CUET UG Biology Booster Test 3-Causes of Species Extinction -

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CUET UG Biology Booster Test 3-Causes of Species Extinction

⏱️ 30 Minutes

❓ 20 Questions

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

CUET UG Biology Booster Test 3-Causes of Species Extinction

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QUESTION 1 OF 20

Analyze the comprehensive impact of 'The Evil Quartet' on global biodiversity:
I. Habitat loss not only includes total clearing but also degradation by pollution, which synergistically threatens species survival.
II. Co-extinction operates independently and is never triggered by habitat loss or over-exploitation.
III. The Evil Quartet is solely responsible for all historical mass extinction episodes recorded in fossil history.
IV. Alien species invasions disrupt local communities primarily by outcompeting or directly preying on native species. Which statements represent analytically sound interpretations of the text?

Answer Review

1 Analyze the comprehensive impact of 'The Evil Quartet' on global biodiversity:
I. Habitat loss not only includes total clearing but also degradation by pollution, which synergistically threatens species survival.
II. Co-extinction operates independently and is never triggered by habitat loss or over-exploitation.
III. The Evil Quartet is solely responsible for all historical mass extinction episodes recorded in fossil history.
IV. Alien species invasions disrupt local communities primarily by outcompeting or directly preying on native species. Which statements represent analytically sound interpretations of the text?

A I and II only

B II and III only

C I, III, and IV only

D I and IV only

💡 Short Explanation

Statement I: NCERT highlights pollution as a form of habitat degradation. Statement II: Co-extinction is often triggered by the loss of a host due to other quartet factors. Statement III: The quartet describes the current anthropogenic extinction crisis, not geological fossil history. Statement IV: Invasives disrupt via competition or predation.

✅ Correct Answer Explanation

Statement I is correct as the text includes habitat degradation by pollution alongside physical loss. Statement IV is correct as the mechanisms of invasive disruption are competition and predation. Statement II is incorrect because co-extinction is a consequence of other losses. Statement III is incorrect because the quartet refers to the current human-induced biodiversity crisis, not historical geological mass extinctions.

❓ Why Other Options Are Incorrect

Option A → Includes statement II (false).
Option B → Includes statement II (false) and III (false).
Option C → Includes statement III (false).

🎯 Strategy

Used: Elimination

Application: Eliminating statements that reference historical geological events (III) or misclassify the trigger-dependency of co-extinction (II).

Final Logic: Current crises ≠ geological history; co-extinction depends on other losses.

🧠 Memory Trick

"Quartet = Modern Man-made."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: The Evil Quartet

2 Which of the following factors does NOT analytically qualify as a direct anthropogenic driver within the framework of the 'Evil Quartet'?

A Conversion of complex ecosystems to agricultural monocultures like soya beans.

B The five episodes of mass extinction of species that happened before humans appeared.

C The deliberate introduction of aquaculture species that escape into natural river systems.

D The transition of resource utilization from sustainable necessity to excessive greed.

💡 Short Explanation

The Evil Quartet describes human-induced extinction. Mass extinctions in the past were natural, pre-human events. Other options describe habitat loss, alien species, and over-exploitation.

✅ Correct Answer Explanation

The 'Evil Quartet' is a framework for understanding current anthropogenic extinction. The mass extinctions that occurred before human arrival are natural geological events and fall outside the scope of the Evil Quartet drivers.

❓ Why Other Options Are Incorrect

Option A → Represents habitat loss.
Option C → Represents alien species invasion.
Option D → Represents over-exploitation.

🎯 Strategy

Used: Odd One Out

Application: Identifying that three options are anthropogenic/human-driven, while B is historical/natural.

Final Logic: Quartet is anthropogenic; mass extinctions in fossil records are natural.

🧠 Memory Trick

"Quartet = Human-era."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: The Evil Quartet

📄 Passage

"Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines."

Analytically interpreting the passage, how does pollution functionally equate to physical deforestation in the context of species survival?

A Both actively convert the land into grasslands for cattle.

B Both result in the physical breaking up of large territories into distinct grids.

C Both constitute a form of habitat degradation that threatens the continued survival of dependent species.

D Both specifically target only migratory bird populations.

💡 Short Explanation

Both reduce the quality/viability of a habitat. They are categorized under "Habitat loss and fragmentation" in the text. The end result for species is the same: survival threat.

✅ Correct Answer Explanation

The text classifies habitat degradation (pollution) and loss (physical removal) as two facets of the same primary driver. Both disrupt the ability of an environment to support its resident species, thus functionalizing them similarly in conservation terms.

❓ Why Other Options Are Incorrect

Option A → Only deforestation (and specifically Amazon clearing) relates to cattle.
Option B → This specifically describes fragmentation, not pollution.
Option D → They target all biodiversity, not just migratory birds.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Aligning the passage's classification of pollution and habitat loss.

Final Logic: Both = Habitat degradation.

🧠 Memory Trick

"Loss + Degradation = Habitat failure."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Habitat Loss

📄 Passage

The text implies that mammals and birds requiring large territories suffer heavily when habitats are fragmented. What ecological reality underpins this vulnerability?

A Smaller fragments cannot sustain the complex trophic needs and wide-ranging behaviors of these species.

B Smaller fragments inherently attract a higher density of alien invasive weeds.

C Small fragments cause animals to immediately transition into obligate parasites.

D Fragmentation forces all mammals to adopt migratory habits.

💡 Short Explanation

Animals needing "large territories" have large range requirements. Fragments provide limited space/resources. Inadequate area = inability to meet survival requirements.

✅ Correct Answer Explanation

Species requiring large territories (like apex predators or long-distance foragers) have high spatial requirements to secure food, mates, and shelter. Fragmentation breaks these ranges into sizes below the species' threshold, causing population collapse.

❓ Why Other Options Are Incorrect

Option B → Invasives are a separate category.
Option C → This is biologically incorrect.
Option D → Fragmentation disrupts migration; it doesn't force it.

🎯 Strategy

Used: Elimination

Application: Evaluating the ecological consequence of spatial restriction for large-range species.

Final Logic: Small space < Large space needed.

🧠 Memory Trick

"Big range needs big space."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Habitat Fragmentation

5 Match the ecological concept to its analytical manifestation in a fragmented landscape.

Column 1	Column 2
1. Mammals requiring large territories	P. Vulnerable to disruptions in seasonal movement corridors
2. Degradation by pollution	Q. Experiences population declines due to reduced contiguous home ranges
3. Obligatory species associations	R. Acts as an invisible driver of habitat loss without physical deforestation
4. Migratory habits	S. Faces cascading extinction if the fragment size eliminates a keystone partner

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

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

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

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

💡 Short Explanation

Large territory = Contiguous home ranges (Q). Pollution = Invisible driver (R). Obligatory associations = Cascading extinction (S). Migratory habits = Movement corridors (P).

✅ Correct Answer Explanation

Mammals with large home range requirements (1) struggle when that home range is fragmented (Q). Pollution (2) is described as degradation (R) rather than physical removal. Obligatory associations (3) represent co-extinction risks (S). Migratory species (4) depend on corridors (P).

❓ Why Other Options Are Incorrect

Mismatched ecological definitions.

🎯 Strategy

Used: Option Grouping

Application: Sorting concepts by their textbook descriptions.

Final Logic: 1-Q, 2-R, 3-S, 4-P.

🧠 Memory Trick

"Pollution = Invisible, Migratory = Corridors."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Habitat Fragmentation/Co-extinction

6 Why are animals with migratory habits acutely susceptible to habitat fragmentation compared to stationary endemic species?

A They require a continuous chain of intact habitats across their route, and severing any link precipitates a population decline.

B They rely exclusively on marine fish for sustenance during migration.

C They are more likely to be hunted by alien species like the Nile perch.

D They mutate rapidly when exposed to edge effects, leading to co-extinction.

💡 Short Explanation

Migration is sequential. Every stage (staging grounds/corridors) is essential. Fragmentation creates breaks in this chain.

✅ Correct Answer Explanation

Migratory species often rely on multiple geographically distinct locations throughout their annual cycle. If fragmentation destroys a stopover site or a movement corridor, the migration cannot be completed, leading to death or reproductive failure.

❓ Why Other Options Are Incorrect

Option B → Not true for all migratory species.
Option C → Alien species is a different category of the Evil Quartet.
Option D → Not a biological fact.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Comparing the dependency of migratory vs. stationary species on intact landscapes.

Final Logic: Chain of habitats = Migration.

🧠 Memory Trick

"Migration = Chain of stops."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Habitat Fragmentation

7 Trace the analytical chain of causality leading to the destruction of the Amazon rainforest.
I. The demand for beef and soya beans rises globally.
II. Millions of species face habitat loss and the 'lungs of the planet' are severely compromised.
III. Vast tracts of ancient, biologically rich ecosystems are cut and cleared.
IV. The land is converted into agricultural monocultures and grasslands.

A I → IV → III → II

B III → I → II → IV

C I → III → IV → II

D IV → I → III → II

💡 Short Explanation

Global demand (I) -> Clearing (III) -> Conversion (IV) -> Ecological loss (II).

✅ Correct Answer Explanation

The sequence follows the economic-to-ecological progression: Global demand (I) incentivizes the cutting of the forest (III), followed by the physical conversion into monocultures/grasslands (IV), ultimately causing mass species loss and loss of "lungs" (II).

❓ Why Other Options Are Incorrect

All other sequences scramble the cause-and-effect relationship.

🎯 Strategy

Used: Substitution

Application: Following the economic/agricultural cycle described.

Final Logic: Demand -> Action -> Conversion -> Loss.

🧠 Memory Trick

"Demand -> Cut -> Farm -> Loss."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Amazon Deforestation

8 Evaluate the profound implications of clearing the Amazon for beef cattle and soya beans:
I. It permanently eradicates a habitat that harbours millions of distinct species.
II. It directly reduces the global photosynthetic capacity, compromising a major source of Earth's oxygen.
III. It is a strictly localized issue with no bearing on the global biodiversity crisis.

A I, II, and III

B II and III only

C I and III only

D I and II only

💡 Short Explanation

I is true: Millions of species. II is true: Lungs of planet = Photosynthesis/Oxygen. III is false: It is a global biodiversity crisis, not localized.

✅ Correct Answer Explanation

Statement I reflects the high biodiversity loss (millions of species). Statement II reflects the Amazon's global role as the "lungs of the planet." Statement III is false because the Amazon's destruction is a central pillar of the global biodiversity crisis, not a localized problem.

❓ Why Other Options Are Incorrect

Options B and C include the false Statement III.
Option A includes Statement III.

🎯 Strategy

Used: Elimination

Application: Removing statements that minimize the global impact of the Amazon crisis.

Final Logic: Amazon = Global impact.

🧠 Memory Trick

"Amazon = Global = Vital."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Amazon Deforestation

9 Match the psychological or socio-economic driver to its long-term biodiversity consequence.

Column 1	Column 2
1. Sustainable human 'need'	P. Destruction of the Amazon for soya bean cultivation
2. Unchecked human 'greed'	Q. Extinction of the passenger pigeon and Steller's sea cow
3. Commercial aquaculture incentives	R. Historical equilibrium with natural resources before the last 500 years
4. Agricultural expansion	S. Illegal introduction of African catfish threatening indigenous species

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

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

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

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

💡 Short Explanation

Sustainable (1) = Equilibrium (R). Greed (2) = Pigeon/Sea cow (Q). Aquaculture (3) = African catfish (S). Ag expansion (4) = Amazon/Soya (P).

✅ Correct Answer Explanation

Historically, human 'need' was limited and in equilibrium (R). 'Greed' drives over-exploitation of species like the pigeon (Q). Aquaculture incentives lead to introductions like the catfish (S). Agricultural expansion is the driver for Amazon deforestation (P).

❓ Why Other Options Are Incorrect

Mismatched socio-economic drivers and their ecological consequences.

🎯 Strategy

Used: Option Grouping

Application: Matching the social drivers to their specific chapter examples.

Final Logic: 1-R, 2-Q, 3-S, 4-P.

🧠 Memory Trick

"Need=Equilibrium, Greed=Over-exploit."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Resource Over-Exploitation

10 When marine fish populations are harvested primarily to satisfy commercial greed rather than basic need, what fundamental biological threshold is analytically breached?

A The threshold of natural predation by alien species

B The reproductive replacement rate, ensuring harvest exceeds the species' ability to replenish

C The geographical boundary separating tropical from temperate ecosystems

D The genetic mutation rate required for niche specialisation

💡 Short Explanation

Over-exploitation is harvesting faster than replenishment. "Need vs. Greed" implies harvest speed exceeding nature's capacity. This is the definition of over-exploitation.

✅ Correct Answer Explanation

Sustainability is defined by harvesting at or below the reproductive replacement rate. When "greed" drives harvesting, the catch exceeds the fish's capacity to reproduce and recover, leading to population collapse.

❓ Why Other Options Are Incorrect

Option A, C, and D are unrelated biological thresholds.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Defining the biological mechanism of over-exploitation (harvest > replenishment).

Final Logic: Over-exploitation = Harvest > Replenish.

🧠 Memory Trick

"Over-exploit = Too much, too fast."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Resource Over-Exploitation

11 Analytically, the rapid extinction of Steller's sea cow and the passenger pigeon CANNOT be attributed to which ecological factor?

A Human over-exploitation

B Intense commercial harvesting

C Vulnerability to human predation techniques

D Obligatory co-extinction triggered by the loss of a pollinator

💡 Short Explanation

Passenger pigeon and Steller's sea cow = Over-exploitation examples. Co-extinction = Obligatory pollinator loss. These are two separate categories of the Evil Quartet.

✅ Correct Answer Explanation

These two species are the textbook examples of over-exploitation. Obligatory co-extinction refers to the loss of species like parasites or specialized pollinators when their host/partner species goes extinct, which is not the cause for the pigeon or sea cow.

❓ Why Other Options Are Incorrect

A, B, and C are all aspects of over-exploitation.

🎯 Strategy

Used: Elimination

Application: Separating the "Over-exploitation" examples from the "Co-extinction" category.

Final Logic: Pigeon/Sea cow = Over-exploitation, not Co-extinction.

🧠 Memory Trick

"Pigeon/Sea cow = Overharvested."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Over-exploitation

12 The passenger pigeon was once an incredibly abundant bird. Analytically, what does its extinction within the last 500 years illustrate about 'The Evil Quartet'?

A That only naturally rare and endemic species are vulnerable to extinction.

B That over-exploitation driven by greed can overcome and eradicate even species with massive population sizes.

C That alien species invasions are the only effective way to eliminate a widespread species.

D That migratory birds are immune to habitat fragmentation.

💡 Short Explanation

Passenger pigeon = Massive population. Extinction = Proves that even abundant species aren't safe. Over-exploitation is the reason.

✅ Correct Answer Explanation

The passenger pigeon case teaches that population size does not guarantee survival if the rate of over-exploitation exceeds the rate of reproduction. It effectively illustrates that humans can eliminate even the most "abundant" species.

❓ Why Other Options Are Incorrect

Option A → Contradicted by the pigeon case.
Option C → Irrelevant to the pigeon case.
Option D → Incorrect and irrelevant.

🎯 Strategy

Used: Elimination

Application: Evaluating the ecological lesson of the passenger pigeon extinction.

Final Logic: Mass abundance + High-greed harvest = Extinction.

🧠 Memory Trick

"Abundant = Not safe."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Over-exploitation

13 Analyze the systemic breakdown in Lake Victoria following the introduction of the Nile perch:
I. The introduction was an isolated event with no cascading effects on the wider food web.
II. The Nile perch acted as an invasive apex predator, decimation native biodiversity.
III. An ecologically unique assemblage of over 200 cichlid species was permanently lost due to competitive exclusion or predation.

A I and II only

B I, II, and III

C I and III only

D II and III only

💡 Short Explanation

I is false: Nile perch caused massive cascading effects. II is true: Apex predator role. III is true: 200+ cichlids lost.

✅ Correct Answer Explanation

The introduction of Nile perch is the classic example of an alien invasive apex predator causing mass extinction in an isolated ecosystem (Lake Victoria). Statement I is incorrect because the extinction of 200 species is, by definition, a massive cascading effect on the food web.

❓ Why Other Options Are Incorrect

Any option containing I is incorrect.

🎯 Strategy

Used: Elimination

Application: Discarding the statement that minimizes the impact (I).

Final Logic: Cascade > Isolated event.

🧠 Memory Trick

"Victoria = 200+ lost."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Alien Species Invasions

14 Sequence the systemic collapse of an ecosystem due to an aquatic alien invasion (e.g., Nile perch / African catfish).
I. The alien species outcompetes or directly preys upon indigenous species.
II. An alien species is introduced unintentionally or deliberately for aquaculture.
III. The indigenous species experience rapid population decline and eventual extinction.
IV. The alien species survives, adapts, and turns highly invasive in the new habitat.

A II → I → IV → III

B I → II → III → IV

C II → IV → I → III

D IV → II → I → III

💡 Short Explanation

Introduction (II) -> Survival/Invasion (IV) -> Competitive/Predatory pressure (I) -> Extinction (III).

✅ Correct Answer Explanation

The logical ecological sequence is: (II) Introduction, (IV) establishment/adaptation in the new habitat, (I) active destruction of the native community through predation or competition, and (III) ultimate extinction of native species.

❓ Why Other Options Are Incorrect

Other sequences logically break the establishment/pressure/extinction flow.

🎯 Strategy

Used: Substitution

Application: Following the "Invasion to Extinction" timeline.

Final Logic: Intro -> Invasiveness -> Pressure -> Extinction.

🧠 Memory Trick

"Intro -> Invasiveness -> Pressure -> Gone."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Alien Species Invasions

15 Match the invasive organism to the precise nature of the threat it poses analytically.

List 1	List 2
1. Nile perch	P. Alien terrestrial weed outcompeting native flora
2. Clarias gariepinus	Q. Aquatic weed causing environmental damage and choking water bodies
3. Eicchornia (Water hyacinth)	R. Apex aquatic predator eliminating endemic cichlid assemblages
4. Parthenium (Carrot grass)	S. Introduced aquaculture species threatening indigenous river catfishes

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

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

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

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

💡 Short Explanation

Nile perch (1) = Apex predator (R). Clarias (2) = Aquaculture threat (S). Water hyacinth (3) = Aquatic weed (Q). Parthenium (4) = Terrestrial weed (P).

✅ Correct Answer Explanation

Nile perch (1) is an apex aquatic predator (R). Clarias (2) is an invasive aquaculture species (S). Eichhornia (3) is an aquatic weed (Q). Parthenium (4) is a terrestrial weed (P).

❓ Why Other Options Are Incorrect

Mismatched threats and organisms.

🎯 Strategy

Used: Option Grouping

Application: Mapping organism to its specific ecological role/impact described in the chapter.

Final Logic: 1-R, 2-S, 3-Q, 4-P.

🧠 Memory Trick

"Nile=Predator, Clarias=Fish, Eichhornia=Aquatic, Parthenium=Terrestrial."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Alien Species Invasions

16 Analytically, why do introduced species like Parthenium and Lantana become profoundly destructive 'invasive weeds' in a new environment like India?

A Because they form immediate obligatory mutualisms with native pollinators.

B Because they transition of human behavior from need to greed.

C Because they lack their natural predators and diseases from their native habitat, allowing unchecked exponential growth.

D Because they only grow in habitats that have been fragmented into very small grids.

💡 Short Explanation

Ecological theory of invasion: Missing control agents (predators/pathogens). This allows exponential spread. This is why they become "invasive."

✅ Correct Answer Explanation

In their native ranges, populations are kept in check by natural herbivores, predators, and pathogens. In a new environment, the absence of these controls leads to "ecological release," allowing the species to outcompete native flora.

❓ Why Other Options Are Incorrect

Option A → Not the mechanism of invasiveness.
Option B → Related to over-exploitation, not alien invasion.
Option D → Weeds often thrive in disturbed habitats, not just small grids.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Selecting the fundamental ecological cause for "invasive" behavior.

Final Logic: No predators = Exponential growth.

🧠 Memory Trick

"No predators = Overgrown."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Alien Species Invasions

17 Which of the following analytically does NOT exemplify the principle of co-extinction?

A The demise of a specialized fig wasp resulting in the failure of its specific fig tree species to reproduce.

B The eradication of a host fish leading to the death of a highly specialized internal parasite.

C The extinction of an obligate pollinator causing the rapid decline of a plant species that cannot self-pollinate.

D The decline of a generalized predator that successfully switches its diet to an invasive weed after its primary prey goes extinct.

💡 Short Explanation

Co-extinction = Obligatory, non-negotiable dependency. Option C describes an animal adapting by changing diet (generalist behavior), not dying due to host extinction.

✅ Correct Answer Explanation

Co-extinction requires an obligatory relationship (the species must have the partner). Option D describes a generalist predator (a survivor) that switches diet, which is the antithesis of the obligatory link that leads to co-extinction.

❓ Why Other Options Are Incorrect

Options A, B, and C are textbook examples of obligate co-extinction.

🎯 Strategy

Used: Elimination

Application: Checking for "obligatory" vs. "generalist" behavior.

Final Logic: Generalist switches diet = Not co-extinction.

🧠 Memory Trick

"Co-extinction = Can't live without."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Co-extinction

18 In the context of the host fish and its parasite assemblage, the loss of biodiversity via co-extinction is termed 'obligatory'. What analytical fact makes the association obligatory?

A The parasite can easily switch to a Nile perch if the native host dies.

B The parasite relies entirely on the physiological, spatial, and nutritional niche provided exclusively by that specific host.

C The host fish intentionally sacrifices itself to protect the parasite.

D The human transition from need to greed mandates the parasite's survival.

💡 Short Explanation

Obligatory = Exclusivity. Parasites need that specific host's niche. No host = No niche = Death.

✅ Correct Answer Explanation

The term 'obligatory' in ecology refers to a dependency that is non-negotiable. For a specialized parasite, the host is its only source of nutrients, habitat, and developmental cues. Without this specific host, it lacks a viable niche to sustain life.

❓ Why Other Options Are Incorrect

Option A → This would be a generalist, not an obligatory associate.

Option C and D → Scientifically irrelevant.

🎯 Strategy

Used: Substitution

Application: Using the biological definition of "obligatory association."

Final Logic: Niche provided by ONLY host = Obligatory.

🧠 Memory Trick

"Obligatory = Exclusive niche."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Co-extinction

19 In exploring the failures of plant-pollinator co-evolved mutualism, which theoretical characteristic would NOT increase the risk of co-extinction?

A High degree of floral specialization tailored strictly to one insect morphology.

B A broad, generalized pollination strategy relying on wind and dozens of insect species.

C Strict synchronization of the plant's blooming period with the insect's short adult lifespan.

D Total geographical isolation of both the plant and the pollinator.

💡 Short Explanation

Specialization (A) + Synchronization (C) + Isolation (D) = High risk. Generalization (B) = Resilience, low risk.

✅ Correct Answer Explanation

Species that rely on many pollinators (generalists) have high resilience; if one pollinator disappears, others can compensate. Specialization is the factor that creates the vulnerability to co-extinction.

❓ Why Other Options Are Incorrect

Options A, C, and D are all factors that intensify dependency, therefore increasing co-extinction risk.

🎯 Strategy

Used: Odd One Out

Application: Distinguishing between a high-risk (specialist) and low-risk (generalist) pollination strategy.

Final Logic: Generalist = Low risk, Specialist = High risk.

🧠 Memory Trick

"Generalist = Resilience."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Co-extinction

20 Evaluate the evolutionary paradox of specialized mutualism in light of human-driven extinction drivers:
I. Evolutionary specialization increases efficiency between partners in stable environments but creates a profound vulnerability when habitats are rapidly degraded by human activity.
II. Co-extinction essentially acts as an ecological multiplier, meaning the loss of one keystone species artificially doubles or triples the extinction rate due to collapsing obligatory webs.
III. The Evil Quartet ensures that specialized mutualistic species are always the first to adapt and become invasive. Which of these analytical statements correctly deduce the consequences described in the text?

A I, II, and III

B II and III only

C I and III only

D I and II only

💡 Short Explanation

I is true: Specialization is efficient but risky. II is true: Co-extinction is a multiplier (loss of host = loss of others). III is false: Specialists are the most likely to go extinct, not become invasive.

✅ Correct Answer Explanation

Statement I correctly identifies the evolutionary "trade-off" (efficiency vs. vulnerability). Statement II correctly defines the "multiplier" nature of co-extinction. Statement III is false: specialized species are inherently the most vulnerable, not the most adaptable, and they do not turn invasive as a consequence of the Evil Quartet.

❓ Why Other Options Are Incorrect

Any option containing III is wrong.

🎯 Strategy

Used: Elimination

Application: Identifying that III contradicts the fundamental concept of specialist vulnerability.

Final Logic: Specialist = Vulnerable, not Adaptive/Invasive.

🧠 Memory Trick

"Specialist = Vulnerable."

📚 Class XII – Biology – Chapter: Biodiversity and Conservation – Topic: Co-extinction

CUET UG Biology Booster Test 3-Causes of Species Extinction

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