🌸Chapter 11
Organisms & Populations
(MCQs)
MCQs: Organisms & Populations
(Set 1: 1–25)
1.
Which
of the following best defines a population?
A) Individuals of different species living in an area
B) All organisms in an ecosystem
C) Group of individuals of same species in a defined area at a given time
D) Individuals of different species competing for resources
Answer: C
Explanation: Population is a group of individuals of the same species
living in a particular area at a specific time.
2.
Population
density refers to:
A) Total number of species in a community
B) Number of individuals per unit area/volume
C) Number of individuals in a population
D) Distribution of individuals among age groups
Answer: B
Explanation: Population density is calculated as the number of
individuals per unit area or volume.
3.
Which
of the following is NOT a type of population dispersion?
A) Clumped
B) Uniform
C) Random
D) Exponential
Answer: D
Explanation: Exponential refers to growth pattern, not dispersion.
4.
A
population with individuals spaced at regular intervals is called:
A) Clumped
B) Random
C) Uniform
D) Aggregated
Answer: C
Explanation: Uniform dispersion occurs when individuals maintain a
relatively constant distance from one another.
5.
What
is carrying capacity?
A) Maximum number of species in a habitat
B) Maximum population size environment can support indefinitely
C) Minimum number of individuals needed to survive
D) Number of births per year
Answer: B
Explanation: Carrying capacity (K) is the maximum population size
that an environment can support sustainably.
6.
Which
population growth curve represents ideal, unlimited growth?
A) S-shaped
B) J-shaped
C) Logistic
D) Exponential limited
Answer: B
Explanation: J-shaped curve represents exponential growth under
ideal conditions.
7.
In
logistic growth, population growth rate decreases because:
A) Food supply is unlimited
B) Death rate decreases
C) Population reaches carrying capacity
D) Birth rate increases
Answer: C
Explanation: Logistic growth (S-shaped curve) slows as population
reaches carrying capacity.
8.
Which
of the following is an example of intraspecific competition?
A) Lion vs Hyena
B) Plants competing for sunlight
C) Tick on dog
D) Bee and flower
Answer: B
Explanation: Intraspecific competition is within the same species.
9.
Which
of the following is an example of interspecific competition?
A) Two deer competing for food
B) Plants competing for water
C) Lion and hyena competing for prey
D) Squirrels storing food
Answer: C
Explanation: Interspecific competition occurs between different
species.
10.
Population
age structure helps in predicting:
A) Carrying capacity
B) Population growth trends
C) Distribution pattern
D) Mortality rate only
Answer: B
Explanation: Age structure indicates the future growth potential
of a population.
11.
Which
age group is responsible for population growth?
A) Pre-reproductive
B) Reproductive
C) Post-reproductive
D) All age groups
Answer: B
Explanation: Reproductive individuals contribute directly to population
growth.
12.
Density-independent
factors affecting populations include:
A) Predation
B) Disease
C) Floods and natural disasters
D) Competition for food
Answer: C
Explanation: Density-independent factors affect populations regardless
of their density.
13.
An
example of clumped dispersion is:
A) Penguins in Antarctica
B) Dandelions in a field
C) Elephants in a forest
D) Oak trees in a plantation
Answer: C
Explanation: Elephants often form groups or herds, showing
clumped dispersion.
14.
Which
equation represents change in population size considering births, deaths,
immigration, and emigration?
A) N = B – D
B) ΔN = (B – D) + (I – E)
C) N = rK
D) ΔN = rN(1-N/K)
Answer: B
Explanation: The population change is ΔN = (Births – Deaths) +
(Immigration – Emigration).
15.
Mutualism
is an interaction where:
A) One species benefits, other is harmed
B) Both species benefit
C) One species benefits, other is unaffected
D) Both species are harmed
Answer: B
Explanation: Mutualism benefits both interacting species.
16.
Predation
can regulate population by:
A) Increasing prey population
B) Limiting prey population
C) Increasing competition
D) Promoting emigration
Answer: B
Explanation: Predators control the population size of prey species.
17.
Population
with a wide base in age pyramid indicates:
A) Stable population
B) Declining population
C) Expanding population
D) Zero growth population
Answer: C
Explanation: Wide base → Many young individuals → Population growth
is high.
18.
An
example of commensalism is:
A) Tick on a dog
B) Lichen
C) Cattle egret and cattle
D) Lion and deer
Answer: C
Explanation: Cattle egret benefits, while cattle are unaffected.
19.
Which
of the following is a physiological adaptation?
A) Thorns of cactus
B) Hump of camel
C) Nocturnal behavior of desert animals
D) Web-building in spiders
Answer: B
Explanation: Hump stores water and fat → internal body function
adaptation.
20.
Random
dispersion occurs when:
A) Individuals repel each other
B) Resources are uniformly distributed
C) Resources are patchy and interactions negligible
D) All individuals form groups
Answer: C
Explanation: Random dispersion occurs due to chance distribution of
resources.
21.
Which
of the following represents logistic growth?
A) Unchecked growth of bacteria in lab
B) Growth of deer population limited by forest resources
C) Human population in last 100 years
D) Exponential growth of algae in pond
Answer: B
Explanation: Logistic growth occurs when resources limit population.
22.
The
term “natality” refers to:
A) Death rate
B) Birth rate
C) Immigration
D) Population density
Answer: B
Explanation: Natality is the number of births per 1000 individuals
per year.
23.
Which
of the following is a density-dependent factor?
A) Flood
B) Fire
C) Disease
D) Earthquake
Answer: C
Explanation: Disease spreads more easily in dense populations.
24.
Which
is an example of amensalism?
A) Penicillium producing antibiotic killing bacteria
B) Lichen on tree
C) Lion eating deer
D) Bee pollinating flower
Answer: A
Explanation: One species is harmed (bacteria), other is unaffected
(Penicillium benefits indirectly).
25.
Carrying
capacity (K) depends on:
A) Number of births only
B) Number of deaths only
C) Availability of resources
D) Immigration only
Answer: C
Explanation: Carrying capacity is determined by environmental
resources like food, space, water.
26.
A
post-reproductive population mainly consists of:
A) Young individuals
B) Adults capable of reproduction
C) Old individuals beyond reproductive age
D) Only juvenile forms
Answer: C
Explanation: Post-reproductive group includes individuals too old to
reproduce, influencing population growth trends.
27.
Which
of the following species interaction harms one species but has no effect on the
other?
A) Mutualism
B) Commensalism
C) Amensalism
D) Parasitism
Answer: C
Explanation: Amensalism → one species is harmed, the other unaffected.
Example: Penicillium killing bacteria.
28.
Population
growth is zero when:
A) Birth rate = Death rate
B) Birth rate > Death rate
C) Birth rate < Death rate
D) Immigration = Emigration
Answer: A
Explanation: Zero growth occurs when natality equals mortality.
29.
An
example of parasitism is:
A) Lichen
B) Tick on dog
C) Bee on flower
D) Cattle egret and cattle
Answer: B
Explanation: Parasite (tick) benefits at the expense of host
(dog).
30.
Which
type of age pyramid indicates declining population?
A) Broad base
B) Uniform width
C) Narrow base
D) Triangular shape
Answer: C
Explanation: Narrow base → few young individuals → declining
population.
31.
Which
of the following is NOT a characteristic of a population?
A) Size
B) Density
C) Dispersion
D) Mutualism
Answer: D
Explanation: Mutualism is species interaction, not a population
characteristic.
32.
Which
factor can shift the carrying capacity (K) of an environment?
A) Natural disasters
B) Availability of resources
C) Disease
D) Competition
Answer: B
Explanation: Changes in food, water, and space can increase or
decrease carrying capacity.
33.
Exponential
population growth is usually observed in:
A) Humans in urban areas
B) Bacteria in lab culture
C) Deer in forest
D) Fish in pond with limited food
Answer: B
Explanation: Exponential growth occurs under ideal conditions with
unlimited resources.
34.
Which
is a morphological adaptation?
A) Camel storing fat in hump
B) Cactus having spines
C) Desert fox being nocturnal
D) Birds migrating seasonally
Answer: B
Explanation: Morphological adaptations are structural features
that help survival.
35.
Population
dispersion affected mostly by competition for resources is:
A) Random
B) Uniform
C) Clumped
D) None
Answer: B
Explanation: Uniform spacing occurs due to territorial behavior or
competition.
36.
Immigration
in a population results in:
A) Increase in deaths
B) Decrease in density
C) Increase in population size
D) Decrease in natality
Answer: C
Explanation: Immigration adds new individuals, increasing
population size.
37.
Emigration
is responsible for:
A) Increasing density
B) Decreasing population size
C) Increasing birth rate
D) None of the above
Answer: B
Explanation: Emigration is the movement of individuals out of a
population, reducing its size.
38.
Which
of the following is a behavioral adaptation?
A) Thorns on rose
B) Camel hump
C) Nocturnal activity in desert animals
D) Tree bark thickness
Answer: C
Explanation: Behavioral adaptations involve activity patterns or
behaviors that enhance survival.
39.
Which
interaction is beneficial to one species but does not affect the other?
A) Predation
B) Commensalism
C) Mutualism
D) Competition
Answer: B
Explanation: Commensalism → one species benefits, the other
unaffected.
40.
Example
of mutualism is:
A) Cattle egret and cattle
B) Lichen (alga + fungus)
C) Tick and dog
D) Lion and deer
Answer: B
Explanation: Lichen consists of alga and fungus benefiting each
other.
41.
Which
factor is density-independent in population regulation?
A) Predation
B) Food limitation
C) Flood
D) Disease
Answer: C
Explanation: Flood affects populations regardless of density.
42.
Population
growth rate is fastest during:
A) Lag phase
B) Log/exponential phase
C) Stationary phase
D) Decline phase
Answer: B
Explanation: Log phase (exponential growth) has maximum growth rate
due to abundant resources.
43.
Carrying
capacity is represented by which symbol?
A) N
B) K
C) r
D) G
Answer: B
Explanation: K denotes maximum population size sustainable by
environment.
44.
Which
age group has no reproductive contribution but affects resources?
A) Pre-reproductive
B) Reproductive
C) Post-reproductive
D) All groups equally
Answer: C
Explanation: Post-reproductive individuals consume resources but do
not contribute to population growth.
45.
Example
of intraspecific competition in animals:
A) Lion vs Hyena
B) Male deer fighting for mates
C) Tick on dog
D) Cattle egret and cattle
Answer: B
Explanation: Competition among same species for resources/mates
is intraspecific.
46.
The
formula ΔN = (B-D) + (I-E) is used to calculate:
A) Birth rate
B) Population change
C) Death rate
D) Growth rate per year
Answer: B
Explanation: ΔN calculates net change in population size
considering all factors.
47.
An
S-shaped growth curve is also called:
A) Exponential growth curve
B) Logistic growth curve
C) Random growth curve
D) J-shaped curve
Answer: B
Explanation: Logistic (S-shaped) curve shows growth slowing near
carrying capacity.
48.
Which
of the following is an example of predation?
A) Lichen
B) Tick on dog
C) Lion hunting deer
D) Cattle egret on cattle
Answer: C
Explanation: Predator (lion) feeds on prey (deer), regulating
population.
49.
Population
with many young individuals has:
A) Declining growth
B) Stable growth
C) Expanding growth
D) Zero growth
Answer: C
Explanation: Broad base → many pre-reproductive individuals → population
expands.
50.
Which
factor does NOT influence population growth directly?
A) Natality
B) Mortality
C) Immigration
D) Mutualism
Answer: D
Explanation: Mutualism affects interactions but does not directly
determine population growth.
51.
Which
of the following best describes clumped dispersion?
A) Individuals evenly spaced
B) Individuals scattered randomly
C) Individuals occur in groups
D) Individuals isolated
Answer: C
Explanation: Clumped dispersion occurs when individuals aggregate in
groups for resources, protection, or social reasons.
52.
Uniform
dispersion is commonly seen in:
A) Trees in forest
B) Penguins
C) Bacteria in culture
D) Herbivores in savannah
Answer: B
Explanation: Penguins maintain territorial spacing, showing
uniform distribution.
53.
Random
dispersion occurs when:
A) Resources are patchy
B) Individuals repel each other
C) Environmental conditions are uniform and interactions negligible
D) There is territoriality
Answer: C
Explanation: Random dispersion occurs due to chance placement
with no strong attraction or repulsion.
54.
Which
growth model is density-dependent?
A) Exponential growth
B) Logistic growth
C) Unlimited growth
D) All of the above
Answer: B
Explanation: Logistic growth slows as population approaches carrying
capacity, making it density-dependent.
55.
Exponential
growth occurs under:
A) Limited resources
B) Ideal conditions with unlimited resources
C) High predation
D) Harsh environment
Answer: B
Explanation: Exponential growth occurs when resources are unlimited
and environmental resistance is minimal.
56.
Which
of the following represents logistic growth?
A) J-shaped curve
B) S-shaped curve
C) Random curve
D) Exponential growth line
Answer: B
Explanation: Logistic growth forms an S-shaped curve, stabilizing
at carrying capacity.
57.
Which
of the following is an abiotic factor regulating population?
A) Predation
B) Disease
C) Food availability
D) Temperature
Answer: D
Explanation: Temperature is an abiotic factor, affecting growth
and survival.
58.
Which
of the following is a biotic factor?
A) Rainfall
B) Soil
C) Predation
D) Temperature
Answer: C
Explanation: Biotic factors include interactions with other living
organisms.
59.
Carrying
capacity can be affected by:
A) Food, water, shelter
B) Age structure
C) Dispersion pattern
D) Natality only
Answer: A
Explanation: Carrying capacity depends on resource availability.
60.
Population
regulation refers to:
A) Unchecked growth
B) Factors maintaining population around carrying capacity
C) Random dispersion
D) Age distribution
Answer: B
Explanation: Regulation maintains population size within
environmental limits.
61.
Which
of the following is an example of intraspecific competition in plants?
A) Trees of same species competing for sunlight
B) Trees of different species competing
C) Deer and elephants feeding on grass
D) Lichen growth on rocks
Answer: A
Explanation: Competition among same species for a resource is
intraspecific.
62.
Example
of interspecific competition in plants:
A) Cactus vs cactus
B) Grass vs shrubs
C) Trees of same species
D) None
Answer: B
Explanation: Competition between different species is
interspecific.
63.
Mutualism
benefits:
A) One species only
B) Both species
C) Neither
D) Only predator
Answer: B
Explanation: Both species gain benefit, e.g., lichen (alga +
fungus).
64.
Predation
helps in:
A) Increasing prey numbers
B) Regulating prey population
C) Reducing carrying capacity
D) Increasing natality
Answer: B
Explanation: Predation controls prey population and maintains
ecosystem balance.
65.
Which
of the following is an example of commensalism?
A) Tick on dog
B) Cattle egret and cattle
C) Lion and deer
D) Lichen
Answer: B
Explanation: Cattle egret benefits; cattle unaffected.
66.
Amensalism
is observed in:
A) Lichen
B) Penicillium secreting antibiotic
C) Bee and flower
D) Cattle egret and cattle
Answer: B
Explanation: Penicillium harms bacteria; Penicillium itself is
unaffected → amensalism.
67.
Which
of the following is a physiological adaptation?
A) Thorns
B) Hump of camel
C) Nocturnal behavior
D) Web-building
Answer: B
Explanation: Physiological adaptation involves internal body
functions.
68.
Nocturnal
activity in desert animals is an example of:
A) Morphological adaptation
B) Physiological adaptation
C) Behavioral adaptation
D) All of the above
Answer: C
Explanation: Behavioral adaptation is activity pattern helping
survival.
69.
Which
of the following is a density-independent factor?
A) Disease
B) Competition
C) Flood
D) Predation
Answer: C
Explanation: Floods affect populations regardless of density.
70.
Density-dependent
factors include:
A) Floods
B) Disease, food limitation, predation
C) Fire
D) Earthquake
Answer: B
Explanation: Disease, food shortage, and predation increase effect
with population density.
71.
Age
pyramids help in:
A) Calculating carrying capacity
B) Predicting population growth trends
C) Estimating mortality only
D) Dispersion patterns
Answer: B
Explanation: Age structure predicts future population growth trends.
72.
Broad-based
age pyramid indicates:
A) Declining population
B) Stable population
C) Expanding population
D) No growth
Answer: C
Explanation: Many young individuals → high reproductive potential →
expanding population.
73.
Narrow-based
age pyramid indicates:
A) Expanding population
B) Declining population
C) Stable population
D) Zero growth
Answer: B
Explanation: Fewer young → population growth slows → declining
population.
74.
Which
of the following is NOT true for exponential growth?
A) Occurs under unlimited resources
B) J-shaped curve
C) Population stabilizes at K
D) Rapid growth rate
Answer: C
Explanation: Exponential growth does not stabilize; logistic
growth stabilizes at carrying capacity.
75.
Logistic
growth differs from exponential growth because:
A) Growth is unlimited
B) Growth slows near carrying capacity
C) Birth rate always exceeds death rate
D) Population decreases immediately
Answer: B
Explanation: Logistic growth is density-dependent and slows as
population approaches K.
76.
Which
of the following is an example of intraspecific competition in animals?
A) Lion vs Hyena
B) Male deer fighting for mates
C) Tick on dog
D) Bee and flower
Answer: B
Explanation: Competition among same species for mates/resources
is intraspecific.
77.
Which
equation represents logistic population growth?
A) ΔN = rN
B) ΔN = rN(1 – N/K)
C) ΔN = B – D
D) ΔN = (B – D) + (I – E)
Answer: B
Explanation: Logistic growth considers carrying capacity (K).
78.
Which
factor contributes to density-dependent population regulation?
A) Earthquake
B) Flood
C) Food limitation
D) Fire
Answer: C
Explanation: Food limitation affects population more as density
increases.
79.
Which
of the following represents exponential growth in a graph?
A) S-shaped curve
B) J-shaped curve
C) Bell-shaped curve
D) Random curve
Answer: B
Explanation: J-shaped curve → population grows rapidly without limit.
80.
Which
interaction benefits one species and harms the other?
A) Mutualism
B) Commensalism
C) Predation
D) Amensalism
Answer: C
Explanation: Predation → predator benefits, prey is harmed.
81.
Which
of the following is an example of commensalism in plants?
A) Lichen
B) Epiphytic orchids on tree branches
C) Tick on dog
D) Lion and deer
Answer: B
Explanation: Epiphytic orchids benefit by getting support; host
tree unaffected.
82.
Which
type of population distribution occurs due to social behavior?
A) Random
B) Uniform
C) Clumped
D) All of the above
Answer: C
Explanation: Social animals like elephants form groups → clumped
dispersion.
83.
Which
factor does NOT directly affect population growth?
A) Natality
B) Mortality
C) Mutualism
D) Immigration
Answer: C
Explanation: Mutualism affects interactions but does not directly
alter population size.
84.
Which
adaptation is physiological?
A) Camel hump
B) Desert fox nocturnal behavior
C) Cactus spines
D) Bird migration
Answer: A
Explanation: Camel stores fat and water → internal physiological
function.
85.
Which
adaptation is morphological?
A) Camel hump
B) Cactus spines
C) Nocturnal desert behavior
D) Web-building
Answer: B
Explanation: Morphological adaptation involves physical structures.
86.
Which
adaptation is behavioral?
A) Thorns
B) Camel hump
C) Nocturnal activity
D) Fat storage
Answer: C
Explanation: Behavioral adaptation includes activity patterns
enhancing survival.
87.
Which
of the following is NOT a biotic factor?
A) Competition
B) Disease
C) Predation
D) Temperature
Answer: D
Explanation: Temperature is abiotic, not living organism
interaction.
88.
Which
population will have zero growth?
A) Birth rate > Death rate
B) Birth rate < Death rate
C) Birth rate = Death rate
D) Birth rate > Death rate + Immigration
Answer: C
Explanation: When natality equals mortality, population remains
stable.
89.
Carrying
capacity depends primarily on:
A) Number of predators
B) Available resources
C) Age structure
D) Birth rate only
Answer: B
Explanation: Carrying capacity (K) is determined by food, water,
shelter availability.
90.
Which
age pyramid shape represents a stable population?
A) Broad base
B) Narrow base
C) Uniform width
D) Inverted
Answer: C
Explanation: Uniform width → equal number of pre-reproductive and
reproductive individuals.
91.
Which
of the following is an example of amensalism?
A) Cattle egret and cattle
B) Penicillium killing bacteria
C) Bee and flower
D) Lion and deer
Answer: B
Explanation: Penicillium harms bacteria; it is unaffected itself
→ amensalism.
92.
Example
of mutualism in animals:
A) Oxpecker and rhinoceros
B) Tick and dog
C) Lion and deer
D) Cattle egret and cattle
Answer: A
Explanation: Both species benefit → oxpecker eats ticks, rhino is
cleaned.
93.
Which
of the following population growth phases has slow initial growth?
A) Lag phase
B) Log phase
C) Stationary phase
D) Decline phase
Answer: A
Explanation: Lag phase → population adjusts to environment before rapid
growth.
94.
Which
phase of population growth has maximum growth rate?
A) Lag phase
B) Log phase
C) Stationary phase
D) Decline phase
Answer: B
Explanation: Exponential growth occurs in log phase due to
abundant resources.
95.
Example
of density-independent factor affecting population:
A) Disease
B) Predation
C) Flood
D) Food limitation
Answer: C
Explanation: Flood affects populations regardless of density.
96.
Which
of the following is an example of density-dependent factor?
A) Flood
B) Disease
C) Fire
D) Earthquake
Answer: B
Explanation: Disease spreads faster in high-density populations.
97.
Which
of the following is a direct measure of population size?
A) Density
B) Dispersion
C) Census (Counting individuals)
D) Age pyramid
Answer: C
Explanation: Direct counting (census) measures actual number of
individuals.
98.
Which
of the following is an indirect method to estimate population size?
A) Total count
B) Quadrat sampling
C) Census
D) Direct observation
Answer: B
Explanation: Quadrat sampling estimates population indirectly,
commonly used for plants.
99.
Which
of the following population interactions involves one species living inside
another?
A) Commensalism
B) Parasitism
C) Mutualism
D) Amensalism
Answer: B
Explanation: Parasite lives on or inside the host, causing harm.
100.
Carrying
capacity (K) is usually reached when:
A) Birth rate > Death rate
B) Birth rate = Death rate
C) Death rate = 0
D) Immigration > Emigration
Answer: B
Explanation: Population stabilizes when births balance deaths,
reaching K.
✅ All 100 MCQs Complete (with answers & explanations)
These MCQs cover all major topics from NCERT Chapter
“Organisms & Populations” including:
- Population characteristics
(size, density, dispersion)
- Population growth (exponential,
logistic)
- Population regulation
(density-dependent/independent factors)
- Age structure and age pyramids
- Species interactions
(mutualism, predation, parasitism, commensalism, amensalism)
- Adaptations (morphological,
physiological, behavioral)
