greater than natality
ⓒ. resource limitation increases as population size approaches carrying capacity
ⓓ. the population stops reproducing after a certain size
Correct Answer: resource limitation increases as population size approaches carrying capacity
Explanation: Logistic growth assumes that environmental resources are finite. As population size rises, individuals compete more strongly for food, space, shelter, or other requirements. This growing limitation reduces the rate of increase even if reproduction continues.
107. Which statement best distinguishes logistic growth from exponential growth?
ⓐ. Logistic growth occurs only in microorganisms, whereas exponential growth occurs only in animals.
ⓑ. Logistic growth ignores resource limits, whereas exponential growth includes carrying capacity.
ⓒ. Logistic growth includes carrying capacity, whereas exponential growth assumes effectively unlimited resources.
ⓓ. Logistic growth uses only birth rate, whereas exponential growth uses only death rate.
Correct Answer: Logistic growth includes carrying capacity, whereas exponential growth assumes effectively unlimited resources.
Explanation: Exponential growth describes increase under highly favourable conditions where limitations are not effectively acting. Logistic growth, in contrast, introduces carrying capacity and shows how growth changes when resources become limiting.
108. When population size becomes equal to carrying capacity in the logistic model, the term $\left(\dfrac{K-N}{K}\right)$ becomes
ⓐ. $1$
ⓑ. $0$
ⓒ. $r$
ⓓ. $N$
Correct Answer: $0$
Explanation: If $N = K$, then the numerator $K-N$ becomes zero. As a result, the whole factor $\left(\dfrac{K-N}{K}\right)$ becomes zero, making growth rate zero in the logistic equation.
109. Assertion: Unlimited population growth cannot continue indefinitely in nature.
Reason: Environmental resources eventually become limiting for the population.
ⓐ. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
ⓑ. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
ⓒ. Assertion is true, but Reason is false.
ⓓ. Assertion is false, but Reason is true.
Correct Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Explanation: Natural environments do not offer endless food, space, and other essentials. As population size increases, these limits become more important and prevent indefinite unrestricted growth. This is exactly why logistic growth is considered more realistic than perpetual exponential increase.
110. A population grows rapidly at first, then its rate of increase slows, and finally the population stabilizes near an upper limit. This pattern is best described as
ⓐ. random fluctuation
ⓑ. exponential growth
ⓒ. negative population growth
ⓓ. logistic growth
Correct Answer: logistic growth
Explanation: This description matches the standard behaviour of logistic growth under limited resources. Early growth can still be fast when population size is well below carrying capacity, but later the increase slows. Eventually the population approaches an upper limit and tends to stabilize near it.
111. Which sequence best describes the usual course of logistic population growth?
ⓐ. Acceleration → lag phase → asymptote → deceleration
ⓑ. Lag phase → deceleration → acceleration → asymptote
ⓒ. Lag phase → acceleration → deceleration → asymptote
ⓓ. Deceleration → lag phase → asymptote → acceleration
Correct Answer: Lag phase → acceleration → deceleration → asymptote
Explanation: Logistic growth does not proceed at the same rate throughout. It often begins with a lag phase, then rises more rapidly during acceleration, and later slows during deceleration as environmental resistance increases. Finally, the curve approaches an upper limit called the asymptote.
112. In the logistic growth equation, when population size $N$ is much smaller than carrying capacity $K$, the term $\left(\dfrac{K-N}{K}\right)$ is approximately
ⓐ. $1$, so growth resembles exponential increase
ⓑ. $0$, so growth stops completely
ⓒ. $K$, so the habitat becomes unlimited
ⓓ. negative, so the population declines rapidly
Correct Answer: $1$, so growth resembles exponential increase
Explanation: When $N$ is very small compared with $K$, the difference $K-N$ is nearly equal to $K$. That makes the fraction $\left(\dfrac{K-N}{K}\right)$ close to 1. Under this condition, the logistic equation behaves almost like $\dfrac{dN}{dt} = rN$.
113. Which statement about carrying capacity is correct?
ⓐ. It is the number of individuals currently present in the habitat.
ⓑ. It is the highest possible growth rate of the population.
ⓒ. It is the maximum population size that available resources can sustain.
ⓓ. It is the number of births needed to balance deaths.
Correct Answer: It is the maximum population size that available resources can sustain.
Explanation: Carrying capacity is a property of the habitat, not simply a count of individuals present at one moment. It represents the upper limit that the environment can support over time with its available resources. A population may remain below it, approach it, or fluctuate around it.
114. If a population temporarily becomes larger than its carrying capacity, the logistic model predicts that
ⓐ. growth will continue at the same rate
ⓑ. the population will tend to decrease toward $K$
ⓒ. the carrying capacity will automatically fall to zero
ⓓ. the intrinsic rate of increase becomes permanently zero
Correct Answer: the population will tend to decrease toward $K$
Explanation: In the logistic equation, when $N$ becomes greater than $K$, the term $(K-N)$ becomes negative. As a result, $\dfrac{dN}{dt}$ becomes negative and the population tends to decline.
115. Which part of the logistic equation directly represents environmental resistance to population growth?
ⓐ. $\left(\dfrac{K-N}{K}\right)$
ⓑ. $e^{rt}$
ⓒ. $N_0$
ⓓ. $(b-d)$
Correct Answer: $\left(\dfrac{K-N}{K}\right)$
Explanation: The factor $\left(\dfrac{K-N}{K}\right)$ adjusts growth according to how close the population is to carrying capacity. When the population is far below $K$, this factor is large and growth is less restricted. As $N$ approaches $K$, the factor becomes smaller and growth slows.
116. A grassland receives improved rainfall over several years, increasing plant productivity and food availability for grazing animals. Which outcome is most likely?
ⓐ. The intrinsic rate of increase must become zero.
ⓑ. The sex ratio of the herbivore population must become equal.
ⓒ. The logistic curve must change into a J-shaped curve permanently.
ⓓ. The carrying capacity for the grazing population may increase.
Correct Answer: The carrying capacity for the grazing population may increase.
Explanation: Carrying capacity depends on how much the habitat can support using its available resources. If rainfall improves plant growth and food becomes more abundant, the environment may support a larger grazer population.
117. Which statement best explains the leveling off seen at the top of a sigmoid growth curve?
ⓐ. Immigration becomes the only process affecting population size.
ⓑ. Population size approaches the carrying capacity of the habitat.
ⓒ. Birth rate becomes greater than death rate indefinitely.
ⓓ. The population enters a phase of unrestricted exponential increase.
Correct Answer: Population size approaches the carrying capacity of the habitat.
Explanation: The upper flattening of the sigmoid curve appears when the population nears the limit that the habitat can sustain. At that stage, environmental resistance becomes strong enough to reduce further net increase. Growth does not continue unchecked because resources are no longer effectively unlimited.
118. Assertion: Logistic growth is often called the Verhulst–Pearl model.
Reason: It describes population growth under conditions where resource limitation becomes important.
ⓐ. Assertion is true, but Reason is false.
ⓑ. Assertion is false, but Reason is true.
ⓒ. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
ⓓ. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Correct Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Explanation: The logistic model is indeed commonly associated with Verhulst and Pearl. Its importance lies in the fact that it incorporates the limiting effect of resources through carrying capacity.
119. A population shows a slow beginning, then rapid increase, and finally a gradual approach to a stable upper limit. Which graph type matches this pattern?
ⓐ. J-shaped growth curve
ⓑ. Straight-line growth curve
ⓒ. S-shaped growth curve
ⓓ. Bell-shaped growth curve
Correct Answer: S-shaped growth curve
Explanation: A sigmoid or S-shaped curve is the classic graphical representation of logistic growth. The slow beginning reflects the lag phase, the middle rise shows rapid increase, and the upper flattening indicates approach to carrying capacity. This pattern differs from the J-shaped curve of exponential growth, which lacks leveling off.
120. Fill in the blank in the most accurate way:
In logistic growth, $K$ does not represent the present population size; it represents the ______ of the habitat.
ⓐ. reproductive age structure
ⓑ. immigration rate
ⓒ. per capita death rate
ⓓ. carrying capacity
Correct Answer: carrying capacity
Explanation: The symbol $K$ stands for the maximum level of population that the habitat can maintain with its available resources. It is therefore best understood as the carrying capacity of the environment. A present population may be lower than $K$, equal to it, or even temporarily above it.
