Part 1 – Population Attributes: Size, Density, Natality, Mortality
Chapter 11 – Organisms and Populations
Subtopic Breakdown (based on NCERT, with exclusions applied)
- Population Attributes
- Population density
- Population size and measurement methods
- Natality (birth rate), Mortality (death rate)
- Age distribution (pyramids)
- Population Growth Models
- Exponential growth
- Logistic growth
- Carrying capacity
- Population Interactions
- Predation
- Parasitism
- Competition
- Commensalism
- Mutualism
Division into 8 Parts (25 MCQs each)
- Part 1: Population attributes – size, density, natality, mortality
- Part 2: Population attributes – age distribution, growth rates
- Part 3: Population growth – exponential model
- Part 4: Population growth – logistic model & carrying capacity
- Part 5: Population interactions – Predation
- Part 6: Population interactions – Parasitism
- Part 7: Population interactions – Competition
- Part 8: Population interactions – Mutualism & Commensalism
Part 1 – Population Attributes: Size, Density, Natality, Mortality
Q1.
The basic unit of ecology that evolves is:
a) Individual
b) Population
c) Community
d) Ecosystem
Answer: b) Population
Explanation:
- (a) Individual → Does not evolve, only shows adaptations.
- (b) Correct → Populations evolve as gene frequencies change.
- (c) Community → Interaction of populations, not unit of evolution.
- (d) Ecosystem → Includes abiotic factors, not basic evolutionary unit.
Q2.
Population density can be defined as:
a) Number of organisms in an ecosystem
b) Number of organisms per unit area or volume
c) Total biomass of a community
d) Number of species in a habitat
Answer: b) Number of organisms per unit area or volume
Explanation:
- (a) Ecosystem → Broader.
- (b) Correct → Density = individuals/area (terrestrial) or /volume (aquatic).
- (c) Biomass → Not density.
- (d) Number of species → Species richness, not density.
Q3.
Which method is most suitable for estimating population density of trees?
a) Quadrat sampling
b) Capture-recapture method
c) Line transect
d) Point count
Answer: a) Quadrat sampling
Explanation:
- (a) Correct → Quadrat is used for stationary organisms like plants.
- (b) Capture-recapture → Used for mobile animals.
- (c) Line transect → Used for large animals (e.g., tigers).
- (d) Point count → Birds, not trees.
Q4.
Which method is used to estimate tiger populations in forests?
a) Quadrat
b) Capture-recapture method
c) Line transect method
d) Biomass estimation
Answer: c) Line transect method
Explanation:
- (a) Quadrat → Plants.
- (b) Capture-recapture → Fish, deer.
- (c) Correct → Line transect used for large mammals.
- (d) Biomass → Productivity, not numbers.
Q5.
Birth rate (natality) in population ecology is expressed as:
a) Number of births per total population
b) Number of births per unit area
c) Number of births per unit time per unit population
d) Total number of new organisms
Answer: c) Number of births per unit time per unit population
Explanation:
- (a) Incorrect → Doesn’t account for time.
- (b) Incorrect → Area not used.
- (c) Correct → Natality = births/time/population.
- (d) Incorrect → Just a count, not a rate.
Q6.
Mortality refers to:
a) Rate of immigration
b) Number of individuals leaving population
c) Death rate per unit population per unit time
d) Decline in growth rate
Answer: c) Death rate per unit population per unit time
Explanation:
- (a) Immigration → Arrival, not death.
- (b) Leaving population → Emigration.
- (c) Correct → Mortality = deaths/time/population.
- (d) Growth rate → Affected but not definition.
Q7.
Which of the following is NOT a population attribute?
a) Birth rate
b) Death rate
c) Age distribution
d) Body size of individuals
Answer: d) Body size of individuals
Explanation:
- (a) Natality → Population attribute.
- (b) Mortality → Population attribute.
- (c) Age distribution → Population attribute.
- (d) Correct → Body size belongs to individuals, not populations.
Q8.
The technique used to estimate fish population in a lake is:
a) Quadrat
b) Capture-recapture method
c) Line transect
d) Satellite imaging
Answer: b) Capture-recapture method
Explanation:
- (a) Quadrat → Stationary organisms.
- (b) Correct → Capture, mark, release, recapture is used for fish.
- (c) Line transect → Large terrestrial animals.
- (d) Satellite → Used for forests, not fish.
Q9.
In a population study, 100 fish were caught, marked and released. Later, 100 fish were captured, 20 of which were marked. What is the estimated population size?
a) 200
b) 400
c) 500
d) 1000
Answer: c) 500
Explanation:
Formula: N = (n1 × n2) / n3
- n1 = 100 marked initially
- n2 = 100 captured later
- n3 = 20 recaptured marked
So N = (100 × 100) / 20 = 500.
Q10.
Which attribute shows whether a population is growing, stable or declining?
a) Age distribution
b) Natality
c) Mortality
d) Density
Answer: a) Age distribution
Explanation:
- (a) Correct → Shape of age pyramid indicates growth/stability/decline.
- (b) Natality → Only birth rate, not full picture.
- (c) Mortality → Only death rate, not full.
- (d) Density → Doesn’t indicate trends.
Q11.
Which type of age pyramid indicates a stable population?
a) Triangular
b) Bell-shaped
c) Urn-shaped
d) Rectangular
Answer: b) Bell-shaped
Explanation:
- (a) Triangular → Expanding population.
- (b) Correct → Bell = stable.
- (c) Urn-shaped → Declining population.
- (d) Rectangular → Not standard ecological term.
Q12.
An age pyramid with broad base and narrow top represents:
a) Declining population
b) Expanding population
c) Stable population
d) Balanced population
Answer: b) Expanding population
Explanation:
- (a) Declining → Urn-shaped.
- (b) Correct → Broad base = high birth rate = expansion.
- (c) Stable → Bell-shaped.
- (d) Balanced → Same as stable.
Q13.
A population with more post-reproductive individuals than pre-reproductive individuals will:
a) Increase
b) Decrease
c) Remain constant
d) Show exponential growth
Answer: b) Decrease
Explanation:
- (a) Increase → Only if more pre-reproductive.
- (b) Correct → More old individuals → decline.
- (c) Constant → Not possible.
- (d) Exponential → Needs many young individuals.
Q14.
Which factor increases population size?
a) Mortality
b) Emigration
c) Immigration
d) Aging
Answer: c) Immigration
Explanation:
- (a) Mortality → Decreases.
- (b) Emigration → Decreases.
- (c) Correct → Immigration increases size.
- (d) Aging → Leads to decline.
Q15.
Which equation correctly represents change in population size?
a) ΔN = (B + I) – (D + E)
b) ΔN = (B – D) + (I × E)
c) ΔN = (B × D) + (I × E)
d) ΔN = B – I – D + E
Answer: a) ΔN = (B + I) – (D + E)
Explanation:
- (a) Correct → Births + Immigration increase; Deaths + Emigration decrease.
- (b, c, d) Incorrect → Wrong operations.
Q16.
Which is a density-independent factor affecting population size?
a) Food supply
b) Predation
c) Flood
d) Disease
Answer: c) Flood
Explanation:
- (a) Food supply → Density-dependent.
- (b) Predation → Density-dependent.
- (c) Correct → Flood affects populations regardless of density.
- (d) Disease → More severe at high density.
Q17.
Which of the following is NOT included in demographic studies of populations?
a) Natality
b) Mortality
c) Age distribution
d) Genome sequencing
Answer: d) Genome sequencing
Explanation:
- (a) Natality → Yes.
- (b) Mortality → Yes.
- (c) Age distribution → Yes.
- (d) Correct → Genomes studied in genetics, not demography.
Q18.
In ecology, natality can be of two types:
a) Absolute and relative
b) Intrinsic and extrinsic
c) Realized and fundamental
d) Absolute and realized
Answer: a) Absolute and relative
Explanation:
- (a) Correct → Absolute = total births; Relative = per unit time/population.
- (b) Intrinsic/extrinsic → Factors in niche.
- (c) Realized/fundamental → Niches, not natality.
- (d) Absolute/realized → Wrong pair.
Q19.
Mortality measured by the number of deaths in a given population per 1000 individuals per year is called:
a) Absolute mortality
b) Relative mortality
c) Crude death rate
d) Specific mortality
Answer: c) Crude death rate
Explanation:
- (a) Absolute → Total deaths.
- (b) Relative → Per unit population/time.
- (c) Correct → Crude death rate used in demography.
- (d) Specific → Not standard ecological term.
Q20.
Which is NOT a method of estimating population density?
a) Capture-recapture method
b) Quadrat sampling
c) Satellite imaging
d) DNA fingerprinting
Answer: d) DNA fingerprinting
Explanation:
- (a) Yes → Used.
- (b) Yes → Used.
- (c) Yes → Used in modern ecology.
- (d) Correct → DNA fingerprinting not for density.
Q21.
Which pyramid is most likely to be observed in a developed country like Japan?
a) Expanding
b) Stable
c) Declining
d) Fluctuating
Answer: c) Declining
Explanation:
- (a) Expanding → Seen in developing countries.
- (b) Stable → Population replacement.
- (c) Correct → Japan has more old than young.
- (d) Fluctuating → Not standard term.
Q22.
If immigration and emigration are equal, then population growth depends on:
a) Birth rate only
b) Death rate only
c) (Birth rate – Death rate)
d) (Birth rate + Death rate)
Answer: c) (Birth rate – Death rate)
Explanation:
- (a) Incorrect → Death rate matters too.
- (b) Incorrect → Birth rate matters too.
- (c) Correct → Net growth depends on difference.
- (d) Incorrect → Addition is irrelevant.
Q23.
Population density is not meaningful for which group of organisms?
a) Mammals
b) Birds
c) Microorganisms
d) Humans
Answer: c) Microorganisms
Explanation:
- (a) Mammals → Meaningful.
- (b) Birds → Yes.
- (c) Correct → Difficult due to huge numbers and distribution.
- (d) Humans → Population density is standard measure.
Q24.
Which is true for an expanding population?
a) Natality > Mortality
b) Mortality > Natality
c) Natality = Mortality
d) Immigration = Emigration
Answer: a) Natality > Mortality
Explanation:
- (a) Correct → More births → growth.
- (b) Incorrect → Decline.
- (c) Incorrect → Stable.
- (d) Incorrect → Migration balance does not determine expansion directly.
Q25.
Which pyramid indicates a declining population?
a) Broad base, narrow top
b) Bell-shaped
c) Urn-shaped
d) Triangular
Answer: c) Urn-shaped
Explanation:
- (a) Broad base → Expanding.
- (b) Bell → Stable.
- (c) Correct → Urn-shaped indicates fewer young.
- (d) Triangular → Expanding.
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