CUET UG Biology Booster Test 3-Population Attributes and Structure -

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CUET UG Biology Booster Test 3-Population Attributes and Structure

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Biology Booster Test 3-Population Attributes and Structure

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QUESTION 1 OF 20

The definition of a population includes sharing or competing for similar resources in a geographical area. Which evolutionary principle relies directly on this competitive interaction at the population level rather than the individual level?

Answer Review

1 The definition of a population includes sharing or competing for similar resources in a geographical area. Which evolutionary principle relies directly on this competitive interaction at the population level rather than the individual level?

A Asexual reproduction dominance

B Age pyramid plotting

C Natural selection operating to evolve desired traits

D Calculation of relative density

💡 Short Explanation

Competitive interaction creates selective pressure. Natural selection acts on individuals but shifts the gene pool of the population. Evolving traits over generations is a population-level evolutionary outcome.

✅ Correct Answer Explanation

Natural selection occurs because individuals within a population compete for limited resources, leading to differential reproductive success. This process shapes the population's genetic makeup over generations, which is the foundational principle of evolution by natural selection.

❓ Why Other Options Are Incorrect

Option A → This is a reproductive mode, not an evolutionary principle driven by competition.
Option B → Plotting is a descriptive statistical tool for demography, not an evolutionary principle.
Option D → Calculation of density is a demographic measurement tool, not an evolutionary process.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Identify the evolutionary process (Natural Selection) that arises from resource competition.

Final Logic: Competition drives selection, which evolves populations.

🧠 Memory Trick

"Competition → Selection → Evolution."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Population Definition

2 Match the ecological concepts to their deeper evolutionary implications as described in the text:

Column 1	Column 2
1. Interbreeding and resource sharing	P. Evolving desired traits
2. Natural selection	Q. Constituting a population
3. Coping with changed environment	R. Population ecology
4. Linking ecology to genetics	S. Individual organism's immediate challenge

A 1-S, 2-R, 3-P, 4-Q

B 1-P, 2-Q, 3-R, 4-S

C 1-Q, 2-P, 3-S, 4-R

D 1-R, 2-S, 3-Q, 4-P

💡 Short Explanation

1 defines what constitutes a population (Q). 2 is the mechanism for evolving desired traits (P). 3 is the immediate task of an individual (S). 4 is the scope of Population Ecology (R).

✅ Correct Answer Explanation

1 matches Q because these define a population. 2 matches P because natural selection is the engine of evolution. 3 matches S because organisms must respond to environmental shifts. 4 matches R because Population Ecology bridges ecology and evolutionary biology.

❓ Why Other Options Are Incorrect

Options A, B, and D → These misalign the ecological and evolutionary concepts.

🎯 Strategy

Used: Substitution

Application: Pair terms with their logical definitions.

Final Logic: C correctly links the definition of population, the mechanism of evolution, the individual's role, and the scope of the study.

🧠 Memory Trick

"Define=Pop; Select=Evolve; Cope=Individual."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Population Attributes

3 Which of the following statements does NOT accurately reflect the reproductive scope of a population in ecological studies?

A The term interbreeding strictly excludes asexual reproduction from forming populations.

B Interbreeding generally implies sexual reproduction.

C A group of asexually reproducing bacteria in a culture plate is considered a population.

D Asexual reproduction populations are evaluated using the same per capita rates as sexual ones.

💡 Short Explanation

Ecological population definitions are inclusive. Asexual groups are considered populations regardless of interbreeding. "Strict exclusion" is inaccurate in ecology.

✅ Correct Answer Explanation

Ecological studies define populations based on shared space and resource competition, not solely on sexual interbreeding. Asexual groups are routinely classified as populations, making Option A factually incorrect regarding ecological scope.

❓ Why Other Options Are Incorrect

Option B → This is a generally accepted convention.
Option C → Bacteria are a classic example of an asexual population.
Option D → Population dynamics (birth/death rates) apply across both reproductive strategies.

🎯 Strategy

Used: Extreme Word Filter

Application: The word "strictly" indicates a rigid rule often not found in ecology.

Final Logic: Ecology does not strictly exclude asexual groups; they are populations.

🧠 Memory Trick

"Ecology is inclusive."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Reproductive Scope

4 Why are all the bacteria in a culture plate considered a population even though they reproduce asexually rather than through sexual interbreeding?

A Because they are macroscopic organisms.

B Because they live in a well-defined area, share resources, and ecological studies generally consider asexual groups as populations.

C Because they possess individual sex ratios.

D Because they exhibit a declining age pyramid.

💡 Short Explanation

Population definition is based on shared space/resources. Asexual groups count as populations. Bacteria are microscopic, not macroscopic.

✅ Correct Answer Explanation

The ecological definition of a population centers on a group of individuals of the same species in a geographical area competing for resources. It does not require sexual reproduction.

❓ Why Other Options Are Incorrect

Option A → Bacteria are microscopic, not macroscopic.
Option C → Asexual populations don't typically have sex ratios in the ecological sense.
Option D → Bacteria growth status isn't described by age pyramids in standard NCERT terms.

🎯 Strategy

Used: Elimination

Application: Eliminate factually incorrect (A, C) or irrelevant (D) statements.

Final Logic: Population is about shared environment and species unity.

🧠 Memory Trick

"Share Area = Population."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Reproductive Scope

5 Analyze the deeper implications of per capita birth rates (b):
Statement I: They are expressed as a decrease in numbers with respect to the members.
Statement II: They indicate the offspring produced per individual over a specific time.
Statement III: They are a population attribute, unassignable to a single individual organism.
Which statements are logically correct?

A I and II only

B I and III only

C II and III only

D I, II, and III

💡 Short Explanation

Births are an increase, not a decrease (I is false). Per capita rate = offspring per individual (II is true). Rates are population properties (III is true).

✅ Correct Answer Explanation

Statement I is false because birth rates represent an increase in population size, not a decrease. Statements II and III are correct; they accurately define the per capita rate as a population metric that cannot be attributed to a single individual's event.

❓ Why Other Options Are Incorrect

Options A, B, and D → All include the false Statement I.

🎯 Strategy

Used: Elimination

Application: Eliminate options containing the incorrect Statement I.

Final Logic: II and III describe birth rates correctly.

🧠 Memory Trick

"Birth = Increase; Rate = Population."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Vital Statistics

6 Arrange the steps to determine the shift in vital statistics over a year for a plant species:
1. Divide the new individuals by the original population size.
2. Determine the initial population size (e.g., 20 lotus plants).
3. Express the final value as per capita births per year (e.g., 0.4 offspring).
4. Count the number of new individuals added through reproduction (e.g., 8 plants).

A 1, 2, 3, 4

B 2, 4, 1, 3

C 4, 2, 1, 3

D 2, 1, 4, 3

💡 Short Explanation

Start with population (2). Count new births (4). Calculate the per capita rate (1). State the unit (3).

✅ Correct Answer Explanation

First, establish the starting population (2). Then, identify the number of new additions (4). Divide the additions by the starting population (1) to get the rate, then finalize the expression (3).

❓ Why Other Options Are Incorrect

Option A, C, and D → These place the steps in a non-functional logical sequence.

🎯 Strategy

Used: Substitution

Application: Order steps based on scientific methodology.

Final Logic: Initial count → New count → Calculation → Final unit.

🧠 Memory Trick

"Baseline → Additions → Ratio → Rate."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Demographic Calculations

7 Which of the following demographic scenarios will NOT result in a per capita rate of 0.2?

A 10 births in a population of 50 per year.

B 8 deaths in a population of 40 per week.

C 4 births in a population of 20 per year.

D 20 deaths in a population of 40 per week.

💡 Short Explanation

A: 10/50 = 0.2 B: 8/40 = 0.2 C: 4/20 = 0.2 D: 20/40 = 0.5

✅ Correct Answer Explanation

Calculation for Option D: 20 deaths / 40 individuals = 0.5. Since the question asks for the scenario that does NOT result in 0.2, this is the correct choice.

❓ Why Other Options Are Incorrect

Options A, B, and C → These all calculate exactly to 0.2.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Calculate each option (Events ÷ Population).

Final Logic: 20/40 is 0.5, not 0.2.

🧠 Memory Trick

"0.2 is 1/5; 20/40 is 1/2."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Demographic Calculations

8 An ecologist observed a laboratory population of fruitflies. Over one week, 6 flies died, resulting in a per capita death rate of 0.15 individuals per fruitfly per week. What was the initial population of the fruitflies before the deaths occurred?

A 30

B 40

C 60

D 90

💡 Short Explanation

Rate = Deaths / Initial Population. 0.15 = 6 / Initial Population. Initial Population = 6 / 0.15 = 40.

✅ Correct Answer Explanation

Using the formula Rate = Deaths ÷ Population, we solve for Population: Population = Deaths ÷ Rate = 6 ÷ 0.15 = 40.

❓ Why Other Options Are Incorrect

Option A, C, and D → These produce incorrect math when substituted back into the rate formula.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Solve the algebraic equation for the unknown (Initial Population).

Final Logic: 6 divided by 0.15 equals 40.

🧠 Memory Trick

"Pop = Events / Rate."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Demographic Calculations

9 If an individual is either male or female, how does the attribute of "sex ratio" uniquely serve the study of population ecology?

A It calculates the exact lifespan of male individuals.

B It allows ecologists to plot the percentage composition of males and females, helping forecast reproductive potential.

C It measures the absolute biomass of the female organisms.

D It converts an asexual group into a sexually interbreeding population.

💡 Short Explanation

Sex ratio tracks gender balance. Gender balance predicts births (reproductive potential). It does not measure lifespan (A) or biomass (C).

✅ Correct Answer Explanation

Sex ratio is a key demographic parameter. By understanding the proportion of males and females, ecologists can gauge the reproductive capacity of the population, which influences future population growth.

❓ Why Other Options Are Incorrect

Option A → Sex ratio is not for individual lifespan.
Option C → Sex ratio is for percentages, not biomass.
Option D → Sex ratio does not change biological reproduction methods.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Identify the primary use of demographic ratios in ecology.

Final Logic: Sex ratio = reproductive potential prediction.

🧠 Memory Trick

"Ratio = Reproduction insight."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Sexual Composition

10 Which of the following is NOT a valid way to express the sexual composition or vital statistics of a population?

A The death rate is 4 individuals dying.

B 60 per cent of the population are females.

C 40 per cent of the population are males.

D The birth rate is 0.4 offspring per lotus per year.

💡 Short Explanation

Rates must be normalized (per capita). "4 individuals dying" is an absolute number, not a rate. Others (B, C, D) are correct population statistics.

✅ Correct Answer Explanation

Vital statistics like birth and death rates must be expressed as "per capita" (number per individual). An absolute number of deaths (4) is a raw count, not a rate, and thus invalid as a vital statistic.

❓ Why Other Options Are Incorrect

Option B, C, and D → These are valid ways to express population metrics.

🎯 Strategy

Used: Elimination

Application: Differentiate between "Raw Count" and "Statistical Rate."

Final Logic: Rates must be per capita.

🧠 Memory Trick

"Rates = per capita, not count."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Vital Statistics

11 Match the age distribution analysis steps to their outcomes in population ecology:

Column 1	Column 2
1. Plotting per cent individuals of a given age	P. Formulates the age pyramid
2. Broad base in the pyramid	Q. Expanding population
3. Narrow base in the pyramid	R. Declining population
4. Analyzing male/female age distribution	S. Human age pyramid structure

A 1-S, 2-P, 3-Q, 4-R

B 1-Q, 2-R, 3-S, 4-P

C 1-R, 2-S, 3-P, 4-Q

D 1-P, 2-Q, 3-R, 4-S

💡 Short Explanation

1 creates the pyramid (P). 2 indicates expansion (Q). 3 indicates decline (R). 4 creates the human age pyramid (S).

✅ Correct Answer Explanation

1 matches P because plotting percentages forms the structure. 2 matches Q because a broad base signals future growth. 3 matches R because a narrow base signals decline. 4 matches S because human pyramids specifically segregate gender.

❓ Why Other Options Are Incorrect

Options A, B, and C → These misalign the demographic features with their correct ecological definitions.

🎯 Strategy

Used: Substitution

Application: Pair descriptions with established demographic outcomes.

Final Logic: D correctly maps all concepts.

🧠 Memory Trick

"Broad base = Expansion."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Age Distribution

12 When an age pyramid structure is constructed, what does an overwhelming proportion of post-reproductive individuals compared to pre-reproductive individuals biologically indicate about the population's future?

A The population is expanding geometrically.

B The population is stable and will maintain its numbers.

C The population is declining because future reproductive potential is critically low.

D The population has a high per capita birth rate.

💡 Short Explanation

Few young (pre-reproductive) = Low birth potential. Many old (post-reproductive) = Death rate outweighs birth rate. Result = Decline.

✅ Correct Answer Explanation

Demographic momentum depends on the number of young individuals entering reproductive age. If this cohort is small compared to the elderly cohort, the population will inevitably shrink.

❓ Why Other Options Are Incorrect

Option A → Expanding populations require many young.
Option B → Stability requires balanced cohorts.
Option D → Birth rates are low in such a demographic structure.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Analyze the impact of age structure on growth potential.

Final Logic: Few young = Declining future.

🧠 Memory Trick

"Low young = Low growth."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Age Distribution

13 Arrange the sequence of analytical observations an ecologist makes when assessing human demographics:
1. Conclude the growth status (growing, stable, declining).
2. Gather data on the age of every male and female in the population.
3. Plot the age distribution of males and females in a diagram.
4. Observe the shape of the resulting age pyramid.

A 3, 2, 1, 4

B 2, 4, 3, 1

C 2, 3, 4, 1

D 1, 2, 3, 4

💡 Short Explanation

Gather data (2). Plot data (3). Observe shape (4). Conclude status (1).

✅ Correct Answer Explanation

Scientific method in demography: Census data gathering (2) → Graphical representation (3) → Shape analysis (4) → Conclusion of growth status (1).

❓ Why Other Options Are Incorrect

Options A, B, and D → These disrupt the logical methodology of ecological analysis.

🎯 Strategy

Used: Substitution

Application: Order steps based on data science workflow.

Final Logic: Raw data → Analysis → Observation → Conclusion.

🧠 Memory Trick

"Data → Plot → Shape → Status."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Human Demographics

14 Evaluate the reflections of growth status in human demographics:
Statement I: A growing population is strictly indicated by a higher percentage of elderly males.
Statement II: The shape of the pyramids directly reflects whether the population is growing, stable, or declining.
Statement III: Human age pyramids generally separate the age distribution of males and females.
Which of the statements are correct?

A II and III only

B I and II only

C I and III only

D I, II, and III

💡 Short Explanation

Statement I is false (growth is defined by young, not elderly). Statement II is true (pyramid shape = status). Statement III is true (human pyramids segregate genders).

✅ Correct Answer Explanation

Statement I is incorrect; growth status is determined by the balance of younger cohorts, not elderly males. II and III are standard facts regarding human population demographics.

❓ Why Other Options Are Incorrect

Options B, C, and D → All include the false Statement I.

🎯 Strategy

Used: Elimination

Application: Eliminate all options including Statement I.

Final Logic: II and III are true.

🧠 Memory Trick

"Growth = Young; Status = Shape."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Human Demographics

15 If a country introduces restraints to limit human population growth, causing the pre-reproductive demographic to shrink significantly over 20 years, what shift will be observed in their age pyramid's growth status?

A From stable to expanding

B From expanding to declining

C From declining to expanding

D The pyramid shape will remain permanently unchanged

💡 Short Explanation

Shrinking pre-reproductive group = Less future growth. Expanding population usually relies on a large young group. If that shrinks, the trend shifts toward decline.

✅ Correct Answer Explanation

Reducing the pre-reproductive group cuts off the supply of future parents. This leads to a narrowing base, which is the hallmark of a declining population status.

❓ Why Other Options Are Incorrect

Option A → Expansion requires an increasing pre-reproductive base.
Option C → This would be the opposite of limiting growth.
Option D → Population structures are highly dynamic.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Relate population restriction policies to demographic outcomes.

Final Logic: Smaller pre-reproductive group = Decline.

🧠 Memory Trick

"Shrink youth = Shrink future."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Population Status

16 Which characteristic is NOT associated with an expanding and growing population's age pyramid?

A A wide, heavy base.

B A higher proportion of pre-reproductive individuals.

C A narrow base with a top-heavy structure.

D High per capita birth rates.

💡 Short Explanation

Expanding = Broad base, not narrow. Narrow base + Top-heavy = Declining. The others (A, B, D) are characteristics of expansion.

✅ Correct Answer Explanation

A narrow base and top-heavy structure indicate a declining population with many elderly and few young. Expanding populations feature wide bases (A), high pre-reproductive counts (B), and high birth rates (D).

❓ Why Other Options Are Incorrect

Options A, B, and D → These are correct characteristics of expanding populations.

🎯 Strategy

Used: Elimination

Application: Select the option describing the opposite of an expanding population.

Final Logic: C describes decline, not expansion.

🧠 Memory Trick

"Expansion = Wide Base."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Population Status

17 Why is total number (N), although generally the most appropriate measure, technically difficult to adopt for a dense laboratory culture of bacteria in a petri dish?

A Because bacteria do not have a defined age pyramid.

B Because counting is impossible or very time-consuming due to the huge population size.

C Because bacteria do not have a per capita death rate.

D Because bacteria are completely devoid of biomass.

💡 Short Explanation

Bacteria are tiny and billions in number. Counting one-by-one is physically impossible. The problem is the sheer scale of the population.

✅ Correct Answer Explanation

In dense microbial cultures, the population count is so high that direct enumeration is impractical, necessitating alternative metrics like relative density or biomass.

❓ Why Other Options Are Incorrect

Option A → Irrelevant to density measurement difficulty.
Option C → Bacteria have death rates.
Option D → Bacteria possess biomass.

🎯 Strategy

Used: Substitution

Application: Identify the practical limitation of counting large populations.

Final Logic: High N makes counting impossible.

🧠 Memory Trick

"Too many = Cannot count."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Measuring Density

18 When assessing the ecological role of a single huge banyan tree against 200 carrot grass plants, why is total numbers considered a limitation?

A Total numbers fail to capture the massive canopy and photosynthetic/community contribution of the banyan tree.

B Carrot grass cannot be counted accurately due to asexual reproduction.

C Total numbers incorrectly assume the banyan tree has a high per capita birth rate.

D The banyan tree does not constitute a population.

💡 Short Explanation

Banyan is one plant but acts like a forest. Count (1) = Insignificant. Role = Massive. Count fails to measure role.

✅ Correct Answer Explanation

The NCERT text highlights that for large, canopy-forming organisms, a raw count of "1" fails to reflect their dominant impact on the ecosystem. Biomass or percent cover is required to capture their true ecological significance.

❓ Why Other Options Are Incorrect

Option B → Carrot grass can be counted.
Option C → Count vs. Birth rate is not the issue.
Option D → The banyan tree is a population member.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Recognize the limitation of "numerical parity" in ecological importance.

Final Logic: Count != Impact.

🧠 Memory Trick

"Count = Number; Need = Impact."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Measuring Density

📄 Passage

Total number is again not an easily adoptable measure if the population is huge and counting is impossible or very time-consuming. If you have a dense laboratory culture of bacteria in a petri dish what is the best measure to report its density? Sometimes, for certain ecological investigations, there is no need to know the absolute population densities; relative densities serve the purpose equally well. For instance, the number of fish caught per trap is good enough measure of its total population density in the lake.

According to the passage, when a population is huge and counting is impossible, what measure serves the purpose equally well for certain ecological investigations?

A Absolute population density

B Sex ratio percentages

C Relative density

D Plotting age groups

💡 Short Explanation

The passage explicitly identifies relative density. The fish trap example illustrates this. Other metrics are not mentioned as alternatives for huge populations.

✅ Correct Answer Explanation

The passage states, "there is no need to know the absolute population densities; relative densities serve the purpose equally well," particularly when the population is large and counting is impossible.

❓ Why Other Options Are Incorrect

Option A → Absolute density is what we are trying to avoid needing.

Option B and D → These are irrelevant to solving the "counting difficulty" issue.

🎯 Strategy

Used: Substitution

Application: Directly retrieve information from the provided passage.

Final Logic: Passage says "relative densities serve the purpose."

🧠 Memory Trick

"Huge population = Relative density."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Alternative Measures

📄 Passage

Based on the passage, the number of fish caught per trap is an example of which alternative measure?

A Relative density

B Per cent cover

C Biomass

D Absolute numbers

💡 Short Explanation

Fish-per-trap is a proxy for population. Proxies are "relative" measures. It is not absolute (total), biomass, or cover.

✅ Correct Answer Explanation

The passage provides the "fish caught per trap" example immediately after discussing relative density, identifying it as the illustrative case for that concept.

❓ Why Other Options Are Incorrect

Option B, C, and D → These are different ecological metrics not represented by a "catch per trap" scenario.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Identify the example given for "Relative density."

Final Logic: Catch-per-trap = Relative density.

🧠 Memory Trick

"Catch per trap = Relative density."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Alternative Measures

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