CBSE Class 12 Biology Organisms and Populations MCQs Set F

Question: A behavioral strategy of adaptation called echolocation is found in –
a) Bats
b) Butterfly
c) Praying mantis
d) Arctic tern
Answer: a

Question: Which one of the following is incorrect?
a) Biological control methods adopted in agricultural pest control are based on the ability of the predator to regulate prey population
b) Predators also help in maintaining species diversity in a community by increasing the intensity of competition among competing prey species
c) In the rocky intertidal communities of the American Pacific Coast, the starfish Pisaster is an important predator
d) In a field experiment, when all the starfish were removed from an enclosed intertidal area, more than 10 species of invertebrates disappeared
Answer: b

Question: An “Urn” shaped population age pyramid represents –
a) Growing population
b) Static population
c) Declining population
d) Threatened population
Answer: c

Question: Logistic growth occurs when there is –
a) Asexual reproduction only
b) Sexual reproduction only
c) No inhibition from crowding
d) A fixed carrying capacity
Answer: d

Question: Some organisms reproduce only once in their lifetimes because they –
a) Invest so much in reproduction that they have insufficient reserves for survival
b) Produce so many offspring at one time that they do not need to survive longer
c) Do not have enough eggs to reproduce again
d) Do not have enough sperm to reproduce again
Answer: a

Question: Which of these is an explanation of why a population can fluctuate once it has reached carrying capacity?
a) The number of organisms decreases but never increases once it reaches carrying capacity
b) All populations experience exponential growth once they reach carrying capacity
c) A population of organisms always grows rapidly once it reaches carrying capacity
d) Limiting factors can influence the number of organisms in a population once it reaches carrying capacity
Answer: d

Question: Which of the following is correct about host-specific parasites?
a) Such parasites can parasitize only a single species of host
b) Both host and parasite tend to co-evolve
c) If the host evolves special mechanisms for rejecting the parasite, the parasite has to evolve mechanisms to counteract and neutralize them to succeed with the host species
d) All
Answer: d

Question: Carrying capacity for a population is estimated at 500; the population size is currently 400; and rmax = 0.01. What is dN/dt?
a) 0.01
b) 0.8
c) 8
d) 50
Answer: b

Question: A population with a larger proportion of older individuals than younger ones will likely –
a) Grow larger and then decline
b) Continue to grow larger indefinitely
c) Grow smaller and may stabilize at a smaller population size
d) Not experience a change in population size
Answer: c

Question: Choose the correct option –
a) Geometric growth produces a J-shaped population growth curve
b) Logistic growth occurs when resources are limiting
c) For exponential growth, the equation is N(t) = N0e^rt
d) All
Answer: d

Question: In a life table, the number of individuals alive at the beginning of the 1-year to 2-year age interval is 800. During this interval, 200 individuals die. The death rate for this interval is –
a) 0.25
b) 200
c) 800
d) 0.2
Answer: a

Question: The evolution of the animal immune system was probably driven by
a) Herbivores pushing the animals toward extinction
b) The selective pressures of parasitic and disease organisms
c) Competition between the animals and their habitats
d) Symbiosis between the animals and their predators
Answer: b

Question: Which of the following statements about competition is false?
a) It can limit the distribution of a species
b) It can limit the abundance of a species
c) It can increase the differences between species
d) It can make two species become more alike
Answer: d

Question: A country that has a stable population is characterized by an age structure that is
a) Largest among post-reproductive years
b) Largest among reproductive years
c) About the same among all groups
d) Largest among pre-reproductive years
Answer: c

Question: The level of competition between species depends on
a) Availability of resources
b) Population density
c) Group interaction of organisms
d) All of the above
Answer: d

Question: Cowbirds lay their eggs in the nests of smaller birds. The fast-developing cowbird chicks hatch first, then push the other baby chicks out of the nest as they hatch. The cowbird is classified as a
a) Pathogen
b) Parasite
c) Mutualist
d) Victim
Answer: b

Question: Statement I- National parks are meant for the welfare of the wild life.
Statement II – National parks are controlled by State Governments.
(a) Both the statements are wrong
(b) Both the statements are right
(c) Statements I is right statement II is wrong
(d) Statements II is right statement I is wrong
Answer: b

Question: Match column I with column II and select the correct option from the codes given below.
Column I Column II
A. Commensalism (i) One inhibited, other unaffected
B. Parasitism (ii) One benefitted, other unaffected
C. Mutualism (iii) Both are benefitted
D. Amensalism (iv) One benefitted, other harmed
(a) A-(iv), B-(ii), C-(iii), D-(i)
(b) A-(iii), B-(iv), C-(ii), D-(i)
(c) A-(ii), B-(iv), C-(iii), D-(i)
(d) A-(ii), B-(iv), C-(i), D-(iii)
Answer: c

Question: Which of the following is false?
I. The human liver fluke, a nematode parasite, depends on two intermediate hosts (snail and fish) to complete its life cycle.
II. The malaria parasite needs a vector (mosquito) to spread to other parasite.
III. The female mosquito is not considered parasite, however it needs our blood for reproduction.
IV. In case of brood parasitism, the eggs of parasitic birds (e.g. cuckoo) are not detected and ejected from the nest because of parasite’s eggs resemble the hosts eggs in morphology and colour.
V. A population of frogs protected from all predators would increase indefinitely.
(a) All
(b) None
(c) Only III
(d) Only V
Answer: d

Question: How many statements are correct?
a. Biomaginification is the natural ageing of a lake by nutrient enrichment of its water
b. After CFC, methane is a major cause of green house effect
c. Ozone is a secondary pollutant in troposphere
d. The thickness of the ozone is measured in Dobson unit
(a) a, b
(b) Only a
(c) c, d
(d) a, b, c
Answer: c

Question: Which one is a physiological adaptation to cold climate?
I. Small body
II. Accumulating glycerol and antifreezing proteins
III. Accumulating ice nucleating protein
IV. Hibernation
(a) Only I
(b) LlLIU
(c) IIJJI
(d) I, II, III, IV
Answer: c

Question: Which is not related to S-shaped population curve?
(a) Environmental resistance suddenly becomes effective
(b) Exponential phase is followed by decline phase
(c) Mass mort ty and population crash occurs
(d) aandc 94. Biotic potential refers to –
(a) Increase of population under optimum condition
(b) Increase of population under given condition
(c) Increase of population under natural condition
(d) Increase of population under stress condition
Answer: d

Question: Which of the following is true concerning exponential growth?
(a) No population can grow exponentially for long.
(b) Exponential growth slows down as the population nears its maximal size
(c) bacterial colonies have been observed to maintain exponential growth for over a month
(d) Exponential growth is commonly observed in large, slow-growing species such as humans and elephants 0
The population growth equation describes a population that-
(a) Grows without limits
(b) Grows rapidly at small population sizes, but whose growth rate slows and eventually stops as the population reaches the number the environment can support
(c) Rapidly overshoots the number the environment can support and then fluctuates around this number
(d) Grows very rapidly and then crashes when the environmental resources are used up
Answer: a

Case-based MCQs

Read the following text and answer the following questions on the basis of the same :
Growth of a population with time shows specific and predictable patterns. Two types of growth pattern of population are exponential and logistic growth. When resources in the habitat are unlimited each species has the ability to realize fully its innate potential to grow in number. Then the population grows in exponential fashion. When the resources are limited, growth curve shows an initial slow rate and then it accelerates and finally slows giving the growth curve which is sigmoid.

Question: The population growth is generally described by the following equation: dN/dt = rN(K – N)/K. What does ‘r’ represent in the given equation?
a) Population density at time t
b) Intrinsic rate of natural increase
c) Carrying capacity
d) The base of natural logarithm
Answer: b

Question: Identify the correct equation that represents the exponential population growth curve:
a) dN/dt = rN
b) dN/dt = rN (K-N/K)
c) Nt = N0e^rt
d) Both a and c
Answer: d

Question: Identify the incorrect statement:
a) Exponential growth occurs in organisms such as lemmings
b) Logistic growth is more realistic
c) Exponential growth has two phases: lag and log
d) In logistic growth, population passes well beyond the carrying capacity of ecosystem
Answer: d

Question: The equation that correctly represents Verhulst-Pearl logistic growth is:
a) dN/dt = rN(K-N)/K
b) dN/dt = rN/K
c) dN/dt = N(K-N)/K
d) dN/dt = r(K-N)/K
Answer: a

Question: Study the population growth curves (A and B) in the given graph and select the incorrect statement:
a) Curve ‘A’ shows exponential growth, represented by equation dN/dt = rN
b) Curve ‘B’ shows logistic growth, represented by equation dN/dt = rN(K-N)/K
c) Exponential growth curve is considered as more realistic than the logistic growth curve
d) Curve ‘A’ can also be represented by equation Nt = N0e^rt
Answer: c

Read the following text and answer the following questions on the basis of the same :
All biomes of the earth constitute the earth’s ecosystem. All flora and fauna occur in the lithosphere, atmosphere and hydrosphere along with their environments. Air, water, soil, biota, temperature and light are the major environmental factors that directly affect the flora and fauna in different geological areas of the earth.

Here is the reformatted and shuffled version of the provided questions, converted into the requested format (Question, a) Option 1, b) Option 2, c) Option 3, d) Option 4, Answer: letter). The questions have been shuffled, and the format has been standardized to match the example provided.

Question: Edaphology is concerned with the study of:
a) Soil
b) Climate
c) Biota
d) Topography
Answer: a

Question: Soil aeration is inversely proportional to:
a) Soil pore spaces
b) Diameter of soil particles
c) Water holding capacity of soil
d) None of the above
Answer: c

Question: Climate of an area depends upon:
a) Altitude of the area
b) Latitude of the area
c) Topography
d) Both a and b
Answer: d

Question: Hydrological cycle is concerned with:
a) Lithosphere
b) Hydrosphere
c) Atmosphere
d) All of these
Answer: d