CUET UG Biology Booster Test 2-Population Attributes and Structure -

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CUET UG Biology Booster Test 2-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 2-Population Attributes and Structure

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QUESTION 1 OF 20

Ecologically, a population lives in groups within a well-defined geographical area. Which of the following is NOT a correct example of a population based on this definition?

Answer Review

1 Ecologically, a population lives in groups within a well-defined geographical area. Which of the following is NOT a correct example of a population based on this definition?

A All the cormorants in a wetland.

B Rats in an abandoned dwelling.

C A single tiger moving randomly across the entire country.

D Lotus plants in a pond.

💡 Short Explanation

A population requires a group of individuals of the same species. A single individual does not constitute a population. Populations must exist within a well-defined geographical area.

✅ Correct Answer Explanation

A population is defined as a group of individuals of the same species living in a specific geographical area. Option C represents a single individual, not a group; therefore, it cannot be considered a population. Options A, B, and D all describe clusters of organisms within defined spaces.

❓ Why Other Options Are Incorrect

Option A → This is a clear group of cormorants in a wetland.
Option B → Rats inhabiting a specific building qualify as a population.
Option D → A collection of lotus plants in a pond forms a population.

🎯 Strategy

Used: Elimination

Application: Eliminate all options that show a group of individuals (A, B, D).

Final Logic: A single individual lacks the group dynamic required for a population.

🧠 Memory Trick

"Populations need a group, not a loner."

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

2 Why is the concept of a population sharing or competing for similar resources crucial for evolutionary biology?

A Because natural selection operates at the population level to evolve desired traits.

B Because resources are completely unlimited in nature.

C Because individual organisms cannot evolve or interact.

D Because competing for resources halts reproduction completely.

💡 Short Explanation

Natural selection acts on individuals but leads to population evolution. Competition for limited resources is the driving force of selection. Populations share the genetic pool that evolves over time.

✅ Correct Answer Explanation

Competition for limited resources creates selective pressures. Since natural selection acts on individuals within a population, the outcome—evolution—is observed at the population level. This linkage between resource sharing and genetic change is central to evolutionary biology.

❓ Why Other Options Are Incorrect

Option B → Resources are inherently limited, not unlimited.
Option C → Individuals do interact; the statement is factually incorrect.
Option D → Competition influences reproductive success but does not "halt" reproduction.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Match the ecological concept (resource competition) with the primary evolutionary process (natural selection).

Final Logic: Resource competition is the catalyst for selection, occurring within a population context.

🧠 Memory Trick

"Resources → Competition → Selection → Evolution."

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

3 Arrange the sequence of events that firmly links population ecology to evolution through reproduction:
1. Natural selection operates to evolve desired traits.
2. A group of individuals potentially interbreeds.
3. Offspring are produced, forming a population.
4. The population copes with a changed environment over generations.

A 3, 1, 2, 4

B 1, 2, 3, 4

C 2, 3, 4, 1

D 2, 3, 1, 4

💡 Short Explanation

Interbreeding (2) leads to reproduction (3). This provides the material for natural selection (1). Selection over generations allows the population to cope (4).

✅ Correct Answer Explanation

The sequence begins with the potential to interbreed (2), resulting in offspring and a formed population (3). This variation provides the substrate for natural selection (1), which, over time, allows the population to adapt or cope with environmental changes (4).

❓ Why Other Options Are Incorrect

Option A → Places offspring production before interbreeding.
Option B → Starts with selection before individuals exist.
Option C → Places selection at the end.

🎯 Strategy

Used: Substitution

Application: Order the steps based on biological causality (Reproduction → Selection → Adaptation).

Final Logic: Interbreeding → Offspring → Selection → Coping.

🧠 Memory Trick

"Breed → Offspring → Select → Adapt."

📚 Class XII – Biology – Chapter: Organisms and Populations – Topic: Population/Evolution link

4 Analyze the following statements regarding the reproductive scope of a population:
Statement I: The term interbreeding solely implies sexual reproduction in all contexts.
Statement II: A group of individuals resulting from asexual reproduction is generally considered a population for ecological studies.
Statement III: Bacteria in a culture plate form a population despite reproducing asexually.
Which of the statements are correct?

A I and II only

B II and III only

C I and III only

D I, II, and III

💡 Short Explanation

Interbreeding is not exclusive to sexual reproduction; bacteria also exchange genetic material (I is false). Asexual groups function as populations in ecology (II is true). Bacteria on a plate are a standard population example (III is true).

✅ Correct Answer Explanation

Statement I is false because "interbreeding" as a population constraint does not preclude asexual lineages, which are also grouped as populations. Statements II and III accurately reflect that ecological population studies include asexually reproducing organisms.

❓ Why Other Options Are Incorrect

Option A → Includes the false Statement I.
Option C → Includes the false Statement I.
Option D → Includes the false Statement I.

🎯 Strategy

Used: Elimination

Application: Eliminate all options that include Statement I.

Final Logic: Statements II and III are ecologically correct.

🧠 Memory Trick

"Asexual groups = Population."

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

5 Match the vital statistic concept to its correct mathematical outcome based on a starting population of 50 individuals:

Column 1	Column 2
1. 10 births occur in one year	P. Death rate = 0.4
2. 5 deaths occur in one week	Q. Birth rate = 0.2
3. 20 deaths occur in one week	R. Birth rate = 0.4
4. 20 births occur in one year	S. Death rate = 0.1

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

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

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

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

💡 Short Explanation

Birth rate = 10/50 = 0.2 (1-Q). Death rate = 5/50 = 0.1 (2-S). Death rate = 20/50 = 0.4 (3-P). Birth rate = 20/50 = 0.4 (4-R).

✅ Correct Answer Explanation

Calculations: 10/50 = 0.2; 5/50 = 0.1; 20/50 = 0.4; 20/50 = 0.4. Matching these to the options results in 1-Q, 2-S, 3-P, and 4-R.

❓ Why Other Options Are Incorrect

Options B, C, and D → These provide incorrect mathematical pairings.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Calculate each rate (Events/50) and match the result.

Final Logic: 10/50=0.2, 5/50=0.1, 20/50=0.4, 20/50=0.4.

🧠 Memory Trick

"Divide by starting number."

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

6 Which statement does NOT correctly apply to per capita death rates?

A They are expressed as a change in numbers with respect to members of the population.

B They are calculated by dividing the number of deaths by the total initial population.

C They represent an attribute of a single individual organism.

D They are utilized to monitor population fluctuations over a specified time interval.

💡 Short Explanation

Per capita rates are statistical aggregates. Individual organisms have binary fates (live/die). Rates are a population property.

✅ Correct Answer Explanation

A per capita rate is a population metric, not an individual one. An individual organism does not have a "death rate"; it has a probability of survival or the event of death itself.

❓ Why Other Options Are Incorrect

Option A → Correctly describes the definition of the rate.
Option B → Correctly describes the mathematical calculation.
Option D → Correctly describes the ecological use of the rate.

🎯 Strategy

Used: Elimination

Application: Identify the option that incorrectly assigns a population-level statistical attribute to an individual.

Final Logic: Per capita rates belong to groups, not individuals.

🧠 Memory Trick

"Rate = Group; Event = Individual."

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

7 If a laboratory population of 60 fruitflies experiences 15 deaths during a week, what is the correct representation of the death rate?

A 0.25 individuals per fruitfly per week

B 4.0 individuals per fruitfly per week

C 0.15 individuals per fruitfly per week

D 2.5 individuals per fruitfly per week

💡 Short Explanation

Death rate = Deaths / Initial population. Calculation: 15 / 60 = 0.25.

✅ Correct Answer Explanation

The death rate is determined by dividing the number of deaths (15) by the initial population (60). 15/60 = 1/4 = 0.25 individuals per fruitfly per week.

❓ Why Other Options Are Incorrect

Options B, C, and D → These are mathematically incorrect values based on the data provided.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Apply the formula: Rate = Deaths ÷ Population.

Final Logic: 15 / 60 = 0.25.

🧠 Memory Trick

"15/60 is 1/4 (0.25)."

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

8 Consider a pond initially having 50 lotus plants. Through reproduction, 15 new plants are added in a year.
Statement I: The current population becomes 65.
Statement II: The birth rate is 0.3 offspring per lotus per year.
Statement III: The birth rate is calculated by dividing 50 by 15.
Which statements are correct?

A I and III only

B II and III only

C I and II only

D I, II, and III

💡 Short Explanation

New population = 50 + 15 = 65 (I is true). Birth rate = 15 / 50 = 0.3 (II is true). Birth rate = Added / Initial (15/50), not 50/15 (III is false).

✅ Correct Answer Explanation

Statement I is correct (50+15=65). Statement II is correct (15/50 = 0.3). Statement III is incorrect as it reverses the formula (should be 15 divided by 50, not 50 divided by 15).

❓ Why Other Options Are Incorrect

Options A, B, and D → These all include the incorrect Statement III.

🎯 Strategy

Used: Elimination

Application: Check the math for the birth rate formula (Added ÷ Initial).

Final Logic: 50+15 is 65, and 15/50 is 0.3.

🧠 Memory Trick

"Add to get total; divide by start to get rate."

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

9 If a population consists of 200 individuals, and the sex ratio is exactly 55 per cent females, how many males are present in this population?

A 110 males

B 90 males

C 45 males

D 55 males

💡 Short Explanation

Total = 200. Female % = 55%. Male % = 100% - 55% = 45%. 45% of 200 = 90.

✅ Correct Answer Explanation

If females are 55%, males must be 45%. Calculating 45% of 200 (0.45 * 200) results in 90 males.

❓ Why Other Options Are Incorrect

Option A → This represents the number of females (55% of 200).

Options C and D → These do not represent the correct percentage of 200.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Convert percentage to count (Count = Total × Percentage).

Final Logic: 200 * 0.45 = 90.

🧠 Memory Trick

"Complementary percentage gives the count."

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

10 Match the percentage of females to the corresponding percentage of males to maintain a valid population sex ratio:

List 1	List 2
1. 40% females	P. 30% males
2. 60% females	Q. 50% males
3. 50% females	R. 40% males
4. 70% females	S. 60% males

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

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

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

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

💡 Short Explanation

Male % = 100% - Female %. 40% F → 60% M (1-S). 60% F → 40% M (2-R). 50% F → 50% M (3-Q). 70% F → 30% M (4-P).

✅ Correct Answer Explanation

In any population, the sum of male and female percentages must equal 100%. The pairs are (40,60), (60,40), (50,50), and (70,30).

❓ Why Other Options Are Incorrect

Options A, C, and D → These provide incorrect mathematical pairings.

🎯 Strategy

Used: Substitution

Application: Pair values that sum to 100%.

Final Logic: A correctly pairs the percentages based on the 100% total rule.

🧠 Memory Trick

"Sum = 100."

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

11 When plotting an age distribution to form an age pyramid, which of the following variables is NOT utilized?

A The percentage of individuals of a given age.

B The total geographic landmass the population covers.

C The specific age groups of the population.

D The composition of individuals at any given time.

💡 Short Explanation

Age pyramids plot demographic percentages against time. Landmass is an environmental descriptor, not a demographic variable. The pyramid relies on age and count data only.

✅ Correct Answer Explanation

An age pyramid is a visual representation of the age-sex structure of a population. Option B (geographic landmass) is irrelevant to calculating the demographic percentages required for the pyramid structure. Options A, C, and D are all integral components of constructing the pyramid.

❓ Why Other Options Are Incorrect

Option A → This is a primary data point for plotting the pyramid.
Option C → Categorizing by age groups is the foundation of the pyramid.
Option D → The composition of the population is what the pyramid intends to display.

🎯 Strategy

Used: Elimination

Application: Eliminate all variables that are essential to the demographic calculation of an age pyramid.

Final Logic: Geographic landmass is unrelated to age-group percentages.

🧠 Memory Trick

"Age Pyramid = Age + Percentage, not Geography."

📚 Organisms and Populations – Topic: Age Distribution

12 An ecologist plots the per cent individuals of a given age group for a population. What specific visual structure is generated from this data that aids in understanding population dynamics?

A A J-shaped curve

B A resource partition plot

C A sigmoid curve

D An age pyramid

💡 Short Explanation

Plotting age groups creates an age pyramid. J-shaped/Sigmoid are for population growth over time. Resource partition is for inter-species interaction.

✅ Correct Answer Explanation

Plotting the percentage of individuals in different age groups results in a graphical structure known as an age pyramid. This shape is used specifically to visualize the demographic state (growing, stable, or declining) of the population.

❓ Why Other Options Are Incorrect

Option A → A J-shaped curve represents exponential population growth.
Option B → Resource partition plots relate to niche specialization between species.
Option C → A sigmoid curve represents logistic growth.

🎯 Strategy

Used: Substitution

Application: Match the defined procedure (plotting per cent of age groups) with the resulting terminology.

Final Logic: The plot of age distribution is the Age Pyramid.

🧠 Memory Trick

"Age plot = Age Pyramid."

📚 Organisms and Populations – Topic: Age Distribution

13 For a typical human age pyramid, arrange the standard age groups from the base of the pyramid to the top:
1. Post-reproductive age group
2. Pre-reproductive age group
3. Reproductive age group

A 1, 2, 3

B 2, 3, 1

C 3, 2, 1

D 2, 1, 3

💡 Short Explanation

Base = Youngest (Pre-reproductive). Middle = Reproductive. Top = Oldest (Post-reproductive).

✅ Correct Answer Explanation

Age pyramids are constructed with the youngest cohort at the bottom (pre-reproductive), moving upward through the middle-aged cohort (reproductive), to the oldest cohort (post-reproductive) at the apex.

❓ Why Other Options Are Incorrect

Option A → Places post-reproductive at the base (incorrect).
Option C → Places reproductive at the base (incorrect).
Option D → Places post-reproductive in the middle (incorrect).

🎯 Strategy

Used: Substitution

Application: Order by chronological/biological age (Youngest → Oldest).

Final Logic: Pre (2) → Reproductive (3) → Post (1).

🧠 Memory Trick

"Bottom = Babies (Pre); Top = Elderly (Post)."

📚 Organisms and Populations – Topic: Human Demographics

14 According to the text, the shape of age pyramids for human populations reflects the growth status. Which of the following is NOT a growth status reflected by these pyramids?

A Growing

B Stable

C Declining

D Mutating

💡 Short Explanation

Growth statuses are limited to Growing, Stable, and Declining. "Mutating" is a genetic term, not a population demographic status.

✅ Correct Answer Explanation

The shape of an age pyramid specifically indicates if a population is expanding (growing), remaining steady (stable), or contracting (declining). "Mutating" is not an ecological demographic status.

❓ Why Other Options Are Incorrect

Option A, B, and C → These are the standard growth statuses used in demographic studies.

🎯 Strategy

Used: Elimination

Application: Filter out the biological term that does not describe a population's numerical growth status.

Final Logic: Mutating refers to DNA change, not population count change.

🧠 Memory Trick

"Grow, Stable, Decline = Statuses."

📚 Organisms and Populations – Topic: Growth status

15 If an age pyramid of a population shows a narrow base and a wider middle and upper section, what growth status does this structural reflection indicate?

A Expanding rapidly

B Declining

C Growing

D Stable

💡 Short Explanation

Narrow base = Fewer young. Wider top = More elderly. Fewer births + More aging = Decline.

✅ Correct Answer Explanation

A narrow base indicates a low proportion of young individuals (pre-reproductive). When the reproductive and post-reproductive segments are larger than the younger segment, the population is experiencing a decline.

❓ Why Other Options Are Incorrect

Option A and C → These require a broad base.

Option D → This requires a more uniform distribution.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Correlate "Narrow base" to population contraction.

Final Logic: Few young = Declining population.

🧠 Memory Trick

"Narrow base = Shrinking face."

📚 Organisms and Populations – Topic: Population Status

16 What demographic characteristic is primarily responsible for a population having a "stable" growth status as reflected in an age pyramid?

A An unusually high number of post-reproductive individuals compared to younger ones.

B The pre-reproductive and reproductive age groups are roughly equal in proportion.

C A completely absent reproductive age group.

D A continuous exponential increase in birth rates.

💡 Short Explanation

Stable = No change. Births must equal deaths. Equalizing the reproductive cohorts creates a stable pyramid profile.

✅ Correct Answer Explanation

A stable population status is characterized by an age pyramid with a vertical or near-vertical shape, meaning the proportion of pre-reproductive individuals is roughly equal to that of reproductive individuals, keeping the population size steady.

❓ Why Other Options Are Incorrect

Option A → High post-reproductive counts usually indicate decline.
Option C → A lack of reproductive individuals leads to extinction.
Option D → Exponential increase indicates an expanding population.

🎯 Strategy

Used: Substitution

Application: Define the equilibrium required for a stable population.

Final Logic: Equal reproductive and pre-reproductive proportions = Stable.

🧠 Memory Trick

"Stable = Balanced proportions."

📚 Organisms and Populations – Topic: Population Status

📄 Passage

Population size, technically called population density (designated as N), need not necessarily be measured in numbers only. Although total number is generally the most appropriate measure of population density, it is in some cases either meaningless or difficult to determine. In an area, if there are 200 carrot grass (Parthenium hysterophorus) plants but only a single huge banyan tree with a large canopy, stating that the population density of banyan is low relative to that of carrot grass amounts to underestimating the enormous role of the Banyan in that community.

Based on the passage, why is relying strictly on the total number (N) to measure population density sometimes misleading in a community?

A Because N cannot be calculated for invasive species.

B Because numbers do not account for the ecological role or physical size/canopy of species like the Banyan tree.

C Because N is only used for laboratory populations of bacteria.

D Because carrot grass cannot be counted accurately.

💡 Short Explanation

Total number (N) only counts units. It ignores biomass or spatial impact. The Banyan example shows how N underestimates ecological dominance.

✅ Correct Answer Explanation

Total number (N) is a simple count. It fails to distinguish between a small, low-impact plant and a massive, ecosystem-shaping organism like a Banyan tree. Thus, counting alone misrepresents their relative importance.

❓ Why Other Options Are Incorrect

Option A → Invasive species can be counted.
Option C → N is used for all populations.
Option D → Carrot grass is countable; the issue is with large species.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Identify the limitation of numerical counts in ecology provided by the passage.

Final Logic: Counts fail to measure the "impact" of huge individuals.

🧠 Memory Trick

"N = Count; Missing = Impact."

📚 Organisms and Populations – Topic: Measuring Density

📄 Passage

According to the passage, comparing 200 carrot grass plants to 1 banyan tree using total numbers results in:

A An accurate representation of the community structure.

B An overestimation of the Banyan tree's role.

C An underestimation of the enormous role of the Banyan tree.

D An exact parity in their ecological biomass.

💡 Short Explanation

Carrot grass = 200 units. Banyan = 1 unit. Counting 1 vs 200 makes the Banyan seem insignificant, which is incorrect.

✅ Correct Answer Explanation

The passage explicitly states that stating the population density of the Banyan is low relative to carrot grass "amounts to underestimating the enormous role of the Banyan."

❓ Why Other Options Are Incorrect

Option A → It is inaccurate.
Option B → It is the opposite of the passage's claim.
Option D → Their biomass is not equivalent.

🎯 Strategy

Used: Substitution

Application: Directly retrieve the author's claim from the passage.

Final Logic: The passage claims counts cause underestimation of the Banyan.

🧠 Memory Trick

"Count = Underestimate Banyan."

📚 Organisms and Populations – Topic: Measuring Density

19 In cases where counting individuals is meaningless or impossible, such as a dense laboratory culture of bacteria in a petri dish, which alternative measure best represents its population size?

A Sex ratio

B Absolute numbers only

C Per capita death rate

D Relative density or per cent cover/biomass

💡 Short Explanation

Bacteria are too numerous to count. Biomass/cover is the scientific standard for large populations. Other options are irrelevant (sex ratio) or wrong (only absolute numbers).

✅ Correct Answer Explanation

When counting individuals is impractical (like bacteri A) or doesn't reflect true size (like trees), ecologists use alternatives like percent cover or biomass to measure density.

❓ Why Other Options Are Incorrect

Option A → Sex ratio is not a measure of size.
Option B → Counting is what is impossible here.
Option C → Death rate is not a size measure.

🎯 Strategy

Used: Elimination

Application: Eliminate options that are either impossible (counting) or inappropriate (sex ratio, death rate).

Final Logic: Biomass is the practical standard for massive/microscopic populations.

🧠 Memory Trick

"Cannot count = Use Biomass."

📚 Organisms and Populations – Topic: Alternative Measures

20 Which specific community scenario heavily relies on biomass or per cent cover as a more meaningful measure of population size rather than total numbers?

A 40 fruitflies in a laboratory flask.

B 20 lotus plants in a small pond.

C A single banyan tree competing with 200 carrot grass plants.

D A small group of Siberian cranes at a wetland.

💡 Short Explanation

Banyan vs. Carrot grass is the specific example from the NCERT text. The size difference is massive. This is the canonical case for using biomass/cover.

✅ Correct Answer Explanation

The Banyan vs. carrot grass scenario is the classic NCERT example provided to explain why simple counts fail to represent population status when species size/influence varies drastically.

❓ Why Other Options Are Incorrect

Options A, B, and D → These involve discrete, countable units of similar or identifiable size where total count is usually sufficient.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Recognize the specific example provided in the textbook.

Final Logic: Banyan/carrot grass is the canonical example of "need for alternative measures."

🧠 Memory Trick

"Banyan = Biomass example."

📚 Organisms and Populations – Topic: Alternative Measures

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